Weather and climate office hours by Weather West: 8/30/2024

welcome everybody to this Friday afternoon live weather and climate office hour I um apologize for re Inc complement slate it's been a bit of a a crazy day crazy week does it feel like it's been a long week for anyone else anyway uh welcome and um hopefully you're enjoying the warm but not that warm of weather in California at the moment uh and the recent reprieve uh of much cooler weather including rain in the in certain parts of the northern quarter of the State uh this past weekend uh very unusual uh August precipitation uh that at least along the North Coast was a multi- inch Soaker uh and the relatively clearer Skies that have been around for the past couple weeks over most of California still some significant smoke being emitted from the coffee pot fire in the southern Sierra Nevada but otherwise not a lot of larger significant fire activity and relatively uh good air quality in a lot of places outside of the usual uh photochemical smog uh air pollution hotspots this time of year in the Inland regions and in The Valleys uh just a reminder that this channel is sponsored Ed by Reas a company that is rethinking Earth system risk uh always uh embed a link to Reas in the video that's available uh for viewing after the live session has ended so can check it out that way uh interesting things going on um globally uh that's for sure uh even as California is not experiencing anything uh record-breaking in the weather department at the moment this seems to been a pattern by the way in recent years when whenever California is experiencing record-breaking weather which has happened a lot over the past decade uh much of the rest of the us out outside of the uh the southwestern States um aren't necessarily experiencing the same kind of extreme weather uh or globally when there's a state of really extreme heat or precipitation in some other places California is pretty quiet the the strongest example of that I think was last year generally speaking uh when there was just this unbelievable Litany of extreme and record-breaking weather events the world over except for California which uh ended up except for last two Winters ago of of course was extremely wet Statewide uh but the spring summer and Autumn um were relatively quiet although again I suppose punctuated by a couple of notable events like hurricane Hillary last summer or it made landfall at near tropical storm strength close to Southern California and brought a lot of Summer rainfall record-breaking summer rainfall in a lot of spots uh to the southern third or Southern half of the state last year nothing like that uh on the horizon or or on the calendar uh of course at the moment in California uh but there was some pretty notable weather as recently as a week ago in the sense uh that there was this low pressure system a distinctly non-tropical low pressure system so a a Pacific uh midl itude temperate uh low pressure system off the West Coast that brought widespread rain to much of uh the northernmost California and most of Western Washington and Oregon record-breaking August rain amounts in some places worth noting that the record daily rainfall uh such as that's a meaningful statistic I would argue that it's usually not but there are a number of calendar days in August throughout California where places in the uh Coastal and Valley regions have a record daily rainfall of 01 in or even just a trace of rainfall meaning that essentially uh the most rainfall that's ever fallen on that calendar date in over a century in some of these places is uh a brief sprinkle that wasn't even fully measurable uh so when we say that some places in California uh will have broken their August daily or their August monthly rainfall record uh by something like a factor of three or four sometimes uh that's simply because uh the Baseline numbers are just so extremely low uh that it doesn't not take a very large amount of water to fall from the sky uh to make up a very large fractional uh change relative to that Baseline so if your average August rainfall is 05 in as it is across much of the coastal part of Northern California if you get a quarter inch of rain you're at 500% of your August average uh quarter inch of rain in August as some places from about dinino County northward experience last week is certainly nothing to sneeze at um much welcomed in terms of what it does for fire risk and really just offering a reprieve from the long dry summer but also it's it's not a Fire season ending amount of water by any means the only place in California where I think the amount of rain that's fallen over the past couple weeks is likely to greatly mitigate Fire season is certainly along the North Coast where some places have seen as much as 3 to 5 in of rain that is quite a lot for August and that is more than enough to essentially mean that the fire activity is going to be quite minimal there unless somehow it doesn't rain until November which up along the North Coast is pretty unlikely uh elsewhere the rain that we've seen um certainly not in the five 3 to 5 in range but locally over an inch in a few spots up by Shasta and some of the Foothills uh including portions uh of the uh very large fire foot footprint from the um Park fire which is now uh essentially uh a nonactive fire at this point I'm not sure if it's officially 100% contained but there really isn't any activity that's notable on its flanks at this at this moment there there had been some concerns about flash flooding I actually I I haven't heard about anything that occurred uh in that footprint on a significant scale which may be either because uh the rains didn't reach that intensity or they weren't quite wide enough but in any case it doesn't sound like there were any major issues this rain was definitely uh net beneficial for the northern quarter of the state where it fell some sprinkles and some brief showers as far south as the Bay Area there were even a couple of places in the Bay Area that saw some moderate downpours uh briefly uh enough to set some again some somewhat dubious day daily rainfall records which don't mean a whole lot in the scheme of things but still uh a nice change of pace but the amount of that fell from the sky uh does not meaningfully say anything about fire season moving forward south of about Central mesino County so we've already had enough warm days this week um to sort of offset the the rain that occurred south of about mesino again that's not true up along the North Coast where it was actually quite wet for a period but for the most part uh we're largely back to where we were before uh a couple weeks ago in terms of vegetation moisture except for that North Northwestern most part of California and it's been relatively warm this week although nothing record-breaking um it feels probably comparatively warmer because we had quite a cool streak uh for a few days there or a better part of a week in some spots including uh what ended up being the uh the coolest uh day on record in places like Reno and in some parts of the High Sierra at the peak uh of the anomalous low pressure system this past weekend which even featured a dusting of an inch or so of snow at the very highest elevations in the Sierra uh that is not common in August uh if you were in the High Rockies um which are mainly a few thousand feet taller uh than most of the peaks in the Sierra that wouldn't have been so unusual but that is unusual uh for the Sierra Nevada uh in August and in some spots there was accumulating snowfall in places where that hadn't happened in 20 or 30 years in August so it has happened before uh but in our warming climate it has become really hard for that to happen in the offseason and so it was especially notable that that happened this past weekend along with a record cool daytime high temperature in Reno uh and and some other places uh no record overnight low temperatures uh on a monthly scale by any means uh but it was definitely cool or even chilly with a dusting of very high elevation snow all in all I don't think this was a weather product that caused too many problems for anybody mostly just offered some relief from the Heat and the exceptional dryness of the first half of Summer and even as the heat has returned right now as I mentioned um it's far from record-breaking and so I think that uh for the month of August much of California will in fact end up eeking out yet another above average month temperature-wise it's mainly because it was warm at the beginning and now the very end of the month uh despite some anomalous coolness uh in the middle of the month and some precipitation so I'll I'll uh throw some maps up on the screen to discuss that uh with a little more detail uh in just a minute or two so I think what what's a lot of folks are interested in at this point moving forward is uh well what does the fall look like and depending on how folks Define it some some people will call it fall on September 1st the atmosphere uh is U thinks otherwise uh usually meteorological seasons are a little bit behind astronomical Seasons largely because of the high heat capacity of water and of the oceans so there is a lot of thermal inertia which means that the Earth's temperatures often lag the position of the sun in the sky which is why you can get some pretty hot days later in Autumn uh when the sun is at a relatively low angle than you can get early in spring when the sun is at an equivalent angle that's because in early spring your thermal enera is pulling you back toward winter a little bit in terms of all the water in the system but in the summer it's uh trying to trying to eek out another few weeks of summer so uh and this is amp and this is uh this is true just about everywhere but it's Amplified even farther in coastal California because the hottest time of year along the coast of California and this is true within about a 10 or 20 mile Coastal strip for almost the entire State a portion of the state that is usually socked in with a pretty consistent Marine layer for most of the summer so the cool moist uh air under a shallow Marine inversion that keeps places foggy and cool on the west side of San Francisco or west side of La San Diego or even up in Eureka uh very different places uh but all feature persistent Marine layer coolness moisture and cloudiness for a lot the warm season that often goes away in September and October because the mean wind pattern uh does not favor as much cold water upwelling offshore so that northwesterly flow winds from the uh the Northwest to Southeast that blow parallel to the coast and for a reason uh through a process known as emman pumping actually directs water perpendicular to the coast so offshore at a 90° angle so the wind is blowing parallel to the coast but that water wants to diverge away from the coast and uh because we um the because essentially uh physics abhor a vacuum uh water's got to come in from somewhere and fill that space from that offer offshore word moving water and where does it come from Well it can't come from the land because you can't uh there there's no infinite water source uh from the shoreline so it's got to come up from underneath so this is known as upwelling because the water is moving upward vertically in the ocean column and as you might expect that ocean water from the deep is cold so that all that cold water coming up from the deep is the reason why Falon islands in the coast of California especially Northern California is so darn cold from about May through July sometimes into August but the reason why things warm up along the immediate Coast late in August and then into September and October especially is because that northwesterly flow usually starts to fade as the sub tropical high pressure system over the the northeastern Pacific uh weakens seasonally so although the sun angle lower although the Inland regions are getting cooler by the time we get to late August and early September the immediate Coast is usually hotter because it's more predisposed to have at least a lack of a marine laay a lack of onshore flow that natural air conditioning Fades but also because we start to see the occurrence of offshore uh land to Sea winds generally east to west or north uh Northeast to Southwest winds across the California coast and that tends to bring Inland air masses to the coast and as you'd expect those Inland air masses are generally drier and warmer than the ones that are being blown out over the ocean so that is why California's Coast tends to see its hottest time of year uh in September or October uh which is even further lagged than that astronomical versus meteorological uh seasonal lag that we get due to the thermal inertia of the Earth all of that is to say there's a reason why many of California's major wind driven wildfires in places like the San Francisco Bay area and in coastal Southern California all the way uh from the Central Coast so the Santa Barbara Co Coast um the the Ventura County Coast Southward all the way uh La orange and San Diego counties is usually late in the season September October sometimes even into November especially in recent years and that's because this is when the offshore winds occur it's when the coast tends to be driest and warmest with the least Marine lay influence and it also happens to coincide um somewhat problematically with the period which vegetation is usually at Peak seasonal dryness we're certainly seeing this this year in the absence of a major uh anomalous tropical moisture event like we got last summer which short circuited this whole process and kept things so sing wet in late August in Southern California we've actually seen a below average Summer monsoon in Southern California across the mountain and desert regions so things are near to below average dryness now in Southern California from the summer following what was a really wet winter and spring so there was a lot of vegetation growth in the grasslands the desert regions and in the chaparal regions with some brush also responding to that added moisture this past spring especially in coastal Central and Southern California where things were most anomalously wet in Winter 2024 but now uh we're reaching Peak seasonal dryness and there are continued expectations that September and October will likely be hotter than average expanding all the way to the coast with no sign of an early arrival of rain this year so essentially the formal Predictive Services from the federal government has suggested a high likelihood of above average large fire activity in coastal Central and Southern California as well as in some places near the Bay Area and in the on the western slopes of the Central and Southern Sierra heading into Autumn and I have no reason to disagree with that in fact that's essentially what I've been uh advising was likely all along unless there was some unexpected widespread precipitation event in August September or October um there was that big precipitation event of course last week up in Far Northwestern California where I do think fire seasion has been substantially mitigated but we've not seen that uh in the Bay Area or Southward uh and so I think there were that that that original prediction is pretty much still holds so I'm going to bring up a few Maps uh you're going to see me transition over uh into uh into this other application you'll briefly see the whole screen uh pop up uh that is uh I still need to find the time to to to figure out how to make that not happen but for now um not a big deal I suppose all right so you'll see my whole screen infinite mirror and now I'm going to go over to the weather model okay so uh as usual this is uh a shout out to Tropical tidbits it's a nice uh freely available weather model data visualization website run by Dr Levi Cohen uh what we see here is and I like to use Ensemble averages most of the time because you're much more likely to get a meaningful signal from a blend of multiple different potential initial conditions rather than just a single model run this Remains the bane of weather apps the world over but anyway that's a topic I've covered before and we'll probably cover again in a future session but suffice it to say that this is a representation of what the atmosphere looks like now again this is the 500 m to a potential height anomaly the red zones show essentially regions where the middle atmospheric pressure is higher than average and blue regions where it is lower than average in a warming climate we see more red than blue because the atmosphere thermally expands on average in a warming climate the 500 M layer if you may remember from previous sessions is the is essentially the half Mass layer of the atmosphere it's a rough demarcation of uh places uh where the atmosphere is um uh it's a rough rough essentially a rough estimation of the altitude at which half of the uh mass of the atmosphere lies above and half lies below so it's well up there halfway up in the mass weighted atmosphere uh for those uh folks who think in exponential functions the half Mass layer of the atmosphere because of the logarithmic nature of the atmospheric pressure is not the half halfway point geometrically speaking so uh the atmosphere becomes uh dramatically less dense as you go up and so um it's not a linear function of height none of that is particularly important to the conversation we're about to have but I just thought that some folks might find that interesting but for the purposes of this conversation red blobs are Ridges of high pressure and blue blobs are regions of unusually low pressure so this is the present in The Ensemble I'm actually going back in time showing yet another trough across the Pacific Northwest that brought some more rain earlier this week this is looking back at Tuesday in California of course it did not rain this week in fact it was actually warmer and hotter than average so they got some more rain up in Washington but not so in California this trough as it moved across the northern Rockies resulted in a major wind storm that caused wildfires in Idaho and Montana and Wyoming to blow up uh which are now remaining very active with a very escalated Wildfire situation across much of Idaho parts of the Great Basin into Nevada as well as Western Montana and parts of Wyoming but that trough uh is now officially out of out of the picture and a strong Ridge this is again uh essentially uh the present uh and actually this is uh this is a slightly older model run so I want to show something um apologies for the clickthrough here uh okay that one isn't fully in yet so I'm going to stick with this one so you can see the the bigger picture so this is today uh and I'm also in the wrong region now so I want to pull that back up to the West okay there we go this is today this is we we got a a stronger Ridge rebuilding o over the Pacific Northwest a weaker ridging over California it's nothing to write home about but it is slightly warmer than average cross Inland areas we are going to get another weaker much weaker uh low pressure system uh this weekend uh moving into Northern California and actually I want to make sure these are the normalized anomalies uh so it looks a little bit different but similar um another low pressure system moving in for a cooling Trend over the holiday weekend so no record-breaking Heat this uh this uh holiday weekend often that September 1st weekend uh we've seen a lot of extreme heat and Wildfire events in recent years we certainly won't have the extreme heat uh there may be some Breezy conditions that could result in some increased Wildfire uh activity but nothing extreme at this point uh I don't think this system is going to bring much if any precipitation anywhere in the west and we can see uh at most a few sprinkles up in Oregon and Washington uh but nothing meaningful uh in in uh California at all so uh a couple of isolated Mountain thunderstorms earlier in this period uh unrel but uh that low pressure system isn't going to do much other than bring cooler temperatures this weekend uh and um coola temperatures this weekend and maybe some isolated thunderstorms up in Oregon uh okay but as we go into later into next week uh it looks like a stronger Ridge is going to build and actually this is going to be a much more notable Heat Wave uh than the one we just experienced in California so this one looks to be pretty widespread a little bit of a double barreled anomaly one again across Southern California Southern Arizona and then another one up in the Pacific Northwest Northern California not quite as anomalous but still u a pretty strong rid much warmer than average as we get into early September so this is about a week from now um this is a pretty strong signal for a major Heatwave especially in Central and Southern California and given the time of year uh it's possible that there could be uh some modest offshore flow with that so if I bring up uh if I bring up the uh Ensemble averaged pressure anomalies here uh you can see that there is and I'm going to bring up my drawing tools to make this a little bit clear here just bringing that up now you do see that there is a little bit of a blob of slightly higher than average surface pressure over Nevada and slightly lower than average pressure over Central California so that kind of gradient might set off some offshore flow it does not look dramatic this does not look like an extreme wind event although there could be some locally stronger winds uh coming off of the CR Nevada as well here uh but generally speaking this is going to be uh a significant Heat Wave uh more so than a significant wind event it looks like uh and as we uh go forward a bit I'm going to bring back uh that normalized height anomaly to bring back the red equals ridging piece um we go out about 10 days uh still higher than average heights across California um out to about 10 days but cooling from what it was and then as we get into the second week in September uh there is a signal for a larger scale trough an early season trough um along the Pacific northwest coast so right now it doesn't look like this is going to extend fully into into California this could be a situation where the North Coast sees a few scattered showers and cooler temperatures in southern California remains warmer than average with uh sort of the the the Bay Area Tahoe IED type Corridor remaining dry Breezy and cooler so uh a relief from the heat um and nothing extreme uh but also uh not looking right now like there's going to be any meaningful chance of precipitation except for maybe a few showers once again along that North Coast there is actually once again as we head towards the middle of September uh a signal for increasing ridging once again uh less extreme than the signal earlier in the month um this is by the way uh the European Ensemble there is a stronger Ridge signal in the American model or at least there was at last check perhaps that has changed looks like that has changed so uh not as strong of a ridge signal heading into mid-september uh it looks like so we'll kind of have a potentially significant heat event just after the holiday weekend coming up uh and then a period of alternating uh above and below average temperatures with some breezes at times probably not uh any precipitation in fact if you look at this going out a couple weeks this is pretty minimal for an ensemble average except perhaps again as I mentioned right along that far North Coast could see some uh some showers elsewhere this is pretty much just noise uh on the Ensemble average heading into midt so not foreseeing any widespread record-breaking heat although the heat about 7 to 10 days from now looks quite significant uh in Central and Southern California and in Arizona as well uh the Pacific Northwest though could see some decent rainfall uh and I still think this means that the likelihood of major Wildfire activity west of the Cascades is not zero but given the rain that's Fallen recently significantly lower than it would have been and maybe even lower in a couple of weeks if this rain falls as well despite the upcoming heat but one thing I will man I will mention and actually this is maybe a good map to draw it on uh because uh it kind of gives you the right sense of things um I I think that you know Fire season is is largely uh largely going to be over about west of that red line so it does include a bit of California uh in the North Coast uh and you know never say never there are actually still some fires you can see on satellite in this region right now burning in heavy Timber so no absolute guarantees but right now this pattern looks like at least uh from from west of the Cascades essentially and including the far North Coast of California I think things are largely done the recent rainfall in this region uh essentially did mitigate Fire season so we are seeing a reprieve because of the precipitation that fell some places saw more than others and the precipitation was patchy but some spots did see over an inch so that is significant but it's also not Fire season ending especially in the context of the record-breaking heat and evaporate of demand we saw earlier this summer in this region so there is a bit of a legacy uh that's going to persist now of course as I mentioned south of about that line uh Fire season uh and and this is essentially true uh in this whole region which includes most of California including all of Central and Southern California uh as well as the Great Basin into Idaho and parts of the Rocky Mountain Front Range as well uh these are areas where we could well continue to see significant fire activity and even above average fire activity over the next couple of months unless something dramatic happens because the seasonal outlook for this region is warmer and generally uh leaning towards drier than average so uh this is uh this includes of course everything uh from about the San Francisco Bay area or so Southward and that's not too surprising given the typical seasonality uh that I mentioned this time of year okay and just to talk a little bit about what we're seeing right now on the satellite Mount this is a l live current view I'll get my drawing tool back up and show a few things of interest um some humous clouds over the sier Nevada but nothing too dramatic otherwise quite clear uh really throughout uh the West Coast this is a pretty clear day along the Pacific coast there's some a limited amount of fog along the immediate Coast but right now even in the even in the Bay Area there's actually a fog free Coast all the way from mesino down past Big Sur so that's pretty impressive um and there there is still some sort of late season Monsoon thunderstorm activity occurring in the four corners region you can see this Big Blob of smoke uh across uh Central Idaho these are the big fires there uh but otherwise a pretty calm day across uh a lot of the West one thing I do want to show is if I can do this there we go just the short way of imagery this is one way it's easy to easier to pick out fires uh a couple items of note here one up in this region uh look all those little black dots up in Idaho and Montana those are all fires there are a lot of fires percolating still and I'm going to zoom in on a couple of regions really quickly to show at the sub Regional scale not a lot of fires uh to talk about in the southwestern California but there is one and this is the one that's generating all that smoke in the sanen valley this is the coffee pot fire which I've in the southern sier Nevada uh which I've circled here uh doing some uh good work actually in terms of reducing fuel loading under modest moderate burning conditions not extremely mild but also not extremely severe so hopefully the net effects of this fire are largely beneficial ecologically at least at the moment but it is burning relatively hot right now uh and it is generating a lot of smoke so that that would be the the primary downside in this setting here um and if I bring back the visible you can see it's a little bit hidden by some cumulus clouds but it looks like it did just send up a brief pyro cumulus cloud so if you're in Fresno this is probably what you're seeing right now if I go back up to Idaho uh what you'll see and actually I want to slight zoom in a slightly different region here maybe I need to go to a localized sector that's the one um that's the wrong imagery um apologies I need to go one further north here we go uh just pointing out again that fire season is very active still up in this region and you can see in this region there are over a dozen black spots all of those are individual wildfires in this region from northern Idaho into the bitter roots of Southwestern Montana and this has been producing a lot of smoke uh a whole lot of smoke in recent days and one more place on this radar Tour on the satellite tour I'm just going to take a look up in Canada um and there are parts of Canada too where wildfires remain quite active and this is starting to get pretty late in the season for that again note uh this and in Northern sasketchewan uh there's quite a bit of boreal forest fire activity going as well I do think the Fire season up in this region is about to wrap up because that's sort of the seasonal expectation but this was another remarkable Wildfire year in western Canada following a record shattering year last year um almost as if it's part of a trend being a little sarcastic there one other thing I wanted to show and then I'll bring back uh my face on here uh is an estimate of okay well how cool has it been the last few days and the answer is if as I mentioned if you've been up uh in uh in the Reno Tahoe area or up in Northwestern Nevada last week has been essentially the coolest such week since at least the late 1970s in your area so that's that's notable we don't see uh cold cold anomalies like that very often these days so your mileage may vary but if you're in the the Tahoe area or in the Reno area or really anywhere sort of in this General vicinity there were patches where it was either the coolest or second coolest um late August period in the last 40 years or so so that's that's uh notable also notable is that throughout most of California the last week has indeed as you'd expect been cooler than average your mileage varies depending on where you are it's been pretty cool relative to aage average in the Southern California metros it's not really been much cooler than average at all in the Bay Area in fact there's even a few spots where it's been warmer than average but this is definitely a case where there's been more cooler than warmer than average but of course this is just over the past week so if I go back to the last 15 days we start to see a different picture still cooler than average in Northern California and Oregon but not so much in Southern California we talk about the last 30 days now we're back into most places in Southern California being warmer than average but then still some pockets of significantly cooler than average up in Northern California so August has been an interesting month because there are Park pockets in the south us that saw their hottest period on record but this is not nearly as widespread as the record heat earlier in the summer and there are places in California that were actually quite cool in August especially in Northwestern California as I mentioned where we saw a lot of the rain but what happens when we go back to the last 60 days this gets us back to early July and even the last 90 days so let's take a look essentially since oh this is actually since June 1st so this is pretty much going to be what the summer anomaly looks like overall for the West even factoring in what was a very cool August in some places California is likely to have experienced its hottest summer on record once again because that's true in all of the places that are bright red what is kind of interesting is there are some places that definitely did not experience their hottest summer on record in fact in this data set there were a few spots up in Northwestern California that experienced some of their cooler uh conditions on record in the last 40 years I'm not sure if this this blob in West Marin is real or a data anomaly but there's clearly some Pockets along the immediate Coast where the summer was not noticeably hot including in parts of the Southern California Metro so again most of California's population lives uh along or west of the squiggly lines in a great minority of the land area and yet to the east of that line this was the hottest summer on record in most of the state so another interesting example and it will also be interesting and we don't have an answer to this so I know folks will ask in the comment section is this a signature of climate change are we going to continue to see really rapid warming as soon as we get 20 miles Inland but not nearly as rapid warming right along the immediate Coast that is possible with California's complex Marine layer Dynamics but there are meteorological reasons to believe that either that or the reverse could be true in the long run if this is just sort of a short-term anomaly or a long-term persistent Trend I think remains to be seen what's really clear though is that everywhere except for the immediate California coast this was either the hottest or second hottest summer on record everywhere uh in the bright red or orange that's the big picture about this summer and yet for much of the California's population which lives in the squiggly Zone here uh that's not really what you experience so that Divergence is interesting I think for a variety of reasons uh and just to just for fun I'll bring up the uh the precipitation percent of average or maybe the precipitation rank is more interesting so that's what is going to be shown here it's essentially the same variable but for precipitation uh showing that overall this is again the last 90 days so this is essentially for summer uh one thing that's interesting because this now encompasses most of the South uh the the Southwestern Monsoon period is that this was a good Monsoon year right around the Four Corners with well above average precipitation in parts of New Mexico uh it was a good water year although this is partly because of that early Prem monsoonal rainfall so whether it was Monsoon or not eh but um in this region generally speaking the summer was pretty good but throughout the rest of the Southwest it wasn't so great uh in the Great Basin this was a pretty poor Monsoon year in some places it was in the driest 10% of all monsoors some parts of uh Arizona including just south of the the Mogan Rim is actually one of the driest monsoons on record and this this was as I mentioned earlier a very poor Monsoon across all of the portions of California that usually do see some meaningful uh I I could extend this even F farther west some meaningful summer uh Monsoon rainfall so in Southeastern California extending all the way into even like the the LA County mountains and deserts this a this was not a very good Monsoon uh one place that did well as I mentioned a place that doesn't usually see much precipitation of any in the summer is far Northwestern California along the North Coast and the Southwest coast of Oregon this is why I think this region is largely uh done with major wildfires this year but everywhere else not so much a couple of areas of concern this fall will be the Front Range of the Rockies uh that's generally been quite dry even locally record dry the Great Basin is going to be continue to be active when it's windy uh we'll get some wind driven Great Basin grass and brush fires in all likelihood and then as I mentioned pretty much uh this area uh this this this whole Zone here uh Fire season very much still ongoing so that's probably all I have uh for the graphics part of today and you're going going to see my face again there we go I'm going to go back into the right window so that I can help out with this all right there okay so now I want to take a look at what folks are saying since I did promise uh that I would try and leave some time for well questions as always but also um a brief ask me anything session at the end interesting there are quite a lot of folks joining today um these are numbers that I usually see when there's a very active weather event so either I found a good time on a Friday afternoon maybe that's part of it when everyone is just about done with the week or uh people are really interested in the weather coming up perhaps for the holiday weekend so either way welcome thanks for joining all right so I'm GNA start going through questions I'm going to start with um actually given we got about 15 20 minutes I think I'm just going to answer uh anything that's comeing this far so I'll prioritize questions about the short-term uh conditions and but I'm also today taking some broader questions since we have some time and I know folks appreciate that and I enjoy answering things off the cuff can't always give you the perfect answer because of course it's all spontaneous and live uh but um I do try and have these sessions periodically and I do try having these uh these uh full uh sessions uh that include um a full hour of ask me anything type content at least periodically so uh haven't scheduled one of those in a while maybe September will be a good time for the next one but for now in the next 15 or 20 minutes um the first question from Paul is now that we're a couple years out from the Epic Lin winter of 2223 do we have any understanding of why it was so unusually wet and cool so if you recall uh 20 winter 2022 2023 was uh both very wet and also very cold in many parts of California with a hugely massive snow pack in the Sierra Nevada either the the second or even in locally the the largest snow pack on record in few places which is remarkable in the context of a warming climate where we're seeing uh on average significant declines in California's snow pack interestingly we're not seeing a decrease in the most extreme snow years or snow events but we are still seeing a decrease in the average amount of Mountain snow how does the math work out on that well as you might have guessed we're still getting snow storms that are every bit as big as the ones we used to get and even individual snow years that are essentially as big as the ones that were in the biggest years in the past but what we're seeing a lot more of our terrible snow years in addition to that so we're seeing a lot more years with abysmal snow conditions and so the average there is that we're getting Less on average so we're actually seeing I think so far recently we've seen an increase in snow pack variability uh there is some indication uh there's actually strong research now suggesting that the extreme snow events in the Sierra and probably generally elsewhere in cold places and at high altitudes and at high latitudes will de increas much more slowly than more tame snow events so picturesque and fun pretty snow events uh are decreasing a lot more a lot faster than the hugely disruptive massive multi- fooot events uh which can make snow management difficult in places that are cold and snowy I mean I've talked this past winter I was up in South Lake Tahoe for uh the a meeting of of Television meteorologists and ski industry folks and one of the big topics of conversation in South Lake Tahoe and really throughout the the Basin uh and and and arguably throughout the Sierra above a certain altitude is that there have been two problems over the past 10 or 15 years and they're almost the exact Polar Opposites of each other some years there's virtually no snow and at least through January early January this past winter it that that was the case up at Tahoe there was pretty terrible snow pack when I was there there just after New Year's that did improve considerably in February but uh the challenge is that we sort of alternating between very poor snow years and then very extreme snow years leads to two very different sets of challenges one is the environmental and economic impacts of a of a area that's quite accustomed to a lot of Tourism for winter snow Sports not having snow to uh encourage people to come up um and also having water scarcity and Wildfire risk in those years followed by years where people who are who haven't spent a lot of time up there in the mountains assuming that every year is as mild as that and so come up end up being unprepared for the massive snowfalls that then follow and it's also difficult to maintain a municipal infrastructure so there were problems two years ago with with roof collapses up in the mountains because of the extremely large and heavy snow loadings that occurred on multiple occasions and it is challenging in a climate that's warming with less snow overall and yet with very large extreme individual snow events you still need to have engineering standards that can um accommodate these occasional but very heavy snow loads so that's a challenge because you're building buildings for a climate that's less snowy on average but still has to be able to accommodate the very snowiest periods which so far haven't become less extreme that's a challenge but even things as as ordinary as for example uh having uh snow plows and clearing roads from snow are you going to maintain a a fleet of of large vehicles and people who are qualified to drive them under extreme weather conditions every year uh in a world where you're having less and less snow you sure need them in some years you sure needed them in 2022 2023 but if we go back to a winter like 2013 2014 I think a lot of those snow plows may not have ever even left the garage so it becomes difficult to allocate resources you know and that's maybe a mundane example unless you're a County uh Public Works director in which case you're probably tearing your hair out uh but you know it's an example of how Divergence between the mean Trend and the extremes can be really in some ways harder than if it was just changing in One Direction or another if it was only seeing less and less snow in all Dimensions or more and more snow in all Dimensions kind of easier to plan for and it's kind of an analogy for California's hydroclimate overall we don't think that it's getting drier or wetter from a precipitation perspective on average there's not a lot of evidence of this but we are seeing more extremely wet and more extremely dry events uh overall which is consistent with what we expect to see in a warming climate so all that's a little bit tangential to the specific question and that's partly uh By Design because I don't H I don't think we have a good answer to why 2022 2023 was so active there's a lot of there's a certain kind of academic meteorological climate paper that exists in the research Community that's kind of like a just so narrative where you trace back uh um a particular weather event of interest is like okay well what caused this event and a lot of these people will go back and say okay well the jet stream was an unusually extended southeasterly position like okay that's true but I mean we we know that an active Pacific jet stream winter you know is is favorable for bringing major storms to California so why was the jet stream at that uh persistently and that unusual active configuration and then the study might go on to say well the mad and Jillian oscillation was uh more active than usual or persistently in a favorable phase for that jet extension for a larger than a longer than usual portion of that winter which is fair and that's an interesting it's an interesting thing to be able to illustrate but you know the the the scientist in me the climate SCI s in in me really wants to know okay but why why was the the Madden Julian oscillation so unusually active and why was that not reflected in the seasonal prediction which was strongly conditioned on uh moderate to strong linia conditions which did occur we did have uh significant linia conditions and yet in California we had a really wet winter and the best explanation really that we have so far is that we do we just do not have very good seasonal scale predictability of large large scale features in the North Pacific and the only statistically robust consistent predictor we have at scale demonstrated scientifically at this point is whether or not Ando the aleno cellon oscillation is in a particularly pronounced state so are we going to have a strong alino event or a strong linia event or at least an upper and moderate event if so that winter is likely going to see the odds of a dry for strong linia or wet for strong alinia winter tilted uh for Central and Southern California in that direction and the opposite being true across the Pacific Northwest but that's a modest tilt on the odds it's a 30 40 maybe in the most extreme years a 50% tilt on the odds U far from 100% And I think what we've realized is that there are other things in the climate coupled ocean climate system coupled ocean atmosphere system I should say that can override that Eno influence so it's there you know it's not like elino and linia connection with hydroclimate are imaginary and it bugs the heck out of me when when folks including some scientists will say oh Eno doesn't matter for California precipitation it absolutely does it's just that there are other things that also matter and they can overwhelm the signal the difference being at this point we don't really have any ability to predict those other things at seasonal scales so even though they might well be be important in a given year and I think this is what happened and this is what some of the evidence shows for 2022 2023 even though those factors ended up being dominant and important we do not have the ability to predict them well in advance full stop and by in advance I mean it's seasonal scales we did have really good subseasonal one to 3 week kind of outlooks in 2022 2023 so that's a that's a that's a success but a few months out we just don't have it for anything other than Eno and so Eno is important but it's not the only game in town so we're going to offer these seasonal predictions on the basis of whether Eno is looking like it's going to be particularly strong or not because it's really the only thing that we at this point think we can predict that far out even though we know with 100% certainty that it's not the only factor of play so in other words linia was correctly predicted in 2022 2023 it exerted whatever influence it was going to exert on the atmosphere and clearly something else was more important that year and some of that may be intrinsically unpredictable internal variability which is effectively at seasonal scales random my personal hypothesis is that we over attribute the amount of that variability that's truly random I I personally think that there are predictable aspects to this that we're just missing so I agree with the folks who showed that the seasonal predictions are not very skillful except with respect to the relationship with Eno I think that's objectively true true but where I differ with the the I don't even know what I think I can call it the mainstream opinion but maybe the the the mode the most common opinion on this which is that a lot of that variability that can't be attributed to elino and linia is theoretically even unpredictable that it is essentially chaos atmospheric chaos in the lorenzian sense and therefore not predictable there's clearly some element of that and maybe maybe it is even the most important piece but I also believe that there are other things going on Beyond Eno that could at least hypothetically be predictable because they are traceable through the Earth system probably mostly ocean patterns to be quite honest because that seems to be where most of our seasonal predictability comes from but possibly also the in some things like the initial state of the stratosphere most weather models and seasonal models do not have a very well represented Stratosphere so they we know that they get certain things wrong because of that the interface Between the Ocean and the atmosphere between the sea ice and the atmosphere there's some indication that Arctic sea ice does play a role in what's going on in the North Pacific at seasonal scales but climent models completely disagree on exactly what that looks like the polar opposite response some modeling configuration say you get a big Ridge with low sea ice but other models say you get a big trough so very wet versus very dry for the same loss and sea ice I don't think we understand that mechanism yet except to say it is clear that you can excite the system in a way that can affect California winter precipitation by messing with Arctic sea ice in these models so there's clearly a node of sensitivity there and I think this may relate to a question that's further down which is this is actually where I think the most interesting application of artificial intelligence in the space is right now I know there's a huge amount of focus on building groundup AI weather and climate models and there's been arguably quite a lot of success there but I also think that the very best ones right now are still comparable to the weather models we already have I mean a lot of these big breaking news headlines and Nature and Science journals and don't get me wrong the scientific advances are amazing to have done this but the net result is that we now have ai weather models that are about as good as uh the the traditional ones that we already have they run a lot faster but they aren't necessarily better and that's partly because most of them are trained on those models that we already have so they become really good essentially at emulating either the model behaviors themselves or the UN hopefully the underlying processes which would be better and there's some evidence that that's happened where I think the interesting Nexus with artificial intelligence and machine learning could be is there a way to sidestep some of this uh can we learn more about how the stratosphere initial condition or the Arctic sea ice or the remote uh subtropical Pacific Ocean temperature conditions might affect California precipitation uh we might not need a full process based model to get some hypotheses there could you build a better statistical model using machine learning and artificial intelligence than trying to Cobble together a fully coupled uh Global circulation model from AI uh based approaches my inclination is yes and I think for me personally the most interesting use of artificial intelligence in the space is to do just that right now which is to improve the pieces of traditional models that we know are weak for numerical reasons so precipitation parameterizations or subgrid scale processes all of this sounds very technical and tricky but I know there's probably at least one or two people from Google or Nvidia on this so just in case you're listening I think the most compelling use case right now is to improve those pieces of weather and climate models that we know are deficient because the bar is low um It's relatively easy to result in something that's better when it comes to uh precipitation uh parameters ation or con triggering convection and models or subgrid scale processes but also in a much bigger picture zooming out abstractly it's also potentially really helpful to be able to uncover hidden relationships at large scales that frankly our existing climate and weather models just don't do a good job of representing so we circumvent them and just say okay here's a tranch of Stratosphere data and ocean data and land surface data and sea ice data and here's what happened with precipitation in California you know it's a bit of a black box but what do you think happens next I know some folks are working on this so far I haven't seen anything that's extremely dramatic or compelling but we might get there and I I'm more to me my my intuition is that it's more realistic to expect large advances in that kind of context first than in getting AI weather models that are greatly Superior to existing physics and process-based ones at least for the moment could prove me wrong I have three papers up on my uh screen you may have seen the tabs that I need to read about this but anyway it's a fast evolving landscape so much longer answer uh than perhaps folks anticipated but I think it addressed a couple of questions Downstream as well next question from Danny take a sip of water can you readdress fuel fire fire fuel hours for those of us still a little confused I think uh this is referring to the notion of 110 100 and 1,000 hour fuels uh this is a reference to the different types of vegetation in wild and firefighting World different kinds of dead and down vegetation uh are referred to as fuels because from the perspective of a fire that's what they are ecologically of course there they're they're something other than just fuel but from the fire's perspective that's what it is and the hours the 110 100 1,000 and even 10,000 as the case may be refers to literally the diameter of the vegetation so 1H hour fuel even a 10-hour fuel might be grass essentially so stems of grass literally uh thinner than the diameter of like a pencil or something uh whereas H hour fuels might be heavier brush so you think your cise chaparal certain species of plants that have um sort of a Woody brush trunk diameters up to a couple inches uh and then you get up into thousand hour fuels that's essentially very these are like the the very largest branches or or even whole trees dead and down on the Florest floor 10,000 hour fuels might be like extremely large diameter trees like if you had a a redwood log on the forest floor or something thing so it refers to progressively wider diameters of actual vegetation tissue it generally does not refer to living vegetation in most cases because live fuel moistures for vegetation that is actively transpiring and bringing water up through the roots is hopefully a lot higher than dead vegetation which no longer has active vascular tissue to bring that water up through the the the the VAC the essentially through the root system and into the plant itself so generally speaking live vegetation and this is one reason why having uh large swaths of dead trees or dead brush and a drought is such a problem from a wildfire perspective is it behaves as dead fuel where those uh Nour fuel moistures become relevant live fuel moistures on the other hand they still vary as a result of the weather but they do so U they're less sensitive to the weather because hopefully there's still some water that the plant can take out from the soil but the basic idea is that with Progressive larger fuel diameters or higher hour based fuel moisture uh designations that's an estimate of the amount of time it takes for that kind of vegetation or dead and down fuel to respond to environmental conditions so for one and 10 hour fuels for example those are grasses if you have one hot dry Day dead grass is going to dry out in a 1 to 10 hours so that same day if you go from wet one day to dry the next if there's dead grass it's going to dry out that same day if there's dead brush it might take closer to 100 hours so 100 hours is about four or five days so it's going to take multiple days of really dry weather for it to dry out th hours well that's uh that's that's a sort of on the order of a month so that's you know these larger logs branches on the forest floor it's going to take about a month of dry conditions for these to dry out and of course 10,000 hours is multiple months essentially so 10,000 R fuels are those huge logs in the fors 4 that are responding primarily to droughts and it takes months or longer for droughts to develop that's that's an explanation of what the fuel moistures uh the designations mean hopefully that's helpful Marty mentions that there's people talking as a fire season is over um well I talked about that um it ain't over uh that's for sure in places like Central and Southern California and possibly uh elsewhere as well um I do think that North Coast of California maybe it's over Southwestern coast of Oregon maybe it's over elsewhere Pacific Northwest things may be getting close to being over East the Cascades it ain't over yet Central and Southern California it's definitely not over yet in fact the peak even may be yet to come in places like Coastal Central and Southern California as is fairly often the case as we go into offshore wind season I don't really know why folks think Fire season is over the hottest months of the year along Coastal California uh are September October a lot of the time that's when offshore wind season is this year we have as I've mentioned in previous sessions a stronger than usual expectation of warmer than average conditions continuing into Autumn so there's just no indication that fire season is going to end early uh in these regions bit of a different story along the North Coast but I I think that we will see a more active than usual Fire season later into the Autumn than is typically the case across Central and Southern California into the Great Basin and even in including parts of the Central and Southern Rockies as well as the Front Range I think there'll be a pretty broad region with active fire conditions lots of good questions uh and I know I'm already past the hour so I'll answer a few more of them um let me just see what came in and I'm going to do a executive decision make an executive decision on which ones are most interesting that I can answer uh the the most succinctly so there's a question about the the Sahara Desert I kind of like that one for the ASP me anything portion let me see what else there is this is a quick one Lauren uh mentions that she's heard she's heard that Santana winds and local Sundowners don't happen together uh for example here in Santa Barbara this column is glass when Ventura has San anas and when we have Sund diners they're calm uh that's usually true and it's essentially because the the pressure gradients that are required are different so essentially you want a pressure gradient for a Santa Ana event it it's it's mainly measuring the difference the pressure differential between um LA county and the the the Inland higher elevation desert so Inland LA County um the most relevant uh I think the most relevant pressure metric there is something like the um the the Las veg Bas to LAX uh sort of U cross-section pressure gradient maybe it's something else uh similar to that but essentially it's like a a Southwest and Northeast axis which is essentially perpendicular to the topography there as uh since in along the transverse ranges of course up on the Central Coast Santa Barbara Ventura counties the Topography is mostly aligned uh in an East westish Direction uh approximately and that's a parallel to the coast the Coast is roughly East West for a brief segment there and the and the the the Topography is also aligned about East West parallel with the coast and then as you go into LA County the coast curves to be more Southeast to northwestward and the mountains also curve a bit so it has to do essentially with the fact that the the reason why you have different big wind events for Sundowners which are mainly Santa Barbara Ventura counties versus Santa anas which can affect other parts of Southern California more broadly is that the direction of the wind is different and therefore the pressure gradient you need you need to be maximized is at a different angle that's the main reason all right let's see here yeah there's a comment that uh up in PDX which I assume is Portland uh 10 years back or so we had that's that very situation I think referring to the extreme Whiplash between very large snow events very occasionally but usually not much at all uh yeah where the snow plows were mostly sold off only to have a major winter storm where it resulted in cars stranded along roads I mean this is essentially what I'm talking about it's true in places like Portland and Seattle that don't see a lot of snow on average but can very occasionally see large snow and ice events it's even true in places like Washington DC that you know you don't have to go too far back to talk about the snow mageddon or snow snowzilla or whatever the the the term was for those specific storms there like you know get two two or three feet of snow in in a 36 hour period in you know the nation's capital is a pretty big deal but you go a lot of years in DC these days where it doesn't really snow more than an inch or two so take your pick flurries or three feet of snow never just a nice three or 4 inch coating it seems so it it does have real practical implications all right so I think I I will take that Sahara question as the last one of the day um so as some folks uh have uh have noted there has been it's been a very wet summer across much of the Sahara Desert uh the Sahara Desert is not normally a wet place as you'd expect in fact some deserts are wher than others of course the Sonoran Desert uh for example in the southwestern United States and and in Northwestern uh Mexico is a relatively wet desert if you will there is a Summer monsoon season and you do sometimes get downpours there in a typical year you may only get a few inches of rain a year but a few inches of rain is more than zero there are many parts of the Sahara Desert that have an average rainfall of essentially zero it it virtually never never Reigns there in modern history and this is true of the interior of Egypt and Algeria and Niger uh and several other places uh several other countries um that have at least a portion of their land in the what is these days effectively No Man's Land There are very few people who live there because there is really just no water at all from any Source across a lot of Sahara except for a couple of very widely scattered oases and in these countries uh in these countries essentially there there is an expectation that you can go years without a single drop of rain uh the summer though it has poured in some of those places and more than once so this wasn't just a a one-off isolated thunderstorm uh but there have been repeated waves of incursions of major tropical moisture well northward into the Sahara including some places that have seen record-breaking rainfall in historical context next and there is indication that there's going to be more to come that the next 2 to four weeks could bring more record-breaking rainfall in the Sahara this is fairly remarkable we may see some interesting ecological effects in the Sahara one interesting thing to note is that the central and southern Sahara is expected in a warming world to potentially see a lot more precipitation in relative terms than it used to and some e colist believe this could lead to a greening of the Southern and Central Sahara the very driest part of it historically perhaps even beginning within our lifetime um it's unclear exactly how quickly this would uh unfold if it does become wetter there permanently uh I would imagine I'm no ecologist but I would imagine you'd first see patchy grasses potentially and some very uh water scarcity tolerant species showing up um and a lot of the Sahara is quite Sandy so it can be more difficult for plants to reestablish it can take more time than you might expect but right now the effects are that there's been major flash flooding in places that have really not seen it before in historical uh context and uh it appears to be related to why there have been relatively few hurricane seeds this year in the Atlantic we saw a ridiculously powerful hurricane very early in the season record-breaking start to the season that kind of petered out partly because all of these African easterly waves which is the term for these atmospheric disturbances that often form hurricane seeds in the Atlantic Basin were much farther north than usual uh and were instead affecting the Sahara rather than um moving essentially through the Sahel and equatorial Africa and emerging uh into the Eastern Atlantic and becoming potential hurricane seeds so it's been an interesting year this may be shifting though at least in terms of hurricanes it does look like the Atlantic is about to enter a very active period at a time time when uh sea surface temperatures in the Gulf of Mexico and Caribbean are at record-breaking levels so if a storm does start to develop there yikes watch out but also the Sahara will be interesting and it is quite possible that this will be the wetest summer on record summer and fall perhaps going back 200 years in some parts of the world so interesting piece of anic data uh in a warming world where climate models insist that this is a region that will see a three or four-fold increase in precipitation as a I mentioned earlier a four-fold increase above a very low Baseline might not be a lot in absolute terms but it could be ecologically transformational and so it'll be interesting to watch that evolve all right I think that's just about it for the day losing my voice a bit so maybe it's for the best but thank you for joining it is very helpful uh when you like the video or share the channel still looking to grow it to at least 10,000 subscribers by the end of the year so that's a short short-term goal that you can contribute directly to uh I will uh probably have another live session later next week if this time later on Friday afternoon is a good one which it appears to be a pretty good one based on the number of folks who have joined today I will probably try doing this again uh at least periodically uh uh at about 2:00 or 3 p.m. on a Friday afternoon all right so with that uh I will um leave you there have a good week again and see you next time