Weather West

Today will be a hot one in the Southland–highs well in excess of 100 degrees in typically hot locations inland and even aproaching 100 degrees on the coast. The hot weather will extend into NorCal, though it won’t be quite so intense there–near 100 in the Central Valley and favored coastal valleys and 80s-90s most everywhere else (except the immediate coast, which won’t see readings much above 70 due to persistent cold sea surface temperatures in the mid to upper 40s). The hot weather will continue for several days longer (but today will likely be the hottest of the current heat wave in many locations).  No real significant weather is seen on the horizon at this time. The monsoon may soon be on Arizona’s doorstep, but there are no imminent threats of monsoonal incursion into CA. All in all, the current pattern is a fairly typical one for early summer. The formerly strong La Nina event in the equatorial Eastern Pacific Ocean has petered out, with some subsurface warm temperature anomalies beginning to develop. This might begin to suggest the possibility of a warm event–El Nino–before next winter. This will need to be watched very closely, as it could have significant implications for the precipitation received in CA during the coming wet season (which, given the currently precarious state of water resources in CA, will be crucial in determining how bad the current drought situation will get).

I will be travelling to South Africa for the next five weeks and may not be able to update Weather West. If I am able to do so, updates will be brief and possibly unrelated to California weather. Moderation of comments will not occur, so my apologies if they continue to be deleted by the Wordpress software. I will be able to begin making full updates again upon my return. 

Quick update today…the locally dramaitc and exciting weather of the last week is now behind us, and a rather more typical pattern of widespread sunshine (outside of coastal morning low clouds) and moderate temperatures (mid 50s to mid 70s on the coast, 75-90 inland). Mountain showers and thunderstorms will still be an isolated issue over the next few days, but will be much weaker and less widespread that in the recent past. Locally, there’s not much to discuss…not heat waves, no interesting cut-off lows, nada.

So…as part of the larger picture…

 La Nina continues to dissipate in the E. Pac., and I believe that it will probably be gone by mid-summer. The first tropical storm of the season is threating to develop in the Eastern Pacific, and this storm actually has the potential to being devastating floods to Central America as it meanders over land and drops 10-20 inches of rain or more in mountain areas. The Arctic sea ice extent…which for much of the winter had been greater than at any point in the last few years, is making a run at supassing last year’s record low. The rate of decrease is significantly greater than last year, so even though it has farther to fall I expect that last year’s all-time record low will be surpassed by the end of this summer. The ice appears to have been extremely thin in some areas–only 1-4 inches–and so it is currently retreating to the north by as much as 50 miles a day. We will see where this leaves us in a few months…

A very impressive severe thunderstorm outbreak took place in Southern California today. These storms were not confined to favored mountain and desert areas, but even produced severe weather near the beach. The retrograding cutoff initiated some strong instability (via cold temps aloft and wildly steep lapse rates) and a west-moving boundary of some sort initiated the storms on a line oriented N-S about 50 miles inland from the coast, which drifted slowly southwest all day. The storms were quite strong at times, producing various types of very rare severe weather reports and even some significant damage. Torrential downpours, on the order of 3 inches per hour, generated widespread flash flooding in many areas, and some serious mudflows occurred in recent burn areas. Even more impressive, however, is what followed the initial downpours. Large hail–some as large as golf balls–pelted inland areas (especially around Redlands–a friend recieved an excited phone call this afternoon from his parents in Redlands that “golf balls” were falling from the sky–and that hail had accumulated as much as 2-3 inches on the ground). Two tornados were reported in SW Riverside County, one of which may have actually been quite strong (especially for California) as news reports and live video showed train cars and semi trucks on the highway overturned. Snow fell at resort level in SoCal (and in the Sierras, too). The storms have died out since sunset, but the action is not over yet. Models are in remarkable agreement that another impulse or two will rotate around the low into SoCal over the next 48 hours, bringing another round or two of thunderstorm activity to coastal areas as well as inland areas. Timing is an issue, so watch the radar screens this weekend. As the core of the low sits around and picks up a bit of moisture, numerous thunderstorms are likely over the mountains in NorCal late Friday through Monday, and some isolated to widely scattered storms are possible just about anywhere. Given the lateness of the season (intensity of insolation) and the unpredictable behavior of cut-off lows, another outbreak of localized severe storms is not out of the question at some point before this system moves out of the picture sometime during the middle of next week.

P.S. The large wildfire in Santa Cruz County burned incredibly intensely today, and this raises serious concerns about the potential fire behavior later this summer and in the fall. Also, if anyone has pictures of the active weather today (or at any time) they would like to share, feel free to send them to me at danielswain@comcast DOT net

A sharp upper trough is bringing strong and gusty winds to much of the state today, with some areas seeing gusts in excess of 50 mph. Winds will actually continue to increase in some areas and will remain gusty and occasionally strong through Friday. The initial cold front brought 2 lines of thunderstorms to the western slopes of the far northern Sierras, which looked very pretty from the Valley. No thunderstorms are really expected today (except perhaps for an isolated cell in the far northern mountains once again), but this will change by tomorrow. As the upper low begins to retrograde from the NE by late Thursday (a very unusual track for any system on the West Coast), a chance of deep moist convection will develop over far Southern California and over the entire length of the Sierras. In SoCal, this includes coastal and valley areas, so this may be a pretty notable event for many. I would expect isolated to scattered thunderstorms over all areas in SoCal on Friday and possibly into Saturday. In the Sierras, uniform scattered coverage will be likely on Thursday. On Friday, as the secondary upper low begins to retrograde and ease SW over NorCal, the chance of thunderstorms in the northern half of the state will increase (as it decreases in the south). Coverage will be scattered to widespread in the Sierras with scattered storms developing in the Coastal Range as well. By late afternoon Friday, some isolated storms could drift off the Sierras into the northern Sacramento Valley (north of Chico or so). Saturday then becomes quite interesting for NorCal, as the low continues to drift SW and instability as a result of very steep lapse rates (strong late-May sun angle, anyone?) increases over all areas. I expect scattered thunderstorms to develop over the Sierras, the Coastal Range, and possible the higher terrain of the Bay Area by late Saturday morning, with coverage increasing in the afternoon. Storms will be able to drift into the Sacramento Valley and possibly even into coastal areas, bringing light showers and perhaps a bit of lightning as they decay. By afternoon, I believe there will even be enough instability to  generate some surface-based convective columns in the Valley, so isolated heavy thundershowers in the Valley and even the Bay Area are possible then. On Sunday, the low continues to stick around and mid-level moisture increases a bit. I expect isolated to widely scattered thunderstorm coverage on Sunday in the Valley and possibly in the Bay Area, with numerous thunderstorms in the Sierras. The low begins to shift a bit (possibly offshore) on Monday, so mountain thunderstorms will certainly continue then but possibly even across other areas. Beyond Monday the pattern becomes very unclear. The models are beginning to indicate that some sort of low may reform out over the far eastern Pacific and then come ashore again in NorCal. If this occurs, we are looking at another (and possibly even more significant round) of thunderstorm activity at some point next week. After a bone-dry spring, it is very odd to see significant precipitation chances as we approach the summer months…

The heat wave that occurred over the past week was truly impressive across most of CA. On the first day of the warm event, when a strong offshore gradient kept winds very breezy overnight and contributed to unprecedented compressional heating in the western Sac. Valley and parts of the Bay Area, leading to overnight “minimum” temperatures ranging from around 70 at the coast to near 90 degrees near Winters and Woodland.  San Francisco eclipsed 90 degrees, the Peninsula hit 100, and inland valley areas went over 105 in NorCal. Even Eureka hit 80 on Saturday. Needless to say, dozens of records were shattered across the region. SoCal was quite hot as well–over 100 in some areas–but fewer records were broken because intense May heat waves are not so rare down there. Regardless, this was a May heatwave to remember statewide. Today, temperatures are much cooler along the coast and cooler but still hot (90-100) in more inland locations. A very dramatic change is quickly approaching, however…

An unseasonably deep trough will force the high pressure system aloft that has been responsible for all the heat lately to the east, ushering in much colder air (both aloft and at the surface) and increasing pressure-gradient derived winds explosively. The gradient between SFO and Las Vegas will be on the order of 22 millibars, which is just about as high as I have ever seen it. A 150+ kt jet will set up in a N-S fashion over the coastal range, creating the potential for some very strong and potentially damaging N/NW winds over the ocean, higher terrain from Eureka south to San Diego, lower N-facing slopes everywhere, and possibly along the western side of the Sacramento Valley as a barrier jet sets up. Winds over the ocean will likely be storm force or higher, with sustained winds of 40-50 kts possible. Fire danger will be quite high, given the drying of fuels that has occurred over the past week. High temperatures will be 30 to locally 40 degrees cooler than the weekend in some places, with the wind making it feel even colder (highs from mid 90s in some coastal areas will drop to the mid 50s). Inland, highs in the Sac. Valley will drop from the 105 range this weekend to around 75 by Thursday. Along with the strong and gusty winds and cooler temperatures will be a good chance of Sierra thunderstorms associated with the front on Tuesday/Wednesday. The models have really been struggling with the upcoming pattern, but it does now appear that there is some potential for convective activity over parts of the state other than just the Sierras. The Coastal Range and far Southern CA coastal areas currently stand the best chance at some isolated thunderstorm activity, but even the SF Bay Area and Sac. Valley could potentially see some shower activity if the retrogressive cutoff low sends a second impulse of energy into the region next weekend as indicated by both the GFS and the ECMWF. We’ll see–a pretty dramatic weather week after a rather boring spring…

 By the way, Chaiten Volcano continues to erupt in Chile. Jeff Masters has posted an article on the possible affect of Chaitens’s eruption on world climate (which is to say: small to none).  Here’s a link…

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=942&tstamp=200805

An impressive heat wave is on the way fro CA. We will apparently be making the transition between spring and summer in about a 48 hour period starting today. Warm, brezzy, and hazy conditions will exist across NorCal today, and SoCal will see typically warm afternoon temps as well. Tomorrow will be much warmer statewide as 850 mb temps begin to skyrocket and compressional heating takes place. Widespread highs 80-90 degrees can be expected outside of immediate coastal areas. Wednesday will see another dramatic jump in temperatures, with widespread highs 85-95 in interior CA with 70s and even 80s along the immediate coast. Thursday will be warmer still–trending quite hot in more inland areas with some record or near-record high temperatures likely. Highs will surpass 100 degrees in the Sacramento Valley, reaching up around 105 in the hotter locales. San Francsico may even hit 90 on Thursday or Friday–pretty unusual for this time of year (or, really, for any time of year). SoCal deserts may get up to around 115 for the first time this year, and locations away from the immediate coastal plain could reach above 95 (up to 105). Friday will be equally hot (if not a few degrees hotter far inland). The ridge that was originally progged to break down quickly looks much more persistent, so widespread highs at least in the 90s will persist into early next week.  Summer, it appears, is here.

The situation in Myanmar following Severe Tropical Cyclone Nargis continues to worsten, as the government there continues to refuse to allow aid workers into the country. Certain relief organizations have stated that if the situation there does not change dramatically in the very near future, disease and starvation following the already devastating storm could claim the lives of more than 1 million people within 1 month of the cyclone. The true death toll from this storm will never be known; there are apparently tens of thousands of human bodies lining all the waterways in southern Myanmar with many more washed out to sea (and showing up on the coastlines of surrounding nations). This is no longer a truly “natural” disaster, though–the storm itself likely killed over 100,000 over the course of a few hours, but the actions of the junta in Myanmar has already claimed at least that many.

Another sobering disaster is just beginning to unfold in central China, where a 7.9 magnitude earthquake has apparently devastated several inland cities. The reported death toll is already approaching 10,000.

 The eruption of Chaiten Volcano in Chile, although spectacular and dramatic in scale and potential to devastate, has thus far killed no one as a result of efficient evacuation of residents by the Chilean navy and good decisions made on the part of the geologic institute in that country. The situation is still very unstable, though, and the volcano is now in its 8th day of continuous moderate to violent eruption. More on that situation as it develops.

A major tornado outbreak  has killed nearly 30 people in the U.S. Midwest this weekend, and this year is on track to have the greatest number of tornados and the greatest number of tornado deaths in history. 

The media coverage of these events (in the United States, at least) has been extremely disappointing, especially given the scope of some of these events. The situation in Myanmar is particularly dire, and public pressure for some sort of intervention could really make an enormous difference in this case, so the lack of news stories about the situation there is distressing and saddening. Fox News (perhaps unsuprisingly?) has insinuated that there is a connection between the events–a claim so sensational and absurd that it very much suprisies me that it made it past editors and fact-checkers and even passed the basic “common sense” test on the part of the news anchors. In any case, I will try to update on all of these events as more information becomes available.

Cyclone Nargis made landfall on May 2nd in the Irrawaddy River Delta region of Myanmar, a densely-populated and exceptionally low-lying area in the far southern part of the country. Details are only just becoming available as a result of the isolation imposed by the oppressive military junta that has controlled the flow of information in and out of the nation for more than four decades. The scope of the damage is immense–although images in the news media are currently showing mostly wind damage from capital city of Rangoon–which is not near the Bay of Bengal, where the vast majority of the incredible devastation has occurred. Nargis was a borderline Cat 3/4 storm at landfall (much like Katrina as it made landfall in LA) but crossed the coast at the worst possible angle–the right front quadrant (the strongest part of the storm) drove a storm surge onshore that may have been nearly 20  feet high. Keep in mind that nearly the entire delta region, which is home to 1-2 million people (or possibly more; population estimates are diffiicult in a country like Myanmar), lies below 30 feet MSL (and there are vast tracts of land lower than 10 feet). Certain states may have experienced near-total or even total inundation, and with very few tall or sufficiently sturdy structures to serve as shelters from the storm surge (not to mention winds gusting over 150 mph), the death toll has been extremely high. The official death toll from disasters in Myanmar tend to be grossy understated by government officials, sometimes by factors of 100. Currently, the official death toll stands at nearly 30,000, with an additional 50,000 reported missing. It is possible that the death toll from this storm may surpass 100,000, especially since aid has yet to arrive in Myanmar (4 days later) because the government refuses to allow Western nations (or even foreign aid workers) into the country.  News from areas that were ostensibly the hardest-hit (along the immediate coast) have yet to reach the outside world. Even if the death toll is capped near where it currently stands, this will have been one of the worst natural disasters (in terms of loss of life) in recent memory (overshadowed only by the 2004 Indian Ocean Tsunami, which claimed the lives of more than 230,000 across coastal Asia and East Africa). The relatively small area affected by the disaster, though, makes this enormous death toll even more staggering. More information about the disaster will probably trickle out of the region over the coming days.

Update: the following are some photographs of Chaiten Volcano in Chile erupting on Tuesday. These are some of the most spectacular images I have ever seen. A full update discussing the volcano, the cyclone in Myanmar, and a possibly upcoming heat wave will occur either Friday or Saturday.

Our extremely dry Spring 2008 continues. NorCal did see some very light precip last week in areas, but it was significantly less than expected (suprise) and some locations up here (Davis, for example) have yet to see even 0.01 in. since February. This has not happened in decades…and at a few reporting stations this is the only time in history this period has been entirely rain-free. There is currently no rain in the offing for the next two weeks, which brings us to mid-May. I really don’t think there’s much hope for more precip for the rest of the “season,” even in NorCal. We could see an odd cutoff or two bring some scattered convective precip at some point if we’re lucky, but there is currently no indication even of this. SoCal has already seen 100 degree plus readings and wildfires have caused evacuations over the past week, so the summer season has effectively started down there already. I do believe that we will see som significant spring heat waves in May that will expand to include more of NorCal that the 90-95 degree Valley heat on Sunday. With the apparent demise of La Nina (having decreased to marginal La Nina strength) and the possible emergence of an El Nino over the next 6 months, I think this summer has the potential to be quite hot and potentially active (reminiscent of summer 2006). The Sonoran heat ridge will likely feature prominently (especially by the second half of summer), which would bring prolonged southeasterly flow and a cT airmass up from interior Mexico. This translates to very hot temperatures and the potential for periods of enhanced monsoonal convection. Obviously, predictions for summer temperature and monsoonal flow are not very skillful this far out, but given the comparison to analogue years, I do think this is a reasonable possibility. Stay tuned.

After an exceptionally and record-breaking dry period in February, March, and most of April, a pattern shift may bring some significant spring precipitation tomorrow and Wednesday in NorCal. That retrogressive low pressure pattern that has brought the cold and windy conditions over the past week (and was originally progged to bring some precipitation) is continuing to evolve, and the large gyre is developing a piece of energy and sending it directly towards NorCal. This system will be fairly decent for late April, bringing a period of soaking to locally heavy rain to many areas north of San Jose. Given the time of year and the decent dynamics involved (inc. several vorticity maxima), isolated thunder will be possible both along the cold front and in the post-frontal airmass in NorCal. 850 mb temps drop to slightly below zero–not nearly as low as yesterday, when snow fell for almost an hour at sea level in Arcata, CA (North Coast–right on the ocean!). As much as an inch of rain could fall in some favored locations, with most Valley and Bay Area locations seeing 0.15-0.45 inches (considering the dryness lately, we’ll take what we can get). Snow levels will be fairly low in the Sierras for the time of year–locally down to 3000 feet or so. There doesn’t look to be a terrible profusion of cold air cumulus behind this system, but some scattered showers and possible isolated thunder (esp. Sac. Valley) do appear possible on Wednesday. SoCal will not see any precip out of this system except perhaps some drizzle/light showers on the Central Coast. After Wednesday, skies clear and temps warm above normal once again. The GFS, however, has been adamant in developing a very deep and persistent trough off the West Coast by day 6, eventually bringing cold and showery weather to  CA for a good portion of the 7-16 day period. Stay tuned–but it looks like there will be at least the potential for some beneficial late-season showers over the next week or so…

Well, after what had looked originally like a promising late-season cold and convective event this weekend, the scenario has trended towards colder, drier, and windy weather for the weekend and into next week. An unseasonbly deep trough and associated low will bring showers and isolated thunderstorms with very low snow levels to all of WA and OR and possibly far N. CA near the Oregon border, but no further south than that. NorCal will be left with much colder air aloft–strong gradient-derived winds on Saturday (above 40 mph in some places  and afternoon highs 55-60. Overnight lows will drop below 40, possibly leading to some frost in sensitive locations in the Central Valley). The models now try to undecut this trough with a Pacific jet by next Tuesday, bringing a weakish low into NorCal on that day with some scattered showers (and, as with essentially any system this time of year, possibly isolated thunder). The GFS has had an impressively bad track record as of late, though, so I will remain extremely skeptical until I actually feel some raindrops before buying into that prognostication. In any case, significant rainfall is not expected anywhere in the state for the forseeable future, and likely for the rest of the season.  It’s important to remember that rainfall in SoCal sometimes does cut off after February (though there is usually at least a couple of shower events). NorCal, on the other hand, tends to see precipitation through April and sometimes May on the average year.  Up here, I haven’t felt a raindrop (except for a literal 5 minute light shower on the immediate coast 1 month ago which apparently didn’t make it inland) since early February. That’s concerning. The wildfire season has already begun in NorCal, and although the snowpack is not too far below average at this point, it’s melting quite quickly. I’m curious to see what occurs with the ENSO over the next 12 months–we’re due for a major El Nino event at some point in the next few seasons. As I’ve mentioned before, the next big El Nino event will almost certainly bring the highest global temps ever recorded–and I’m curious what effect that may have on atmospheric river (Pineapple Express-type) events in CA.  Only time will tell, I suppose. It’s going to be a long and dry summer, in any case…