Weather West

A particularly strange and rare event has unfolded over the past 24 hours off of the southern and central California coast. A complex of strong to severe thunderstorms developed over the near-shore waters off of Los Angeles County yesterday evening and moved northwest through the night, affecting immediate coastal areas and producing one of the best light shows this part of the state has seen in quite some time. Nearly 2000 cloud to ground lightning strikes–with many more in-cloud strikes–are thought to have occurred through the course of the event. Radar reflectivities reached over 65 dbz over water, which is indicative of large hail. Some rainfall did occur over the immediate coast, where up to 0.25 inches fell. The complex of storms morphed by about 3 AM into a very unusual formation–a swirling doughnut of showers and thunderstorms clustered around a center that was rain (and at times even cloud) free. This “eye” has been clearly visible on satellite and radar imagery for hours, and continues to be evident as the mesoscale circulation churns off the Monterey County coast. I personally have never seen anything like this in CA before. The vorticity maximum at the core of the cyclonic feature is fairly strong, so this may account for some of the atmospheric spin, but the rest appears to have come from sources that many of us may be more familiar with–the Catalina Eddy and other low-level terrain-induced atmospheric currents that commonly direct the marine layer to spin around during the summer months. Certainly, it’s worth a look at the satellite imagery just to get a look at this incredible convective circulation over CA.

For the next 24-48 hours, I think the models are handling the current situation extremely poorly, so a forecast based on satellite trends is probably most prudent. There is a lot of moisture and instability out there, so some more unexpected thunderstorm activity is certainly possible. A surge of clouds is currently about to enter the San Joaquin Valley from the southeast, so it is possible that these could develop further.

 The longer-term is interesting, as well. Briefly: GFS and ECMWF both bring precip to NorCal during this period from an unseasonably deep eastern Pacific storm system. This would be rather unheard-of, and there would probably be a convective threat associated with any such system. Stay tuned…

Yesterday’s monsoonal incursion into Northern California did manage to bring localized light shower activity. Lightning was reported along the Napa/Yolo County line (upwards of 500 strikes) and in the northern Sacramento Valley (along with a few isolated strikes in the northwestern interior). A number of wildfires/brushfires were started by these mostly dry strikes, but nearly all have now been contained. San Francisco set a new daily record for rainfall on August 5th with–you guessed it–0.01 inch. Local very light showers ( now mostly virga) and a few lightning strikes continue in NorCal this evening, but outside of the mountains this should be over by tomorrow.

The long range is currently looking more interesting than it has in a while. The GFS and the ECMWF both develop a significant cut-off low somewhere over CA in the 6-10 day period. Depending on the depth of the low and especially on its placement–we could be in for a period of interesting weather for CA. If the low is sufficiently deep and set up shop off the coast of CA, excessive amounts of subtropical moisture will be drawn into the state from the SE  sparking numerous showers and thundestorms. If we can get an E Pac tropical system thrown in the mix by days 4/5, things will get even more intersting. Of couse, if the low forms directly over the state, precip will likely be limited to the Sierras in the form of isolated afternoon thunderstorms, though a summer “Santa Ana”-type event could also occur, generating enormous fire weather concerns. This is certainly worth keeping an eye on…

Quick update this afternoon. The poorly-modeled monsoonal surge (but aren’t they all?) is already underway, with flash flooding already having been reported in Twentynine Palms and more thunderstorms popping elsewhere. Tuesday/Wednesday will be the main days for shower/thunderstorm potential, and due to the very high PWs as high as 1.75 inches flash flooding will probably be more of a threat than dry lightning. Some storms are possible in the Bay Area and especially over far northern coastal areas as a result of some moisture pooling off the coast which will be able to interact with a coastal wave. Coastal SoCal may actually have lesser chances for thunder with this event than Eureka, for example.  More later…

I am now  back in the States and fully able to begin discussing California weather once again. I do have some weather and weather-related photos from southern Africa that will be posted on the main Weather West site in the near future.

Locally in California, the weather is currently very typical of mid-summer. Temperatures are warm to locally hot inland and seasonably cool near the coast. This may change a bit going into next weekend if the ECMWF is right in developing southeast flow aloft by next Saturday, but at this point it appears unlikely.

 The Telegraph Fire, which erupted near the Yosemite National Park western entrance gate on Friday as a result of target practice shooting, has exploded in size over the past 24 hours and is already nearing 30,000 acres. Many towns are currently threatened directly by the blaze, and Cal Fire has just reported that significant structure loss has already occurred. Temperatures there in the fire are will be over 95 degrees every day this week, humidities will be low, and there will be occasional breezes. Also, the fuels in that area have not burned previously in 100 years of record-keeping. We’ll be hearing a lot more about this fire…stay tuned…

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.