After what has thus far been a remarkably quiet summer in California, a significant and potentially very noticeable pattern change is currently underway. A Rex Block has developed over the far Eastern Pacific and the West Coast over the past day or so, forced (at least in part) by blocking induced by the remnants of Tropical Storm Lee current wreaking havoc in the Eastern states. The upper-level low currently located over northern Nevada will retrograde very slowly over Northern California over the next 24 hours and eventually set up shop off of the Central California coast this weekend, staying nearly stationary until at least early next week. As the low begins to move offshore, counterclockwise circulation will induce southeast and easterly flow over the northern 2/3 of the state, advecting monsoonal moisture into Northern and Central California from the Desert Southwest. Most of this moisture will be at mid and upper-levels, and any convection that develops on Friday or early Saturday will likely contain little or no rain, leading to a potentially widespread threat of dry lightning. By later in the weekend and possibly continuing into early next week, this flow will probably contain enough moisture to result in wetting rains in most thunderstorms as lofted moisture from diurnal storms serves to moisten the lower levels with time.
GFS forecast of retrogressive upper-level low on Friday
Not only will there be the threat of dry lightning this weekend, but easterly flow will result in downsloping, offshore winds in the Sierra foothills, Central Valley, and possibly the Bay Area. The triple threat of hot, potentially gusty offshore winds, low surface humidity, and possible dry lightning will probably cause some fire-related problems this weekend. This system also has the potential to bring multiple rounds of lightning to unusual areas, including the Central Valley and the Bay Area. Much of Southern California may miss out on the deep convective activity as it will remain in a pronounced dry slot for much of the event, though some potential for dynamically-forced elevated convection does exist over almost the entire state at some point during the next 5 days.
The numerical models are currently in disagreement regarding the evolution of the pattern after next Monday. It does not appear that this cutoff will be in any hurry to leave, however, and the risk of at least mountain thunderstorms (and possibly elsewhere) may continue straight through the next week. Stay tuned!
© 2011 WEATHER WEST
Interesting times!
I saw in the other post that La Nina is making a comeback, which I think seems odd. I wonder if this means another very snowy winter for Vermont (last year was I think the third snowiest on record, or something, in much of the state). This will mean trouble since our roads won’t be fully repaired by then… but at least maybe it means less rain on snow events. Though, the last la nina did not act how they usually do (wet in socal, dumping of snow in the Sierras, more nor’easters than a normal la nina).
Also, does anyone know how much it costs to get a minimal weather station that can automatically record precipitation (and temperature and wind I guess) and upload it to the Internet?
redlands on September 8, 2011 at 10:49 pm said:
I read the article on the predicted — La Nina. I looked at my rainfall totals for 2010-2011 — Redlands received 19.29 — which is above normal for Redlands — average is about 12-14 inches . Although 10.46 we got in the month of December — In 4 days — Dec-19-Dec-22 Redlands received 8.79 of rain —- We had 14 days where we had measureable rain —- 11 days in a row with measureable rain —– highest one day total was 2.99 —- The 10.46 is the most rain for the month of December or any other month — it smashed the record for wettest month. I dont think this will happen for another 20/30 yrs or more . But if u take away the month of December 2010 — Redlands would of gotten a measly 8.88 of rain for the 2010-2011 rain season. My question is — Is this normal for a La Nina ??? — Getting drenched in a short period then basically going dry ?? Thoughts ? Comments
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Dan the Weatherman
on September 8, 2011 at 11:02 pm said:
Some of the stronger La Nina years such as 1955-56 and 1973-74 have had relatively short very wet periods followed by long dry periods in between. I think one of the worst La Nina years (a 2nd year La Nina) was 1971-72 in which Los Angeles received 6.57? of rain in December (a period similar last December) and a whopping .26? fell from January to June! Something went terribly wrong down here during that winter, and I believe that is the driest January – April on record for the area.
A cluster of thunderstorms that formed during the early afternoon over the Sierra Foothills moved west/southwest clear across the San Joaquin Valley, over the Diablo Range, and into the Bay Area. Here on the SF Peninsula, I saw nearly continuous lightning for a time (with numerous CG strokes), and some very gusty winds up to 40 mph. Brief rain did fall…barely enough to wet the ground in places (0.01 or 0.02 inches). Sounds like some fires were sparked in the hills. I can’t say that I’ve ever before seen discrete convective cells survive the trek from the Sierra to the offshore waters. There will probably be more to come through the weekend, though the threat of dry lightning will begin to decrease as column moisture increases.
Boy did it cool down quickly here in Socal! It was about 100 degrees the day before yesterday (Sept. 7) and it barely got over 80 here today. The marine layer moved in this evening and is overcast right now with a temperature of about 65. It definitely is beginning to feel more like early October instead of early September. However, I have a feeling we aren’t quite done with the summer heat yet, despite that there aren’t any hot spells forecast for the next week.
Marine layer is turning hostile in some parts of the area. This is like a June 3rd 2008 event.
Severe thunderstorms for Orange County.
Just saw these storms on the radar and some of them had really high reflectivity, looks like hail! One of the weakening cells clipped my parents’ place in northern Torrance and they told me they had some heavy rain and lightning. More on the way!
Are the storms just cruising through the marine layer? Isn’t ‘inhaling’ marine air death for storms? Are they high-based or something? Very strange…
My guess inyo is that the outflow from the thunderstorms last night in the high desert intereacted with the upper level low and the ML provied the moisture in the lower levels for the beaches and valley.
Sounding like the situation could be very dangerous over the next few days, for California.
There is a thunderstorm over the area here in Orange right now. First it started with thunder about 25 minutes ago in the distance, and it got closer, and then I saw a flash of lightning almost overhead, immediately followed by a loud crack, and then there was a brief heavy downpour. I am still hearing thunder in the distance as I type and it is currently still sprinkling a little bit.
The cell has moved to the north and west of Orange and I don’t see any more cells currently developing as of yet that will move over the area. However, it is still early in the day and with daytime heating and an unstable atmosphere, more very well could develop later on.
What is odd is that there is still a solid marine layer overcast (stratus) over the area and the thunderstorms occurred above it, so I didn’t actually see the rain-producing clouds. It normally isn’t overcast like this at the same time when thunderstorm activity occurs, especially with the brief downpour that occurred with very large raindrops.
Very impressive cells in Orange County now! This low is not willing to disappoint…
Yes…very impressive indeed. These storms are popping out of the blue. However, as fast as they develop they fall apart…that is the sucky part. I had a 70 dbz storm heading my way , but by the time it arrived in my area it was 30 dbz only… =’(
I got nothing more than a few drops today. I watched every storm that got near the area die a horrible death.
lol
same here =/
.07″ fell here in Orange from that brief heavy downpour Saturday morning.
Sounds like next week could be the first Santa Ana wind and a big time heatwave.
The LA NWS discussion didn’t quite specify exactly where this offshore flow progged for next week would be, and their coverage area (CWA as it is called) is from San Luis Obispo to Los Angeles. If there are any offshore winds, most likely they will probably be in the northern areas, as it is too early for Santa Anas down here just yet. More than likely, it would be a weak offshore flow that would lead to some really hot weather, which is quite normal for early to mid-September.
Was an interesting day in Redlands, Ca – today 9/12/11 — started out this morning with a low of 51.7 or 52 and ended the day with a high of 99.9 or 100 – which is a 48 degree increase in temperature — think that would be one of the largest spreads in temps at my station — might be a record would have to check – but it is impressive
just got a quick shower on the outskirts of a tstorm, lightning was striking all around though. Crestline / lake arrowhead areas got hit with large pea size hail, looks like a massive storm moving north of the salton sea
Alan – I heard on the Weather Channel them mentioning that Highland ,Ca received hail — i forget the size — but it had to be big for them to mention it —- I heard several thumps/noise during the night/morning — We didnt get any measureable rain – noticed a few dried drops on my wind shield that i just cleaned on Monday afternoon You hear anything bout hail in Highland, Ca
No i didn’t, but i’m sure they must have, the storm traveled a narrow path as it was very wet from the highland walmart at the bottom of the hill, to lower running springs, the upper portion where i live hardly got a few drops that morning, lower down there was mud flows across the 330, small but you could tell it was a torrential downpour…
That has to be the largest thunderstorm complex in quite a number of years for the low desert. V_V To bad I am stuck here today otherwise it might be a great day to chase.
Nicholas — too bad we didnt get anything out of it —
Nothing fell here in Orange today, either, as all the activity was limited to the inland valleys near the mountains, in the mountains, and in the desert areas with impressive cumulonimbus clouds visible to the north and east this afternoon. I read that there was flash flooding in areas east of the Coachella Valley this morning, and on TV I saw there was also flash flooding in Henderson, NV (suburb of Las Vegas).
Not quite on topic but after 30 + years of horrible water pressure and seeing many large trees fall during thunderstorms/heavy rains the city has decided to cut these trees around my block here in my part of Whittier. I have seen these fall in thunderstorm in late August 1998, Thunderstorm in December 2000 I think on new years eve, seen quite a few fall in 2004/2005 season, seen one fall in January 2010, and one fall last winter.
http://www.whittierdailynews.com/ci_18907278
If the current GFS is correct, then the pattern should become much more active after this week’s mini heat wave! I have to say….things are much more active than normal. I hope for a repeat of what we had last week. Last week was just insane. I have never seen a Severe thunderstorm complex( 70DBZ+) off the coast of Orange Country in my life before. Especially, in September.
what was even stranger was that thunderstorms were even forming on top of the marine layer. It can’t get any weirder than that!
hi Daniel not sure if you or any of you saw the GFS but it has the 1st cold fron of the fall season for N CA at 192hrs with more rain comeing at 300
that would be on the 00z
Excerpt from tonight’s 9:00 San Diego NWS Discussion:
THE LONG RANGE MODELS ARE SUGGESTING AN UPPER LEVEL LOW WILL FORM SOMEWHERE OVER THE SOUTHERN CALIFORNIA COASTAL WATERS WEDNESDAY. THIS UPPER LOW MEANDERS SOUTHWARD TOWARD NORTHERN BAJA THURSDAY AND FRIDAY. ITS CYCLONIC FLOW WILL TAP INTO A SUBTROPICAL MOISTURE PLUME WEST OF MAINLAND MEXICO NEAR 20N LATITUDE LATE IN THE WEEK. EXPECT
TO SEE SOME MID AND HIGH CLOUDS NEXT WEEKEND…BUT THE AVAILABLE MOISTURE DOES NOT LOOKS SUFFICIENT AT THIS TIME TO MENTION A CHANCE OF SHOWERS.
There could be some potential excitement next week for possible showers / thunderstorms in parts of Socal if the low entrains enough moisture and the positioning of the low is favorable for the region. It certainly bears watching as things may change as the time period approaches.
5-9 day period looking potentially quite interesting right now. As has happened several times in the past few years (and occasionally to dramatic effect, especially in NorCal), West Pacific tropical cyclone activity may contribute to a significant out-of-season storm event late next weekend into early next week. Still too early to hang my hat on the details, but the potential is there for a rain/wind event in NorCal and possibly a dynamically-forced convective event futher south if the rather impressive longitudinal flow out ahead of the storm can tap some subtropical moisture over SoCal. This will probably warrant a post later this week…stay tuned.
Sounds interesting —- Was 101 in Redlands, Ca today 9/18/11 — sat was 85 fri was 84 —-
Have you all found WeatherSpark yet? There’s some really neat stuff there… for instance, check out this long radar loop of the recent thunderstorms in southern California. You should be able to figure out how to change the time based on the URL… you can change the location by dragging the map around.
There’s some ground clutter but it’s easy to tell what’s real and what isn’t.
http://weatherspark.com/#!maps;ws=30547;m=32.713,-123.106,36.079,-114.817;play=1;act0=2011/9/8,19:00;act1=2011/9/14,3:00;ropts=loop:1,alpha:0.7,speed:12;msl=temperatureC;mol=radar
Wow that is real nice. Its better than GR LEVEL X.
Oh wow, 12z GFS is really interesting… It actually brings a tropical storm or its remnants toward Southern California! Something to watch over the next couple of days…though I highly doubt this is going to happen. If it does, then this year is going into the record books.
Yeah that’s awesome, since yesterday it has intensified for socal, but like you said, we’ll wait and see………..
Yup…its the waiting game. 18z also shows this tropical storm/remnant scenario for southern California. I wonder what the 0z model shows….
the 0z of the GFS still has it
http://mag.ncep.noaa.gov/GemPakTier/MagGemPakImages/gfs/20110921/00/gfs_namer_264_1000_500_thick.gif
http://mag.ncep.noaa.gov/GemPakTier/MagGemPakImages/gfs/20110921/00/gfs_namer_276_1000_500_thick.gif
Yeah, but precipitation over socal with this model is much less.
I remember reading that in the 20′s a tropical storm hit So Cal and it was a La Nina year.
That is impressive…though I wonder how a tropical storm would compare to our winter storms. Would it be like our strongest winter storm (04-5) ?
Or would a tropical storm be like what we had December last year with few days of steady rain?
it all so has a storm at the end of the run
Never thought about this, from San Diego NWS 9am discussion:
THIS MIGHT BE A GOOD EXAMPLE OF OUR GEOGRAPHICAL LIMITS ON THE MODELS. BEING IN THE SOUTHWEST CORNER OF THE COUNTRY…WE ARE ON THE EDGE OF THE RICH U.S. DATA USED AS MODEL INPUTS. SINCE THE OCEAN AND MEXICO OFFER VERY LITTLE DATA…THE MODEL PERFORMANCE WITH THESE WEATHER FEATURES FROM THE WEST OR SOUTH CAN BE VERY SKETCHY. WHAT THIS MEANS IS THAT WE WILL KEEP A CAREFUL AND SUSPICIOUS EYE ON THAT MOISTURE IN MEXICO AND WHAT ACTUALLY HAPPENS WITH IT THE NEXT COUPLE DAYS…
Last few GFS runs show the beaches and valleys getting shafted from the moisture feed.
As I have thought….the most recent GFS models have completely removed the idea of bringing remnants of a tropical storm to socal.
Computer models showing a lightning show in a few hours over North West LA County if it’s right.
There appears to be a band of showers offshore that are moving parallel to the coastline. If the low moves a bit to the east, this line would be more over land. There is currently a 20% chance of showers or thunderstorms in the Orange County coastal areas tonight and tomorrow morning. I will certainly be on the lookout for any lightning activity tonight.
New and somewhat unexpected dry lightning event over much of near-coastal SoCal today; could spread as far north as the Bay Area this evening. In the long term, it appears that an E Pac tropical system will be west of southern Baja CA coincident with deep S/SWly flow due to a trough well west of CA next week. That could lead to another interesting weather scenario by next weekend. Stay tuned!
Here some pics I took from the Whittier area today. Looking South East towards Orange county.
http://img.photobucket.com/albums/v681/packerfan10/DSC08183.jpg
http://img.photobucket.com/albums/v681/packerfan10/DSC08184.jpg
There were quite interesting looking altocumulus clouds today and thunderheads toward the mountains. There were even a few sprinkles at my house here in Orange late this afternoon. I thought that I may see some lightning tonight from the clouds to the north, as it looked unstable, but they dissipated a little while later and didn’t see anything.
It was very smoggy here early this afternoon, but the air quality improved as the day wore on.
Whoa. Days 7-9 are going to be worth paying attention to if the synoptic scale setup depicted by the past few GFS runs (especially the 00z) is even close to correct…
tonight 00z is back on that but i want too see the 06 12 and 18z showing the same thing for the next few runs be for we jump the gun on this all so i noteed on tonight 00z why the N E drys out CA starts seeing rain this could be a wet oct starting too setup but 1st i want too see the other mode runs like the 06 12 and 18z show the same thing has the 00z did
Daniel — what does it say ??? rain, heat — Tell us
Hurricane Hilary could weaken and move fairly close to California by next weekend, bringing a major influx of tropical moisture. Given the amplitude of an unseasonbly deep trough due in next weekend, it’s actually possible that the remnant circulation center and associated deep convection could move over the SoCal Bight next Saturday and Sunday. In NorCal, the interaction of the incoming trough and deep tropical remnant moisture could lead to some very interesting weather as well. Expect an update within the next 48 hours as this continues to evolve…
too night 00z was wet starting with this weekend and with then storms evere few days it looks like
looks like the rainey season wants too start sooner this year
Its looking more likely that the beaches and valleys will miss out on any moisture.
Don’t count on that. This is a pretty interesting setup, and only the GFS operational run has Hilary going so far east. The ECMWF brings a much more dramatic influx of moisture to the entire state of CA, and the other dynamical hurricane models are also tracking Hilary farther west than the GFS. Still has some bust potential, to be sure, but I’d certainly not give up on this one yet. That sharp trough to our west on Saturday could really draw up quite a bit of moisture with strong and deep southerly flow…
Daniel holy we cows look what 174hr shows OMG if tonight 00z plans out we would be seeing rain wind and major flooding
DAMN, you’re right. It looks like it could be three years in a row with October super storms for NorCal.
Wow that was quick. I dont think I have ever seen the NWS put rain in and take it out of the forecast so quick. Had a 20% chance of rain in the forecast for Friday and like that its gone.
Well, things over the Pacific are pretty chaotic right now. Dramatic swings in medium-range numerical forecasts are common during the fall over the west coast, but the spread over the past 72 hours has been truly remarkable. Right now, several factors are in play: powerful Hurricane Hilary as it moves northward west of Baja California, a weakening trough moving into Central California this weekend, and now a potentially very powerful mid-latitude cyclone in NorCal early next week. The models have been struggling profoundly with this extremely dynamic pattern, and it seems that the downstream energy now progged to affect NorCal next week may be forcing greater ridging in the short term over the West Coast, which has screwed up the phasing of remnant Hilary moisture and the incoming trough in the present model solutions. What’s going to happen? It is really too hard to tell at this point. I still think that Hilary moisture has a pretty good chance at producing at least scattered convective activity from the Los Angeles area southward by this weekend, though I’m not so sure anymore regarding Central California. The trough this weekend for Central and Northern California could be a bust, though some solutions bring in enough dynamics for convective activity even in the absence of Hilary moisture. Finally, the storm currently on the horizon for Sunday/Monday is looking stronger with each model run, which is pretty impressive for late September. As has been noted, this system looks a lot like the extremely anomalous and powerful October storms that have occurred twice in the past three years, though this would be even earlier than either of those two. In short…it’s about to get pretty interesting out there…
Daniel i have nevere seen the mode runs do this be for the 06z 12z and 18z all showed this about the same thing we are looking at may be are 1st major storm of the season
if this storms comes ture this may end fire season and give a vary good start on the rainy season
18z is nuts for N CA next Tuesday – Wednesday… could be looking over 4″ across the foothills if these passed several GFS runs are right.
Forecast of very low confidence continues. I guess I can’t could that moisture out just yet for So Cal. Trends are trying to bring it back this way.
I really haven’t been watching the models lately, but I have been reading the NWS Forecast Discussions for San Diego, Los Angeles, and San Francisco, and it looks as if there is a slight chance of showers / t-storms in Socal this weekend, and we may have our first fall storm of the season around the middle of next week. It would be nice if we get a good soaking before our first major Santa Ana of the season to help keep the fire threat down.