Unusual weather for June. Not so much that there were thunderstorms, but that the thunderstorms were in part the result of an unseasonably strong jet embedded in the base of an offshore upper level low.

It's a bit of a stretch, but an argument could be made that these storms were a calling card of an increasingly energetic atmosphere, and a developing El Niño.

Downtown Los Angeles (USC) recorded a total of 0.02 inch of rain Wednesday. The rainfall increased the water year precipitation total for Los Angeles to 8.95 inches, which is 6.16 inches below normal.

It's not often that a trace of rainfall sets a record, but that was the case at Camarillo Airport and Palmdale, which had not previously recorded precipitation on June 3. The 0.03 inches recorded at Sandberg was also a record. Here's a CNRFC graphic with some 24 hour rainfall totals in Los Angeles County.

Several factors point to an increased probability of El Niño conditions developing over the next few months. Among them, Equatorial Pacific SSTs have increased, and the subsurface heat content is the highest it's been since the El Niño of 2006-07.

But as the short-lived 2006-07 El Niño event demonstrates, an El Niño is more than just warm Pacific equatorial SSTs. Through complex forcing and feedback mechanisms, the atmosphere and oceans have to cooperate on a global scale. Generally speaking the momentum of the atmosphere increases when there is an El Niño, and decreases during a La Nina.

And it looks like the atmospheric momentum may be increasing. Orbits of the Global Wind Oscillation (GWO), a measure of atmospheric momentum, have been shifting upward, in the direction of more energetic values usually associated with an El Niño.

However, an El Niño is not a done deal. The climate system is just leaning in that direction. As climate scientist Klaus Wolter has previously pointed out, in a similar situation in 1973-1975, the climate fell back into a La Niña for another year. But at this point it appears we may be diverging from that analog case. (See June 6 Weathernotes.) We'll see!

Update 06/05/09. Unseasonably strong 110+ kt jet overhead as upper low center moves onshore in Central California. At 7:15 this morning, Intellicast composite radar showed most of the shower activity occurring to the north of Los Angeles, but there has been scattered showers in the Los Angeles area as well, with measurable rain recorded at a number of stations. Here's an archived copy of a NWS Public Information Statement with some preliminary rainfall totals as of 5:00 p.m.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

An unseasonably strong, late season Pacific storm system brought rain to much of California Friday and Saturday, including some areas of Southern California.

Los Angeles basin and valley areas generally recorded a trace of precipitation, but some stations in the Ventura mountains recorded as much as 0.3 inch. Here is an archived copy of a NWS Public Information Statement, with some precipitation totals from around the area.

Heavier rain occurred in Central California. A new rainfall record for May 1 was set in Sacramento, and higher elevations of the Sierra received about a foot of snow. Enhanced southwesterly, sub-tropical flow, and enhanced convection associated with the phase 7 MJO may have contributed to the strength of the system.

SSTs have warmed in the equatorial Pacific, and at least for the moment, orbits of the GWO have shifted to a more ENSO neutral stance. Some longer term ENSO forecasts are now predicting warm ENSO conditions to develop by next Winter.

A warming trend is expected in Southern California over the next several days, with high temperatures in the valleys near 90 by mid-week.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Downtown Los Angeles (USC) happened to be under the right cloud yesterday, and recorded 0.02 inch of rain. There's a continuing chance of showers in Southern California through the weekend. The area could use some rain. The last storm to produce more than a couple tenths of inch of rain at Downtown Los Angeles was back on February 24, 2008 -- more than eight months ago.

Last year, California's rain season might have been scripted by Dr. Jekyll and Mr. Hyde. Lowland rain totals and the Sierra snowpack were well above normal through the end of February, and then the spigot was turned off. The storm track shifted north, and California had its driest March to May on record. (The March 29, 2008 post in Ed Berry's Atmospheric Insights blog describes the events that may have led to and maintained this shift.)

Which rain season personality will emerge this Winter? Earlier this year the equatorial Pacific tried to transition to El Nino, but the atmosphere didn't cooperate. As measured by the Multivariate ENSO Index (MEI), the ENSO state has returned to the weak La Nina threshold. And as measured by the Global Wind Oscillation (GWO), an uncooperative atmosphere has continued to cycle through a La Nina base state.

This suggests a winter precipitation outlook with a La Nina flavor -- similar to last year. This precipitation map, generated by the ESRL-PSD Composite ENSO plots page, shows the mean November-March precipitation for the U.S. during 9 La Niña events from 1948 to the present. The average La Niña rainfall indicated for coastal Southern California is in the 7.0-10.5 inch range. Last season's November-March rainfall in Downtown Los Angeles was about 12 inches.

Here's the current Nov-Dec-Jan precipitation outlook issued October 16 by the Climate Prediction Center. The "EC" means an equal chance of below normal, near normal, or above normal precipitation. The IRI Multi Model Seasonal Forecast for Nov-Dec-Jan is similar. We'll see!

Update 11/4/08. Here are the NWS Public Information Statements with preliminary rainfall totals for the period from Friday evening to Sunday morning, and from overnight last night to 10:00 a.m. this morning. The current Climate Prediction Center 6-10 day and 8-14 Precipitation Outlooks project below normal rainfall for Southern California. In Atmospheric Insights, Ed Berry paints a scenario with an extended North Pacific Jet collapsing into a strong western U.S. trough in the week 2-3 timeframe. We'll see!

Update 11/1/08. Did a trail run this morning in the Pt. Mugu State Park Area. Over the course of 3+ hours watched 2-3 waves of convection march northeast from the Santa Barbara Channel across the Oxnard Plain. We were showered on a few times, but were very happy to be east of these training T-storms and heavy rain. Here is a NWS Public Information Statement with some rainfall totals as of 11:00 a.m.

More information concerning Southern California weather can be found using our WEATHER LINKS page.

Sunday's storm added more rain to Southern California's unexpectedly wet water year totals, and more snow to the Sierra snowpack. This rain season western storms have reduced drought classifications by as much as three steps in some areas of California and four in Arizona.

As of February 4, Downtown Los Angeles (USC- KCQT) has recorded 12.13 inches of rain since July 1-- about 4.5 inches above normal for the date. Here is an archived PDF of a NWS Public Information Statement with some preliminary rainfall totals for Sunday's storm.

Sierra snow course measurements for February 1 are coming in and manual measurements are confirming what automatic snow sensors have already reported -- that the Sierra snowpack is well above normal for the date.

Will the wet western weather continue? The GFS and ECMWF medium range models, and NCEP and PSD ensembles are forecasting a generally quiescent, rain free period for Southern California over the next several days, and into the extended period. Today's NWS 6-10 Day and 8-14 Day Precipitation Outlooks for Southern California are indicating Below Normal precipitation.

However, there are suggestions (see Atmospheric Insights) that sometime around February 15-20, the currently active MJO may more or less phase with the GWO, and amplify La Nina to produce a energetic, extended Pacific jet and west coast trough, similar to what occurred around January 3, 2008. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.