Weathernotes Archive August 2006

Westerly Windbursts May Signal El Niño Onset.
Weathernotes for Thursday, August 18, 2006.
(Any updates will be found at the end of this discussion.)

TAO/TRITON zonal wind data and Climate Data Assimilation System (CDAS) 850-hPa Wind Anomalies indicate a westerly windburst is occurring in the western equatorial Pacific. The CDAS wind data shows several anomalous windbursts occurring since the beginning of July. From July 1, the Southern Oscillation Index (SOI) has dropped from -9 to about -16. Depth-averaged temperatures exceed 1.0°C in a large area of the central equatorial Pacific, and 1.5°C in a area of the eastern equatorial Pacific.

All of this would seem to indicate an ocean state poised on the edge of a late onset El Niño event. Dr. Klaus Wolter's Multivariate ENSO Index (MEI) for June/July increased to 0.64, and as Dr. Wolter points out, this is a an increase of more than 1.2 standard deviations in three months, and moves the MEI above the weak El Nino threshold, as defined by the index.

However, the IRI ENSO Quick Look issued August 17, 2006 states that neutral conditions exist in the tropical Pacific, and that the probability of neutral conditions continuing through October 2006 is approximately 60%. CPC's El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued August 10 also expects neutral conditions to continue for the next one to three months, and says there's a 50% chance that weak El Niño conditions will develop by the end of 2006. In their August 9th ENSO Wrap-Up the Australian Bureau of Meteorology comments that the overall ENSO status remains neutral, and that most models in their Summary of ENSO Forecasts continue to forecast neutral ENSO conditions.We'll see!

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

Record July Heat. New El Niño Developing?
Weathernotes for Thursday, August 3, 2006.
(Any updates will be found at the end of this discussion.)

This July you didn't have to run an ultramarathon in Death Valley to experience extreme heat. According to the NWS, Pierce College in Woodland Hills recorded a new all time high temperature for that station of 119°F. This was the highest temperature ever recorded at an NWS observation site in Los Angeles County. Triple digit highs were recorded at Pierce College a record 24 days of July.

Temperature records were broken across the area. July was the warmest month (of any month) on record at Burbank Airport and Paso Robles Airport. It was the warmest July on record for several NWS stations, including Downtown Los Angeles, U.C.L.A., LAX, Long Beach, Lancaster, Sandberg, Camarillo, Santa Barbara, and Santa Maria. For additional details and information see the NWS Public Information Statement (archived copy, PDF) issued August 1, 2006.

Is a new El Niño developing? Depth averaged and surface temperatures in the eastern equatorial Pacific cooled somewhat over the last two weeks in the far eastern Pacific, but an area of depth averaged temperature anomaly exceeding 1°C in the central Pacific has become more pronounced. The Southern Oscillation Index (SOI) has been vacillating around -10 since June 1. However, in their July 26th ENSO Wrap-Up the Australian Bureau of Meteorology comments that the overall ENSO status remains neutral, and that most models in their Summary of ENSO Forecasts continue to forecast neutral ENSO conditions. We'll see!

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