Golden Gate Weather Services

There has been considerable information disseminated in recent days in regards to Atmospheric Rivers; some of it factual and some so much so.  Here are a couple pretty good resources:

NOAA ESRL Atmospheric River (AR) Info page
http://www.esrl.noaa.gov/psd/atmrivers/

ESRL Real-time AR Modeling
http://www.esrl.noaa.gov/psd/psd2/coastal/satres/data/html/ar_detect_gfs.php

Dettinger - Scripps Presentation on Atmospheric Rivers in California
http://www.scwa.ca.gov/files/docs/outreach/calendar/extreme-events/Atmosperic%20Rivers%20Dettinger%20EE%203-14-12.pdf

The approaching weather system has the potential to be the wettest storm since before December of 2012; but is a very long way from being a "drought buster".  To put it in context, I have looked at both San Francisco rainfall and the rainfall for the 8-Station Index (8SI, which averages rainfall in the Northern Sierra Nevada from about Interstate 80 to Mount Shasta).

So far in the 2013-2014 rainfall season San Francisco has had just over 3 inches of rain since July 1st, or about 22% of the 13.59 inches normal to date amount.  Forecasts are that over the weekend San Francisco may see about 2 more inches of rain; but it would take four more of these 2-inch storms to erase the over 10 inch rainfall deficit.

Likewise the 8-Station Index has had about 20 percent (4.9") of their normal 27" to date.  The forecast of the weekend is for as much as 5 inches falling in the 8SI area, But again it would take the equivalent of at least four more 5" storms to get the Index to near in this watershed.

The bottom line is that even though the "storm door is open" it will need to remain open for there to be a significant easing of the drought.

Tomorrow (February 5) is National Weatherperson's Day.  Thanks to all my friends and colleagues for all the wonderful work that you do.  The date commemorates the birth of John Jeffries, a Boston physician and one of America's first weathermen. He was born on Feb 5, 1744 and kept weather records from 1774 to 1816.

In the current (Jan/Feb) issue of Weatherwise I have written about the impacts of weather on baseball.  The full text is available online at http://www.weatherwise.org/Archives/Back%20Issues/2014/January-February%202014/rain-delays-full.html.  Enjoy.

On Thursday (Feb 6) professional golfers will tee it up on the Monterey Peninsula for the AT&T National Pro-Am Golf Tournament.  And as is sometimes the case, it looks like the weather may play a factor.  Here's an analysis of its impact on previous tournaments.   http://ggweather.com/pebble.htm

...preliminary based upon today's forecast high temps, but values should not change more than 0.1 degree, if at all...

January 2014 is going into the record books as the driest and warmest on record at many locations around the state.

San Francisco - 
- Rainfall - 0.06 inches.  Previous record 0.26" in 1920
- Driest first 7 Months of the rainfall season - 2.14".  Previous record 2.26" in 1917-1918.
- Average max temp - 64.0 degrees F.  Normal 56.5, anomaly +7.6 deg.  Previous record 62.6 in 2003.

San Jose -
- Rainfall - 0.12 inches.  Previous record 0.27" in 1984
- Average max temp - 65.9 degrees F.  Normal 58.1, anomaly +7.8 deg.  Previous record 63.8 in 2003.

Redding -
- Rainfall - 0.42 inches.  Record 0.38" in 2007
- Average max temp - 68.3 degrees F.  Normal 55.3, anomaly +13.0 deg.  Previous record 63.0 in 2009.

Sacramento -
- Rainfall - 0.15 inches.  Record 0.05" in 2007
- Average max temp - 65.9 degrees F.  Normal 53.6, anomaly +12.1 deg.  Previous record 60.5 in 2012.

Fresno -
- Rainfall - 0.59 inches.  Previous record 0.04" in 1976
- Average max temp - 66.7 degrees F.  Normal 54.6, anomaly +12.1 deg.  Previous record 61.4 in 1986.

Los Angeles -
- Rainfall - 0.00 inches.  Ties record 0.00" in 2003
- Average max temp - 75.4 degrees F.  Normal 66.4, anomaly +8.1 deg.  Record 65.4 in 1986.

San Diego -
- Rainfall - 0.01 inches.  Record 0.00" in 1948
- Average max temp - 70.5 degrees F.  Normal 64.8, anomaly +5.7 deg.  Record 71.4 in 2003.

Jan Null, CCM
Golden Gate Weather Services

With the progs continuing to show a dry pattern through the end of the month there have been a number of comments and inquiries about how common it is to get zero or very little rain in October.
 
Here are some factoids in regards to the past 164 years of San Francisco October rainfall dating back to 1849.

- There have been 13 previous years (8% of the time) when there have been no measurable (i.e.,≥ 0.01") in October.
- There have been a total of 32 years (19%) with a tenth of an inch or less for the month.
- Ironically both the wettest (49.27" in 1861-62) and driest (7.42" in 1850-51) rainfall seasons (i.e., July 1 - June 30)  in SF history have occurred in years when there was no rain in October.
- The average rainfall for the season after an October with less than a tenth of an inch of rain is 21.04". 

- Normal (1981-2010) San Francisco rainfall in October in 1.12 inches and there are normally  4 days with measurable rainfall. 

See:  http://ggweather.com/sf/monthly.html

Jan Null, CCM
Golden Gate Weather Services
http://ggweather.com
jnull@ggweather.com

Climatologically California temperatures were all over the map for September 2013 with huge variations.  Average monthly maxima ranged from 3.5 degrees above normal at Eureka to -3.8 below at Redding, only 100 miles apart.  In between san Francisco was "normal" with a 0.0 degree anomaly.

Rainfall likewise saw huge anomaly differences with positive anomalies in the north half of the state and below normal in the south.  Eureka had over 5 times their normal rainfall (517%) with a monthly total of 3.05" and San Jose's 0.66' was 367% of normal. 

See http://ggweather.com/calif/sep2013.htm

The Autumnal Equinox is this Sunday, September 22 at 1:44 pm pdt (2044 UTC).  See http://ggweather.com/seasons.htm.

Typhoon Usagi in the western Pacific is currently entering the Luzon Strait between Taiwan and the Philippines and on a direct track toward Hong Kong.  See:

Bob Henson of UCAR has put together an excellent analysis of recent flooding in Colorado titled "Inside the Deluge".  See http://www2.ucar.edu/atmosnews/opinion/10250/inside-colorado-deluge?utm_source=AtmosNews&utm_campaign=b3c15d48ce-Atmosnews_2013_09_209_20_2013&utm_medium=email&utm_term=0_80502e816e-b3c15d48ce-53337165