Not the Driest on Record - San Francisco

The overnight rainfall (through 7 am Friday, Feb 28)  has pushed San Francisco's seasonal rainfall to 7.57".  While still a paltry amount, this means that the 2013-2014 rainfall season (July 1-Jun 30) will NOT be the driest in the 165 years since rainfall records began in SF in 1849.  And given the expected rainfall through the rest of the day, this season may jump into 3rd place.   The Ten Driest Seasons were:
1850    7.42"
1975    7.95"
1897    9.38"
1863   10.08"
1958   10.46"
1919   10.46"
1876   11.04"
1976   11.06"
1971   11.06"
1917   11.47"
(See http://ggweather.com/sf/season.html)

And it should be noted that the normal San Francisco rainfall for the remaining four months (Mar-Jun) is still another 5.60".

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High Pressure Blues

Back during the California drought of 1975-77 I was an Intern at the National Weather Service and decided to be "clever" and write the California Weather Summary on Valentine's Day 1977 in poetic verse titled "High Pressure Blues".  (NWS management was not amused)  I'm sure all will agree that it's a good thing that I can make my living as a meteorologist and not as a poet. 

However,  the meteorology is certainly just as apropos  for the current drought.   An image of the original teletype message can be seen

and is replicated below.


High Pressure Blues

Strong High Pressure
Remains firmly entrenched...
Blocking all storm
That might leave us drenched.

Light offshore breezes
Are warming the air...
To unseasonable readings
Under skies fair and warm.

Temps in the 70s
Were found all around...
And marks over 80
In the south state were found.

Some rain would be nice
With snow in the mountains...
Enough to fill up the dams
Or even some ountains.

But the new forecast says
It's more sunny days...
With patches of fog
And afternoon haze.

E Jan Null
Feb 14, 1977

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California Storm Rainfall Summaries

The rainfall totals across northern California were very impressive, but 4-day totals dropped off rapidly into central California.  Many locales in the north more than doubled their season to-date totals, jumping from percent of normal (PON) values in the teens to PON's in the 30% to 40% range.  See http://ggweather.com/feb2014rain.htm

But the important takeaway is that while this is a great start, the north half of the state would still need on the order of 4 more equivalent storm systems to get close normal.


The very important Northern Sierra 8-Station Index also jumped significantly; doubling with over 5 inches to 9.58" to-date.  This is approximately 35% of normal, up from 18% on Wednesday.  See http://cdec.water.ca.gov/cgi-progs/queryDaily?s=8si&d=today


There have been some rain totals of over 20 inches being reported for Mt. Tamalpias.  However In light of surrounding locations this seems to be a bogus.  Kentfield's big-time 96-hour total of 11.83" would appear to be more representative.  See https://marin.onerain.com/sensor.php?site_id=1555&device_id=1&view_id=3

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Atmospheric Rivers

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

 

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Numbers Don't Add Up

While I like the visual, the numbers don't add up. The normal accumulated rainfall for the 8-Station Index (8SI) from Oct 2011 through January 2014 is 126.5 inches, and actual accumulated amount has been 92.0 inches. That's a deficit of 34.5 inches. Given http://www.cnrfc.noaa.gov/precipForecast.php?cwa=RSA... a conservative forecast precipitation amount for the 8SI would be about 5 inches or about 14% of the deficit. Given a 5-gallon bucket (640 ounces), 14% would be 90 ounces or 9 of the displayed 10-oz mugs.

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No Drought Buster

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.

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National Weatherperson's Day

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.

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Pebble Beach Golf Weather

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

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WARMEST AND DRIEST JANUARY ACROSS CALIFORNIA

...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

 

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