[pct-l] Fwd: [Weather and Climate News] March 9, 2009

Mon Mar 9 15:47:06 CDT 2009

---------- Forwarded message ----------
From: <weather_and_climate_news at water.ca.gov>
Date: Mon, Mar 9, 2009 at 1:40 PM
Subject: [Weather and Climate News] March 9, 2009
To: weather_and_climate_news at water.ca.gov

Water Supply Status
Governor's Drought Emergency Proclamation
Upcoming Events

As of a month ago, it hadn't rained in weeks.  February 1 status numbers
were all rather weak, with statewide storage at 66% of average, snowpack
at   62% of average, and statewide precipitation at 65% of average.
Then it hit.  A number of good storms moved in starting February 12,
drawing to a close on about March 5.  While not an entire season's worth
of precip fell during that time; no, this wasn't a record wet spell, it
did boost a number of key variables.

Today we have:
Statewide snowpack March 1 course measurement: 81 % of average.
Sensor statewide snowpack estimate: 90 % of average for today's date.
Northern Sierra 8-Station precipitation index:  98% of average (36.0").
Southern Sierra 5-Station precipitation index: 105% of average (32.0").
Statewide reservoir End of Feb storage due 3/12; likely to be in the
lower 70's for % of average.

The question is this: Does it need to continue?  Yes. The season could
not shut off now, like it did last spring, or we'd be hurting.  2008 saw
the driest spring on record for the state, with the 8-Station getting on
3.4" for March, April, and May, when they normally tally 12.9".  Last
year, La Nina was a big factor in the spring shutdown, although it can
lead to a variety of weather outcomes.  If the season cut off, we'd have
72% of a water year total in the Northern Sierra, coming pretty close to
the values at the end of the last two water years; 75% for 06-07, and
70% for 07-08.  Although this years' 36.0" so far is better than we
ended all of last year.  Not quite the good 50.0" normal, and a running
3-year deficit causes soil moisture and reservoir and groundwater
impacts.

Here is the breakdown by month for the Northern Sierra 8-Station
precipitation index.  In simple terms, January was horrible.  Feb and
March have been good to us.

January Total:          3.1"    Percent of Monthly Jan Average: 34%
Jan Monthly Average:    9.0"

February Total:         11.8" Percent of Monthly Feb Average:    148%
Feb Monthly Average:    8.0"

March Total:            6.4"    Percent of Monthly March Average:   93%
March Monthly Average:  6.9"

The difference between pre-wet and post-wet periods is impressive. The
Feather River Basin received about half of what it has in the bucket for
the year since Valentine's Day (14.1" out of current seasonal total of
approximately 30" through Feb. Average season is 45" over that 7-station
basin).  Pre- and post- storm reservoirs:

Mo/Day/Yr       2/1/09  3/1/09  3/9/09
All figures are %cap/%avg

Shasta Res      31%/45% 43%/58% 53%/70%
Oroville        29%/43% 38%/54% 47%/64%
Folsom Res      25%/48% 43%/76% 61%/105%

Ideally, the goal is to have the reservoirs at or very near average for
this time of year.  As we move past flood control requirement time
frames, more runoff from any upcoming storms can be stored.  Additional
water use and environmental restrictions play a big role in available
water supply, as well.  Many small to medium sized reservoirs have
really come up, but the big ones have plenty of room for more!  Here is
a quick reservoir status table that is updated daily on CDEC:

http://cdec.water.ca.gov/cgi-progs/reservoirs/RES

Watch for the next B120, a real compendium for supply information and
forecasts.  The March 1 issuance will come out tomorrow:

http://cdec.water.ca.gov/snow/bulletin120/

The GFS model is trying to be optimistic going into the next couple of
weeks, meaning there may be a few minor systems developing, but still a
ways out.  The next 7-10 days' trend is below normal and dry.

La Nina conditions are still in place, but the cold pool is not as
strong over the tropical Pacific as it had been earlier in the winter.
The forecast is for La Nina conditions to weaken this spring. For a
quick graph of the targeted ocean SST's, over the last year, go to page
10 of the weekly Climate Prediction Center's web discussion:

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_ev
olution-status-fcsts-web.pdf

Here is the place to start if that link gets cut off:

http://www.cpc.ncep.noaa.gov/

This may be good, in that last year's cool conditions played a role in
NorCal's spring shut off.  But a lack of strong La Nina is no guarantee
of wet spring, either!  Not an easy forecast.

Weekly SNOTEL reports look good across most of the west, although CA,
OR, and WA don't have quite the numbers of other states:

http://www.wrcc.dri.edu/snotelanom/basinpren.html

The new DWR Drought site has been launched.  Recent Drought News
includes the Governor's proclamation.  The Drought Links includes a
Frequently Asked Questions section and information on Where Does My
Water Come From?, which is a great Water Education Foundation site that
provides background on the complex water source regions for various
parts of the State. The site has information on economic projections of
the impact of the drought, daily reservoir and snowpack numbers, CA
drought status, financial assistance, and conservation tips.  It grows
weekly, and hopefully will become a good one-stop site for drought
information:

www.water.ca.gov/drought

Apologies for such a long gap between newsletters.  Author couldn't
create one while on assignment to another office.  Frequency may stay
low for the near term, then low over summer.  It wasn't budget related,
contrary to inquiry! :)

EL

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