Сан Франциско, California

... January 2010 regional climate summary...

Summary for the San Francisco Bay area and Monterey Bay area...

January 2010 was a wet month... mostly because of a series of powerful
storms that swept through California during the third week of the
month. January temperatures were slightly above normal... due in large
part to mild overnight temperatures during the second half of the
month.

The first half of January was dry as high pressure held firm along
the West Coast and deflected most incoming Pacific storms well to
our north. One weather system managed to bring light to moderate
rainfall to the region on the 12th... but otherwise the first half of
January was mostly devoid of precipitation. Light winds and a stable
airmass under the persistent ridge of high pressure allowed dense fog
to develop across portions of the San Francisco Bay area during the
first ten days of January.

The second half of January was very wet as a strong and moist flow
across the Pacific finally reached the West Coast. The weather
pattern during the second half of the month was typical of patterns
that develop during strong El Nino Winters. Beginning on the
18th... a parade of powerful storms slammed into California... each
arriving about one day apart. Periods of heavy rain and strong winds
pummeled the region from the 18th through the 23rd. Although rain was
heavy at times... there was enough of a break between heavy rain
events to allow water levels to drop on area rivers and streams
before the next storm rolled in. Therefore... widespread flooding did
not occur. However... our region did not escape flooding entirely. The
Willow Brook creek flooded portions of Petaluma on the 20th. Also...
the Pescadero creek in San Mateo County peaked a bit above flood
stage on that same day.

Rainfall totals for the week of the 17th were impressive. Total
rainfall amounts from the 17th through the 22nd include:

.North Bay
Cazadero 1558'... ... ... ... ... ... ..13.46 inches
Venado 1260'... ... ... ... ... ... ... .10.40
mount St Helena 4140'... ... ... ... . 7.21
Santa Rosa... ... ... ... ... ... ... ... 6.09
Santa Rosa Airport... ... ... ... ... . 7.32
Kentfield... ... ... ... ... ... ... ... . 8.34
San Rafael... ... ... ... ... ... ... ... 8.68
Napa... ... ... ... ... ... ... ... ... ... 6.45

.San Francisco peninsula... East and South Bay
Redwood City... ... ... ... ... ... ... . 5.27
Oakland museum... ... ... ... ... ... .. 4.87
Hayward Airport... ... ... ... ... ... . 3.98
San Francisco Airport... ... ... ... . 4.76
San Francisco downtown... ... ... ... 4.57
Moffett field... ... ... ... ... ... ... 3.95
Concord Airport... ... ... ... ... ... . 4.16
Livermore Airport... ... ... ... ... .. 2.75
Richmond... ... ... ... ... ... ... ... .. 5.49
San Jose Airport... ... ... ... ... ... 3.54
Morgan Hill... ... ... ... ... ... ... .. 6.11
Gilroy... ... ... ... ... ... ... ... ... . 5.00

.Santa Cruz Mountains
Mount Umunhum 3090'... ... ... ... ... 10.24
Ben Lomond 2630'... ... ... ... ... ... 9.10
La Honda 872'... ... ... ... ... ... ... 6.73
Corralitos 327'... ... ... ... ... ... . 5.21
las Trampas 1760'... ... ... ... ... .. 5.32

.Monterey Bay area
Monterey... ... ... ... ... ... ... ... .. 4.17
Salinas... ... ... ... ... ... ... ... ... 3.27
Carmel Valley... ... ... ... ... ... ... 4.58
Santa Cruz... ... ... ... ... ... ... ... 4.88
Hollister... ... ... ... ... ... ... ... . 4.78
King City... ... ... ... ... ... ... ... . 3.51

.Monterey County mountains
Mining Ridge 3288'... ... ... ... ... .13.14
Anderson Peak 3368'... ... ... ... ... 10.04
Three Peaks 3362'... ... ... ... ... .. 9.97
Chalk Peak 3432'... ... ... ... ... ... 9.99
Arroyo Seco 980'... ... ... ... ... ... 8.25
Big Sur 450'... ... ... ... ... ... ... . 7.63

In addition to heavy rainfall... three storms from the 18th
through the 20th produced strong and gusty winds across the area.
Wind gusts of between 50 and 70 mph were common on those days and
resulted in downed trees and numerous power outages.

The storms that impacted the region during the third week in
January were powerful enough... and contained enough unstable air... to
generate several thunderstorm events across our area. Many of the
thunderstorms that rumbled across the region produced hail and a
several of the storms reached severe levels. A weak tornado touched
down in eastern Contra Costa County on the 23rd. All told... during
the week of January 17th... the National Weather Service office in
Monterey issued two tornado warnings... five severe thunderstorm
warnings... and five special marine warnings for the San Francisco and
Monterey Bay areas.

A blast of colder air arrived late in the week... dropping snow
levels as low as 1400 feet on Friday the 22nd. Nearly four inches of
snow accumulated atop Mount Hamilton.

Barometric pressure readings dropped to very low levels on Thursday
the 21st. At noon that day... barometric pressure readings at area
airports fell to between 28.85 to 28.95 inches of Mercury.
Historic data on barometric pressure is sparse and so its difficult
to say how close these values came to setting records. In any case...
these pressure readings are extraordinarily low for our region.

The weather became more tranquil during the final week of January
with only light to moderate rainfall amounts. For the month as a
whole... rainfall totals were generally about 150% of normal.
Portions of interior Monterey County and San Benito County
accumulated in excess of twice their average January rainfall.

Year-to-date (ytd) rainfall totals took a big jump during the second
half of January. On the 15th of the month... ytd rainfall totals were
generally only about 70 to 80 percent of normal. By the end of
the month ytd totals increased to 100 to 130 percent of normal.

High temperatures for the month were generally below normal... mostly
due to significant cloud cover during the second half of the month.
The largest negative high temperature anomalies were in the north
and East Bay valleys... where several foggy days during the first
half of the month kept temperatures cool. Mostly cloudy conditions
during the second half of the month helped hold nighttime
temperatures up. Average minimum temperatures for January were above
normal at all reporting locations and in a few cases considerably
above normal. No daily record temperature records were set or tied
during January 2010.



        ... January regional temperature summary...

                                departure departure
                   avg normal from avg normal from
location high high normal low low normal

North Bay...

Angwin 51.2 52.9 -1.7 40.6 38.0 2.6
Kentfield 53.1 56.2 -3.1 43.9 40.4 3.5
Napa 55.9 57.5 -1.6 42.6 39.1 3.5
Petaluma M 57.2 M M 38.2 M
Saint Helena 55.3 57.4 -2.1 42.6 36.9 5.7
San Rafael 52.6 56.2 -3.6 44.2 41.3 2.9
Santa Rosa 56.3 57.6 -1.3 42.5 38.7 3.8
Sonoma 54.8 58.2 -3.4 41.6 37.2 4.4

San Francisco peninsula...

Half Moon Bay 59.6 58.7 0.9 45.8 43.2 2.6
Pacifica M 56.5 M M 45.7 M
Redwood City 56.9 58.5 -1.6 42.5 39.8 2.7
San Francisco
Airport 55.6 56.1 -0.5 46.8 42.9 3.9
San Francisco
downtown 55.7 57.5 -1.8 47.7 46.4 1.3
Woodside M 60.0 M M 36.6 M

East Bay...

Berkeley 57.7 56.6 1.1 44.6 44.2 0.4
Concord 55.0 57.2 -2.2 43.9 41.6 2.3
Fremont 57.7 58.8 -1.1 43.9 42.6 1.3
Livermore 55.1 57.0 -1.9 41.1 37.4 3.7
Martinez 54.0 55.0 -1.0 40.7 39.1 1.6
Mount Diablo
Junction 53.6 55.6 -2.0 42.9 39.2 3.7
Newark 57.7 57.6 0.1 43.8 42.0 1.8
Oakland 58.9 57.3 1.6 45.8 44.8 1.0
Richmond M 57.7 M M 42.9 M

South Bay and Santa Cruz County...

Ben Lomond 60.3 61.4 -1.1 40.2 37.1 3.1
Gilroy 59.4 59.8 -0.4 42.5 37.7 4.8
Los Gatos 57.3 58.6 -1.3 40.4 38.5 1.9
Mount Hamilton 48.1 49.4 -1.3 39.8 37.5 2.3
San Jose 58.1 58.4 -0.3 43.9 41.6 2.3
Santa Cruz 60.4 60.7 -0.3 43.3 39.9 3.4
Watsonville 61.6 60.5 1.1 43.3 39.3 4.0

Monterey and San Benito counties...

Big Sur station M 60.0 M M 43.2 M
Carmel Valley 63.3 63.6 -0.3 41.6 38.7 2.9
Hollister 58.7 60.8 -2.1 42.2 38.0 4.2
King City 63.1 62.8 0.3 42.2 35.8 6.4
Monterey 59.2 60.1 -0.9 45.8 43.9 1.9
Pinnacles National
Monument 61.8 61.6 0.2 36.4 32.8 3.6
Salinas 63.2 62.5 0.7 43.3 41.3 2.0


        ... January regional precipitation summary...

                             average
                   Jan Jan percent
location total precip of normal

North Bay...

Angwin 13.07 8.15 160
Calistoga M 7.74 M
Cloverdale M 8.82 M
Fort Ross M 7.46 M
Healdsburg M 8.80 M
Kentfield 13.28 9.60 138
Muir Woods 11.29 7.37 153
Napa 9.19 5.35 172
occidental 16.22 11.69 139
Petaluma M 5.33 M
Saint Helena 12.24 7.40 165
San Rafael 12.39 7.38 168
Santa Rosa 9.48 6.13 155
Sonoma 8.44 6.52 129

San Francisco peninsula...

Half Moon Bay 6.40 5.55 115
Pacifica 8.94 6.28 142
Palo Alto M 3.24 M
Redwood City 6.33 4.19 151
San Francisco
Airport 5.97 4.45 134
San Francisco
downtown 6.66 4.53 147
Woodside M 6.52 M

East Bay...

Berkeley 7.66 5.45 141
Concord 6.17 3.78 163
Fremont 4.36 3.05 143
Livermore 3.53 2.99 118
Martinez 6.43 4.25 151
Mount Diablo
Junction 9.07 4.76 191
Newark 4.64 2.96 157
Oakland 6.25 4.85 129
Richmond 6.36 4.91 130

South Bay and Santa Cruz County...

Ben Lomond 14.76 10.18 145
Gilroy 6.14 4.32 142
Los Gatos 8.57 4.94 173
Mount Hamilton 6.64 4.42 150
San Jose 4.58 3.03 151
Santa Cruz 8.19 6.49 126
Watsonville 6.12 4.72 130

Monterey and San Benito counties...

Big Sur station M 9.13 M
Carmel Valley 5.85 3.49 168
Hollister 4.58 2.91 157
King City 4.62 2.21 209
Monterey 6.54 4.19 156
Pinnacles National
Monument 7.68 3.20 240
Salinas 4.48 3.00 149


   ... daily precipitation records for January 2010...

                                  record old
                                  precip record
date location (inches)

1/19 San Francisco Airport 1.55 1.07 in 1962

1/20 San Jose 1.28 1.26 in 1894


        ... monthly ranks for downtown San Francisco...

Average high temperature... .55.7... .59th coolest
average low temperature... ..47.7... .21st warmest
monthly rainfall... ..6.66 inches... .38th wettest


Note: this climatological data is preliminary. For official
certified climatological data please contact the National
climatic data center at 828-271-4800 or http://www.Ncdc.NOAA.Gov.
Official values as determined at the above web site may take
several months for authentication and publication.