Record Heat Friday
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A very warm air mass combined with a thermal trough at the Coast brought record heat to the Bay Friday.
A thermal trough is usually responsible for all of our heat waves. A thermal trough forms from rising air over an area of intense heat. This happens quite often in the Central Valley.
You can think of the thermal trough as a valley of low pressure in which air sinks to fill the void left by the rising air.
This trough usually sits over the Central Valley and draws cooler air from the ocean to air condition the Bay and Coast. This is why it’s so windy in the Bay and through the Carquinez Strait to the Delta communities. On Friday, an area of high pressure steered this trough offshore. This stopped the cooling sea breeze, ocean water temperatures in the upper 50s chills the air, stagnated our air, which allowed the heat to build to record levels.
As high pressure moves east today and tomorrow, the trough will move east also and return to the Central Valley and our onshore flow will bring cooler air to the Coast and Bay today (first) and Inland tomorrow (second).
STATION NEW RECORD OLD RECORD
MOFFETT FIELD 101° 98 SET IN 2008
OAKLAND DOWNTOWN 95°(T) 95 SET IN 1977
OAKLAND AIRPORT 94° 90 SET IN 2008
SAN FRANCISCO AIRPORT 95° 90 SET IN 2008
SAN FRANCISCO DOWNTOWN 96° 88 SET IN 2004
SAN JOSE 101°(T) 101 SET IN 2008
MONTEREY 94° 87 SET IN 1977
SALINAS 99° 92 SET IN 1962
SALINAS AIRPORT 97° 92 SET IN 1962
SANTA CRUZ 99° 97 SET IN 1962
Friday's highs were also the hottest temperatures
recorded this year for these stations except the
Salinas Airport which reached 99° on April 21st.
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