EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 920 PM PDT SAT JUN 19 1999
...SYNOPSIS...
THE WEATHER PATTERN OVER SAN DIEGO WILL CHANGE LITTLE THROUGH MONDAY
AS THE FLOW ALOFT WILL BE WEAK. A TROUGH OF LOW PRESSURE WILL MOVE
INTO THE PACIFIC NORTHWEST...BUT THIS WILL DO LITTLE TO AFFECT OUR
WEATHER. LOW CLOUDS WILL BE THE DOMINANT FEATURE AT THE COAST WITH
ONLY PARTIAL AFTERNOON CLEARING AT THE BEACHES. OTHERWISE...SKIES
WILL BE CLEAR. HURRICANE ADRIAN AT 8 PM WAS AT 16.9N/107.3W AND WAS
MOVING WEST-NORTHWEST AT 15 MPH.
...DISCUSSION...
CONDITIONS THIS EVENING SEEM TO BE ABOUT AN AVERAGE OF THOSE
EXPERIENCED LAST NIGHT AND THE NIGHT BEFORE. THE MARINE LAYER DEPTH
IS CHANGING LITTLE AS THE NKX SOUNDING IS ALMOST A REPEAT OF
YESTERDAY. ACARS SOUNDINGS ALSO SHOW LITTLE CHANGE.
THE MODELS...INCLUDING 00Z ETA/NGM AS WELL AS SMALLER SCALE
RUC/COAMPS INDICATE ONLY MINOR CHANGES IN THE LOCAL WIND PATTERNS
THROUGH MONDAY. THE ONSHORE PRESSURE GRADIENTS MAY DECREASE SLIGHTLY
SUNDAY AS HIGH PRESSURE AT THE SURFACE SHIFTS WEST A BIT NEAR/WEST
OF 140W OVER THE PACIFIC. THE STEERING CURRENTS ALOFT IN OUR AREA
ARE EXTREMELY LIGHT WITH NEARLY CALM WINDS BETWEEN ABOUT 300 AND 600
MB AND JUST A LIGHT SE WIND...NOT ENOUGH TO TRANSPORT MONSOONAL
MOISTURE INTO OUR AREA...AROUND 700 MB. WHEN STEERING CURRENTS ARE
THIS LIGHT...PERSISTENCE IS USUALLY A GOOD BET.
ADRIAN IS NOW A HURRICANE...AND 850-500 MB MEAN FLOW IN THE AREA OFF
THE SW COAST OF MAINLAND MEXICO TAKES IT ON A WNW PATH. SST VALUES ARE
BELOW NORMAL ALONG THE BAJA W COAST...SO EVEN IF IT STEERS NORTH OF
ITS EXPECTED PATH...IT SHOULD HAVE LITTLE OR NO IMPACT ANYWHERE NW
OF THE S TIP OF BAJA.
THE FLOW ALOFT WILL START TO INCREASE SLIGHTLY MONDAY DUE TO THAT
PAC NW TROUGH BUT NOT ENOUGH TO REALLY CHANGE THE WEATHER. A SLIGHT
BUILDING EAST TO OUR AREA OF THE HIGH PRESSURE ALOFT OVER THE
PACIFIC MAY BRING SLIGHT WARMING TO THE COAST TUE/WED. THIS IS THE
TYPE OF HIGH PRESSURE PATTERN ALOFT WHICH CAN REDUCE THE ONSHORE
FLOW. 00Z MRF HAD THIS...AND THIS IS MORE EVIDENT ON THE NEW 12Z SAT
ECMWF SO MAYBE WE CAN FINALLY SEE AN AVERAGE OR ABOVE-AVERAGE
TEMPERATURE DAY AT LINDBERGH...ESPECIALLY SINCE OUR LOCAL SST VALUES
ARE NOW NORMAL...EVEN THOUGH THEY ARE BELOW NORMAL 300 MI N AND S
ALONG THE COAST. THIS WARMING WILL BE SHORT LIVED AS MRF AND
TO A SMALLER EXTENT ECMWF HAVE A TREND BACK TO TROUGHING LATE IN THE
WEEK.
THE CURRENT FORECAST LOOKS FINE...THOUGH ANY DENSE FOG THAT OCCURS
SHOULD BE VERY LOCAL. NO ZONE UPDATE WILL BE ISSUED THIS EVENING.
SAN 0000
.SAN...NONE.
MAXWELL