Richard
Final Approach
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- Feb 27, 2005
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Ack...city life
I'm posting this here so we can all learn. Scott, would you please explain what is going on here? The bold highlights are mine, in that section of the discussion it sounds like a gust front but I don't understand the dynamics of how a southerly wind and wx approaching from the NW would result in this. What's going on? Actually, it sounds like a lo level trof developing, but that's a WAG. Thanks a bunch.
FXUS66 KMTR 050645
AFDMTR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1045 PM PST SAT MAR 4 2006
.DISCUSSION...DEEP UPPER LOW/VERTICALLY STACKED STORM SYSTEM IS
CENTERED NEAR 44N/137W THIS EVENING. A JET MAX CAN BE SEEN ON
SATELLITE DROPPING INTO THE BASE OF THE UPPER TROUGH...AND THIS JET
WILL PROVIDE FURTHER ENHANCEMENT OVERNIGHT TO AN ALREADY INTENSE
STORM SYSTEM. LIGHT WARM ADVECTION PRECIP HAS BEEN APPROACHING THE
NORTH BAY COAST THIS EVENING. ANTICIPATE RAINFALL WILL BEGIN IN
THE NORTH BAY BY MIDNIGHT. INITIALLY RAINFALL WILL BE RATHER LIGHT
AND CONFINED TO THE NORTH BAY. THE WEATHER ITEM OF MOST CONCERN OVER
THE NEXT 12 HOURS WILL BE THE INCREASING SOUTHERLY WINDS AS THE
SURFACE GRADIENT BETWEEN A HIGH OVER SOUTHERN CA AND THE
APPROACHING STORM SYSTEM STEEPENS. AS THE FRONT APPROACHES ON
SUNDAY...WINDS ALOFT WILL INCREASE (AS HIGH AS 60 KTS AT 925
MB AS FORECAST BY THE NAM JUST OFF POINT REYES BY MIDDAY SUNDAY).
ALTHOUGH THE SURFACE GRADIENT WILL BEGIN TO SLACKEN BY SUNDAY
AFTERNOON...STRONG WINDS ALOFT AND GOOD MIXING ALONG THE FRONT WILL
PRODUCE A BURST OF HIGHER WINDS AT THE SURFACE JUST PRIOR TO FRONTAL
PASSAGE. THUS...WILL MAINTAIN A HIGH WIND WARNING THROUGH SUNDAY IN
THE NORTH BAY. FURTHER TO THE SOUTH...PRESSURE GRADIENTS AND WINDS
ALOFT ARE NOT FORECAST TO BE AS IMPRESSIVE AS IN THE NORTH BAY...BUT
THE NAM IS FORECASTING THE DEVELOPMENT OF A SURFACE WAVE ON THE FRONT
ON SUNDAY AND THIS WILL LIKELY RESULT IN HIGHER WIND SPEEDS THAN
OTHERWISE WOULD BE THE CASE. THUS...WILL CONTINUE THE HIGH WIND
WARNING FOR ALL ZONES ON SUNDAY. WINDS ARE PROJECTED TO EASE FROM N
TO S WITH FRONTAL PASSAGE AND HIGH WINDS ARE NOT EXPECTED TO BE A
PROBLEM AFTER ABOUT SIX PM ON SUNDAY...EXCEPT PERHAPS THE MONTEREY
BAY AREA WHERE STRONG WINDS COULD CONTINUE AHEAD OF THE FRONT INTO
SUNDAY EVENING. MAY NEED TO EXTEND THE HIGH WIND WARNING INTO SUNDAY
EVENING FOR THE SOUTHERN ZONES.
THE WAVE THAT IS FORECAST TO DEVELOP ALONG THE FRONT WILL FURTHER
SLOW THE SOUTHWARD PROGRESSION OF THE HEAVY PRECIP BAND ASSOCIATED
WITH THE FRONT. THE MODELS HAVE BEEN SLOWING THIS SYSTEM WITH EACH
RUN SINCE LAST EVENING AND THE 00Z NAM AND 00Z GFS BOTH CONTINUE
THIS TREND. BOTH MODELS HOLD HEAVY PRECIP OVER THE NORTH BAY
THROUGH MID-TO-LATE AFTERNOON SUNDAY...AND THEN SLOWLY SHIFT IT
SOUTH THROUGH THE REMAINDER OF THE BAY AREA LATE SUNDAY
AFTERNOON AND SUNDAY EVENING...AND FINALLY SOUTH TO THE MONTEREY BAY
AREA LATE SUNDAY NIGHT. WITH THE SLOWER MOVEMENT...RAINFALL TOTALS
ARE NOW PROJECTED TO BE HIGHER THAN WHAT WAS FORECAST AT THIS TIME
YESTERDAY....
...the rest of the discussion talks of rainfall totals and snow elevations.
FXUS66 KMTR 050645
AFDMTR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1045 PM PST SAT MAR 4 2006
.DISCUSSION...DEEP UPPER LOW/VERTICALLY STACKED STORM SYSTEM IS
CENTERED NEAR 44N/137W THIS EVENING. A JET MAX CAN BE SEEN ON
SATELLITE DROPPING INTO THE BASE OF THE UPPER TROUGH...AND THIS JET
WILL PROVIDE FURTHER ENHANCEMENT OVERNIGHT TO AN ALREADY INTENSE
STORM SYSTEM. LIGHT WARM ADVECTION PRECIP HAS BEEN APPROACHING THE
NORTH BAY COAST THIS EVENING. ANTICIPATE RAINFALL WILL BEGIN IN
THE NORTH BAY BY MIDNIGHT. INITIALLY RAINFALL WILL BE RATHER LIGHT
AND CONFINED TO THE NORTH BAY. THE WEATHER ITEM OF MOST CONCERN OVER
THE NEXT 12 HOURS WILL BE THE INCREASING SOUTHERLY WINDS AS THE
SURFACE GRADIENT BETWEEN A HIGH OVER SOUTHERN CA AND THE
APPROACHING STORM SYSTEM STEEPENS. AS THE FRONT APPROACHES ON
SUNDAY...WINDS ALOFT WILL INCREASE (AS HIGH AS 60 KTS AT 925
MB AS FORECAST BY THE NAM JUST OFF POINT REYES BY MIDDAY SUNDAY).
ALTHOUGH THE SURFACE GRADIENT WILL BEGIN TO SLACKEN BY SUNDAY
AFTERNOON...STRONG WINDS ALOFT AND GOOD MIXING ALONG THE FRONT WILL
PRODUCE A BURST OF HIGHER WINDS AT THE SURFACE JUST PRIOR TO FRONTAL
PASSAGE. THUS...WILL MAINTAIN A HIGH WIND WARNING THROUGH SUNDAY IN
THE NORTH BAY. FURTHER TO THE SOUTH...PRESSURE GRADIENTS AND WINDS
ALOFT ARE NOT FORECAST TO BE AS IMPRESSIVE AS IN THE NORTH BAY...BUT
THE NAM IS FORECASTING THE DEVELOPMENT OF A SURFACE WAVE ON THE FRONT
ON SUNDAY AND THIS WILL LIKELY RESULT IN HIGHER WIND SPEEDS THAN
OTHERWISE WOULD BE THE CASE. THUS...WILL CONTINUE THE HIGH WIND
WARNING FOR ALL ZONES ON SUNDAY. WINDS ARE PROJECTED TO EASE FROM N
TO S WITH FRONTAL PASSAGE AND HIGH WINDS ARE NOT EXPECTED TO BE A
PROBLEM AFTER ABOUT SIX PM ON SUNDAY...EXCEPT PERHAPS THE MONTEREY
BAY AREA WHERE STRONG WINDS COULD CONTINUE AHEAD OF THE FRONT INTO
SUNDAY EVENING. MAY NEED TO EXTEND THE HIGH WIND WARNING INTO SUNDAY
EVENING FOR THE SOUTHERN ZONES.
THE WAVE THAT IS FORECAST TO DEVELOP ALONG THE FRONT WILL FURTHER
SLOW THE SOUTHWARD PROGRESSION OF THE HEAVY PRECIP BAND ASSOCIATED
WITH THE FRONT. THE MODELS HAVE BEEN SLOWING THIS SYSTEM WITH EACH
RUN SINCE LAST EVENING AND THE 00Z NAM AND 00Z GFS BOTH CONTINUE
THIS TREND. BOTH MODELS HOLD HEAVY PRECIP OVER THE NORTH BAY
THROUGH MID-TO-LATE AFTERNOON SUNDAY...AND THEN SLOWLY SHIFT IT
SOUTH THROUGH THE REMAINDER OF THE BAY AREA LATE SUNDAY
AFTERNOON AND SUNDAY EVENING...AND FINALLY SOUTH TO THE MONTEREY BAY
AREA LATE SUNDAY NIGHT. WITH THE SLOWER MOVEMENT...RAINFALL TOTALS
ARE NOW PROJECTED TO BE HIGHER THAN WHAT WAS FORECAST AT THIS TIME
YESTERDAY....
...the rest of the discussion talks of rainfall totals and snow elevations.
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