SWODY3
SPC AC 030729
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0229 AM CDT SUN APR 03 2011
VALID 051200Z - 061200Z
...SYNOPSIS...
THE 03/00Z ECMWF IS IN GREATER AGREEMENT WITH THE 02/21Z SREF MEAN
500 MB HEIGHTS...BUT REMAINS A LITTLE SLOWER THAN THE 03/00Z GFS AND
SWD WITH STRONGER FORCING ALOFT INTO THE SERN STATES BY 12Z TUESDAY.
EACH MODEL MOVES THIS TROUGH OFF THE EAST COAST TUESDAY NIGHT. IN
THE LOW LEVELS...GIVEN TIMING DIFFERENCES WITH THE MID-UPPER LEVEL
TROUGH...THE INITIAL POSITION OF THE COLD FRONT AT 12Z TUESDAY
VARIES BETWEEN THE ECMWF...GFS AND SREF MEAN SURFACE PRESSURE FIELD.
THE LATTER TWO MODELS AND A MAJORITY OF THE SREF MEMBERS POSITION
THIS FRONT FROM THE MID ATLANTIC COAST SWWD THROUGH NRN FL AT THE
START OF DAY 3...WITH THE ECMWF MORE INLAND FROM CENTRAL VA TO ERN
GA. DESPITE THESE DIFFERENCES...MODELS DO AGREE THE COLD FRONT WILL
MOVE OFF THE EAST COAST THIS FORECAST PERIOD AND SWD THROUGH THE FL
PENINSULA.
...FL PENINSULA...
MOISTENING OF THE AIR MASS ACROSS THE FL PENINSULA IS EXPECTED PRIOR
TO THE START OF DAY 3 /TUESDAY/...WITH SURFACE DEWPOINTS IN THE MID
60S LIKELY OVER NRN/CENTRAL FL AND AROUND 70F ALONG THE WEST COAST
AND OVER S FL. DESPITE MODEST MIDLEVEL LAPSE RATES /6.5-7 C PER KM/
ACROSS FL...SURFACE HEATING S OF THE COLD FRONT COMBINED WITH THE
AVAILABLE MOISTURE SHOULD RESULT IN MODERATE INSTABILITY. SHOWERS
AND TSTMS WILL BE LIKELY AS THE COLD FRONT MOVES SWD ENCOUNTERING
THE UNSTABLE AIR MASS. STRONGER FORCING FOR ASCENT SHOULD REMAIN N
OF FL WITH VEERING LOW LEVEL WINDS TENDING TO LIMIT LOW LEVEL
CONVERGENCE...AND THE POTENTIAL FOR MORE WIDESPREAD ROBUST UPDRAFTS.
MODEL GUIDANCE SUGGESTS A WEAK IMPULSE MAY MOVE ACROSS FL TO
SUPPORT PRE-FRONTAL CONVECTIVE DEVELOPMENT...IN ADDITION TO THE
CONVECTION EXPECTED ALONG THE FRONT. EFFECTIVE BULK SHEAR IS
EXPECTED TO DECREASE THROUGH THE DAY WHICH WILL TEND TO LIMIT THE
OVERALL SEVERE WEATHER THREAT.
...SERN GA AND ERN CAROLINAS...
GIVEN MODEL DIFFERENCES WITH THE PLACEMENT OF THE COLD FRONT ACROSS
THESE STATES AT THE START OF DAY 3...A 5 PERCENT SEVERE WEATHER
THREAT IS BEING INTRODUCED. IF THE ECMWF IS THE MORE CORRECT MODEL
IN LATER OUTLOOKS...THEN PARTS OF THIS REGION MAY NEED TO BE
UPGRADED TO A SLIGHT RISK. DESPITE WEAK INSTABILITY WITH NWD EXTENT
ACROSS THIS REGION...STRONG SLY LOW LEVEL WINDS WOULD SUPPORT AT
LEAST A DAMAGING WIND THREAT DURING THE FIRST HALF OF THE PERIOD
PRIOR TO THE FRONT MOVING OFFSHORE.
..PETERS.. 04/03/2011
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