Spring Hill, Florida Area

[ROLLTIDE]

000
FXUS62 KTBW 191734
AFDTBW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL
134 PM EDT SAT SEP 19 2009

.SHORT TERM (TONIGHT-MONDAY)....MID LEVEL TROUGH OVER THE
ATLANTIC COAST WILL LIFT TO THE NORTHEAST AS A RIDGE OVER THE
PENINSULA BUILDS NORTH. THE MID LEVEL RIDGE AXIS WILL LINGER OVER
THE PENINSULA AND CENTRAL GULF THROUGH THE PERIOD. AT THE
SURFACE...HIGH PRESSURE WILL REMAIN IN PLACE OVER THE PENINSULA AS
THE REMNANTS OF FRED WILL EDGE CLOSER THE SE COAST.

FOR THE REST OF TODAY...MAINTAINED THE HIGHEST POPS FURTHER SOUTH
AS SOME EXCESS MOISTURE OVER S FL IS EXPECTED TO SHIFT NORTH. A
PERSISTENT EASTERLY FLOW WILL LIKELY GIVE WAY TO A WEAK SEA BREEZE
CIRCULATION STARTING FURTHER NORTH AND WORKING IT`S WAY SOUTH
THROUGH THE AFTERNOON...AS WAS THE CASE YESTERDAY. THEREFORE
SCATTERED SHOWERS AND THUNDERSTORMS SHOULD FORM LATER THIS
AFTERNOON AND PERSIST THROUGH THE EVENING BEFORE PUSHING OFF SHORE
LATER TONIGHT. CONVECTION ALONG THE SEA BREEZE WILL STRUGGLE TO
DRIFT EAST OF THE I 75 CORRIDOR.

FOR TOMORROW...SIMILAR PATTERN IN PLACE BUT WITH HIGHER PWATS
SPREADING ACROSS THE REGION...DECIDED TO RAISE POPS TO 50%. MODELS
HINT AT A STRONGER SEA BREEZE CIRCULATION SO WE COULD SEE BETTER
STORM COVERAGE FURTHER EAST.

FOR MONDAY...THE REMNANTS OF FRED BEGINS TO DRIFT NORTH OF THE
BAHAMAS. MODELS DIVERGE ON THE PLACEMENT OF THIS SYSTEM. NAM
BRINGS IT TOWARDS THE EAST CENTRAL FL COAST WHILE GFS AND ECMWF
KEEP IT FURTHER NORTH. DECIDED TO TAKE A BLEND OF THE GFS AND
ECMWF AND INTRODUCE A NE FLOW OVER THE INTERIOR SHIFTING TO AN
EASTERLY FLOW OVER THE COAST. KEPT SCATTERED STORMS IN THE
AFTERNOON FORECAST.

TEMPS FOR THE SHORT TERM WILL REMAIN CLOSE TO CLIMO.

.LONG TERM (MONDAY NIGHT - SATURDAY)...THE GFS/ECMWF ARE FAIRLY
CONSISTENT THROUGH MOST OF THE LONG TERM PERIOD WITH SYNOPTIC
SCALE FEATURES THEN DIVERGE SOME TOWARD THE END. STRONG UPPER
RIDGING WILL DEVELOP OVER THE PENINSULA AND ADJACENT GULF/ATLANTIC
WATERS THROUGH MUCH OF THE UPCOMING WORK WEEK IN RESPONSE TO A
STRONG DEVELOPING CUT OFF CLOSED LOW OVER THE CENTRAL U.S./4
CORNERS REGION. AT THE SURFACE HIGH PRESSURE TO THE NORTH OF THE
STATE WILL MAINTAIN AN EASTERLY WIND FLOW ACROSS THE FORECAST AREA
AS THE REMNANTS OF FRED MOVES WEST-NORTHWEST TOWARD THE CAROLINA
COAST LATE TUESDAY INTO WEDNESDAY. AMPLE MOISTURE (PW`S 1.8 -2"
RANGE) WITHIN THE EASTERLY FLOW COMBINED WITH DAYTIME HEATING WILL
HELP TO GENERATE SCATTERED DIURNAL SHOWERS AND THUNDERSTORMS (NEAR
CLIMO POPS ~40%) ALONG THE SEA BREEZE CIRCULATIONS EACH
DAY..DURING THE AFTERNOON AND EARLY EVENING HOURS.

AS MENTIONED ABOVE DIFFERENCES IN THE MODELS DEVELOP TOWARD THE END OF
THE WEEK AND INTO THE UPCOMING WEEKEND (FRIDAY/SATURDAY) AS THE GFS
FLATTENS AND RETROGRADES THE UPPER RIDGE WEST ALLOWING FOR AN EASTERN
U.S. UPPER TROUGH AN ATTENDANT COLD FRONT TO APPROACH FROM THE NORTH.
THE ECMWF ON THE OTHER HAND MAINTAINS STRONG UPPER RIDGING OVER THE
REGION AS THE AFOREMENTIONED CLOSED LOW FINALLY STARTS TO OPEN UP AND
LIFTS SLOWLY OUT TO THE NORTHEAST WELL TO THE NORTH OF THE REGION.
THESE DIFFERENCES IN THE MODELS LEADS TO LOW FORECAST CONFIDENCE DURING
THIS TIME FRAME...BUT GIVEN THE REX TYPE BLOCKING PATTERN THROUGH MUCH
OF THE PERIOD...PREFER THE MORE STAGNANT AND SLOWER CHANGING UPPER
AIR PATTERN DEPICTED BY THE ECMWF VS THE GFS...SO WILL KEEP RAIN CHANCES
NEAR CLIMO FOR NOW FOR BOTH DAYS AND WAIT TO SEE IF BETTER CONTINUITY
DEVELOPS AMONG THE MODELS DURING THE COMING WEEK. INCREASING HEIGHTS
AND WARMING TEMPERATURES ALOFT FROM THE BUILDING UPPER RIDGE WILL RESULT
IN ABOVE NORMAL TEMPERATURES WITH DAYTIME HIGHS CLIMBING TO AROUND 90
ALONG THE COAST...AND LOWER 90S INLAND...WITH OVERNIGHT LOWS IN THE MID
TO UPPER 70S.



&&

.AVIATION...BRIEF MVFR CONDITIONS MAY IMPACT THE TERMINAL SITES AFTER
20Z THIS AFTERNOON AND LAST THROUGH THE EARLY EVENING HOURS AS SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS DEVELOP ALONG THE WEST COAST SEA
BREEZE. OUTSIDE OF THE CONVECTION VFR CONDITIONS ARE EXPECTED. THE SHOWERS
AND STORMS SHOULD WIND DOWN THIS EVENING AFTER 02Z WITH VFR CONDITIONS
EXPECTED AT ALL SITES OVERNIGHT INTO SUNDAY MORNING.

&&

.MARINE...EASTERLY WINDS CURRENTLY RANGE FROM 6-8KT NEAR THE COAST
TO ABOUT 10-12 KT OFFSHORE. WITH HIGH PRESSURE DRAPED ACROSS THE
WESTERN GULF AND A PERSISTENT EAST FLOW OUTSIDE OF THE AFTERNOON
SEA BREEZE CIRCULATION...NOT EXPECTING ANY MARINE CONCERNS OUTSIDE
OF SOME ISOLATED THUNDERSTORMS IN THE LATE EVENING TO EARLY
MORNING HOURS. SEAS TO REMAIN IN THE 1-3 FT RANGE.


&&

.FIRE WEATHER...


&&

.PRELIMINARY POINT TEMPS/POPS...
TPA 76 89 76 90 / 20 50 20 40
FMY 74 91 75 92 / 20 50 20 40
GIF 75 91 75 91 / 20 50 20 40
SRQ 75 90 74 89 / 20 50 20 40
BKV 72 90 72 90 / 20 50 20 40
SPG 78 88 78 88 / 20 50 20 40

&&