Spring Hill, Florida Area
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09-23-2009, 02:29 PM
Post: #926
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Spring Hill, Florida Area
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FXUS62 KTBW 231733 AFDTBW AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TAMPA BAY RUSKIN FL 133 PM EDT WED SEP 23 2009 .SYNOPSIS...ALOFT NORTH AMERICA EARLY THIS AFTERNOON - A RIDGE REACHES FROM SW CANADA TO SOUTH CA...A LOW SPINS ALONG THE NE/KS BORDER...TROUGHING OVER EASTERN CANADA BRUSHES NEW ENGLAND...AND A RIDGE STRETCHES FROM MEXICO TO THE SE U.S. AT THE SURFACE...A LOW IS OVER EASTERN NE/KS WITH A FRONT SOUTH TO TX. A STATIONARY FRONT EXTENDS FROM TX COASTAL WATERS TO THE LOWER GREAT LAKES. HIGH PRESSURE OVER THE OPEN ATLANTIC ALONG LATITUDE 40 NORTH RIDGES TO THE U.S. COAST BETWEEN FL AND THE MID-ATLANTIC STATES. AN INVERTED TROUGH...THE REMNANTS OF FRED...EMBEDDED IN THE SOUTH SIDE OF THE SURFACE RIDGE IS ALONG THE FL TO NC COAST. && .SHORT TERM (TONIGHT - FRIDAY)...THE PATTERN ALOFT THE NATION CHANGES LITTLE WITH THE UPPER RIDGE DOMINATING AS IT SETTLES SOUTHWARD ACROSS THE AREA. THE INVERTED TROUGH/REMNANTS OF FRED/ DISSIPATES AS IT LIFTS UP TO THE NW WHILE THE ATLANTIC HIGH PRESSURE WEAKENS AND SAGS SOUTH...ALLOWING THE GRADIENT TO SLACKEN WITH EASTERLY FLOW OVER FL AND THE GULF. THE EAST COAST MORNING CONVECTION DISSIPATED FOR THE MOST PART BEFORE REACHING THE CWA. HOWEVER..A FEW SHOWERS SHOWERS AND THUNDER- STORMS ARE NOW OVER AND EAST OF CHARLOTTE AND LEE COUNTIES. WITH THE MOIST ATMOSPHERE AND THE EXPECTED SEA BREEZE...THE CURRENT POPS OF 30-50-40 FROM COASTAL WATERS TO INTERIOR SEEM REASONABLE AND WILL LEAVE AS IS. ACTIVITY WILL BECOME ISOLATED AND THEN END IN THE EARLY EVENING. LIGHT ENE WINDS ALONG WITH ANY RESIDUAL MOISTURE COULD RESULT IN LATE NIGHT PATCHY FOG FROM PINELLAS...HILLSBOROUGH...AND POLK NORTH AND PLACED IN THE GRIDS AND FORECASTS. FOR THU AND FRI...THE PATTERN CONTINUES WITH SCATTERED AFTERNOON... ISOLATED EVENING SHOWERS/THUNDERSTORMS AS THE SEA BREEZE BOUNDARY PROVIDES A FOCUS. THE UPPER RIDGE SHIFTING SOUTH WILL SUPPRESS POPS FROM 40/50 THU TO 30 FRI. IN ADDITION THE RIDGE WILL HELP KEEP TEMPERATURES ABOVE NORMAL BY A COUPLE OF DEGREES. .LONG TERM (FRIDAY NIGHT - WEDNESDAY)...MODELS REMAIN FAIRLY CONSISTENT DURING THE FIRST HALF OF THE LONG TERM...THEN DIFFER SOME WITH RESPECT TO TIMING AND SPEED OF THE NEXT UPSTREAM COLD FRONT PROGD TO APPROACH THE REGION LATE IN THE WEEKEND AND INTO EARLY NEXT WEEK WITH THE ECMWF CONTINUING TO BE FASTER THAN THE GFS. GIVEN THE DIFFERENCES WILL CONTINUE WITH A BLEND FOR NOW UNTIL BETTER MODEL CONTINUITY DEVELOPS. AS FOR THE DETAILS OF THE FORECAST DEEP LAYERED RIDGING OVER THE DEEP SOUTH AND FLORIDA WITH A SURFACE RIDGE AXIS WELL TO THE NORTH WILL REMAIN IN CONTROL THROUGH EARLY MONDAY. DRY AIR ADVECTING IN FROM THE ATLANTIC COMBINED WITH INCREASED SUBSIDENCE FROM THE UPPER RIDGE WILL KEEP RAIN CHANCE BELOW NORMAL (POPS 20% AT BEST) AND TEMPERATURES ABOVE NORMAL THROUGH THE PERIOD. DURING EARLY NEXT WEEK A DEVELOPING UPPER TROUGH OVER THE EASTERN U.S. WILL SUPPRESS THE UPPER RIDGE SOUTHWARD AS AN ATTENDANT COLD FRONT MOVES INTO THE DEEP SOUTH. AS MENTIONED ABOVE DIFFERENCES IN THE MODELS LEADS TO LOW CONFIDENCE AND SOME UNCERTAINTY IN THE FORECAST WITH RESPECT TO JUST HOW FAR SOUTH THIS FRONT WILL MOVE. SEEING THAT MOST OF THE UPPER SUPPORT ASSOCIATED WITH IT WILL REMAIN WELL TO THE NORTH OF THE REGION CONTINUE TO PREFER THE SLOWER LOOKING GFS SOLUTION WITH THE FRONT LIKELY TO STALL AND WASH OUT ACROSS THE CENTRAL PENINSULA ON TUESDAY. GIVEN THIS WILL DEPICT POPS IN THE 30-40% RANGE OVER THE NATURE COAST ON MONDAY WITH 20% POPS CONTINUING CENTRAL AND SOUTH...THEN WILL SHOW A 20-40% POP GRADIENT SOUTH TO NORTH ON TUESDAY AS THE FRONT SAGS INTO THE REGION. MODELS STILL SHOW SIGNIFICANTLY DRIER AIR MOVING INTO WEST CENTRAL FLORIDA ON WEDNESDAY IN THE WAKE OF THE FRONT AS SURFACE HIGH PRESSURE BUILDS IN FROM THE NORTH. TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH TUESDAY...THEN RETURN TO NEAR NORMAL ON WEDNESDAY. && .AVIATION...BRIEF MVFR CEILINGS AND VISIBILITIES MAY IMPACT THE TERMINAL SITES FROM MID AFTERNOON (AFTER 20Z) ON THROUGH THE EARLY EVENING AS SCATTERED SHOWERS AND ISOLATED STORMS DEVELOP OVER THE REGION. OUTSIDE OF THE CONVECTION VFR CONDITIONS ARE EXPECTED. THE SHOWERS AND STORMS WILL WIND DOWN BY MID EVENING TONIGHT...WITH VFR CONDITIONS EXPECTED AT ALL TERMINAL SITES OVERNIGHT...BUT SIMILAR TO THIS MORNING MAY AGAIN SEE SOME BRIEF IFR/LIFR CEILINGS DEVELOP TOWARD SUNRISE ON THURSDAY MORNING NEAR KTPA/KPIE TERMINALS. && .MARINE...HIGH PRESSURE CONTINUES OVER THE COASTAL WATERS THROUGH THE END OF THE WEEK WITH EASTERLY WINDS...EXCEPT SHIFTING TO ONSHORE IN AFTERNOON SEA BREEZES NEAR THE COAST. THE HIGH PRESSURE WILL SAG SOUTH DURING THE WEEKEND AND MON WITH WINDS BECOMING SE AND THEN SW OR WEST. SPEEDS WILL BE AROUND 10KT OR LESS WITH THE MAIN CONCERN ISOLATED TO SCATTERED THUNDERSTORMS. && .FIRE WEATHER...NO CONCERNS. && .PRELIMINARY POINT TEMPS/POPS... TPA 75 91 76 92 / 20 50 20 30 FMY 76 92 74 92 / 20 50 20 30 GIF 74 92 75 93 / 20 40 20 30 SRQ 74 90 74 92 / 20 50 20 30 BKV 73 91 73 92 / 20 50 20 30 SPG 78 90 79 90 / 20 50 20 30 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...NONE. Twitter updates we will follow you back http://twitter.com/Hardcoreweather Now on Facebook We will like you back http://www.facebook.com/pages/Hardcorewe...466?v=wall |
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