FXUS62 KMLB 172001 AFDMLB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MELBOURNE FL 401 PM EDT TUE SEP 17 2013 .DISCUSSION... TONIGHT... AMPLIFIED PATTERN ALOFT OVER THE CONUS CONTINUES AS A TROUGH PUSHES OFF THE EASTERN SEABOARD. AT THE SURFACE...HIGH PRESSURE BUILDING DOWN THE COAST IS TIGHTENING OUR LOCAL PRESSURE GRADIENT...LEADING TO AN INCREASE IN LOW LEVEL WINDS AND SUBSEQUENTLY AN INCREASE IN SPEED CONVERGENCE. THIS SPEED CONVERGENCE IN THE LOWER LEVELS WILL LIKELY BE THE PRIMARY MECHANISM FOR SHOWER DEVELOPMENT OVER THE NEARSHORE COASTAL WATERS. ONSHORE FLOW WILL PUSH ANY SHOWERS AND THUNDERSTORMS THAT DEVELOP OVER THE ATLANTIC TOWARDS THE COAST...AND A FEW SITES MAY SEE MULTIPLE BOUTS OF HEAVY RAINFALL...ESPECIALLY FROM SEBASTIAN INLET SOUTH. WEDNESDAY-THURSDAY... THE OVERALL WEATHER PATTERN REMAINS RELATIVELY UNCHANGED...WITH AMPLE ATMOSPHERIC MOISTURE AND A COMPRESSED PRESSURE GRADIENT ACROSS THE PENINSULA (4-5 MB DIFFERENCE FROM JAX-MIA). EASTERLY FLOW WILL TRANSPORT SHOWERS ONSHORE OUR COASTAL COUNTIES DURING THE MORNING HOURS. SHOWER ACTIVITY WILL HAVE A HARD TIME MAKING IT INLAND UNTIL SOLAR INSOLATION DESTABILIZES THINGS A BIT. A DIFFUSE EAST COAST SEA BREEZE AND LEFTOVER OUTFLOW BOUNDARIES FROM THE ATLANTIC CONVECTION WILL LIKELY PROVIDE THE TRIGGER FOR SCATTERED SHOWER AND ISOLATED THUNDERSTORM DEVELOPMENT OVER THE INTERIOR TOMORROW AFTERNOON. .LONG TERM (MODIFIED PREVIOUS DISCUSSION)... FRI...THE LOCAL PRESSURE GRADIENT SLACKENS AND ONSHORE FLOW WEAKENS IN RESPONSE TO THE HIGH TO THE NORTH WEAKENING AND MOVING FARTHER INTO THE ATLANTIC. FRI APPEARS TO BE THE DRIEST DAY OF THE WEEK AS BOTH MODELS STILL SHOW A PUSH OF DRIER AIR AS A SHORTWAVE RIDGE MOVES ACROSS THE SOUTHEAST. SAT-TUES...THE 00Z GFS CHANGED ITS TUNE DRAMATICALLY EARLIER THIS MORNING IN THE EVOLUTION OF THE BROAD AREA OF LOW PRESSURE OVER THE GULF OF MEXICO OVER THE WEEKEND INTO EARLY NEXT WEEK. IT NOW DEPICTS A CONSIDERABLY STRONGER UPPER LEVEL TROUGH/LOW SWINGING THROUGH THE MISSISSIPPI AND TENNESSEE VALLEYS...ALONG WITH STRONG BAROCLINIC CYCLOGENESIS ALONG THE NORTHERN GULF AND EAST COAST. THIS SWINGS THROUGH A DECENT COLD FRONT THROUGH MOST OF THE STATE LEAVING BEHIND A VERY UNORGANIZED AREA OF LOWER PRESSURE ALONG THE FRONT IN THE BAY OF CAMPECHE. THE 12Z GFS SUBSEQUENTLY BACKED OFF ON SUCH A BULLISH EVOLUTION...DEPICTING A WEAKER LOW PRESSURE SYSTEM AND KEEPING A COLD FRONT FURTHER TO OUR NORTH. THE 00Z ECMWF REMAINS CLOSE TO THE PREVIOUS MODEL SOLUTIONS WITH A WEAKER TROUGH AND BROADER DOUBLE BARRELED (BAROCLINIC NORTH/TROPICAL SOUTH) AREA OF LOW PRESSURE OVER THE GULF ON SUN WHICH THEN LIFTS OUT IN THE GENERAL VICINITY OF FLORIDA AND THE BAHAMAS INTO MID NEXT WEEK. BOTH SCENARIOS LOOK COMPLEX...AND THE UNCERTAINTIES IN INTENSITY AND STRUCTURE OF ANY LOW THAT WOULD POTENTIALLY IMPACT THE AREA ARE QUITE LARGE. BUT REGARDLESS OF HOW THIS FEATURE DEVELOPS...IT APPEARS WE ARE HEADED TOWARD A WETTER PERIOD FOR AT LEAST THE FIRST HALF OF NEXT WEEK. && .AVIATION... DEEP EASTERLY FLOW WILL KEEP A CHANCE OF ONSHORE MOVING SHOWERS ACROSS OUR COASTAL SECTIONS...WITH SLIGHTLY HIGHER CHANCES FROM KVRB-KFPR-KSUA. INLAND SITES SHOULD REMAIN RAIN FREE DURING THE OVERNIGHT PERIOD AFTER SHOWERS DISAPPATE THIS EVENING. EASTERLY FLOW BETWEEN 5-10 KTS CONTINUES OVERNIGHT...SLIGHTLY HIGHER AT COASTAL SITES. && .MARINE... COMPRESSED SURFACE PRESSURE GRADIENT ELEVATES WINDS AND SEAS TONIGHT. WAVES UP TO 6 FEET ARE ADVERTISED FOR OUR OFFSHORE LEGS FROM SEBASTIAN INLET NORTH. SMALL CRAFT SHOULD EXERCISE CAUTION OVERNIGHT TONIGHT IN THESE AREAS. HIGHER COVERAGE OF SHOWERS AND ISOLATED STORMS EXPECTED FROM CAPE CANAVERAL SOUTH. WED-THURS...MODERATE ONSHORE FLOW CONTINUES INTO WEDNESDAY... ESPECIALLY NORTH OF SEBASTIAN INLET WITH EAST-NORTHEAST WINDS AROUND 15KTS...OCCASIONALLY 15-20KTS WELL OFFSHORE. WINDS SOUTH OF THE INLET WILL BE AROUND 10-15KTS UNDER A WEAKER GRADIENT. THERE WILL BE A SLOW DECLINE OF WINDS INTO THURSDAY AS THE HIGH TO THE NORTH WEAKENS WITH WINDS BECOMING 10-15KTS BY LATE IN THE DAY. THE LONG EAST-NORTHEAST FETCH WILL KEEP SEAS ELEVATED BOTH DAYS WITH 4-6FT NEARSHORE AND UP TO 7 FEET WELL OFFSHORE NORTH OF THE CAPE. THIS IS THE FIRST MODEL RUN SHOWING SEAS MAKING IT UP THAT HIGH...AND IF IT PERSISTS AN SCA FOR SEAS MAY BE NEEDED. DOMINANT WAVE PERIODS WILL LIKELY BE MIXED BETWEEN THE 5-6SEC WIND WAVE AND 12-14 SEC SWELL. FRI-SUN...ONSHORE FLOW SLOWLY WEAKENS ON FRI AND SAT AS HIGH TO THE NORTH ALSO WEAKENS AND MOVES FURTHER INTO THE ATLANTIC. EAST-SOUTHEAST WINDS AROUND 10KTS. SEAS SLOWLY SUBSIDE TO 4-5FT ON FRI AND 3-4FT SAT. BEYOND SAT...FORECAST BECOME UNCERTAIN AS MODEL SOLUTIONS DIFFER IN HANDLING A BROAD LOW FORECAST TO MOVE ACROSS THE GULF AND FLORIDA EARLY NEXT WEEK. && .PRELIMINARY POINT TEMPS/POPS... DAB 76 87 75 86 / 30 40 30 30 MCO 74 90 73 90 / 20 40 10 30 MLB 76 87 77 87 / 30 50 30 30 VRB 74 89 75 88 / 30 50 40 40 LEE 74 91 73 89 / 20 40 10 30 SFB 75 90 73 89 / 20 40 10 30 ORL 75 90 75 89 / 20 40 10 30 FPR 75 87 74 88 / 30 50 40 40 && .MLB WATCHES/WARNINGS/ADVISORIES... FL...NONE. AM...NONE. && $$ AVIATION/FORECASTS...ULRICH RADAR/IMPACT WEATHER....LASCODY PALMBAYWEATHER.info
Posted on: Tue, 17 Sep 2013 20:01:30 +0000
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