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Show Area Forecast Discussion - Key West, FL (Florida Keys) Selection: |
| #512391 (Received by flhurricane at: 8:29 PM 21.May.2012) AFDKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 822 PM EDT MON MAY 21 2012 .DISCUSSION... .CURRENTLY... THE MORNING SOUNDING WAS ALMOST IDENTICAL TO LAST EVENINGS SOUNDING WITH PLENTY OF DRY AIR IN THE MID LAYERS OF THE ATMOSPHERE. WATER VAPOR SATELLITE LOOP SHOWS MOISTURE RETURNING TO THE MID LAYERS FROM THE SOUTH AS CYCLONIC CURVATURE APPEARS TO BE DEVELOPING ALOFT NORTH OF THE YUCATAN CHANNEL...AND THE EVENING SOUNDING SUPPORTS THE IDEA OF MORE MOISTURE ENTERING THE AREA WITH 1.8 INCHES OF PWAT...0.3 INCHES MORE THAN THE PREVIOUS TWO RELEASES. A FEW SHOWERS HAVE POPPED UP NEAR THE WESTERN EDGE OF KEY WEST ON THE KBYX RADAR THIS EVENING. SOME OF THE CUBAN SEA BREEZE HAS ENTERED THE STRAITS BEYOND 30 NM SOUTH OF THE ISLAND CHAIN AND IS FALLING APART. THE OUTFLOW BOUNDARIES FROM THIS EARLIER CONVECTION ARE MOVING NORTHWARD AND WE WILL WAIT TO SEE IF ANY SHOWERS SPAWN FROM THESE. WINDS ARE LIGHT OUT OF THE SOUTHEAST AROUND 10 KNOTS AT C-MAN STATIONS...AND 5 TO 10 KNOTS AT THE ISLAND TERMINALS. .FORECAST... THE CYCLONIC CURVATURE IN THE WATER VAPOR IS AN INDICATION OF A MID LEVEL LOW BEGINNING TO FORM NEAR THE YUCATAN CHANNEL. MODEL GUIDANCE HAS BEEN SHOWING THIS POSSIBILITY FOR SEVERAL DAYS AND HAS GOOD AGREEMENT IN TIMING BUT SOME SUBTLE DIFFERENCES IN INTENSITY. WITH THAT IN MIND PLENTY OF SHEAR THROUGH THE ENVIRONMENT WILL LIMIT THE DEVELOPMENT OF THE LOW AND HELP TO BREAK IT APART WEDNESDAY AS A UPPER LEVEL TROUGH MOVES OVER THE EASTERN GULF OF MEXICO. AS FOR RAIN CHANCES ALONG THE KEYS...EXPECT NO CHANGES IN THE FORECAST DUE TO THE ADDITION OF MOISTURE AND THE FAVORABLE ENTRANCE REGION OF THE UPPER LEVEL JET NEAR THE KEYS FOR THE NEXT FEW DAYS. && .MARINE... LIGHT AND VARIABLE EAST TO SOUTHEAST BREEZES NEAR 10 KNOTS WITH SCATTERED SHOWERS AND A FEW THUNDERSTORMS DEVELOPING TONIGHT MAINLY OVER THE FLORIDA STRAITS. MOVEMENT OF INDIVIDUAL CELLS WILL BE NEAR 5 KNOTS OR LESS. WINDS WILL EVENTUALLY TURN OUT OF THE EAST AND SOUTHEAST AND FRESHEN TOWARD THE END OF THE WEEK. && .AVIATION... SHORT-LIVED MVFR CEILINGS ARE POSSIBLE AT EYW AND MTH TONIGHT. DUE TO THE BRIEF NATURE (LESS THAN 30 MINUTES) OF POTENTIAL MVFR CEILINGS...ONLY VFR CONDITIONS WILL BE ADVERTISED IN THE TERMINAL FORECASTS TONIGHT. PROLONGED MVFR CONDITIONS ARE POSSIBLE AT EYW AND MTH TUESDAY AFTERNOON. FORECAST CONFIDENCE OF MVFR CONDITIONS TUESDAY AFTERNOON IS NOT HIGH ENOUGH TO INCLUDE IN THE TERMINAL FORECASTS AT THIS TIME. && .CLIMATE... ON THIS DATE IN KEYS WEATHER HISTORY...IN 1875...THE HIGH TEMPERATURE IN KEY WEST WAS ONLY 74 DEGREES. THIS SET THE DAILY RECORD FOR COOLEST MAXIMUM TEMPERATURE MEASURED IN KEY WEST ON MAY 21ST...A RECORD WHICH STILL STANDS 137 YEARS LATER. TEMPERATURE RECORDS AT KEY WEST DATE BACK TO 1872. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ |
| #512321 (Received by flhurricane at: 2:59 PM 21.May.2012) AFDKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 253 PM EDT MON MAY 21 2012 .DISCUSSION... SHOWER COVERAGE HAS BEEN ISOLATED OVER MOST OF THE SERVICE AREA FOR MUCH OF THE DAY. HOWEVER...IN THE LAST HOUR OR TWO...A CUMULUS CONGESTUS CLOUD LINE WHICH HAD BEEN HOVERING OVER OR NEAR THE LOWER KEYS SINCE LATE MORNING...BEGAN TO GROW WITH SEVERAL SHOWERING CLOUDS WETTING COMMUNITIES BETWEEN BIG PINE KEY AND KEY WEST. THE LARGE-SCALE WEATHER PATTERN HAS NOT CHANGED IN ANY ABRUPT WAY FOR SEVERAL DAYS. THE KEYS STILL LIE AT THE INTERFACE BETWEEN SPRING AND SUMMER...MIDLATITUDES AND TROPICS...DRY AND WET...WHICH IS NOT THAT UNUSUAL FOR LATE MAY. A DEEP PLUME OF RICH TROPICAL MOISTURE RESIDES OVER THE NORTHWEST CARIBBEAN SEA JUST SOUTH OF THE SERVICE AREA...AND THIS PLUME IS LIKELY TO AT LEAST BRUSH THE AREA ON AND OFF FOR SEVERAL DAYS. A PERSISTENT BROAD LOW-LEVEL TROUGH WILL REMAIN FROM THE KEYS TO THE YUCATAN WHILE A LARGE-SCALE TROUGH AND ASSOCIATED UPPER JET AND MIGRATORY DISTURBANCES WILL REMAIN FROM THE KEYS NORTHWARD. THIS ALL POINTS TO A CONTINUED UNSETTLED WEATHER PATTERN FOR MUCH OF THE WEEK WITH ABOVE-AVERAGE CLOUD COVER...RAIN CHANCES...AND RAINFALL TOTALS. FORECAST REASONING HAS NOT CHANGED APPRECIABLY IN AT LEAST A FEW CYCLES...AND WE WILL NOT BE MAKING ANY MAJOR ADJUSTMENTS FOR THIS PACKAGE. && .MARINE... LIGHT AND VARIABLE BREEZES WILL PREVAIL TONIGHT WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. WINDS WILL EVENTUALLY TURN OUT OF THE EAST AND SOUTHEAST AND FRESHEN TOWARD THE END OF THE WEEK. && .AVIATION... A CUMULUS LINE WILL BE POSSIBLE AT THE KEY WEST TERMINAL THROUGH 00Z...SO BRIEF MVFR CIGS AND/OR VIS WILL BE POSSIBLE. ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE POSSIBLE OVERNIGHT AT BOTH KEY WEST AND MARATHON ISLAND TERMINALS...BUT EXACT TIMING IS UNCERTAIN. LIGHT AND VARIABLE WINDS WILL BECOME SOUTHEAST BETWEEN 6 AND 10 KNOTS AFTER 00Z. && .PRELIMINARY POINT TEMPS/POPS... KEY WEST 76 84 78 87 / 50 50 50 40 MARATHON 76 86 78 89 / 50 50 50 40 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ |
| #512294 (Received by flhurricane at: 11:14 AM 21.May.2012) AFDKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 1106 AM EDT MON MAY 21 2012 .DISCUSSION... A REVIEW OF MORNING GEOSTATIONARY SATELLITE IMAGES FROM THE VISIBLE CHANNEL SHOWS A LARGE AREA OF CLEAR SKIES OVER MUCH OF THE EASTERN GULF OF MEXICO AND FLORIDA PENINSULA. MEANWHILE...WIDESPREAD CLOUDINESS WITH EXTENSIVE CUMULUS CONVECTION COVERS THE NORTHWESTERN CARIBBEAN SEA...AND PORTIONS OF CUBA...THE YUCATAN CHANNEL...AND THE STRAITS OF FLORIDA. THE FLORIDA KEYS LIE AT THE INTERFACE BETWEEN THESE TWO DISTINCT WEATHER REGIMES. THE RADIOSONDE BALLOON BORNE ALOFT BY NATIONAL WEATHER SERVICE DATA COLLECTION METEOROLOGISTS EARLIER THIS MORNING REVEALED VERY WEAK WINDS IN THE BOUNDARY LAYER WHICH INCREASED ONLY MODESTLY UP TO ABOUT 20000 FEET ABOVE GROUND LEVEL. MODERATE TO STRONG WESTERLIES PREVAILED IN THE UPPER TROPOSPHERE...AS IS TYPICAL EVEN FOR LATE MAY AT THIS LOCATION. A DEEP DRY LAYER EXTENDED DOWN TO ABOUT 13000 FEET ELEVATION...WITH MUCH WETTER AIR BELOW. RECENT DOPPLER RADAR SCANS SHOW ISOLATED COVERAGE OF SHOWERS...WITH MOST DEVELOPING OVER THE STRAITS OF FLORIDA WHERE THERMODYNAMIC CONDITIONS ARE MORE FAVORABLE. IT APPEARS SYNOPTIC-SCALE VERTICAL MOTION WILL BE NEUTRAL THIS AFTERNOON...SO SIGNIFICANT CHANGES TO VERTICAL THERMODYNAMIC PROFILES ARE UNLIKELY. HEATING OVER ADJACENT LAND AREAS OF PENINSULAR SOUTH FLORIDA AND CUBA WILL INITIATE SEA BREEZES AND CUMULUS CONVECTION WHICH IS LIKELY TO INCREASE IN COVERAGE AND INTENSITY THROUGH LATE AFTERNOON. AFTERNOON SHOWERS ARE ALSO POSSIBLE OVER OR NEAR THE LOWER KEYS DUE TO DIFFERENTIAL LAND/SEA HEATING. LIMITING FACTORS WILL BE THE EXTENT OF DRY AIR ENTRAINMENT AT LOW LEVELS...ESPECIALLY CONSIDERING THAT SIGNIFICANTLY LOWER-TROPOSPHERIC AIR IS NOT FAR AWAY AT ALL TO THE NORTH. FOR NOW...THE EXISTING FORECASTS HANDLE THE SITUATION WELL. WE WILL MONITOR LATEST OBSERVATIONAL TRENDS FOR ANY CHANGES TO CURRENT REASONING. && .MARINE... LIGHT AND VARIABLE BREEZES WILL BECOME EAST AND FRESHEN TO NEAR 10 KNOTS THIS AFTERNOON. SCATTERED SHOWERS WITH A FEW THUNDERSTORMS WILL DEVELOP OVER PORTIONS OF FLORIDA KEYS COASTAL WATERS. MOVEMENT OF INDIVIDUAL CELLS WILL BE NEAR 5 KNOTS OR LESS...WITH VARIABLE MOTION VECTORS DUE TO VERY LIGHT WINDS IN THE LOWER ATMOSPHERE. && .AVIATION... THROUGH 00Z...VFR CONDITIONS WILL PREVAIL AT BOTH KEY WEST AND MARATHON ISLAND TERMINALS...BUT SHORT PERIODS OF MVFR CIGS ARE POSSIBLE THROUGH THE AFTERNOON NEAR THE KEY WEST ISLAND TERMINAL GIVEN CLOSE PROXIMITY TO A CUMULUS CLOUD LINE. WINDS WILL AVERAGE BETWEEN 5 AND 9 KNOTS FROM 130 DEGREES. SCATTERED CLOUDS ARE EXPECTED WITH BASES AT 2000-2500 AND 8000 FEET RESPECTIVELY. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ |
| #512226 (Received by flhurricane at: 4:38 AM 21.May.2012) AFDKEY AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS NATIONAL WEATHER SERVICE KEY WEST FL 429 AM EDT MON MAY 21 2012 .DISCUSSION... CURRENTLY - A LIGHT PRESSURE PATTERN REMAINS IN PLACE ACROSS THE KEYS...WITH AN AREA OF LOWER PRESSURE ACROSS THE WESTERN CARIBBEAN...THE ATLANTIC RIDGE RETREATED TO THE EAST...AND A WEAK TROPICAL CYCLONE OFF THE GEORGIA COAST. CONVECTIVE ACTIVITY HAS BEEN QUITE SUBDUED OVERNIGHT...WITH ONLY ISOLATED SHOWERS DETECTED ACROSS THE KEYS AND SURROUNDING WATERS. THIS IS DUE TO NO UPPER LEVEL SUPPORT...AND VIRTUALLY NO FLOW ACROSS THE FORECAST AREA. RADIATIONAL COOLING HAS ALLOWED TEMPERATURES FALL INTO THE LOWER 70S IN SHELTERED LOCATIONS...BUT MOST SENSORS ARE REPORTING MID TO UPPER 70S...WITH DEW POINTS NEAR 70. FORECAST - CONSIDERABLE UNCERTAINTY REMAINS DUE TO THE PRESENCE OF AN AMORPHOUS AREA OF LOWER PRESSURE IN THE WESTERN CARIBBEAN...AND AN APPROACHING SHORTWAVE TROUGH THAT WILL AMPLIFY A WEAK TROUGH IN THE SOUTHERN STREAM RUNNING ACROSS THE GULF OF MEXICO AND SOUTH FLORIDA. FOR TODAY...A WEAK SURFACE FLOW AND AS OF YET...NOTHING GOING ON ALOFT SHOULD ALLOW FOR A LOW CHANCE OF PRECIPITATION TODAY. THE MOST LIKELY SOURCE OF PRECIPITATION WILL BE ISLAND CLOUD LINES. THE SHORTWAVE TROUGH WILL MOVE THROUGH THE WEAK SOUTHERN STREAM TROUGH ON TUESDAY...EXITING AND CUTTING OFF IN THE ATLANTIC TUESDAY NIGHT INTO WEDNESDAY. THIS SHOULD REINFORCE THE DRY AIR ALOFT WITH THE DRY SUBSIDENT FLOW ON TROUGHS WESTERN FLANK. BEFORE THE DRY AIR ALOFT ARRIVES...THE NEARNESS OF DEEP TROPICAL MOISTURE ALONG WITH ANY INTERACTION BETWEEN THE SHORT WAVE TROUGH AND THE LOW LEVEL CARIBBEAN TROUGHING JUSTIFIES KEEPING AT LEAST A HIGH CHANCE POPS FOR TONIGHT INTO TUESDAY NIGHT. IT IS TOO EARLY TO TELL WHAT THE EXACT EVOLUTION OF THE CARIBBEAN TROUGHING WILL BE...BUT IT DOES APPEAR THAT THE ATLANTIC RIDGE WILL EVENTUALLY BUILD WESTWARD...FLUSHING THE TROUGH AND ASSOCIATED MOISTURE WESTWARD WITH IT. FOR NOW WILL MAINTAIN THE ABOVE NORMAL POPS THROUGH THE FORECAST PERIOD...TRENDING DOWNWARDS THIS WEEKEND. && .MARINE... A WEAK SURFACE FLOW WILL PREVAIL ACROSS KEYS WATERS THROUGH AT LEAST TONIGHT. THERE IS SIGNIFICANT UNCERTAINTY IN WIND SPEEDS FROM TUESDAY THROUGH WEDNESDAY NIGHT...DEPENDING ON THE EVOLUTION OF AN AREA OF LOWER PRESSURE IN THE WESTERN CARIBBEAN. FOR NOW WILL ADVERTISE GENTLE TO MODERATE BREEZES FROM EARLY MID WEEK AND BEYOND. && .AVIATION... THROUGH 00Z/22ND...OUTSIDE OF A FEW SPELLS OF MVFR CEILINGS ASSOCIATED WITH A CLOUD LINE ESPECIALLY AT THE KEY WEST AIRPORT...VFR CONDITIONS WILL PREVAIL AT THE ISLAND TERMINALS. VARIABLE WINDS AT LESS THAN 5 KNOTS WILL BECOME EAST TO SOUTHEAST AT LESS THAN 10 KNOTS BY AFTERNOON. && .PRELIMINARY POINT TEMPS/POPS... KEY WEST 86 76 83 78 / 30 50 50 50 MARATHON 87 76 86 78 / 30 50 50 50 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ |
