FXUS62 KMLB 070742
AFDMLB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MELBOURNE FL
242 AM EST MON DEC 7 2009
.DISCUSSION...
TODAY AND TONIGHT...RUC/RTMA SURFACE ANALYZES AND LATEST BUOY OBS
STILL INDICATING A WEAK LOW OVER SOUTHEAST FLORIDA AND THE FLORIDA
STRAIT BETWEEN THE MAINLAND AND GRAND BAHAMA ISLAND. MIAMI AND
WEST PALM BEACH RADARS WERE DETECTING SHOWERS IN THE STRAIT FROM
WEST PALM SOUTH. RUC CARRIES THIS FEATURE THROUGH THE AFTERNOON
WHILE THE GFS IS HAVING A HARDER TIME RESOLVING THE FEATURE BUT
DOES PLACE LOWS IN FLORIDA BAY AND EAST IN THE NORTHERN.CENTRAL
BAHAMA ISLANDS. THE WEAK LOWS SUPPORTED BY VORT MAXES MOVING
QUICKLY WEST TO EAST IN THE PROGRESSIVE MID/UPPER LEVEL FLOW. HIGH
PRESSURE CENTERED OVER THE MID ATLANTIC STATES CONTINUES TO EAST
INTO THE WESTERN ATLANTIC AND KEEPS CENTRAL FLORIDA IN AN
ONSHORE... EAST TO SOUTHEAST...FLOW TODAY AND TONIGHT. MAIN IMPACT
OF THE LOW WILL BE TO TIGHTEN THE PRESSURE GRADIENT...INCREASE
WINDS A FEW KNOTS ABOVE GUIDANCE AND ENHANCE MOISTURE CONVERGENCE
OVER THE SOUTHERN PORTIONS OF THE MARINE AND PUBLIC FORECAST
ZONES. CARRYING 20 POP FOR THE COASTAL COUNTIES AS THE MOISTURE
CONVERGENCE LOOKS TO BE ENOUGH FOR ISOLATED SHOWERS ANYTIME TO
COME OFF THE ATLANTIC. IN SPOTS WERE CIRRUS IS NOT BLOCKING LOWER
CLOUD LAYERS MARINE LAYER STRATOCU CAN BE SEEN MOVING EAST TO WEST
ALONG THE BOTTOM OF THE HIGH PRESSURE OVER THE MID ATLANTIC
STATES. FOR TONIGHT WOULD HAVE PREFERRED TO GO ABOVE MAV SINGLE
DIGIT POP GIVEN THE DEEPENING ONSHORE FLOW HOWEVER...1000-700MB
WINDS LOOK JUST TOO LIGHT FOR ANY SIGNIFICANT OVERNIGHT COASTAL
CONVERGENCE SHOWERS TO FORM.
TUES...TWO SFC LOWS LIFT INTO THE MIDWEST AND DEEP SOUTH OUT OF THE
CENTRAL PLAINS AND WESTERN GULF BY LATE TUESDAY...PUTTING THE FL
PENINSULA INTO THE WARM SECTOR AS A WARM FRONT PASSES WELL TO OUR
NORTH AND WEST. SOUTH-SOUTHEAST FLOW WILL BRING DECENT WARM AIR
ADVECTION AND MOISTURE INTO THE AREA...WITH AFTERNOON HIGHS CLIMBING
INTO THE LOW 80S AND DEWPOINTS INTO THE UPPER 60S/NEAR 70. KEPT A
SLIGHT CHANCE FOR LATE AFTN POPS RESERVED NORTH OF THE I-4 CORRIDOR
CLOSER TO THE WARM FRONT OVER THE DEEP SOUTH.
WED-FRI...STRONG MID LATITUDE SFC LOW MOVES EAST FROM THE MIDWEST ON
WEDNESDAY WITH THE MAIN SYSTEM OVER THE LOWER GREAT LAKES AND A
SECONDARY LOW FORMING OFF THE CAROLINAS. THE POLAR AND SUBTROPICAL
JETS ARE EXPECTED TO BE PHASED ACROSS THE MID CONTINENT AT THIS
TIME...AS 500 MB FLOW REMAINS RELATIVELY ZONAL ACROSS THE COUNTRY.
WITH THE MAIN SFC LOW WELL OFFSHORE THE CANADIAN MARITIMES BY THURS
MORNING...AND LITTLE UPPER DYNAMICS...THE COLD FRONT ASSOCIATED WITH
THE LOW WILL LIMP ACROSS THE PENINSULA WED AFTN INTO THURS NIGHT.
FOR NOW...CAPPED POPS AROUND 30% FOR THAT TIME FRAME AS PINPOINTING
AN EXACT PERIOD FOR THE BEST RAIN CHANCES IS STILL A LITTLE
UNCERTAIN. TEMPERATURES WILL REMAIN WARM AND MUGGY INTO WEDNESDAY AS
THE REGION REMAINS IN ROBUST S-SW FLOW.
THE 07/00Z ECMWF IS MORE ROBUST WITH THE SFC LOW BUILDING INTO THE
SOUTHEAST ON FRIDAY...WHICH IN TURN PUSHES THE SFC FRONT FAR ENOUGH
SOUTH TO CLEAR CENTRAL FLORIDA THURS NIGHT. THE ECMWF IS ALSO ABOUT
12 HORUS SLOWER WITH THE NEXT SHORTWAVE SWINGING THROUGH THE
SOUTHERN TIER AS THE FLOW SPLITS AND THE SOUTHERN JET BECOME MORE
ACTIVE. THIS RESULTS IN TIMING DIFFERENCE BETWEEN THE GFS AND ECMWF
IN HOW QUICKLY THE NEXT SFC LOW LIFTS OUT OF THE WESTERN GULF INTO
THE SOUTHEAST. HAVE SPLIT THE DIFFERENCE FOR THE MOMENT AND
INTRODUCED A SLIGHT CHANCE OF POPS FOR FRI AND FRI NIGHT AS THE AREA
IS PLACED ONCE AGAIN INTO THE WARM SECTOR OF AN APPROACHING SYSTEM.
SAT-SUN...THE TIMING OF MID LEVEL INDIVIDUAL DISTURBANCES IN THE
SOUTHERN STREAM INTO NEXT WEEKEND ARE EVEN HARDER TO PIN
DOWN...RESULTING IN NOTABLE MODEL DIFFERENCES IN THE DEVELOPMENT
AND POSITION OF SFC LOWS. THE TAKE AWAY STORY WILL BE THAT THE
WEATHER WILL REMAIN ACTIVE INTO THE LATTER PART OF THE WEEKEND.
&&
.AVIATION...07/00Z SOUNDINGS SHOWING SOUTHWEST WINDS 15 KNOTS OR
MORE FROM AROUND 4-5000 FEET AND ABOVE WHILE BOUNDARY LAYER WINDS
WERE SOUTH TO SOUTHEAST 10 KNOTS OR LESS. THIS IS USUALLY A GOOD SET
UP FOR STRATUS OR STRATOCU AND THE MAIN QUESTION OVERNIGHT IS HOW
LOW THE CEILINGS WILL GO. THE MODELS SHOW ONSHORE FLOW IN THE
BOUNDARY LAYER WITH SOUTH/SOUTHWEST FLOW ABOVE...SO THE STRATOCU
MIGHT NOT DIMINISH DURING THE OVERNIGHT. I ESSENTIALLY MAINTAINED
THE PREVIOUS SET OF TAFS SHOWING IFR CEILINGS FOR THE NORTH. ANY
BREAK IN THE STRATOCU COULD LEAD TO IFR VISIBILITIES TOO.
&&
.MARINE...
TODAY AND TONIGHT...WEAK CIRCULATION OVER SOUTHEAST FLORIDA AND
NORTHWESTERN BAHAMA ISLANDS TIGHTENING GRADIENT BETWEEN IT AND
HIGH PRESSURE OVER THE MID ATLANTIC JUST ENOUGH FOR WINDS TO BE A
FEW KNOTS ABOVE GUIDANCE...10 TO 15/AROUND 15 KNOTS. SHOWERS
ANYTIME IN THE LOW LEVEL MOISTURE CONVERGENCE.
TUE-WED...WINDS WILL INCREASE FROM THE SE TUE AS HIGH PRESSURE MOVES
OFFSHORE EASTERN SEABOARD. WINDS SHIFT BACK TO THE SOUTHWEST
WEDNESDAY AS CTRL FL WILL BE IN THE WARM SECTOR OF LOW PRESSURE
SYSTEM MOVING ACROSS THE SOUTHEAST STATES. DEPENDING ON THE EXACT
TRACK OF THE LOW...COULD SEE AN INCREASE TO 15-20 KTS...ESPECIALLY
OFFSHORE AS LOW TRACKS NE. THERE WILL BE A CHANCE FOR SHOWERS WITH
THE FRONTAL PASSAGE FROM NORTH TO SOUTH OVER THE WATERS WED AND WED
EVE. SEAS 2-4FT NEARSHORE/3-5FT OFFSHORE.
THURS-SAT...COLD FRONTAL PASSAGE WILL BRING GUSTY NW-NE WINDS THURS
AFTERNOON INTO EARLY FRIDAY. WINDS QUICKLY FLOP AROUND TO THE EAST
AND EVENTUALLY TO THE SOUTH-SOUTHEAST BY SATURDAY AS ANOTHER SYSTEM
PULLS NE OUT OF THE WESTERN GULF INTO THE DEEP SOUTH AND THE FL
PENINSULA IS BACK IN THE WARM SECTOR. SOME MODEL DIFFERENCES IN THE
TIMING OF THE SYSTEMS DEVELOPMENT...SO NOT AS CONFIDENT ON THE
TIMING OF THE WINDS COMING AROUND TO THE S-SW BY SAT EVE. SEAS 2-4FT
NEARSHORE/3-5FT OFFSHORE...WITH THE POSSIBILITY OF LOCALLY HIGHER
SEAS IN THE GULF STREAM LATE THURS AND FRI AS WINDS COME AROUND TO
THE NE AND EAST.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 76 62 81 69 / 20 10 10 20
MCO 78 62 82 67 / 10 10 10 20
MLB 78 66 82 71 / 20 10 10 10
VRB 79 64 84 69 / 20 10 10 10
LEE 76 60 81 66 / 10 10 20 20
SFB 77 61 82 68 / 10 10 10 20
ORL 78 61 82 68 / 10 10 10 20
FPR 79 62 84 69 / 20 10 10 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...NONE.
AM...NONE.
&&
$$
SHORT TERM/AVIATION...WIMMER
LONG TERM....MOSES
