[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 011805
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU NOV 01 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
THE CENTER OF TROPICAL STORM NOEL WAS CENTERED NEAR 25.0N 77.4W
AT 01/1800 UTC OR NEAR NASSAU BAHAMAS...NOW MOVING TOWARD THE
N-NE NEAR 12 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 993 MB.
MAXIMUM SUSTAINED WIND SPEED ARE 55 KT WITH GUSTS TO 65 KT. SOME
ADDITIONAL STRENGTHENING IS POSSIBLE LATER TODAY. SEE THE NHC
FORECAST ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND THE PUBLIC ADVISORY UNDER MIATCPAT1/WTNT31 KNHC FOR MORE
DETAILS. NUMEROUS MODERATE TO STRONG CONVECTION ASSOCIATED WITH
THE SYSTEM IS MOSTLY LIMITED TO WITHIN 180 NM NE SEMICIRCLE.
SIGNIFICANT RAINFALL ACCUMULATIONS ARE EXPECTED OVER PORTIONS OF
THE BAHAMAS...WITH MINIMAL ACCUMULATIONS EXPECTED OVER SE
FLORIDA. A TROPICAL STORM WARNING REMAINS IN EFFECT FOR THE
CENTRAL AND NW BAHAMAS. THE WARNING FOR SE FLORIDA HAS BEEN
DISCONTINUED. THE STORM IS EXPECTED TO ACCELERATE TO THE NE AND
BECOME EXTRATROPICAL IN ABOUT 36 HRS. WHILE THE STORM IS
EXPECTED TO MOVE AWAY FROM FLORIDA...THE MARINE THREAT WILL NOT
END. STRONG N WINDS AND LARGE NE SWELLS ARE EXPECTED TO PERSIST
THROUGH MUCH OF THE UPCOMING WEEKEND...AS NOEL BECOMES AN
INTENSE EXTRATROPICAL CYCLONE OVER THE NW ATLC AND INTERACTS
WITH STRONG HIGH PRESSURE OVER THE MIDDLE AND EASTERN PORTIONS
OF THE UNITED STATES. SEE HIGH SEAS FORECAST UNDER AWIPS HEADER
NFDHSFAT1 AND STATEMENTS FROM LOCAL WEATHER OFFICES FOR DETAILS.

...TROPICAL WAVES...
TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 74W/75W S OF 18N
MOVING W 5-10 KT OVER THE PAST 24 HOURS. IT IS DIFFICULT TO TELL
EXACTLY WHERE THIS WAVE IS LOCATED AS MUCH OF THE ASSOCIATED
ENERGY HAS BECOME EMBEDDED WITHIN THE CLOUDINESS ASSOCIATED WITH
THE TRAILING TROUGH OF NOEL. THE MIMIC TPW ANIMATION SHOWS A WWD
MOVING SURGE OF DRY AIR WORKING ITS WAY ACROSS THE CARIB BEHIND
THE WAVE OVER THE LAST 48 HOURS. HOWEVER...GIVEN THAT THE FLOW
AROUND NOEL AND ITS TRAILING TROUGH HAVE UNDOUBTEDLY TAKEN OVER
THE FLOW IN THE REGION...THE WAVE WILL LIKELY BE DROPPED FROM
THE 1800 UTC MAP.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N14W 8N22W 5N33W 8N43W 4N53W.
SCATTERED MODERATE CONVECTION IS WITHIN 220NM EITHER SIDE OF THE
AXIS BETWEEN 18W-24W. SIMILAR ACTIVITY IS WITHIN 150NM N AND
90NM S OF THE AXIS BETWEEN 24W-32W. A TROUGH IS EMBEDDED IN THE
ITCZ ALONG 40/41W FROM 5N-16N...THAT IS GENERATING ISOLATED
SHOWERS/TSTMS WITHIN 90 NM OF THE AXIS. THIS MAY ACTUALLY BE THE
TROPICAL WAVE THAT APPEARS TO HAVE PASSED DAKAR AROUND 12Z OCT
27. HOWEVER...GIVEN ITS RATHER POOR SATELLITE APPEARANCE HAVE
OPTED TO MAKE THE FEATURE A TROUGH.

DISCUSSION...
GULF OF MEXICO...
TIGHT PRES GRADIENT BETWEEN TROPICAL STORM NOEL AND STRONG HIGH
PRES TO ITS N IS KEEPING N TO NE WINDS STRONG ACROSS THE E
GULF AS NOTED IN BUOY DATA AND RECENT SCATTEROMETER PASSES.
WINDS GENERALLY RELAX IN THE W GULF AS THE GRADIENT SLACKENS.
MOSAIC DOPPLER RADAR SHOWS BROKEN UP BANDS OF NOEL PUSHING
ACROSS S AND CENTRAL FLORIDA AND THE STRAITS. MOST OF THIS
ACTIVITY THINS OUT EVEN FURTHER AS IT TRAVERSES INTO THE GULF.
THE FLOW ALOFT IS FAIRLY ZONAL TO THE N OF A FLAT UPPER RIDGE
CENTERED OVER THE CARIBBEAN. A WEAK SHORTWAVE TROUGH OVER THE
FLORIDA PENINSULA IS BENDING THE UPPER FLOW MORE NW/WNW IN THE
ERN GULF. THIS SHORTWAVE AND A STRONGER ONE TO FOLLOW WILL BE
THE STEERING ELEMENTS CAUSING NOEL TO ACCELERATE TOWARD THE NE.
WATER VAPOR IMAGERY REVEALS WIDESPREAD DRY AIR ACROSS THE REGION
WHICH IS HELPING TO SUPPRESS SIGNIFICANT SHOWER
ACTIVITY...ESPECIALLY S OF 27N.

CARIBBEAN SEA...
SATELLITE IMAGERY AND DOPPLER RADAR DATA FROM CAMAGUEY CUBA
REVEAL HEAVY RAINS OVER THE ERN PORTION OF THE COUNTRY.
ADDITIONAL RAINFALL ACCUMULATIONS OF 2 TO 4 INCHES ARE EXPECTED
OVER EASTERN CUBA AND HISPANIOLA...WHERE THESE RAINS COULD CAUSE
LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. THE COMBINATION OF
A TRAILING TROUGH HANGING SWD FROM TROPICAL STORM NOEL...ALONG
21N80W 10N79W...IS GENERATING SCATTERED SHOWERS AND TSTMS
GENERALLY BETWEEN 73W AND 83W. THE STRONGEST SMALL CLUSTERS ARE
CURRENTLY LOCATED BETWEEN THE CAYMAN ISLANDS AND THE SW TIP OF
HAITI. ANOTHER CLUSTER OF MODERATE CONVECTION IS NEAR THE GULF
OF HONDURAS WITHIN 60NM OF 17N85W.  THE AIR DRIES OUT SOME TO
OVER THE FAR NW CARIBBEAN DRIVEN BY FRESH NWLY WINDS. THE E
CARIB IS FAIRLY TRANQUIL UNDER MODERATE TRADE WIND FLOW AND
DRIER MID/UPPER AIR ADVECTED INTO THE REGION BY NLY WINDS
BETWEEN AN UPPER LOW E OF THE AREA AND AN UPPER HIGH CENTERED
BETWEEN HISPANIOLA AND COLOMBIA.

ATLANTIC OCEAN...
THE MAIN STORY IS TROPICAL STORM NOEL WHICH HAS BEGUN ITS TURN
TO THE N-NE NEAR THE WESTERN BAHAMAS. FOR STORM SPECIFICS SEE
THE SPECIAL FEATURE SECTION ABOVE. IN ADDITION TO THE WIND FIELD
DIRECTLY ASSOCIATED WITH NOEL...THE TIGHT PRES PATTERN SET UP
BETWEEN THE TROPICAL STORM AND STRONG HIGH PRES NE OF BERMUDA IS
PRODUCING STRONG GUSTY WINDS...OCCASIONALLY TO GALE FORCE W OF
70W...AND LARGE SEAS OVER MUCH OF THE WRN ATLC. A JASON
ALTIMETER PASS FROM EARLY THIS MORNING REVEALED SEAS OF 12-14 FT
OVER THE STRAITS OF FLORIDA...WHICH WAS UNDERDONE BY ALL
AVAILABLE WAVE MODEL GUIDANCE. STRONG WINDS AND LARGE SEAS
EXPECTED TO PERSIST OVER THE WRN PORTION OF THE AREA OVER THE
NEXT COUPLE OF DAYS AS NOEL TRANSITIONS TO A POWERFUL
EXTRATROPICAL STORM. DEBRIS MOISTURE FROM NOEL'S CONVECTIVE MASS
STRETCHES FAR TO THE E ROUGHLY N OF 23N W OF ABOUT 55W. THIS
MOISTURE IS THEN FEEDING INTO THE MOISTURE ASSOCIATED WITH AN
UPPER TROUGH NEAR 50W N OF 25N. THIS TROUGH IS PROVIDING SOME
SUPPORT FOR A SLOW MOVING FRONTAL BOUNDARY WHICH ENTERS THE AREA
NEAR 32N35W AND EXTENDS MAINLY W ALONG 27N44W 28N67W. THE FRONT
IS HELPING TO TIGHTEN THE GRADIENT...WITH THIS MORNINGS QUIKSCAT
PASS SHOWING NE/E WINDS 20-30 KT BEHIND THE BOUNDARY.

A CUT-OFF UPPER LOW IN THE TROPICAL ATLC NEAR 11N53W IS
PRODUCING A SMALL AREA OF CLOUDINESS AND ISOLATED SHOWERS FROM
10N-14N BETWEEN 49W-53W. AN UPPER SW TO WLY JET EXISTS TO THE E
OF THIS UPPER LOW AND STRETCHES E TO THE COAST OF SENEGAL. THE
REMAINDER OF THE E ATLC IS FAIRLY QUIET UNDER MODERATE SFC
RIDGING AND AN ELONGATED UPPER RIDGE/TROUGH PATTERN.

$$
WILLIS




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