[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 311136
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST MON DEC 31 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1115 UTC

...SPECIAL FEATURE...
A LARGE LOW PRES SYSTEM IS LOCATED ABOUT 850 NM SW OF THE AZORES
NEAR 26N36W. A FORTUITOUS REPORT FROM DRIFTING BUOY 62901 AT 00Z
REPORTED A PRES OF 1004.6 MB VERY NEAR THE LOW-LEVEL
CENTER...ACCORDINGLY THE MIN PRES WAS DROPPED TO 1004 MB.
HOWEVER...THE OVERALL CLOUD PATTERN HAS DETERIORATED SINCE THAT
TIME SO IT IS POSSIBLE THAT THE PRES MAY HAVE INCREASED
SLIGHTLY. EARLIER THIS MORNING...CONVECTION WAS MOST ORGANIZED
IN THE NW QUADRANT AND WAS GENERALLY MODERATE IN NATURE...CLOUD
TOPS NEAR -60 C...ACROSS THE QUADRANT. THIS CONVECTION HAS NOW
ROTATED TO THE SW QUADRANT AND HAS GENERALLY DECREASED IN AERIAL
COVERAGE AS MODERATE CONVECTION IS CONFINED FROM 25N-27N BETWEEN
37W-39W. AN ASCAT PASS AROUND 00Z REVEALED A FEW 45 KT WIND
VECTORS NEAR THE SWATH EDGE IN THE NW SEMICIRCLE...WHERE THE
PRESSURE GRADIENT IS TIGHTEST DUE TO HIGH PRES CENTERED TO THE
NW. AT ABOUT THE SAME TIME...A VERY CONVENIENT JASON ALTIMETER
PASS CROSSED THE CIRCULATION REPORTING MAX SEAS NEAR 26 FT AND A
300 NM 12 FT SEA RADII N OF THE CENTER. MORE RECENTLY...A QSCAT
PASS AROUND 0830Z SHOWED A FEW BELIEVABLE 40 KT WIND VECTORS W
OF THE CENTER.

AFTER MEANDERING ABOUT FOR THE PAST SEVERAL DAYS THE SYSTEM
APPEARS TO BE ON A CONSISTENT SW HEADING AS AN UPPER SHORTWAVE
HAS PASSED TO THE NE ALLOWING A BUILDING MID-LEVEL RIDGE TO BE
THE MAIN STEERING ELEMENT. NUMERICAL MODEL GUIDANCE IS IN GOOD
AGREEMENT IN CONTINUING THIS MOTION AS IT WEAKENS TO AN OPEN
TROUGH. THIS LOW...OR WHAT EVER IS LEFT OF IT...WILL LIKELY GET
PICKED UP AND ABSORBED BY A LARGE UPPER TROUGH AND FRONTAL ZONE
LATER THIS WEEK.

...THE ITCZ...
THE ITCZ EXTENDS FROM THE LIBERIA COAST NEAR 6N10W ALONG 3N15W
2N23W 3N36W EQ45W. SCATTERED MODERATE CONVECTION IS FROM 2N-4N
BETWEEN 46W-49W. A WEAK TROUGH ALONG 43W IS ENHANCING SCATTERED
MODERATE CONVECTION WITHIN 180 NM E OF THE AXIS FROM 3N-5N.

...DISCUSSION...
GULF OF MEXICO...
A LINGERING FRONTAL BOUNDARY IS GRADUALLY WEAKENING AND
BEGINNING TO STALL ONCE AGAIN FROM THE BIG BEND AREA OF FLORIDA
NEAR 29N83W TO THE BAY OF CAMPECHE AND THEN NWD ALONG THE E
SLOPES OF THE SIERRA MADRE MOUNTAINS IN MEXICO ALONG 27N87W
19N94W 22N99W. MOSAIC DOPPLER RADAR REVEALS THINNING WEAK LINES
OF SHOWERS AND ISOLATED TSTMS AHEAD OF THE FRONT OVER CENTRAL
FLORIDA.  BROKEN CLOUDS AND ISOLATED TO SCATTERED SHOWERS ARE
ANTICIPATED WITHIN 120 NM W OF THE FRONT. SCATTERED SHOWERS AND
TSTMS ARE AHEAD OF THE FRONT MAINLY E OF 89W IN STRONG SWLY FLOW
ALOFT. A BIG AIRMASS CHANGE IS ON THE WAY AS A STRONG COLD FRONT
MOVES INTO THE NW WATERS MON EVENING AND TRACKS RAPIDLY ACROSS
THE AREA...CLEARING THE ENTIRE REGION BY TUE EVENING. NLY GALE
FORCE WINDS ARE FORECAST BEHIND THE FRONT USHERING IN POSSIBLY
THE COLDEST AIR OF THIS WINTER SEASON FOR SOME PARTS OF THE
GULF.

CARIBBEAN SEA...
TRANQUIL CONDITIONS PREVAIL ACROSS THE CARIB BENEATH AN
AMPLIFIED MID TO UPPER HIGH CENTERED JUST S OF HAITI. WIDESPREAD
DRY AIR ALOFT IS EVIDENT ON WATER VAPOR IMAGES ESPECIALLY
E OF THE HIGH WHERE THE FLOW ALOFT IS CONFLUENT DUE TO THE
PRESENCE OF AN ELONGATED TROUGH E OF THE AREA. THIS STABLE
AIRMASS IS SUPPRESSING THE DEVELOPMENT OF ORGANIZED DEEP
CLOUDINESS. PATCHY MID-HIGH LEVEL CLOUDS ARE STREAMING NWD ON
THE W SIDE OF THE HIGH W OF 80W. A FEW SHORT LIVED TSTMS HAVE
POPPED UP DURING THE OVERNIGHT HOURS NEAR THE YUCATAN CHANNEL
ENHANCED BY STRONG SWLY FLOW ALOFT. TRADE WINDS ARE ON THE
STRONG SIDE IN THE S CENTRAL CARIB AND EXPECTED TO REMAIN THAT
WAY OVER THE NEXT COUPLE OF DAYS. NLY WINDS ARE ANTICIPATED TO
INCREASE TO NEAR GALE FORCE IN THE NW CARIB BEHIND A STRONG COLD
FRONT TUE NIGHT AND WED.

ATLANTIC OCEAN...
BESIDES FOR THE SPECIAL FEATURE DISCUSSED ABOVE...THE ATLC
REGION IS VERY QUIET WITH HIGH PRES RIDGING DOMINATING THE SFC
PATTERN SUPPORTED BY CENTERS LOCATED N OF THE DISCUSSION AREA.
IN THE MID AND UPPER LEVELS...A SPRAWLING AMPLIFIED RIDGE
CENTERED IN THE CARIB COVERS THE AREA W OF 55W. SCATTERED CLOUDS
AND A FEW SHOWERS ARE OVER FLORIDA AND THE ATLC WATERS W OF 75W
ASSOCIATED WITH DIFFLUENCE ALOFT BETWEEN THIS RIDGE AND A TROUGH
FARTHER W. LARGE SCALE TROUGHING COVERS A GOOD PORTION OF THE
CENTRAL AND E ATLC EXTENDING FROM THE SPECIAL FEATURE SW TO THE
LESSER ANTILLES. A SWLY JET...WITH CORE WINDS OF 100 KT OR
SO...ORIGINATES JUST E OF THE TROUGH BASE NEAR 12N56W AND
EXTENDS NE TO AFRICA THRU 23N16W. UPPER DIFFLUENCE TO THE RIGHT
OF THE JET AXIS IS GENERATING AND ADVECTING DENSE MID-HIGH LEVEL
CLOUDS AND EMBEDDED SHOWERS WITHIN 480 NM S OF THE AXIS.

$$
CANGIALOSI




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