[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 201751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST WED DEC 20 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...
CENTRAL AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...
NORTHEASTERN 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
1730 UTC.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 5N10W 5N22W 4N36W 2N50W. THE ITCZ IS
VERY QUIET EXCEPT FOR SCATTERED MODERATE CONVECTION WITHIN 120
NM EITHER SIDE OF THE AXIS BETWEEN 35W-50W.

...DISCUSSION...
GULF OF MEXICO...
ABUNDANT MOISTURE...ASSOCIATED WITH A LARGE LOW PRES SYSTEM IN
THE CENTRAL U.S...COVERS MUCH OF THE CENTRAL AND WRN GULF OF
MEXICO. MOSAIC DOPPLER RADAR FROM THE SE U.S. SHOWS BANDS OF
SCATTERED SHOWERS AND TSTMS FEEDING NWD IN THE WARM SECTOR
ACROSS E TEXAS AND LOUISIANA. THIS MOISTURE THEN ROTATES AROUND
A MID-UPPER LEVEL HIGH ALIGNED FROM THE YUCATAN PENINSULA ACROSS
CENTRAL FLORIDA AND INTO THE W ATLC. DRY STABLE AIR ALOFT IS
HOLDING ALONG AND E OF THE RIDGE AXIS. AT THE SFC...DISTANT HIGH
PRES CENTERED IN THE MID-ATLANTIC REGION IS ENHANCING RIDGING.
THIS HIGH PRES ALONG WITH SLIGHTLY LOW PRES TO THE E OF THE AREA
IS PRODUCING STIFF 15-20 KT E TO NE FLOW IN THE E AND MIDDLE
GULF. THESE WINDS ARE VEERING MORE TO THE S-SE IN THE W GULF ON
THE PERIPHERY OF THE RIDGE AND NEAR THE LOW PRES SYSTEM IN THE
CENTRAL U.S. THE WEATHER WILL BECOME INTERESTING IN THE REGION
LATER THIS WEEK AS A COLD FRONT MOVES TOWARD THE TEXAS COAST
TOMORROW. A CONSIDERABLE AMOUNT OF MOISTURE WILL LIKELY BE
ADVECTED INTO THE REGION AHEAD OF THE FRONT ON FRI AND THIS
WEEKEND. GALE CONDITIONS ARE IN THE FORECAST BEHIND THE FRONT IN
THE W GULF ON SUN.

CARIBBEAN SEA...
PLENTY OF DRY AIR ALOFT...ASSOCIATED WITH UPPER LEVEL CONFLUENCE
BETWEEN AN UPPER LOW NEAR JAMAICA AND A TITLED UPPER RIDGE
ACROSS THE E GULF AND WRN ATLC...IS IN PLACE ACROSS THE WRN
CARIBBEAN KEEPING CONDITIONS VERY QUIET. SOME SMALL PATCHES OF
CLOUDINESS AND SCATTERED SHOWERS ARE POPPING UP ON THE E SIDE OF
THE UPPER SYSTEM NEAR THE CENTER ACROSS ERN JAMAICA...E CUBA AND
THE SE BAHAMAS. THE REMAINDER OF THE CARIBBEAN IS DOMINATED BY
UPPER LEVEL ZONAL WESTERLY FLOW. MODEST DRY AIR ALOFT COVERS
THIS AREA E OF 70W. TRADE WINDS ARE GENERALLY IN THE 15-20 KT
INTERVAL. THESE WINDS WILL LIKELY INCREASE SOME OVER THE NEXT
COUPLE DAYS AS SFC HIGH PRES CURRENTLY IN THE MID-ATLANTIC U.S.
MOVES TO THE SE TIGHTENING THE PRES GRAD.

ATLANTIC OCEAN...
SLIGHT UPPER LEVEL RIDGING EXTENDS FROM THE SE GULF ACROSS THE
BAHAMAS AND WRN-MOST ATLC. THIS FLOW THEN FOLDS INTO AN UPPER
TROUGH WHICH COVERS THE AREA BETWEEN 50W-70W N OF 23N. AN
ASSOCIATED COLD FRONT JUST CLIPS THE NRN PORTION OF THE AREA
ALONG 32N61W 29N75W 30N79W THEN STATIONARY TOWARD THE S GEORGIA
COAST. THIS FRONT IS MOISTURE STARVED WITH ONLY A NARROW LINE OF
LOW CLOUDS MARKING THE FRONT...MAKING IT EASY TO LOCATE. A SURGE
IN NLY WINDS AND PATCHES OF LOW-LEVEL STRATO-CU CLOUDS ARE
WIDESPREAD BEHIND THE BOUNDARY. A SFC TROUGH LIES TO THE S OF
THE COLD FRONT ANALYZED FROM THE DOMINICAN REPUBLIC NEWARD ALONG
22N62W 25N58W. SCATTERED SHOWERS ARE WITHIN 120 NM OF THE
BOUNDARY. A MODEST DEEP-LAYER RIDGE LIES TO THE E OF THE TROUGH
COVERING THE REGION BETWEEN 28W-50W N OF 20N. THE SFC HIGH IS
ANALYZED AT 1021 MB NEAR 30N41W. PLENTY OF DRY STABLE AIR AND
FAIR WEATHER IS ASSOCIATED WITH THIS DEEP RIDGING. THE
SUBTROPICAL E ATLC IS DOMINATED BY DEEP-LAYERED TROUGHING. THE
SFC LOW IS FAIRLY WEAK ANALYZED AT 1016 MB NEAR 29N28W. MOST OF
THE ASSOCIATED WEATHER...WHICH IS IN THE FORM OF WEAKENING
SCATTERED SHOWERS AND ISOLATED TSTMS...LIES TO THE E OF THE LOW
PRES CENTER N OF 24N BETWEEN 18W-26W. BASED UPON THE LATEST VIS
IMAGES...THE SYSTEM APPEARS TO BE FRONTAL...SO THE ASSOCIATED
BOUNDARIES WILL BE INTRODUCED ON THE SFC MAP AT 18Z. IN THE DEEP
TROPICS...EXTENSIVE WLY UPPER LEVEL FLOW COVERS THE ENTIRE AREA
ON THE N SIDE OF A VERY BROAD UPPER HIGH CENTERED NEAR 5N41W.
CONVECTION IS LIMITED TO A SMALL PORTION OF THE ITCZ WHERE
UPPER LEVEL DIFFLUENCE IS STRONGEST BETWEEN 35W-50W FROM 3N-6N.

$$
CANGIALOSI


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