[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200548
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE OCT 20 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 26W S OF 18N MOVING W NEAR 12 KT. THE
WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM ACROSS THE
EASTERN TROPICAL ATLC AS OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY. GLOBAL MODEL GUIDANCE FIELDS OF 850 MB RELATIVE
VORTICITY AND 700 MB STREAMLINES ALSO DEPICT CYCLONIC TURNING IN
THE VICINITY OF THE WAVE AXIS BETWEEN 23W-29W. SCATTERED SHOWERS
ARE LOCATED E OF THE WAVE FROM 14N-19N BETWEEN 21W-26W.

TROPICAL WAVE IS ALONG 42W FROM 7N-16N MOVING W NEAR 15 KT. THE
WAVE APPEARS TO BE MOVING BENEATH A HIGHLY SHEARED ENVIRONMENT
AS ENERGY IS BEING STRETCHED NORTHWESTWARD ACROSS THE CENTRAL
ATLC. THIS SHEAR IS LIMITING PRECIPITATION TO A FEW ISOLATED
SHOWERS FROM 14N-17N BETWEEN 38W-43W.

TROPICAL WAVE IS ALONG 64W S OF 12N MOVING W NEAR 15 KT. AN AREA
OF DEEP LAYER MOISTURE IS MOVING ACROSS INTERIOR EASTERN
VENEZUELA AND PORTIONS OF THE SE CARIBBEAN. STRONG SUBSIDENCE
ALOFT OVER THE EASTERN CARIBBEAN IS INHIBITING ANY DEEP
CONVECTION ASSOCIATED WITH THE WAVE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N13W 11N25W 12N28W 12N33W 9N40W
8N44W 7N60W. A 1011 MB SURFACE LOW IS EMBEDDED WITHIN THE AXIS
CENTERED NEAR 12N35W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 10N-15N BETWEEN 30W-35W. ELSEWHERE...CLUSTERS
OF ISOLATED MODERATE CONVECTION IS FROM 4N-8N BETWEEN 11W-25W.

...DISCUSSION...

GULF OF MEXICO...
A 1025 MB SURFACE HIGH CENTERED OVER EASTERN GEORGIA NEAR 34N83W
EXTENDS A SURFACE RIDGE OVER FLORIDA...THE ENTIRE GULF OF MEXICO
AND EASTERN MEXICO. NE WINDS UP TO 25 KT DOMINATE OVER THE
EASTERN GULF AS DEPICTED BY AN EARLIER QUIKSCAT PASS AROUND 20/
0000 UTC...THEN GRADUALLY DIMINISHING TO E-SE 10-15 KT OVER THE
NW GULF AS HINTS OF RETURN FLOW IS BEGINNING ACROSS THE SOUTHERN
U.S. PLAINS. THIS SURFACE HIGH IS SUPPORTED ALOFT BY A STABLE
DRY AND COOLER AIRMASS ON THE BACKSIDE OF UPPER LEVEL TROUGHING
OVER THE WESTERN ATLC...FLORIDA PENINSULA AND EASTERN GULF E OF
85W. NWLY WINDS ALOFT AND VERY STRONG SUBSIDENCE ARE OVER THE
GULF AND FLORIDA PENINSULA. THE SURFACE RIDGE IS FORECAST TO
SHIFT GRADUALLY EASTWARD REMAINING MOSTLY OVER MUCH OF THE GULF
THROUGH MID-WEEK WITH SE SURFACE RETURN FLOW TO BE WELL
DEVELOPED ACROSS THE WESTERN GULF BY WEDNESDAY AHEAD OF THE NEXT
COLD FRONT TO ENTER THE NW GULF WATERS LATE THURSDAY.

CARIBBEAN SEA...
AN UPPER LEVEL TROUGH IS OVER THE WESTERN ATLC AND GULF OF
MEXICO DIPPING SOUTH THROUGH THE YUCATAN CHANNEL AND INTO THE NW
CARIBBEAN. THIS UPPER LEVEL TROUGHING SUPPORTS A STATIONARY
FRONT THAT EXTENDS INTO THE CARIBBEAN SEA THROUGH THE WINDWARD
PASSAGE AND CONTINUES ALONG 19N80W TO THE NE HONDURAS COAST NEAR
16N85W. LOW-LEVEL CONVERGENCE IN THE VICINITY OF THE FRONTAL
BOUNDARY COUPLED WITH UPPER LEVEL DIFFLUENCE E OF THE UPPER
LEVEL TROUGH ARE GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS
WITHIN 150 NM EITHER SIDE OF THE FRONTAL BOUNDARY. TO THE SOUTH
OVER THE SW CARIBBEAN...A 1006 MB LOW CENTERED NEAR 13N81W IS
PRODUCING NUMEROUS SHOWERS AND SCATTERED STRONG TSTMS FROM THE
ITCZ AXIS ALONG 7N TO 16N BETWEEN 76W-87W...INCLUDING PORTIONS
OF NICARAGUA...COSTA RICA AND WESTERN PANAMA. AN UPPER LEVEL
RIDGE IS POSITIONED ACROSS THE SW CARIBBEAN W OF 70W AND IS
ENHANCING THIS CONVECTION. E OF 70W...UPPER LEVEL TROUGHING AND
GENERALLY DRY STABLE AIR ALOFT ARE NOTED ON WATER VAPOR IMAGERY
WITH ELY TRADE WINDS UP TO 20 KT. A FEW ISOLATED LOW-LEVEL
SHOWERS ARE OCCURRING OVER THE NE CARIBBEAN N OF 16N E OF 69W.

ATLANTIC OCEAN...
A STATIONARY FRONT ENTERS THE DISCUSSION AREA NEAR 31N65W AND
EXTENDS S-SW TO THE WINDWARD PASSAGE NEAR 20N73W. SCATTERED
SHOWERS AND TSTMS ARE OCCURRING WITHIN 150 NM EITHER SIDE OF THE
FRONT. THIS FRONT IS SUPPORTED ALOFT BY A SHARP UPPER LEVEL
TROUGH W OF 63W WITH AXIS ALONG 32N73W TO THE NW BAHAMAS AND
YUCATAN CHANNEL. A WEAKNESS IN THE SUBTROPICAL RIDGE IS ANALYZED
AS A SURFACE TROUGH THAT EXTENDS FROM 21N54W TO 31N51W. LOW-
LEVEL CONVERGENCE NEAR THE SURFACE TROUGH IS GENERATING ISOLATED
SHOWERS N OF 20N BETWEEN 52W-60W. FARTHER EAST...AN ELONGATED
UPPER LEVEL LOW IS CENTERED NEAR 23N46W. THE UPPER LOW STRETCHES
NE TO 28N37W AND SW TOWARDS THE LESSER ANTILLES AND OVER THE
EASTERN CARIBBEAN SEA NEAR 13N67W. MID-LEVEL LIFT AND UPPER
LEVEL DIFFLUENCE IN ASSOCIATION WITH THE UPPER LOW ARE
GENERATING SCATTERED SHOWERS AND TSTMS COVERING AN AREA FROM
18N-28N BETWEEN 41W-51W. ELSEWHERE ACROSS THE REMAINDER OF THE
EASTERN ATLC...A SURFACE RIDGE EXTENDS SE FROM A 1023 MB HIGH
CENTERED NEAR 36N41W TO THE W AFRICA COAST NEAR WESTERN SAHARA.

$$
HUFFMAN





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