[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201120
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 27W S OF 18N MOVING W NEAR 10 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
AND ISOLATED MODERATE CONVECTION ARE LOCATED E OF THE WAVE FROM
13N-18N BETWEEN 22W-27W.

TROPICAL WAVE IS ALONG 44W FROM 8N-13N 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 INHIBITING ANY DEEP CONVECTION...HOWEVER...A
FEW ISOLATED SHOWERS ARE FROM 13N-18N BETWEEN 40W-44W.

TROPICAL WAVE IS ALONG 65W S OF 11N MOVING W NEAR 12 KT. THIS
WAVE HAS BECOME INCREASINGLY DIFFICULT TO TRACK AS A MAJORITY OF
THE WAVE IS INTERACTING WITH PORTIONS OF INTERIOR VENEZUELA.
STRONG SUBSIDENCE ALOFT OVER THE EASTERN CARIBBEAN AND NORTH
CENTRAL VENEZUELA IS INHIBITING ANY DEEP CONVECTION ASSOCIATED
WITH THE WAVE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 9N13W 9N25W 11N29W 12N33W 11N36W
10N42W 9N45W 8N61W. A 1009 MB SURFACE LOW IS EMBEDDED WITHIN THE
AXIS CENTERED NEAR 13N35W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 10N-16N BETWEEN 31W-35W. ELSEWHERE...CLUSTERS
OF ISOLATED MODERATE CONVECTION ARE FROM 3N-7N BETWEEN 13W-21W.

...DISCUSSION...

GULF OF MEXICO...
A 1026 MB SURFACE HIGH CENTERED OVER CENTRAL GEORGIA NEAR 33N84W
EXTENDS A SURFACE RIDGE OVER FLORIDA...THE ENTIRE GULF OF MEXICO
AND EASTERN MEXICO. NE WINDS UP TO 25 KT ARE OBSERVED OVER THE
EASTERN GULF GRADUALLY DIMINISHING TO E-SE WINDS OF 10-15 KT
OVER THE NW GULF AS RETURN FLOW IS W OF 93W TO ACROSS THE
SOUTHERN U.S. PLAINS. THIS SURFACE HIGH IS SUPPORTED ALOFT BY A
STABLE AND RELATIVELY DRY 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
NOTED ON WATER VAPOR IMAGERY OVER THE GULF AND FLORIDA PENINSULA
THIS MORNING. 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 OVER WESTERN
HISPANIOLA NEAR 20N72W AND CONTINUES ALONG 18N80W TO THE NE
HONDURAS COAST NEAR 15N84W. 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 1010 MB
LOW CENTERED NEAR 13N81W IS PRODUCING NUMEROUS SHOWERS AND
SCATTERED TSTMS FROM THE ITCZ AXIS ALONG 8N TO 16N BETWEEN
75W-86W...INCLUDING PORTIONS OF NICARAGUA...COSTA RICA AND
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 15N E OF 70W.

ATLANTIC OCEAN...
A STATIONARY FRONT ENTERS THE DISCUSSION AREA NEAR 31N64W AND
EXTENDS S-SW TO NW HISPANIOLA NEAR 20N72W. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE OCCURRING WITHIN 120 NM EITHER SIDE OF THE
FRONT AND OVER THE AREA FROM 21N-25N BETWEEN 71W-78W. THIS FRONT
IS SUPPORTED ALOFT BY A SHARP UPPER LEVEL TROUGH W OF 65W WITH
AXIS ALONG 32N70W TO THE NW BAHAMAS AND YUCATAN CHANNEL. A
WEAKNESS IN THE SUBTROPICAL RIDGE IS ANALYZED AS A SURFACE
TROUGH THAT EXTENDS FROM 21N53W TO 29N51W. LOW-LEVEL CONVERGENCE
NEAR THE SURFACE TROUGH IS GENERATING ISOLATED SHOWERS N OF 21N
BETWEEN 52W-60W. FARTHER EAST...AN ELONGATED UPPER LEVEL LOW IS
CENTERED NEAR 21N50W. THE UPPER LOW STRETCHES NE TO 28N38W AND
SW TOWARDS THE LESSER ANTILLES AND OVER THE EASTERN CARIBBEAN
SEA NEAR 13N66W. 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 40W-52W.
ELSEWHERE ACROSS THE REMAINDER OF THE EASTERN ATLC...A SURFACE
RIDGE EXTENDS SE FROM A 1024 MB HIGH CENTERED NEAR 36N39W TO THE
W AFRICA COAST NEAR WESTERN SAHARA.

$$
HUFFMAN



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