[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 281803
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE OCT 28 2008

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 48W/49W S OF 17N MOVING W NEAR 15 KT.
WAVE IS AT THE LEADING EDGE OF A WESTWARD-MOVING SURGE IN DEEP
LAYER MOISTURE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. ALSO...CIMSS WAVETRAK PRODUCT SHOWS THAT LOW LEVEL
CYCLONIC CIRCULATION IS MAXIMIZED ALONG WAVE AXIS. SCATTERED
MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF WAVE AXIS N
OF 10N.

TROPICAL WAVE IS ALONG 60W FROM 10N-18N MOVING W 10-15 KT.
SURFACE OBSERVATIONS AND A RECENT QUIKSCAT PASS INDICATE
CYCLONIC CURVATURE IN LOW LEVEL WIND FIELD NEAR THE WAVE AXIS.
ADDITIONALLY...VISIBLE SATELLITE IMAGERY DEPICTS A SHARP
INVERTED-V SIGNATURE IN CLOUD PATTERN COINCIDING WITHIN THE WAVE
AXIS. LOW LEVEL CONVERGENCE IS SUPPORTING ISOLATED SHOWERS
WITHIN 90 NM E OF WAVE AXIS.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 12N14W 7N29W 9N42W 8N50W 6N61W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120 NM
EITHER SIDE OF ITCZ AXIS BETWEEN 19W-28W. ISOLATED MODERATE
CONVECTION IS WITHIN 240 NM N OF ITCZ AXIS BETWEEN 29W-36W.
ISOLATED MODERATE CONVECTION IS WITHIN 150 NM S OF ITCZ AXIS
BETWEEN 43W-47W. ALSO...A SURFACE TROUGH IS EMBEDDED WITHIN THE
ITCZ...AND THIS TROUGH EXTENDS FROM 6N40W TO 11N40W TO 15N38W.
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF
THIS SURFACE TROUGH N OF 13N.

...DISCUSSION...

GULF OF MEXICO...
A MODIFIED CONTINENTAL POLAR AIRMASS IS FIRMLY IN PLACE OVER THE
GULF REGION IN THE WAKE OF A STRONG COLD FRONT THAT HAS PUSHED
SE OF THE GULF REGION. THIS AIRMASS IS BEING SUPPORTED BY A
STRONG 1036 MB SURFACE HIGH IN THE PLAINS OF THE CONUS. SURFACE
DEWPOINTS ALONG THE N GULF COAST ARE IN THE 20S AND 30S...WHILE
TEMPERATURES ARE IN THE 50S AND 60S. THESE TEMPERATURES ARE WELL
BELOW SEASONAL AVERAGES. WEAK LOW-LEVEL INSTABILITY RESULTING
FROM THIS COOLER AIR MOVING OVER THE RELATIVELY WARMER GULF
WATERS IS CAUSING STRATOCUMULUS DEVELOPMENT OVER MUCH OF THE
GULF. THIS FRONT IS ALSO BEING SUPPORTED BY A DEEP TROUGH OVER
THE E CONUS...WITH STRONG MID/UPPER-LEVEL WESTERLY WINDS OVER
THE N AND CENTRAL GULF. DRY AIR EMBEDDED WITHIN THE DEEP TROUGH
IS GENERALLY INHIBITING ANY DEEP CONVECTION OVER THE GULF. UPPER
LEVEL MOISTURE STREAMING NORTHEASTWARD FROM THE E PACIFIC REGION
INTO THE S GULF IS RESULTING IN INCREASED CLOUDINESS OVER THE SW
GULF...ESPECIALLY WITH A COLD FRONT IN E MEXICO EXTENDING FROM
22N99W TO 20N97W TO 18N95W. ADDITIONALLY...STRONG N TO NE WINDS
ARE BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN
STORM FORCE WINDS IN THE E PACIFIC REGION.

CARIBBEAN SEA...
MOIST SOUTHWESTERLY FLOW ALOFT COVERS THE NW GULF...WHERE TWO
COLD FRONTS ARE PRESENT. ONE COLD FRONT EXTENDS FROM CENTRAL
CUBA NEAR 22N78W TO 19N82W TO E HONDURAS NEAR 16N86W. LOW LEVEL
CONVERGENCE AND INCREASED MOISTURE NEAR THIS FRONT ARE
SUPPORTING ISOLATED MODERATE CONVECTION WITHIN 90 NM SE OF THE
FRONT. THE OTHER COLD FRONT MARKS THE LEADING EDGE OF A MUCH
COOLER AND DRIER MODIFIED CONTINENTAL POLAR AIRMASS. THIS FRONT
EXTENDS FROM W CUBA NEAR 23N81W TO 21N85W TO THE YUCATAN
PENINSULA NEAR 18N92W. DEEP LAYER DRY AIR IS INHIBITING DEEP
CONVECTIVE DEVELOPMENT ALONG THIS SECOND COLD FRONT...THOUGH
BANDS OF ENHANCED CLOUDINESS ARE FOUND WITHIN 30 NM EITHER SIDE
OF THIS SECOND COLD FRONT. FARTHER TO THE SE...AN UPPER LEVEL
RIDGE AXIS EXTENDS FROM AN UPPER HIGH OVER THE SW ATLC NEAR
21N67W TO N COLOMBIA NEAR 12N72W. SOUTHWESTERLY FLOW ALOFT W OF
THE UPPER RIDGE CONTINUES TO TRANSPORT DEEP MOISTURE INTO THE SW
CARIBBEAN...WHERE ISOLATED SHOWERS ARE PRESENT S OF 12N W OF
75W. ACROSS THE CENTRAL AND E CARIBBEAN...DEEP LAYER DRY AIR AND
SUBSIDENCE S OF THE UPPER HIGH ARE RESULTING IN GENERALLY FAIR
WEATHER. ADDITIONALLY...A SURFACE TROUGH EXTENDS FROM SE OF THE
DOMINICAN REPUBLIC NEAR 18N69W TO N OF PUERTO RICO NEAR 19N65W
INTO THE SW ATLC NEAR 21N63W. VISIBLE SATELLITE IMAGERY DEPICTS
WEAK CYCLONIC MOTION IN THE LOW LEVEL CLOUD ELEMENTS AROUND THIS
SURFACE TROUGH.

ATLANTIC OCEAN...
A DEEP LAYER TROUGH IS OVER THE E CONUS AND W ATLC...AND STRONG
MID/UPPER LEVEL FLOW IS ROTATING AROUND THE BASE OF THE TROUGH
INTO THE W ATLC. DEEP LAYER DRY AIR EMBEDDED WITHIN THE TROUGH
IS RESULTING IN GENERALLY FAIR WEATHER OVER THE W ATLC IN THE
WAKE OF A COLD FRONT THAT EXTENDS FROM 32N67W TO 25N71W TO
CENTRAL CUBA NEAR 22N78W. HOWEVER...ATMOSPHERIC LIFT IN MOIST
SOUTHWESTERLY FLOW ALOFT IS SUPPORTING ISOLATED MODERATE
CONVECTION WITHIN 60 NM EITHER SIDE OF THE COLD FRONT. ANOTHER
COLD FRONT EXTENDS FROM 32N71W TO 27N74W TO W CUBA NEAR 23N81W.
THIS SECOND COLD FRONT MARKS THE LEADING EDGE OF A MUCH COOLER
AND DRIER MODIFIED CONTINENTAL POLAR AIRMASS. DEEP LAYER DRY AIR
IS INHIBITING DEEP CONVECTIVE DEVELOPMENT ALONG THIS SECOND COLD
FRONT...THOUGH BANDS OF ENHANCED CLOUDINESS ARE FOUND WITHIN 60
NM EITHER SIDE OF THIS SECOND COLD FRONT. ALSO...A SURFACE
TROUGH EXTENDS FROM SE OF THE DOMINICAN REPUBLIC NEAR 18N69W TO
N OF PUERTO RICO NEAR 19N65W INTO THE SW ATLC NEAR 21N63W...WITH
WEAK LOW LEVEL CYCLONIC CIRCULATION EVIDENT NEAR THIS SURFACE
TROUGH BASED ON VISIBLE SATELLITE IMAGERY. FARTHER TO THE E...AN
UPPER LEVEL RIDGE AXIS EXTENDS FROM AN UPPER HIGH OVER THE SW
ATLC NEAR 21N67W TO 27N61W TO 32N58W...AND A DEEP LAYER TROUGH
AXIS EXTENDS FROM 32N50W TO 30N51W TO 25N53W. THIS DEEP LAYER
TROUGH IS SUPPORTING A SURFACE TROUGH THAT EXTENDS FROM 31N46W
TO 28N49W TO 23N53W. A RECENT QUIKSCAT PASS INDICATES CYCLONIC
CURVATURE IN THE LOW LEVEL WIND FIELD ALONG THIS SURFACE
TROUGH...AND ISOLATED MODERATE CONVECTION IS OCCURRING WITHIN 60
NM EITHER SIDE OF THIS SURFACE TROUGH S OF 28N. FARTHER TO THE
E...A DEEP LAYER TROUGH IS N OF 26N E OF 29W AND SHARPENS TO THE
SW WITH AN AXIS EXTENDING FROM NEAR 26N39W TO THE TROPICAL ATLC
NEAR 13N53W. DRY AIR EMBEDDED WITHIN THE TROUGH IS INHIBITING
DEEP CONVECTIVE DEVELOPMENT NEAR THIS FEATURE. ADDITIONALLY...
THIS TROUGH IS SUPPORTING A COLD FRONT THAT EXTENDS FROM N OF
THE CANARY ISLANDS NEAR 32N11W TO 30N21W TO 32N27W...WITH A BAND
OF INCREASED CLOUDINESS WITHIN 60 NM EITHER SIDE OF THE COLD
FRONT. OVER THE TROPICAL ATLC...AN EAST-TO-WEST UPPER RIDGE IS
ALONG 12N BETWEEN THE AFRICAN COAST AND 47W...AND A SURFACE
TROUGH IS EMBEDDED WITHIN THE ITCZ...WHICH EXTENDS FROM 6N40W TO
11N40W TO 15N38W. SCATTERED MODERATE CONVECTION IS WITHIN 120 NM
EITHER SIDE OF THIS SURFACE TROUGH N OF 13N...WHICH IS BEING
ENHANCED BY UPPER LEVEL DIVERGENCE NEAR THE UPPER RIDGE AXIS.

$$
COHEN



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