[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 200559
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON OCT 19 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...
A 1009 MB SURFACE LOW IS CENTERED IN THE NW CARIBBEAN NEAR
18N87W...OR ABOUT 85 NM E OF THE COAST OF BELIZE. BROAD LOW
LEVEL CONVERGENCE AROUND THE LOW...COUPLED WITH UPPER LEVEL
DIVERGENCE OVER THE NW CARIBBEAN...IS SUPPORTING SCATTERED
MODERATE/ISOLATED STRONG CONVECTION WITHIN 240 NM OF THE SURFACE
LOW. SOME SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE BEFORE IT
MOVES INLAND OVER BELIZE OR THE YUCATAN PENINSULA IN A DAY OR
TWO. REGARDLESS OF DEVELOPMENT...LOCALLY HEAVY RAINFALL IS
EXPECTED OVER PORTIONS OF HONDURAS...GUATEMALA...BELIZE...AND
THE YUCATAN PENINSULA OVER THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 43W/44W S OF 18N MOVING W 10-15 KT.
SATELLITE IMAGERY DEPICTS INVERTED-V SIGNATURE IN CLOUD
COVERAGE...ALONG WITH COUNTERCLOCKWISE MOTION OF CLOUD ELEMENTS
IN THE VICINITY OF THE WAVE AXIS. CIMSS WAVETRAK PRODUCT
CONFIRMS PRESENCE OF LOW LEVEL COUNTERCLOCKWISE CIRCULATION NEAR
WAVE AXIS. THIS WAVE ALSO COINCIDES WITH A BROAD WESTWARD-MOVING
DEEP LAYER MOISTURE SURGE BASED ON TOTAL PRECIPITABLE WATER
PRODUCT FROM CIMSS. ISOLATED MODERATE CONVECTION IS FROM 14N-26N
BETWEEN 34W-48W...WHICH IS BEING DRAWN NORTHWESTWARD ON THE NE
PERIPHERY OF AN UPPER LOW CENTERED NEAR 20N49W. ALSO...SCATTERED
MODERATE CONVECTION IS FROM 10N-14N BETWEEN 45W-51W.

TROPICAL WAVE IS ALONG 65W S OF 14N MOVING W 10-15 KT. WAVE IS
NOT PARTICULARLY WELL-DEFINED BASED ON SATELLITE IMAGERY...
THOUGH IT DOES COINCIDE WITH A NORTH-TO-SOUTH DEEP LAYER
MOISTURE MAXIMUM. ISOLATED MODERATE CONVECTION IS WITHIN 210 NM
EITHER SIDE OF WAVE AXIS N OF 10N...AND SCATTERED MODERATE
CONVECTION IS WITHIN 180 NM EITHER SIDE OF WAVE AXIS S OF 7N.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 14N17W 8N29W 10N42W 9N50W 9N61W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 9N-14N
BETWEEN 14W-22W...AFFECTING W PORTIONS OF SENEGAL...GAMBIA...
AND GUINEA-BISSAU. ISOLATED MODERATE CONVECTION IS FROM 4N-7N
BETWEEN 24W-35W. ISOLATED MODERATE CONVECTION IS WITHIN 150 NM
N OF AXIS BETWEEN 37W-41W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH AXIS EXTENDS FROM THE CENTRAL FLORIDA PENINSULA
TO THE BAY OF CAMPECHE...WHICH IS SUPPORTING A STATIONARY FRONT
THAT EXTENDS FROM MIDWAY BETWEEN THE FLORIDA KEYS AND CUBA NEAR
24N81W TO 23N86W TO THE BAY OF CAMPECHE NEAR 21N91W TO OVER
INLAND MEXICO NEAR 18N92W. WEAK ATMOSPHERIC LIFT IN RELATIVELY
MOIST SOUTHWESTERLY FLOW ALOFT DOWNSTREAM OF THE UPPER TROUGH
AXIS IS SUPPORTING BANDS OF CLOUDINESS AND ISOLATED SHOWERS
WITHIN 60 NM EITHER SIDE OF THE STATIONARY FRONT...IMPACTING
PORTIONS OF THE SE GULF. FURTHER TO THE NW...AN UPPER RIDGE AXIS
STRETCHES FROM S TEXAS TO THE SOUTHERN APPALACHIANS. SUBSIDENCE
AND DRY AIR IN NW FLOW ALOFT BETWEEN THIS UPPER RIDGE AND THE
AFOREMENTIONED UPPER TROUGH ARE RESULTING IN FAIR WEATHER ACROSS
MUCH OF THE NW AND CENTRAL GULF...ESPECIALLY AS A SURFACE RIDGE
EXTENDS INTO THE NW GULF FROM THE SE CONUS. ADDITIONALLY...WITH
A SURFACE RIDGE PRESENT OVER MEXICO...AND A SURFACE TROUGH OFF
THE COAST OF W MEXICO EXTENDING FROM 14N91W TO 9N97W...STRONG
WINDS CONTINUE TO BLOW THROUGH THE ISTHMUS OF TEHUANTEPEC
RESULTING IN GALE FORCE WINDS IN THE NEARBY E PACIFIC REGION.

CARIBBEAN SEA...
MOIST SW FLOW ALOFT E OF THE UPPER TROUGH AXIS IN THE GULF IS
BEGINNING TO PROPAGATE OVER THE NW CARIBBEAN...WHERE UPPER LEVEL
DIVERGENCE CONTINUES TO SUPPORT CONVECTION. THIS CONVECTION IS
BEING ENHANCED BY BROAD SURFACE CONVERGENCE AROUND A 1009 MB
SURFACE LOW NEAR 18N87W. PLEASE SEE THE SPECIAL FEATURES SECTION
ABOVE FOR MORE INFORMATION ON THIS SYSTEM. FURTHER TO THE
E...SCATTERED MODERATE CONVECTION IS FROM 12N-20N BETWEEN
73W-80W...AFFECTING E CUBA AND JAMAICA. THIS CONVECTION IS BEING
ENHANCED BY UPPER LEVEL DIFFLUENCE NEAR AND N OF AN UPPER RIDGE.
THIS RIDGE EXTENDS FROM AN UPPER HIGH NEAR 16N65W TO THE NW
CARIBBEAN NEAR 15N82W. FARTHER TO THE E...CONVECTIVE COVERAGE IS
LIMITED AS A RESULT OF SUBSIDENCE AND DRY AIR NEAR THE UPPER
HIGH. HOWEVER...ISOLATED MODERATE CONVECTION IS OCCURRING ACROSS
THE SE CARIBBEAN IN THE VICINITY OF THE TROPICAL WAVE ALONG 65W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER PORTIONS OF
COSTA RICA...PANAMA...NICARAGUA...N COLOMBIA...AND NW VENEZUELA
IS IMPACTING THE NEARBY SW CARIBBEAN WATERS. THIS CONVECTION IS
BEING ENHANCED BY A 1008 MB SURFACE LOW OVER N VENEZUELA NEAR
9N75W AND GREATER INSTABILITY OVER HIGHER TERRAIN.

ATLANTIC OCEAN...
AN UPPER TROUGH IS OVER THE W ATLC...AND IS SUPPORTING A SURFACE
COLD FRONT THAT EXTENDS FROM 32N66W TO 28N70W TO 26N75W.
ALSO...A STATIONARY FRONT EXTENDS FROM 26N75W TO 25N78W TO
MIDWAY BETWEEN THE FLORIDA KEYS AND CUBA NEAR 24N81W. WEAK
ATMOSPHERIC LIFT IN SW FLOW ALOFT DOWNSTREAM OF THE UPPER TROUGH
AXIS...AND MID/UPPER-LEVEL MOISTURE...ARE SUPPORTING CLOUDINESS
AND ISOLATED SHOWERS WITHIN 60 NM EITHER SIDE OF THE COLD FRONT
AND STATIONARY FRONT. TO THE NW OF THESE FRONTS...DEEP
CONVECTION IS BEING SUPPRESSED BY SUBSIDENCE IN NW FLOW ALOFT
UPSTREAM OF THE UPPER TROUGH AXIS. FARTHER TO THE E...A COMPACT
UPPER LOW IS CENTERED NEAR 20N49W...AND AN UPPER HIGH IS
CENTERED NEAR 22N36W. DEEP LAYER SOUTHEASTERLY FLOW BETWEEN
THESE FEATURES IS DRAWING DEEP LAYER MOISTURE NORTHWESTWARD NEAR
THE TROPICAL WAVE ALONG 43W/44W...RESULTING IN ISOLATED MODERATE
CONVECTION FROM 14N-26N BETWEEN 34W-48W. FARTHER TO THE E...A
1026 MB SURFACE HIGH IS CENTERED NEAR 31N35W...AND A SURFACE
RIDGE EXTENDS FROM THIS HIGH TO THE S NEAR 12N32W...WITH
SUBSIDENCE AND STABLE CONDITIONS AROUND THE SURFACE HIGH AND
SURFACE RIDGE PREDOMINATING OVER MUCH OF THE E ATLC. ALSO...AN
UPPER TROUGH IS PRESENT OVER THE NE ATLC N OF 22N AND E OF
22W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN THIS TROUGH.

$$
COHEN

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