[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202340
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED NOV 20 2013

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...
TROPICAL STORM MELISSA IS CENTERED NEAR 37.2N 44.9W AT 20/2100
UTC OR ABOUT 850 NM W OF THE AZORES MOVING ENE AT 26 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED
WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. WIDELY SCATTERED
MODERATE CONVECTION IS FROM 36N-40N BETWEEN 44W-49W. SEE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24
KNHC FOR MORE DETAILS.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 08N13W TO
06N18W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM
06N18W TO 03N25W TO 05N31W TO 04N43W. A SURFACE TROUGH IS
ANALYZED ON THE WESTERN EXTENT OF THE AXIS FROM 04N44W TO
11N45W. SCATTERED MODERATE CONVECTION IS FROM 03N-15N BETWEEN
12W-23W...FROM 01N-06N BETWEEN 23W-31W...AND WITHIN 150 NM
EITHER SIDE OF A LINE FROM 02N31W TO 07N45W.

...DISCUSSION...

GULF OF MEXICO...
SOUTHWEST TO WESTERLY FLOW IS NOTED ON WATER VAPOR IMAGERY OVER
THE GULF BASIN THIS EVENING EAST OF AN APPROACHING MIDDLE TO
UPPER LEVEL TROUGH WITH AXIS EXTENDING FROM OVER SOUTHERN TEXAS
NEAR 28N98W SW TO 22N106W. AS OF 20/2100 UTC...A STATIONARY
FRONT EXTENDS ACROSS THE SOUTHERN FLORIDA PENINSULA INTO THE
GULF NEAR 27N82W TO 26N87W WHERE THE FRONT WEAKENS SOMEWHAT OVER
THE CENTRAL GULF AND RESUMES A MORE NOTICEABLE PRESENCE OVER THE
NW GULF FROM 26N93W TO THE TEXAS COAST NEAR 29N96W. WHILE THE
SOUTHWESTERLY FLOW IS ADVECTING MOISTURE OVER MUCH OF THE
BASIN...THE FRONTAL BOUNDARY IS PROVIDING LOW-LEVEL MOISTURE
CONVERGENCE TO GENERATE A COUPLE SPECIFIC AREAS OF CONVECTION
THIS EVENING. ONE AREA OF SCATTERED SHOWERS AND TSTMS IS
OCCURRING ACROSS THE WESTERN GULF IN THE VICINITY OF THE FRONT
FROM 25N-29N BETWEEN 91W-95W...AND THE OTHER AREA OF SCATTERED
SHOWERS AND ISOLATED TSTMS IS OCCURRING PRIMARILY SOUTH OF THE
STATIONARY FRONT AND EAST OF A SURFACE TROUGH AXIS ANALYZED FROM
THE FRONT NEAR 27N86W SOUTHWARD TO THE NE YUCATAN PENINSULA NEAR
21N88W ACROSS THE SE GULF WATERS N OF 24N. E-SE WINDS ARE
EXPECTED TO PERSIST FROM THIS EVENING THROUGH LATE FRIDAY WHEN
THE NEXT COLD FRONT IS EXPECTED TO EMERGE OFF THE TEXAS AND
LOUISIANA COASTS LATE FRIDAY INTO EARLY SATURDAY WITH N-NE WINDS
SPREADING ACROSS THE BASIN THROUGH THE UPCOMING WEEKEND.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONE IS CENTERED OVER THE WESTERN
CARIBBEAN NEAR 14N78W AND IS PROVIDING MUCH OF THE BASIN E OF
80W WITH DRY NORTHWEST TO WESTERLY FLOW ALOFT. IN ADDITION...A
BROAD UPPER LEVEL TROUGH IS NOTED ON WATER VAPOR IMAGERY E OF
70W BUT IS HOWEVER REMAINING VERY DRY AND STABLE ALOFT. WITH
OVERALL STABILITY ALOFT DOMINATING...CONDITIONS AT THE SURFACE
REMAIN FAIRLY TRANQUIL WITH ONLY A FEW AREA OF ISOLATED LOW-
TOPPED SHOWERS OCCURRING THIS EVENING IN THE VICINITY OF WEAK
SURFACE TROUGHS. ONE SURFACE TROUGH IS ANALYZED FROM 15N77W TO
THE WINDWARD PASSAGE NEAR 20N74W THAT IS PROVIDING FOCUS FOR
ISOLATED SHOWERS FROM 13N-20N BETWEEN 69W-78W AND THE OTHER
SURFACE TROUGH EXTENDS FROM 11N80W TO 15N84W WITH ISOLATED
SHOWERS AND TSTMS OCCURRING MOSTLY INLAND ACROSS NICARAGUA AND
EASTERN HONDURAS FROM 12N-16N BETWEEN 83W-86W. OTHERWISE...
ANOTHER AREA OF ISOLATED SHOWERS IS OCCURRING WITHIN 90 NM
EITHER SIDE OF A LINE FROM 18N62W TO 15N68W. FINALLY...A FEW
ISOLATED SHOWERS AND TSTMS ARE NOTED S OF 10N...INCLUDING INLAND
PORTIONS OF PANAMA DUE TO THE CLOSE PROXIMITY OF THE MONSOON
TROUGH ANALYZED ALONG 09N BETWEEN NORTHERN COLOMBIA AND EXTREME
SOUTHERN COSTA RICA. TRADES ARE FORECAST TO REMAIN 20 KT OR LESS
THROUGH THE REMAINDER OF THE WEEK INTO THE UPCOMING WEEKEND.

...HISPANIOLA...
CURRENTLY A FEW ISOLATED LOW-TOPPED SHOWERS ARE OCCURRING OVER
PORTIONS OF HISPANIOLA AND THE SOUTHERN AND WESTERN COASTAL
WATERS STRETCHING INTO THE CENTRAL CARIBBEAN SEA. WHILE THIS LOW-
LEVEL MOISTURE CONTINUES TO LINGER...ALOFT MIDDLE TO UPPER LEVEL
NORTHWESTERLY FLOW IS PROVIDING A VERY DRY AND STABLE
ENVIRONMENT LIMITING OVERALL DEEPER CONVECTION. A WEAK PRESSURE
GRADIENT REMAINS OVER THE ISLAND AND GIVEN THE STABILITY...FAIR
CONDITIONS AND TRANQUIL WEATHER IS EXPECTED OVER THE NEXT FEW
DAYS WITH THE EXCEPTION OF A FEW ONSHORE-MOVING PASSING ISOLATED
SHOWERS.

ATLANTIC OCEAN...
A DEEP LAYERED LOW NOTED OFF THE COAST OF NOVA SCOTIA NEAR
46N57W SUPPORTS A COLD FRONT ANALYZED FROM 32N58W SW TO 29N67W
WHERE IT BECOMES STATIONARY WESTWARD TO THE FLORIDA PENINSULA
NEAR 27N80W. WHILE THE MIDDLE TO UPPER LEVEL DYNAMICS ARE FOUND
WELL NORTH OF THE DISCUSSION AREA...ISOLATED SHOWERS AND TSTMS
ARE OCCURRING WITHIN 90 NM EITHER SIDE OF THE FRONTAL BOUNDARY.
THE FRONTAL BOUNDARY IS EXPECTED TO REMAIN STATIONARY AND
GRADUALLY WEAKEN THROUGH LATE THURSDAY AS SURFACE RIDGING BUILDS
IN ACROSS THE SW NORTH ATLC FROM THE NORTH. ACROSS THE REMAINDER
OF THE SW NORTH ATLC...A WEAK SURFACE RIDGE REMAINS TO THE SE OF
THE FRONT FOCUSED ON A 1018 MB HIGH CENTERED NEAR 26N64W.
FARTHER EAST...THE MIDDLE TO UPPER LEVEL LOW ASSOCIATED WITH
TROPICAL STORM MELISSA IS CENTERED NEAR 37N45W AND EXTENDS A
TROUGH AXIS SOUTHWARD TO 18N60W. WHILE MELISSA CONTINUES TO RACE
TO THE NORTHEAST...SURFACE TROUGHING RESULTS OVER THE CENTRAL
ATLC FROM 18N53W TO 24N47W TO 29N45W AND PROVIDES FOCUS FOR LOW-
LEVEL MOISTURE CONVERGENCE. THIS CONVERGENCE ALONG WITH A LARGE
AREA OF UPPER LEVEL DIFFLUENCE EAST OF THE UPPER LEVEL TROUGH IS
GENERATING SCATTERED SHOWERS AND TSTMS WITHIN 180 NM EITHER SIDE
OF A LINE FROM 16N50W TO 32N38W. FINALLY...THE REMAINDER OF THE
EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED
BY A 1023 MB HIGH CENTERED NEAR 32N27W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
HUFFMAN


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