[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 190002
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED DEC 18 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.

...ITCZ/MONSOON TROUGH...
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS ALONG 04N12W TO
06N29W...THEN RESUMES WEST OF A SURFACE TROUGH FROM 06N31W TO
0S47W. A MIDDLE TO UPPER LEVEL LOW CENTERED NW OF THE CAPE VERDE
ISLANDS SUPPORTS THE SURFACE TROUGH WHICH AXIS EXTENDS FROM
16N24W TO 05N31W. SOUTHWESTERLY FLOW JUST EAST OF THE CYCLONIC
CIRCULATION ALOFT IS GENERATING DIFFLUENCE TO SUPPORT NUMEROUS
MODERATE CONVECTION FROM 13N-22N BETWEEN 20W-28W AND SCATTERED
MODERATE CONVECTION ELSEWHERE FROM 04N-23N EAST OF 30W.
SCATTERED MODERATE CONVECTION IS ALSO WITHIN 140 NM N OF THE
ITCZ BETWEEN 32W-40W.

...DISCUSSION...

GULF OF MEXICO...
WATER VAPOR IMAGERY DEPICT A BROAD MIDDLE TO UPPER LEVEL TROUGH
MOVING ACROSS THE WESTERN ATLC WITH A BASE EXTENDING OVER THE
FLORIDA PENINSULA AND EASTERN GULF. A MIDDLE TO UPPER LEVEL
RIDGE WITH AXIS ACROSS THE CENTRAL U.S.A EXTENDS INTO THE
WESTERN GULF. ACROSS THE WHOLE BASIN BOTH WATER VAPOR AND SSMI
TPW IMAGERY SHOW VERY DRY AIR WHICH IS HINDERING CONVECTIVE
ACTIVITY. SURFACE RIDGING ANCHORED BY A 1028 MB HIGH OVER
CENTRAL ALABAMA FURTHER SUPPORTS THE STABILITY AT THE LOWER AND
MIDDLE LEVELS. EXCEPT FOR THE NW GULF WHERE E-SE WIND FLOW OF 5
KT DOMINATES...THE REMAINDER BASIN IS UNDER NORTHEASTERLY WINDS
IN THE RANGE OF 10 TO 15 KT. AS THE HIGH PRESSURE AREA CONTINUES
TO SHIFT EASTWARD TONIGHT INTO EARLY THURSDAY...E-SE FLOW WILL
ESTABLISH ACROSS THE BASIN. AN AREA OF LOW PRESSURE IS FORECAST
ACROSS THE WESTERN GULF ON FRI AFTERNOON ASSOCIATED WITH THE
NEXT COLD FRONT EXPECTED TO EMERGE OFF THE TEXAS AND LOUISIANA
COASTS EARLY SUNDAY.

CARIBBEAN SEA...
SOUTH-SOUTHWESTERLY WIND FLOWING AROUND AN UPPER-LEVEL RIDGE
CENTERED OVER THE CARIBBEAN ADVECTS PLENTY OF MOISTURE TO THE
WESTERN BASIN. THE MOISTURE ALOFT AS WELL AS LOW-LEVEL MOISTURE
CONVERGENCE FROM THE TRADEWINDS ALONG THE COASTLINES FROM BELIZE
TO SOUTHERN NICARAGUA SUPPORT SCATTERED SHOWERS S OF 19N W OF
80W. IN THE SW BASIN S OF 12N...SCATTERED SHOWERS ARE BEING
FURTHER ENHANCED BY THE MONSOON TROUGH THAT EXTENDS JUST SOUTH
OF PANAMA TO A 1009 MB LOW ON NW COLOMBIA NEAR 08N75W. UPPER
LEVEL WEST-NORTHWESTERLY FLOW IS ACROSS THE REMAINDER BASIN
WHICH REMAINS VERY DRY AND STABLE THUS SUPPORTING MOSTLY FAIR
SKIES AND CONDITIONS OVER HISPANIOLA...PUERTO RICO...AND THE
LESSER ANTILLES. A FEW PASSING ISOLATED SHOWERS ARE HOWEVER
POSSIBLE ACROSS THE EASTERN CARIBBEAN AS THESE SHOWERS REMAIN
EMBEDDED WITHIN TRADE WINDS RANGING FROM 15 TO 25 KT.

...HISPANIOLA...
DRY AND STABLE AIR PREVAIL ALOFT AND AT THE LOWER LEVELS THUS
SUPPORTING FAIR WEATHER CONDITIONS ACROSS GREATER PORTIONS OF
THE ISLAND. SATELLITE IMAGERY INDICATE ONLY LOWER LEVEL
CLOUDINESS AND ISOLATED SHOWERS ACROSS THE SOUTHERN ISLAND S OF
19N AND ADJACENT COASTAL WATERS. TRADEWINDS ARE EXPECTED TO
CONTINUE ACROSS THE ISLAND WITH WINDS INCREASING SLIGHTLY
THURSDAY INTO FRIDAY DUE TO A STRENGTHENING PRESSURE GRADIENT
ACROSS THE REGION. THE STRONG TRADES WILL PERSIST DURING THE
UPCOMING WEEKEND.

ATLANTIC OCEAN...
A BROAD MIDDLE TO UPPER LEVEL TROUGH MOVING ACROSS THE WESTERN
ATLC WITH A BASE EXTENDING OVER THE FLORIDA PENINSULA AND
EASTERN GULF SUPPORTS A COLD FRONT ANALYZED FROM 30N69W TO
28N74W AND A DISSIPATING STATIONARY FRONT FROM 30N63W TO 25N71W
TO 22N77W. ISOLATED SHOWERS AND TSTMS ARE WITHIN 90 NM E-SE OF
THE DISSIPATING STATIONARY FRONT. THE REMAINDER CENTRAL AND
EASTERN ATLC N OF 21N IS UNDER THE INFLUENCE OF A LARGE AREAL
SURFACE RIDGE ANCHORED BY A 1032 MB HIGH CENTERED NEAR 33N30W.
SEE THE ITCZ SECTION FOR INFORMATION ABOUT A SURFACE TROUGH AND
ASSOCIATED CONVECTION OVER THE E ATLC.

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

$$
NR


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