000
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