631  
AXNT20 KNHC 031759  
TWDAT  
 
TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL  
159 PM EDT FRI NOV 3 2017  
 
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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH  
1745 UTC.  
   
.ITCZ/MONSOON TROUGH
 
 
THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR  
10N14W TO 08N19W. THE INTERTROPICAL CONVERGENCE ZONE EXTENDS FROM  
08N19W TO 07N28W TO 09N38W WHERE IT IS BISECTED BY THE TROUGH  
ALONG THE POSITION FROM 14N37W TO 09N40W TO 04N41W. IT RESUMES  
TO THE W OF THE TROUGH AT 08N41W TO 08N49W TO NEAR 10N55W.  
SCATTERED MODERATE CONVECTION IS WITHIN 120 NM N OF THE ITCZ  
BETWEEN 25W AND 30W, WITHIN 120 NM S OF THE AXIS BETWEEN 29W AND  
34W AND WITHIN 30 NM OF THE MONSOON TROUGH AXIS BETWEEN 15W AND  
22W. SCATTERED MODERATE MODERATE TO ISOLATED STRONG CONVECTION IS  
OBSERVED TO THE S OF THE ITCZ WITHIN 60 NM OF LINE FROM 06N13W TO  
04N16W, AND WITHIN 30 NM OF LINE FROM 03N25W TO 03N30W.  
   
..DISCUSSION
 
 
GULF OF MEXICO...  
 
STRONG UPPER ZONAL FLOW PREVAILS THROUGHOUT THE SE UNITED STATES  
AND GULF OF MEXICO. A JETSTREAM BRANCH IS ACROSS THE CENTRAL PART  
OF THE BASIN IS ADVECTING BROKEN HIGH CLOUDS ESE FROM 21N TO 28N  
AND TO THE E OF TEXAS. AT THE SURFACE, A 1023 MB HIGH IS ANALYZED  
OVER THE BORDER BETWEEN WESTERN S CAROLINA AND NE GEORGIA. A WELL  
ENTRENCHED RIDGE EXTENDS FROM THIS HIGH CENTER SOUTHWESTWARD TO  
ACROSS SOUTHERN LOUISIANA AND TO THE NORTHERN PART OF THE SW GULF.  
THE ASSOCIATED PRESSURE GRADIENT IS ALLOWING FOR GENERALLY GENTLE  
TO MODERATE NE TO E WINDS OVER THE BASIN, EXCEPT IN THE FAR  
WESTERN SECTION WHERE WINDS ARE GENTLE TO MODERATE, SE TO S IN  
DIRECTION. THE GULF IS VOID OF DEEP CONVECTION AS VERY LIMITED  
LOW-LEVEL MOISTURE IN COMBINATION WITH THE SUBSIDENCE ALOFT AND  
THE STRONG ZONAL WINDS ARE NOT CONDUCIVE THIS TYPE FOR THIS TYPE  
OF CONVECTION TO DEVELOP. LATEST SATELLITE IMAGERY SHOWS SMALL  
PATCHES OF LOW-LEVEL MOISTURE MOVING QUICKLY SW OVER THE  
SOUTHEASTERN GULF. ISOLATED SHOWERS ARE POSSIBLE WITH THESE  
CLOUDS. LITTLE OVERALL CHANGES ARE EXPECTED WITH THE CURRENT  
WEATHER PATTERN OVER THE AREA THROUGH SUNDAY.  
 
CARIBBEAN SEA...  
 
IN THE UPPER LEVELS, A SMALL ANTICYCLONE IS CENTERED NEAR 16N74W,  
WITH A RIDGE STRETCHING WNW TO ACROSS BELIZE AND THE SOUTHERN  
YUCATAN PENINSULA, AND ANOTHER RIDGE EXTENDING SOUTHEASTWARD TO  
FAR NE VENEZUELA. WATER VAPOR IMAGERY SHOWS ASSOCIATED STRONG  
SUBSIDENCE COVERING JUST ABOUT THE ENTIRE SEA, EXCEPT THE FAR  
WESTERN SECTION S OF 18N AND W OF 77W, AND OVER THE EXTREME  
SOUTHEASTERN PORTION OF THE SEA. THE DRY AIR RESULTING FROM THE  
SUBSIDENCE IS INHIBITING DEEP CONVECTION FROM DEVELOPING ACROSS  
THE OPEN WATERS OF THE BASIN. ONLY PATCHES OF LOW-LEVEL MOISTURE  
WITH ISOLATED SHOWERS AND THUNDERSTORMS MOVING WESTWARD ARE SEEN  
OVER THESE WATERS, INCLUDING THE WATERS JUST SW OF THE WINDWARD  
PASSAGE. IN THE WESTERN PORTION S OF 18N AND W OF 77W SCATTERED  
MODERATE ISOLATED STRONG CONVECTION IN CLUSTERS ARE OBSERVED  
WHERE LOW-LEVEL CONVERGENCE EXISTS ALONG WITH THE ADDITIONAL  
FACTOR OF A SURFACE TROUGH THAT IS JUST ALONG THE COASTS OF  
SOUTHERN HONDURAS TO THAT OF COSTA RICA. THIS ACTIVITY SHOULD  
REMAIN ACTIVE INTO SATURDAY NIGHT.  
 
LOW-LEVEL MOISTURE RELATED TO A SURFACE TROUGH NEARING THE WINDWARD  
ISLANDS FROM THE ATLANTIC BASIN IS NOTED S OF 14N AND E OF 63W.  
ISOLATED SHOWERS ARE OCCURRING WITH THIS MOISTURE. THIS MOISTURE  
WILL GRADUALLY INCREASE THROUGH SATURDAY, WITH THE POSSIBILITY OF  
SOME SCATTERED SHOWER AND THUNDERSTORM ACTIVITY MOVING OVER THIS  
PART OF THE SEA. PRESENTLY, IT APPEARS MOST OF THIS ACTIVITY  
SHOULD REMAIN JUST TO THE E OF THE ISLANDS AS UPPER LEVEL WINDS  
SHEAR OFF THE TOPS OF THE DEEPER CONVECTION.  
   
..HISPANIOLA
 
 
PATCHES OF LOW-LEVEL MOISTURE WITH SCATTERED SHOWERS ARE MOVING  
QUICKLY WESTWARD JUST OFFSHORE THE NORTHERN AND SOUTHERN COASTS OF  
HISPANIOLA. SOME SHOWERS ARE AFFECTING PORTIONS OF THESE COASTS.  
WITH ABUNDANT DRY SINKING AIR ALOFT OVER AND NEAR THE ISLAND, THE  
SHOWER ACTIVITY IS EXPECTED TO BE RATHER SHALLOW AS IT CONTINUES  
IN A WESTWARD MOTION OVER THE NEXT COUPLE OF DAYS.  
 
ATLANTIC OCEAN...  
 
A WELL-DEFINED SURFACE TROUGH IS ANALYZED OVER THE WESTERN ATLANTIC  
FROM NEAR 30N74W TO A SMALL AND WEAK LOW-LEVEL SWIRL AT 26N75W AND  
TO THE SE BAHAMAS. A SHORTWAVE TROUGH EMBEDDED IN THE WESTERLY  
FLOW ALOFT HAS TRIGGERED OFF SCATTERED MODERATE ISOLATED STRONG  
CONVECTION TO THE NE OF THE TROUGH N OF 29N BETWEEN 71W AND 75W.  
THE SHORTWAVE TROUGH WILL SHIFT EASTWARD THROUGH SUNDAY AS A  
LONGWAVE TROUGH DEVELOPS OVER THE FAR WESTERN PORTION OF THE AREA.  
THE SURFACE TROUGH WILL CONTINUE WESTWARD TO NEAR 78W TO INCLUDE  
THE VICINITY OF THE NW BAHAMAS ON SUNDAY.  
 
TO THE E OF THE UPPER MENTIONED FEATURES, AN UPPER-LEVEL LOW IS  
LOCATED OVER THE CENTRAL ATLANTIC NEAR 32N54W, WITH A SHARP UPPER  
TROUGH STRETCHING S TO 28N54W AND SOUTHEASTWARD TO NEAR 18N52W TO  
NEAR 13N51W. AT THE SURFACE A WEAK TROUGH EXTENDS FROM 32N52W TO  
A DISSIPATING LOW AT 27N56W AND TO NEAR 25N59W. ONLY ISOLATED  
SHOWERS ARE ALONG AND WITHIN ABOUT 60-90 NM OF THE TROUGH. A BROAD  
UPPER-LEVEL DIFFLUENT FLOW PATTERN IS PRESENT TO THE E OF THE  
UPPER-LEVEL LOW AND TROUGH. LATEST SATELLITE IMAGERY SHOWS  
ABUNDANT MOISTURE IN THE FORM OF MULTILAYER CLOUDS WITH NUMEROUS  
SHOWERS AND SCATTERED THUNDERSTORMS TO THE N OF 19N BETWEEN 45W  
AND 53W. THE MAJORITY OF THIS MOISTURE ALONG WITH SHOWER AND  
THUNDERSTORMS IS ADVECTING NORTHWARD. BROKEN TO SCATTERED MID  
AND HIGH LEVEL CLOUDS ARE STREAMING EASTWARD FROM THE ABUNDANT  
MOISTURE AREA TOWARDS 20W, WHILE AT THE SURFACE AND LOW-LEVELS  
SCATTERED TO BROKEN LOW CLOUDS WITH ISOLATED SHOWERS ARE NOTED.  
THE AFOREMENTIONED SHOWER AND THUNDERSTORM ACTIVITY IS FORECAST  
TO REMAIN QUITE ACTIVE DURING THE NEXT 24 TO 48 HOURS. A SURFACE  
TROUGH IS ANALYZED OVER THE DEEP TROPICS ALONG A POSITION FROM  
14N37W TO 09N40W TO 04N41W. THIS TROUGH IS MOVING WESTWARD  
AROUND 15 KT. SCATTERED MODERATE CONVECTION IS SEEN TO ITS NW  
WITHIN 30 NM OF LINE FROM 13N42W TO 14N37W, AND IS BEING AIDED  
BY UPPER-LEVEL DIVERGENCE OCCURRING E OF THE UPPER LEVEL TROUGH  
AXIS THAT IS ALONG 28N54W TO 18N52W TO 13N51W. OTHER SCATTERED  
MODERATE CONVECTION IS SOUTHEAST OF THE TROUGH WITHIN 30 NM OF A  
LINE FROM 05N32W TO 05N40W.  
 
TO THE W OF THE UPPER TROUGH DESCRIBED IN ABOVE PARAGRAPH, A  
SURFACE TROUGH IS ANALYZED FROM NEAR 22N54W TO 16N58W TO NEAR  
09N60W. ALTHOUGH THE UPPER AIR OVER THIS TROUGH IS VERY DRY AS  
NOTED IN THE LATEST WATER VAPOR IMAGERY DEPICTING ABUNDANT  
MODERATE TO STRONG SUBSIDENCE OVER THE TROUGH, AN UPPER LEVEL  
DISTURBANCE RIDING SOUTHEASTWARD IN THE UPPER NW FLOW IS HELPING  
TO PRODUCE AN AREA OF SCATTERED MODERATE ISOLATED STRONG  
CONVECTION ALONG AND WITHIN 120 NM E OF THIS TROUGH FROM 09N TO  
13N. THE TROUGH WILL MOVE ACROSS MOST OF THE LESSER ANTILLES  
TONIGHT INTO SATURDAY AND ACROSS THE EASTERN CARIBBEAN SEA  
SATURDAY. THE TROUGH SHOULD BRING SCATTERED SHOWER AND  
THUNDERSTORM ACTIVITY TO MAINLY THE WINDWARD ISLANDS, AND  
ISOLATED SHOWERS TO THE REST OF THE LESSER ANTILLES THROUGH  
SATURDAY.  
 
FOR ADDITIONAL INFORMATION PLEASE VISIT  
HTTP://WWW.HURRICANES.GOV/MARINE  
 

 
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