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Atlantic Tropical Weather Discussion



000
AXNT20 KNHC 050001
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL 
805 PM EDT SAT JUL 04 2015

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... 

...GALE IN THE CARIBBEAN...

A GALE WARNING CONTINUES FOR THE SW CARIBBEAN FROM 11N TO 13N 
BETWEEN 73W AND 78W THROUGH SUNDAY NIGHT. THESE WINDS ARE 
GENERATED BY A TIGHT PRESSURE GRADIENT BETWEEN THE STRONG 
SURFACE RIDGE THAT PREVAILS OVER THE ATLC AND LOWER SURFACE 
PRESSURE OVER COLOMBIA. SEE THE LATEST NWS HIGH SEAS FORECAST 
UNDER AWIPS/WMO HEADERS MIAHSFAT2/FZNT02 KNHC FOR MORE DETAILS.

...TROPICAL WAVES... 

A TROPICAL WAVE IS MOVING OVER THE EASTERN TROPICAL ATLANTIC 
WITH AXIS EXTENDING FROM 16N37W TO 06N39W...MOVING W AT ABOUT 20 
TO 25 KT OVER THE PAST 24 HOURS. ALTHOUGH SSMI TPW INDICATES 
MODERATE TO HIGH MOISTURE S OF 12N IN THE WAVE ENVIRONMENT... 
CURRENT METEOSAT ENHANCED IMAGERY DEPICTS A BROAD AREA OF 
SAHARAN DUST SURROUNDING THIS WAVE WHICH IS INHIBITING 
SIGNIFICANT CONVECTION.

A TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLANTIC WITH AXIS 
EXTENDING FROM 13N46W TO 03N49W...MOVING AT 15 TO 20 KT OVER THE 
PAST 24 HOURS. SSMI TPW SHOWS THIS WAVE IS EMBEDDED IN AN 
ENVIRONMENT OF HIGH MOISTURE S OF 11N. METEOSAT ENHANCED IMAGERY 
INDICATES SAHARAN DUST N OF 11N. ISOLATED MODERATE CONVECTION IS 
FROM 07N TO 11N BETWEEN 44W AND 53W. 

A TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN WITH AXIS 
EXTENDING FROM 18N75W TO 11N78W...MOVING W AT AROUND 20 KT OVER 
THE PAST 24 HOURS. SSMI TPW SHOWS THIS WAVE IS EMBEDDED IN A 
MODERATELY MOIST ENVIRONMENT. CURRENT METEOSAT ENHANCED IMAGERY 
DEPICTS A BROAD AREA OF SAHARAN DUST PREVAILING ACROSS THE 
CARIBBEAN AND IN THE ENVIRONMENT OF THIS WAVE WHICH IS 
INHIBITING CONVECTION.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE TROPICAL 
ATLANTIC NEAR 17N16W TO 09N24W WHERE THE ITCZ BEGINS AND 
CONTINUES TO NEAR 09N37W...THEN RESUMES W OF A TROPICAL WAVE 
NEAR 08N39W TO 08N47W. OTHER THAN CONVECTION ASSOCIATED WITH THE 
CENTRAL ATLC TROPICAL WAVE...NO CONVECTION IS NOTED. 

...DISCUSSION...

GULF OF MEXICO...

AN UPPER LEVEL LOW IS CENTERED OVER THE CENTRAL GULF NEAR 24N88W 
AND DOMINATES THE MAJORITY OF THE BASIN WITH CYCLONIC FLOW 
ALOFT. TWO AREAS OF UPPER LEVEL DIFFLUENCE ARE BEING CREATED BY 
THIS LOW...THE FIRST IS LOCATED ACROSS THE NORTHERN GULF BETWEEN 
THE BASE OF AN UPPER TROUGH OVER THE SOUTHERN US AND THE UPPER 
LOW. ISOLATED MODERATE CONVECTION IS N OF 29N BETWEEN 85W AND 
94W. THE OTHER AREA OF DIFFLUENCE IS ACROSS THE FL STRAITS AND 
THE BAHAMAS. ISOLATED SHOWERS ARE E OF 83W S OF 25N OVER THE SE 
GULF. A 1021 MB HIGH CENTERED ALONG THE FL WEST COAST NEAR 
29N83W IS A WESTERN EXTENSION OF A BROAD SURFACE RIDGE FROM THE 
CENTRAL ATLC TO THE TX COAST. LIGHT ANTICYCLONIC SURFACE WINDS 
ARE E OF 87W. SE TO SW WINDS OF 10 TO 15 KT COVER THE REMAINDER 
OF THE BASIN. THE BASE OF THE UPPER TROUGH OVER THE SOUTHERN US 
WILL DIG EAST-SOUTHEAST TO THE FL PANHANDLE ON SUNDAY. THIS WILL 
HELP TO ENHANCE SHOWER AND THUNDERSTORM ACTIVITY OVER THE NE 
GULF TONIGHT THROUGH SUNDAY. 

CARIBBEAN SEA... 

THE BASIN IS UNDER THE INFLUENCE OF A LARGE SAHARAN AIRMASS 
WHICH CONTINUES TO INHIBIT ANY SIGNIFICANT CONVECTION. A 
TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN. PLEASE SEE THE 
TROPICAL WAVES SECTION FOR MORE DETAILS. A STRONG PRESSURE 
GRADIENT BETWEEN STRONG HIGH PRESSURE OVER THE SUBTROPICAL ATLC 
AND LOWER PRESSURE OVER COLOMBIA IS PRODUCING PERSISTENT GALE 
FORCE WINDS OVER A PORTION OF THE SW CARIBBEAN. PLEASE SEE THE 
SPECIAL FEATURES SECTION FOR MORE DETAILS. ELSEWHERE TRADE WINDS 
OF 20 TO 30 KT EXTEND AS FAR NORTH AS 18N BETWEEN 67W AND 82W 
WHICH IS PRODUCING SEAS OF 8 TO 14 FEET. EXPECT LITTLE CHANGE 
OVER THE NEXT 24 HOURS. 

...HISPANIOLA... 

ISOLATED AFTERNOON AND EVENING THUNDERSTORMS OVER INLAND 
PORTIONS OF HISPANIOLA WILL DIMINISH BY LATE THIS EVENING WITH 
THE LOSS OF DAYTIME EVENING. THE PRESENCE OF SAHARAN DUST AND 
LACK OF SIGNIFICANT MOISTURE WILL MAINTAIN ONLY ISOLATED 
COVERAGE OF AFTERNOON AND EVENING THUNDERSTORMS AGAIN ON SUNDAY. 

ATLANTIC OCEAN... 

A WEAK UPPER RIDGE BETWEEN THE UPPER LOW OVER THE GULF OF MEXICO 
AND AN UPPER LOW OVER THE ATLC NEAR 27N69W IS PRODUCING AN AREA 
OF UPPER LEVEL DIFFLUENCE SUPPORTING SCATTERED THUNDERSTORMS 
FROM 24N TO 29N BETWEEN 76W AND THE FL PENINSULA. THE UPPER LOW 
ITSELF SUPPORTS ISOLATED WEAK CONVECTION FROM 27N TO 31N BETWEEN 
70W AND 74W. FARTHER EAST...A CONVECTION FREE SURFACE TROUGH 
EXTENDS FROM 26N54W TO 23N55W. A 1030 MB HIGH CENTERED NEAR 
34N42W ANCHORS A BROAD SUBTROPICAL SURFACE RIDGE THAT DOMINATES 
THE MAJORITY OF THE SUBTROPICAL NORTHERN ATLC. TWO TROPICAL 
WAVES ARE OVER THE TROPICAL NORTHERN ATLC. PLEASE SEE THE 
TROPICAL WAVES SECTION FOR MORE DETAILS. 

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

$$ 

LATTO


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