Tropical Weather Discussion
Issued by NWS

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000
AXNT20 KNHC 251750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUL 25 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1645 UTC.

...SPECIAL FEATURES...

A TIGHT PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE WESTERN
ATLC AND LOWER PRESSURES OVER S AMERICA WILL SUPPORT GALE FORCE
WINDS TONIGHT AND AGAIN ON MONDAY NIGHT WITHIN 120 NM OF THE NW
COAST OF COLOMBIA. SEAS TO 14 FT WILL BE POSSIBLE. PLEASE SEE
THE LATEST HIGH SEAS FORECAST UNDER AWIPS/WMO HEADERS
MIAHSFAT2/FZNT02 FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE EASTERN ATLC WITH AXIS EXTENDING
FROM 15N24W TO 07N24W...MOVING W AT AROUND 15 KT. A 1012 MB LOW
IS ALONG THE WAVE NEAR 11N25W WITH DEEP MOISTURE IN THE WAVE
ENVIRONMENT S OF 14N. SCATTERED MODERATE CONVECTION IS FROM 06N
TO 12N BETWEEN 22W AND 28W.

A TROPICAL WAVE IS OVER THE CENTRAL ATLC WITH AXIS EXTENDING
FROM 14N43W TO 06N44W...MOVING W AT 10 TO 15 KT OVER THE PAST 24
HOURS. THIS WAVE IS DEPICTED WELL IN MODEL 700 MB STREAMLINES
WITH AN INVERTED TROUGH FROM 41W TO 49W. MUCH OF THIS WAVE IS
EMBEDDED IN DRY AIR EMBEDDED IN SAHARAN DUST N OF 9N...WHICH IS
INHIBITING CONVECTION ALONG THE WAVE.

A TROPICAL WAVE IS BEGINNING TO CROSS THE WINWARD ISLANDS WITH
AN AXIS EXTENDING FROM 17N59W TO 07N61W...MOVING W AT 15 TO 20
KT OVER THE PAST 24 HOURS. A SURGE IN DEEP MOISTURE IS NOTED
JUST AHEAD OF THE WAVE...WITH A WIND SHIFT FROM CALM TO SE AT 20
KT AT TOBAGO THIS MORNING AS THE WAVE PASSED. SCATTERED MODERATE
CONVECTION IS FROM 09N TO 14N BETWEEN 60W AND 64W.

A TROPICAL WAVE IS OVER THE GULF OF HONDURAS...CENTRAL
AMERICA...AND E PAC. FOR MORE INFORMATION ON THIS WAVE PLEASE
SEE THE PACIFIC TROPICAL WEATHER DISCUSSION UNDER AWIPS HEADER
MIATWDEP FOR MORE DETAILS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR
13N16W TO 07N34W...WHERE THE ITCZ BEGINS AND EXTENDS FROM 07N34W
TO 03N48W. OTHER THAN CONVECTION ASSOCIATED WITH THE EASTERN
ATLC TROPICAL WAVE...SCATTERED MODERATE CONVECTION IS WITHIN 200
NM OF THE ITCZ/MONSOON TROUGH AXIS W OF 35W.

...DISCUSSION...

GULF OF MEXICO...

AN UPPER TROUGH THAT EXTENDS FROM THE NW ATLC TO THE FL
PENINSULA SUPPORTS A FRONTAL SYSTEM OVER N FL WITH A PRE-FRONTAL
TROUGH THAT EXTENDS FROM 29N86W TO CENTRAL FL NEAR 28N81W AND
OVER THE W ATLC. THE COMBINATION OF DEEP MOISTURE...LOW LEVEL
CONVERGENCE WITH THE SURFACE TROUGH...AND UPPER LEVEL
DIFFLUENCE AROUND THE BASE OF THE UPPER TROUGH IS SUPPORTING
CLUSTERS OF MODERATE CONVECTION WITH EMBEDDED THUNDERSTORMS FROM
25N TO 29N BETWEEN 89W AND THE FL PENINSULA. ELSEWHERE OVER THE
GULF...A SURFACE RIDGE AXIS EXTENDS FROM THE W ATLC TO THE W
CUBA AND NW OVER THE GULF TO THE TX COAST. GENTLE TO MODERATE
ANTICYCLONIC WINDS ARE OVER THE GULF S OF THE SURFACE TROUGH. W
TO NW WINDS OF 10 TO 15 KT ARE N OF THE TROUGH. A COLD FRONT
WILL ENTER THE NE GULF TONIGHT AND MERGE WITH THE SURFACE TROUGH
ON SUNDAY. THIS PORTION OF THE GULF WILL BE THE FOCUS OF ONGOING
CONVECTION THROUGH THIS TIME PERIOD.

CARIBBEAN SEA...

AN ELONGATED UPPER-LEVEL LOW CONTINUES OVER THE W CARIBBEAN
DOMINATING THE AREA W OF 73W WHILE AN UPPER-LEVEL HIGH CENTERED
OVER THE ATLANTIC WATERS E OF THE LESSER ANTILLES EXTENDS W
REACHING THE CENTRAL CARIBBEAN BASIN. UPPER LEVEL DIFFLUENCE
AROUND THE BASE OF THE UPPER LOW SUPPORTS ISOLATED MODERATE
CONVECTION OVER THE SW CARIBBEAN FROM 09N TO 12N W OF 81W.
ANOTHER AREA OF UPPER LEVEL DIFFLUENCE OVER THE NW CARIBBEAN
SUPPORTS SHOWERS AND ISOLATED THUNDERSTORMS FROM 20N TO 23N
BETWEEN 80W AND 86W. A TROPICAL WAVE IS BEGINNING TO IMPACT THE
LESSER ANTILLES. PLEASE REFER TO THE TROPICAL WAVES SECTION FOR
MORE DETAILS. A TIGHT PRESSURE GRADIENT BETWEEN A RIDGE OF HIGH
PRESSURE OVER THE W ATLC AND LOWER PRESSURES OVER S AMERICA
SUPPORTS FRESH TO STRONG TRADE WINDS S OF 17N BETWEEN 72W AND
81W. GENTLE TO MODERATE TRADE WINDS ARE ELSEWHERE OVER THE
CARIBBEAN. WINDS N OF COLOMBIA ARE EXPECTED TO INCREASE TO GALE
FORCE LATER TONIGHT AND AGAIN ON MONDAY NIGHT. PLEASE SEE THE
SPECIAL FEATURES SECTION FOR MORE DETAILS. OVER THE NEXT 24
HOURS CONVECTION IS EXPECTED TO SPREAD W OVER THE EASTERN
CARIBBEAN WITH A TROPICAL WAVE.

...HISPANIOLA...

DRY AIR IS INHIBITING CONVECTION OVER THE ISLAND TODAY. A
WESTWARD MOVING TROPICAL WAVE WILL BRING AN INCREASE IN MOISTURE
TO THE ISLAND BY LATE SUNDAY...WITH SHOWERS AND ISOLATED
THUNDERSTORMS POSSIBLE LATE SUNDAY THROUGH SUNDAY NIGHT.

ATLANTIC OCEAN...

AN UPPER TROUGH OVER THE NW ATLC SUPPORTS A COLD FRONT THAT
ENTERS THE AREA OF DISCUSSION NEAR 31N76W TO N FL NEAR 30N82W. A
PRE-FRONTAL SURFACE TROUGH EXTENDS FROM 30N76W TO CENTRAL FL
NEAR 28N82W. SCATTERED SHOWERS AND THUNDERSTORMS ARE FROM 25N TO
31N BETWEEN 70W AND THE FL PENINSULA...INCLUDING THE NORTHERN
BAHAMAS. SCATTERED MODERATE CONVECTION IS FROM 27N TO 31N
BETWEEN 57W AND 62W. THIS CONVECTION IS ASSOCIATED WITH UPPER
LEVEL DIFFLUENCE BETWEEN THE NW ATLC UPPER TROUGH AND AN UPPER
LOW CENTERED NEAR 27N65W. A 1028 MB HIGH CENTERED NEAR 34N34W
DOMINATES THE CENTRAL AND EASTERN ATLC W OF 50W WITH GENERALLY
FAIR WEATHER. TWO TROPICAL WAVES ARE OVER THE TROPICAL N ATLC.
PLEASE REFER TO THE TROPICAL WAVES SECTION FOR MORE DETAILS.
OVER THE NEXT 24 HOURS THE COLD FRONT WILL MOVE S AND BECOME
STATIONARY FROM CENTRAL FL TO NEAR 30N75W. CONVECTION WILL
REMAIN LIKELY WITHIN 200 NM OF THIS FRONTAL BOUNDARY.

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

$$

LATTO



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