Tropical Weather Discussion
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000
AXNT20 KNHC 260006
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURES...

A TIGHT PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE SW N
ATLC AND LOWER PRESSURE OVER COLOMBIA IS FORECAST TO SUPPORT
GALE-FORCE WINDS STARTING EARLY SUNDAY MORNING...WHICH ARE
EXPECTED TO CONTINUE THROUGH SUNDAY AFTERNOON. ASSOCIATED SEAS
WILL RANGE FROM 11 TO 14 FT. 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 ASSOCIATED WITH A 1012
MB LOW NEAR 12N26W...MOVING W AT APPROXIMATELY 15 KT.
ENHANCEMENTS OF METEOSAT IMAGERY SHOW THE WAVE IS BEING ENGULFED
BY SAHARAN DRY AIR WHILE DUST COVERS THE WAVE NORTHERN
ENVIRONMENT THAT CURRENTLY LACKS CONVECTION. SCATTERED MODERATE
CONVECTION IS SOUTH OF THE LOW AND THE MONSOON TROUGH FROM 08N
TO 11N BETWEEN 23W AND 28W BEING SUPPORTED BY A MODERATE MOIST
ENVIRONMENT AS DEPICTED BY SSMI TPW IMAGERY.

A TROPICAL WAVE IS OVER THE CENTRAL ATLC WITH AXIS NEAR 45W...
MOVING W AT 15 KT. METEOSAT SAL AND DUST TRACKING PRODUCTS AND
RGB IMAGERY SHOW SAHARAN DRY AIR AND DUST OVER THE WAVE
ENVIRONMENT...THUS HINDERING CONVECTIVE ACTIVITY.

A TROPICAL WAVE IS OVER THE EASTERN CARIBBEAN WITH AXIS NEAR
65W...MOVING W AT APPROXIMATELY 20 KT. SSMI TPW IMAGERY SHOW DRY
AIR DOMINATES THE WAVE ENVIRONMENT...EXCEPT SE OF THE WAVE AXIS
WHERE A SMALL SURGE OF DEEP MOISTURE ENHANCES ISOLATED SHOWERS S
OF 16N...INCLUDING THE WINDWARD ISLANDS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM THE AFRICAN COAST NEAR
12N16W TO A 1012 MB LOW NEAR 12N26W TO 08N36W. THE ITCZ BEGINS
NEAR 07N39W TO THE COAST OF FRENCH GUIANA NEAR 04N52W. OTHER
THAN CONVECTION ASSOCIATED WITH THE EASTERN ATLC TROPICAL
WAVE...SCATTERED MODERATE CONVECTION IS FROM 08N TO 15N E OF
20W.

...DISCUSSION...

GULF OF MEXICO...

AN UPPER-LEVEL TROUGH IS OVER THE NW ATLC WITH BASE EXTENDING S-
SW TO THE NE FLORIDA PENINSULA ADJACENT WATERS. THIS TROUGH
ALOFT SUPPORTS A COLD FRONT ACROSS THE NORTHERN FLORIDA
PENINSULA FROM 29N80W NW TO 30N84W WHERE IT TRANSITIONS TO A
STATIONARY FRONT. EAST OF THE UPPER TROUGH...A BROAD RIDGE
CENTERED OVER OKLAHOMA COVERS THE GULF OF MEXICO AND GENERATES A
DIFFLUENT WIND ENVIRONMENT OVER THE FLORIDA PENINSULA THAT ALONG
WITH ABUNDANT MOISTURE SUPPORT SCATTERED SHOWERS AND TSTMS
EXTENDING WEST TO THE EASTERN GULF E OF 90W. ELSEWHERE OVER THE
GULF...A BROAD SURFACE RIDGE OVER THE ATLC EXTENDS AN AXIS SW
ACROSS CENTRAL-SOUTHERN FLORIDA AND COVERS THE ENTIRE BASIN. THE
SURFACE RIDGE OVER THE GULF IS BEING ANCHORED BY A 1016 MB HIGH
NEAR 24N90W THAT IS FORECAST TO DISSIPATE WITHIN THE NEXT 24
HOURS. THIS RIDGE IS PROVIDING VARIABLE LIGHT WINDS ACROSS THE
GULF...EXCEPT THE NE BASIN WHERE N-NW WINDS OF 15 KT DOMINATE.
THE COLD FRONT IS FORECAST TO BECOME STATIONARY DURING THE NEXT
24 HOURS WITH A LOW CENTER DEVELOPING E OF CENTRAL
FLORIDA...WHICH WILL MOVE ACROSS THE PENINSULA TO THE E BASIN
MONDAY AFTERNOON. SHOWERS AND TSTMS ARE FORECAST TO REMAIN IN
PLACE FOR THE NE GULF DURING THIS PERIOD.

CARIBBEAN SEA...

AN ELONGATED UPPER-LEVEL LOW CONTINUES TO DOMINATE ACROSS
WESTERN CARIBBEAN WATERS WHILE A BROAD RIDGE CENTERED W OF
DOMINICA COVERS THE REMAINDER BASIN. UPPER-LEVEL DIFFLUENT WIND
FLOW BETWEEN THESE UPPER FEATURES ALONG WITH SHALLOW MOISTURE
SUPPORT ISOLATED SHOWERS AND TSTMS ALONG CUBA AND ADJACENT
SOUTHERN WATERS AS WELL AS WESTERN HISPANIOLA. A TROPICAL WAVE
IS OVER THE EASTERN CARIBBEAN MAINLY EMBEDDED IN A DRY
ENVIRONMENT WITH DUST BEING REPORTED OVER THE LEEWARD ISLANDS.
ISOLATED SHOWERS ARE SE OF ITS AXIS EXTENDING TO THE WINDWARD
ISLAND. SEE TROPICAL WAVES SECTION FOR FURTHER INFORMATION. A TIGHT
PRESSURE GRADIENT BETWEEN A RIDGE OVER THE SW N ATLC AND LOWER
PRESSURE OVER COLOMBIA SUPPORTS NE TO E WINDS OF 25 TO 30 KT
FROM 11N TO 13.5N BETWEEN 73W AND 77W WITH ASSOCIATED SEAS OF 9
TO 12 FT. ELSEWHERE FROM 10N TO 15N BETWEEN 72W AND 80W WINDS
ARE FROM THE NE-E RANGING FROM 20 TO 25 KT WITH SEAS FROM 8 TO
11 FT. THE REMAINDER OF THE CARIBBEAN S OF 16N BETWEEN 75W AND
82W HAVE WINDS OF 20 KT OR LESS WITH SEAS TO 9 FT PRIMARILY IN
NE TO E SWELL. WINDS N OF COLOMBIA ARE EXPECTED TO INCREASE TO
GALE FORCE EARLY SUNDAY MORNING. PLEASE SEE THE SPECIAL FEATURES
SECTION FOR MORE DETAILS.

...HISPANIOLA...

DIFFLUENT WIND FLOW ALOFT BEING GENERATED BY AN ELONGATED UPPER-
LEVEL LOW ACROSS THE WESTERN CARIBBEAN AND A BROAD RIDGE
CENTERED W OF DOMINICA COMBINED WITH SHALLOW MOISTURE SUPPORT
ISOLATED SHOWERS AND TSTMS OVER HAITI. SHOWERS ARE EXPECTED TO
CONTINUE OVERNIGHT SHIFTING TO THE WINDWARD PASSAGE. HOWEVER, A
TROPICAL WAVE IS EXPECTED TO MOVE S OF THE ISLAND ON
SUNDAY...INCREASING THE CHANCES OF SHOWERS MAINLY FOR THE E-SE
ISLAND.

ATLANTIC OCEAN...

AN UPPER-LEVEL TROUGH IS OVER THE NW ATLC WITH BASE EXTENDING S-
SW TO THE NE FLORIDA PENINSULA ADJACENT WATERS. THIS TROUGH
ALOFT SUPPORTS A COLD FRONT ANALYZED FROM 30N75W SW TO
29N80W...NW ACROSS THE FLORIDA PENINSULA TO 30N84W WHERE IT
TRANSITIONS TO A STATIONARY FRONT. EAST OF THE UPPER TROUGH...A
BROAD RIDGE CENTERED OVER OKLAHOMA COVERS THE GULF OF MEXICO AND
GENERATES A DIFFLUENT WIND ENVIRONMENT OVER THE FLORIDA
PENINSULA AND THE SW N ATLC WATERS. THIS DIFFLUENT ENVIRONMENT
ALOFT ALONG WITH ABUNDANT MOISTURE IN THE SW N ATLC SUPPORT
SCATTERED SHOWERS AND TSTMS N OF 25N W OF 74W. SIMILAR
CONVECTION IS OBSERVED N OF 27N BETWEEN 56W AND 64W. THE
REMAINDER BASIN IS BEING DOMINATED BY SURFACE RIDGING AND FAIR
WEATHER.

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

$$
NR



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