[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 180005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI JUL 17 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.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE E ATLC WITH AXIS E OF THE CAPE VERDE
ISLANDS NEAR 20W...MOVING W AT 15 KT. THE WAVE IS ASSOCIATED
WITH A 1012 MB LOW NEAR 15N20W AND SSMI TPW IMAGERY INDICATE IS
EMBEDDED MAINLY IN SHALLOW MOISTURE. METEOSAT RGB AIRMASS...DUST
AND SAL TRACKING IMAGERY INDICATE THE PRESENCE OF SAHARAN DRY
AIR AND DUST IN THE WAVE ENVIRONMENT...WHICH IS SUPPORTING LACK
OF CONVECTION.

A TROPICAL WAVE IS OVER THE CENTRAL ATLC WITH AXIS APPROXIMATELY
ALONG 45W...MOVING W AT 15 KT. THE WAVE IS AHEAD OF A 1012 MB
LOW EMBEDDED IN THE MONSOON NEAR 10N39W. ABUNDANT MOISTURE
ASSOCIATED WITH THE LOW AND A DIFFLUENT WIND ENVIRONMENT AT THE
MIDDLE LEVELS SUPPORT SCATTERED MODERATE CONVECTION FROM 05N-13N
BETWEEN 35W AND 47W. SSMI TPW AND METEOSAT DUST AND SAL TRACKING
IMAGERY INDICATE THE PRESENCE OF SAHARAN DRY AIR AND DUST IN THE
REMAINDER WAVE ENVIRONMENT THAT ALONG WITH STRONG DEEP LAYER
WIND SHEAR HINDER CONVECTION.

A TROPICAL WAVE IS OVER THE W CARIBBEAN SEA WITH AXIS NEAR
81W...MOVING W AT 15-20 KT. SSMI TPW INDICATE THE WAVE IS MAINLY
EMBEDDED IN A MODERATE MOIST AIRMASS. HOWEVER...STRONG DEEP
LAYER WIND SHEAR HINDER CONVECTION.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO
10N25W TO A 1012 MB LOW NEAR 10N39W TO 11N44W. THE INTERTROPICAL
CONVERGENCE ZONE AXIS EXTENDS FROM 07N48W TO THE COAST OF GUYANA
NEAR 07N58W. ASIDE FROM CONVECTION ASSOCIATED WITH THE TROPICAL
WAVE ALONG 45W...SCATTERED MODERATE TO STRONG CONVECTION IS FROM
05N-10N BETWEEN 22W-31W.

...DISCUSSION...

GULF OF MEXICO...

A BROAD RIDGE COVERING GREAT PORTIONS OF THE ATLC BASIN EXTENDS
AN AXIS SW ACROSS THE CENTRAL AND SOUTHERN FLORIDA PENINSULA AND
THE GULF OF MEXICO E OF 93W. IN THE GULF...THE RIDGE IS ANCHORED
BY A 1018 MB HIGH NEAR 25N87W THAT PROVIDES VARIABLE WINDS OF 5
TO 10 KT ACROSS THE BASIN. A 1013 MB LOW IS OVER NORTHERN
FLORIDA EXTENDING A TROUGH ALONG THE PENINSULA TO 26N81W.
ABUNDANT MOISTURE BEING ADVECTED FROM THE SE CONUS AND THE SW N
ATLC TO THE PENINSULA ALONG WITH DIVERGENT WIND FLOW ALOFT
SUPPORT SCATTERED MODERATE CONVECTION AND ISOLATED TSTMS THAT
EXTEND TO THE E GULF N OF 25N E OF 89W. THE RIDGE IS FORECAST TO
REMAIN NEARLY STATIONARY AND ANCHORED ACROSS THE EAST-CENTRAL
GULF WATERS THROUGH LATE SATURDAY. CONVECTION ACROSS THE NE GULF
IS EXPECTED TO CONTINUE THROUGH SATURDAY NIGHT.

CARIBBEAN SEA...

GENERALLY NORTHERLY FLOW ALOFT IS NOTED ON WATER VAPOR IMAGERY W
OF 82W ON THE WESTERN PERIPHERY OF AN UPPER LEVEL LOW CENTERED
SE OF JAMAICA NEAR 15N75W...S-SW WIND FLOW DOMINATES ACROSS THE
E CARIBBEAN E OF 70W ASSOCIATED WITH A BROAD RIDGE OVER THE
CENTRAL TROPICAL ATLC. A TROPICAL WAVE IS MOVING ACROSS THE WESTERN
BASIN ASSOCIATED WITH A MODERATE MOIST ENVIRONMENT EXTENDING TO
THE CENTRAL CARIBBEAN. HOWEVER...STRONG DEEP LAYER WIND SHEAR S
OF 18N E OF 82W HINDER THE DEVELOPMENT OF CONVECTION. OVER THE
NW CARIBBEAN...BOTH THE MOISTURE AND DIFFLUENT WIND FLOW AT THE
MIDDLE LEVELS SUPPORT ISOLATED SHOWERS AND TSTMS N OF 18N W OF
77W...INCLUDING JAMAICA AND CUBA. THIS CONVECTION EXTENDS TO
WESTERN HISPANIOLA AND THE WINDWARD PASSAGE. A GENERALLY TIGHT
PRESSURE GRADIENT BETWEEN A RIDGE OVER THE ATLC EXTENDING ACROSS
THE NORTHERN BASIN AND LOWER PRESSURE OVER COLOMBIA SUPPORT NE
TO E WINDS OF 20 KT TO 25 KT FROM 11.5N TO 14N BETWEEN 69W AND
72W. TRADES OF 15 KT DOMINATE ELSEWHERE. THESE WINDS ARE
EXPECTED TO PERSIST THROUGH THE UPCOMING WEEKEND GENERALLY
BETWEEN 70W-80W.

...HISPANIOLA...

MODERATE MOISTURE ASSOCIATED WITH THE PASSAGE OF A TROPICAL WAVE
CURRENTLY OVER THE W CARIBBEAN COVERS THE WESTERN PORTION OF THE
ISLAND. AT THE MIDDLE LEVELS...A RIDGE ANCHORED OVER THE SW N
ATLC AND AN INVERTED TROUGH ALONG 77W GENERATE DIFFLUENT WIND
FLOW ACROSS WESTERN DOMINICAN REPUBLIC...HAITI AND THE WINDWARD
PASSAGE...THUS SUPPORTING A CLUSTER OF MODERATE CONVECTION AND
ISOLATED TSTMS. THIS OVERALL SYNOPTIC REGIME IS EXPECTED TO
PERSIST AND GENERATE CONVECTION THROUGH SATURDAY MORNING.

ATLANTIC OCEAN...

AN MIDDLE TO UPPER LEVEL TROUGH N OF THE AREA OF DISCUSSION
CONTINUE TO SUPPORT A STATIONARY FRONT...WHICH ASSOCIATED
MOISTURE ADVECTS ACROSS THE SW N ATLC WATERS WHERE IT CONVERGES
WITH MOISTURE INFLOW FROM THE NW CARIBBEAN WATERS...THUS
ENHANCING ISOLATED SHOWERS AND TSTMS N OF 23N W OF 66W. THE
REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE
OF A SURFACE RIDGE ANCHORED BY A 1022 MB HIGH CENTERED NEAR
26N64W AND A 1022 MB HIGH CENTERED NEAR 32N47W. HIGH PRESSURE
AND RIDGING WILL CONTINUE TO BE THE MAIN FEATURE ACROSS THE
BASIN DURING THE NEXT TWO DAYS.

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

$$
NR
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