[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 160004
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU AUG 15 2013

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
2322 UTC.

...SPECIAL FEATURES...
TROPICAL STORM ERIN IS CENTERED NEAR 15.0N 27.5W AT 15/2100 UTC
OR ABOUT 210 NM W-SW OF THE CAPE VERDE ISLANDS MOVING W-NW AT 12
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB AND THE
MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUST TO 45 KT.
SCATTERED MODERATE CONVECTION IS FROM 12N-17N BETWEEN 24W-30W.
SEE LATEST FORECAST/ADVISORY UNDER AWIPS/ WMO HEADERS
MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS.

A TROPICAL WAVE ASSOCIATED WITH A 1009 MB LOW PRESSURE IS OVER
THE YUCATAN PENINSULA WITH AXIS EXTENDING FROM 24N88W...ALONG
BELIZE TO HONDURAS NEAR 15N88W. THE SYSTEM IS MOVING W-NW NEAR
10 KT. THE UPPER LEVEL ANTICYCLONIC CIRCULATION SUPPORTING THIS
SYSTEM HAS WEAKENED AND ITS REMNANTS ARE OVER THE NW CARIBBEAN
SEA WHERE DIVERGENT WINDS CONTINUE TO SUPPORT A LARGE BUT
DISORGANIZED AREA OF RAINSHOWERS AND TSTMS FROM 15N-25N BETWEEN
82W-89W. NORTHWESTERLY DEEP LAYER ENVIRONMENTAL WIND SHEAR IS
ASSISTING IN KEEPING THIS CONVECTION MOSTLY E OF THE WAVE AXIS.
DEVELOPMENT OF THIS SYSTEM IS NOT ANTICIPATED WHILE IT MOVES
OVER LAND...BUT THERE IS STILL POTENTIAL FOR DEVELOPMENT ONCE IT
MOVES OVER THE GULF OF MEXICO ON FRIDAY. FURTHER IN TIME...THE
LOW IS FORECAST TO MOVE TOWARD THE CENTRAL GULF OF MEXICO WHERE
THE UPPER-LEVEL WINDS WOULD ONLY FAVOR SLOW DEVELOPMENT...IF
ANY. CURRENTLY...THIS SYSTEM HAS A MEDIUM CHANCE...50
PERCENT...OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48
HOURS. RAINSHOWERS AND TSTMS ARE EXPECTED TO CONTINUE TO IMPACT
THE YUCATAN PENINSULA TODAY AND EXTEND TO THE SW GULF IN LESS
THAN 24 HOURS.

...TROPICAL WAVES...
A TROPICAL WAVE IS OVER THE CENTRAL TROPICAL ATLANTIC EXTENDING
AN AXIS FROM 21N45W TO 12N45W AND MOVING W NEAR 10 KT. TOTAL
PRECIPITABLE WATER IMAGERY SHOW THE WAVE CONTINUE EMBEDDED
WITHIN A MODERATE MOIST ENVIRONMENT AT THE LOWER LEVELS.
HOWEVER...METEOSAT SATELLITE IMAGERY SHOW SAHARAN DUST AND DRY
AIR SPREADING OVER THE WAVE ENVIRONMENT WHICH IS SUPPRESSING
CONVECTION.

A TROPICAL WAVE IS APPROACHING THE EASTERN CARIBBEAN. ITS AXIS
EXTENDS FROM 22N58W TO 12N59W AND IS MOVING NEAR 15 KT. TOTAL
PRECIPITABLE WATER INDICATE THAT MOISTURE HAS AMPLIFIED WITHIN
ITS ENVIRONMENT BUT REMAINS MODERATE. METEOSAT SATELLITE IMAGERY
SHOW THIS WAVE IS ON THE LEADING EDGE OF A SAHARAN DRY AIRMASS
WHICH IS SUPPRESSING CONVECTION.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS IN THE ATLC BASIN COMMENCES W OF
TROPICAL STORM ERIN NEAR 12N29W AND CONTINUES TO 13N45W 08N54W.
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS ALONG 08N54W TO
06N58W. BESIDES THE CONVECTION ASSOCIATED WITH THE TROPICAL
STORM AND WAVES ALREADY DISCUSSED...SCATTERED MODERATE
CONVECTION IS WITHIN 250 NM S OF THE MONSOON TROUGH AXIS BETWEEN
29W-48W AND WITHIN 200 NM N OF IT BETWEEN 50W-54W.

...DISCUSSION...

GULF OF MEXICO...
A TROPICAL WAVE ASSOCIATED WITH A 1009 MB LOW PRESSURE IS
CURRENTLY OVER THE YUCATAN PENINSULA PROVIDING THE SOUTHERN GULF
WITH SURFACE TROUGHINESS. SCATTERED MODERATE CONVECTION AND
TSTMS ASSOCIATED WITH THIS SYSTEM ARE OVER THE YUCATAN
PENINSULA...YUCATAN CHANNEL AND SE GULF S OF 25N BETWEEN 82W-
88W. THIS CONVECTION IS BEING ENHANCED BY MIDDLE TO UPPER LEVEL
DIFFLUENCE AND REMAINS MOSTLY E OF THE WAVE AXIS DUE TO
NORTHWESTERLY DEEP LAYER ENVIRONMENTAL WIND SHEAR. A BROAD
MIDDLE TO UPPER LEVEL TROUGH EXTENDING ACROSS THE CENTRAL AND
EASTERN STATES IS SUPPORTING A STATIONARY FRONT IN THE NW BASIN
ALONG 21N91W TO 28N95W. SCATTERED SHOWERS AND TSTMS ARE WITHIN
100 NM EITHER SIDE OF THE FRONTAL BOUNDARY BETWEEN 90W-94W. A
PREFRONTAL TROUGH IS OVER THE NE GULF FROM 30N85W TO 26N90W WITH
ISOLATED SHOWERS WITHIN 30 NM EITHER SIDE OF ITS AXIS.
OTHERWISE...FAIR WEATHER IS OVER THE REMAINDER BASIN SUPPORTED
BY A TONGUE OF DRY AIR IN THE LOWER AND MIDDLE LEVELS.

DEVELOPMENT OF THE TROPICAL DISTURBANCE IS NOT ANTICIPATED WHILE
IT MOVES OVER LAND...BUT THERE IS STILL POTENTIAL FOR
DEVELOPMENT ONCE IT MOVES OVER THE GULF OF MEXICO ON FRIDAY.
FURTHER IN TIME...THE LOW IS FORECAST TO MOVE TOWARD THE CENTRAL
GULF OF MEXICO WHERE THE UPPER-LEVEL WINDS WOULD ONLY FAVOR SLOW
DEVELOPMENT...IF ANY. RAINSHOWERS AND TSTMS ARE EXPECTED TO
CONTINUE TO IMPACT THE YUCATAN PENINSULA TODAY AND EXTEND TO THE
SW GULF IN LESS THAN 24 HOURS.

CARIBBEAN SEA...
AN UPPER LEVEL ANTICYCLONIC CIRCULATION IN THE NW CARIBBEAN SEA
WHICH HAS BEEN SUPPORTING THE TROPICAL DISTURBANCE NOW OVER THE
YUCATAN PENINSULA HAS WEAKENED. HOWEVER...DIVERGENT WINDS FROM
ITS REMNANTS CONTINUE TO SUPPORT A LARGE BUT DISORGANIZED AREA
OF RAINSHOWERS AND TSTMS FROM 15N-25N BETWEEN 82W-89W.
NORTHWESTERLY DEEP LAYER ENVIRONMENTAL WIND SHEAR IS ASSISTING
IN KEEPING THIS CONVECTION IN THIS REGION OF THE BASIN OR MOSTLY
E OF THE DISTURBANCE. CONVECTION ASSOCIATED TO THIS SYSTEM
EXTENDS ACROSS EASTERN CUBA AND ADJACENT WATERS BETWEEN THIS
PART OF THE ISLAND AND JAMAICA. FURTHER EAST OVER THE
HISPANIOLA...UPPER LEVEL DIFFLUENCE FROM AN INVERTED TROUGH OVER
THE CENTRAL BASIN AND RIDGING TO THE EAST FROM AN ANTICYCLONE
CENTERED NEAR 20N53W SUPPORTS ISOLATED SHOWERS AND TSTMS OVER
HAITI AND WESTERN DOMINICAN REPUBLIC. OTHERWISE...A SAHARAN DRY
AIRMASS IS MOVING ACROSS THE CENTRAL AND EASTERN CARIBBEAN
SUPPORTING FAIR WEATHER CONDITIONS.

LOW-LEVEL MOISTURE WILL BE ON THE INCREASE FOR THE LESSER
ANTILLES AND REMAINDER EASTERN CARIBBEAN OVER THE NEXT 24 HOURS
AS A TROPICAL WAVE ENTERS THE REGION.

HISPANIOLA...
UPPER LEVEL DIFFLUENCE FROM AN INVERTED TROUGH OVER THE CENTRAL
CARIBBEAN AND RIDGING TO THE EAST FROM AN ANTICYCLONE CENTERED
NEAR 20N53W SUPPORTS ISOLATED SHOWERS AND TSTMS OVER HAITI AND
WESTERN DOMINICAN REPUBLIC. THESE SHOWERS MAY PERSIST UNTIL
FRIDAY MORNING WHEN A DRY AIRMASS ENTERS THE ISLAND.
HOWEVER...WEATHER CONDITIONS ARE EXPECTED TO DETERIORATE FRIDAY
AFTERNOON AS THE TROPICAL WAVE CURRENTLY E OF THE LESSER
ANTILLES MOVES ACROSS THE MONA PASSAGE.

ATLANTIC OCEAN...
UPPER LEVEL DIFFLUENCE FROM THE WEAK ANTICYCLONE THAT SUPPORTS
THE TROPICAL DISTURBANCE OVER THE YUCATAN PENINSULA AND THE
BROAD TROUGH SUPPORTING THE STATIONARY FRONT N OF THE AREA
SUPPORTS SCATTERED SHOWERS AND TSTMS OVER CENTRAL FLORIDA AND
THE BAHAMAS FROM 24N-29N W OF 76W. FURTHER EAST...A NOW WEAK
MIDDLE TO UPPER LEVEL LOW CENTERED NEAR 29N65W SUPPORTS A
SURFACE TROUGH ANALYZED FROM 34N64W TO 28N70W. LOW-LEVEL
CONVERGENCE IN THE VICINITY OF THE SURFACE TROUGH ALONG WITH
UPPER LEVEL LIFT PROVIDED BY THE UPPER LEVEL LOW IS GENERATING
SCATTERED SHOWERS AND TSTMS FROM 29N-33N BETWEEN 66W-71W.
OTHERWISE...ASIDE FROM THE TROPICAL WAVES AND TROPICAL STORM
ALREADY DISCUSSED ABOVE...A SURFACE RIDGE ANCHORED BY A 1026 MB
HIGH CENTERED NEAR 34N46W DOMINATES THE REMAINDER BASIN THAT
ALONG WITH DRY AIR IN THE LOWER AND MIDDLE LEVELS SUPPORT FAIR
WEATHER.

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

$$
RAMOS


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