[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 221804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 22 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
1745 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM IDA AT 22/1500 UTC IS NEAR 20.5N
47.5W. IDA IS MOVING TOWARD THE EAST-SOUTHEAST...OR 120 DEGREES
AT 7 KNOTS. THE MINIMUM CENTRAL PRESSURE IS 1005 MB. THE MAXIMUM
SUSTAINED WIND SPEED IS 40 KNOTS WITH GUSTS TO 50 KNOTS. PUBLIC
ADVISORIES ABOUT TROPICAL STORM IDA ARE BEING ISSUED UNDER THE
WMO HEADER WTNT35 KNHC...AND UNDER THE AWIPS HEADER MIATCPAT5.
FORECAST/ADVISORIES ABOUT TROPICAL STORM IDA ARE BEING ISSUED
UNDER THE WMO HEADER WTNT25 KNHC...AND UNDER THE AWIPS HEADER
MIATCMAT5. CONVECTIVE PRECIPITATION...SE OF THE
CENTER...NUMEROUS STRONG FROM 18N TO 20N BETWEEN 45W AND 47W.
NUMEROUS MODERATE FROM 16N TO 21N BETWEEN 41W AND 48W. SCATTERED
MODERATE FROM 21N TO 26N BETWEEN 33W AND 44W.

...TROPICAL WAVES...

A TROPICAL WAVE IS OVER THE E ATLC WATERS WITH AXIS E OF THE
CAPE VERDE ISLANDS NEAR 22W...MOVING W AT 5-10 KT WITHIN THE
LAST 24 HOURS. CIRA LAYER PRECIPITABLE WATER IMAGERY SHOW THE
WAVE IS MAINLY EMBEDDED IN A MODERATE MOIST ENVIRONMENT FROM THE
SURFACE TO 850 MB. HOWEVER...THE IMAGERY ALSO SHOW DRY AIR IN
THE WAVE ENVIRONMENT WHICH IS LIMITING THE CONVECTION TO
ISOLATED MODERATE FROM 09N TO 18N E OF 27W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM WESTERN AFRICA NEAR 12N16W TO
07N24W TO 07N35W. THE ITCZ EXTENDS FROM 07N35W TO 07N41W TO
08N48W. ASIDE FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVE...SCATTERED MODERATE CONVECTION IS S OF THE MONSOON TROUGH
FROM 04N TO 10N E OF 23W.

...DISCUSSION...

GULF OF MEXICO...

A BROAD AREA OF LOW PRESSURE EXTENDS FROM THE NW ATLC SW TO AN
INVEST AREA OF 1008 MB NEAR 34N73W FROM WHICH A COLD FRONT
EXTENDS SW TO JACKSONVILLE FLORIDA. FROM THERE...THE FRONT
TRANSITIONS TO A STATIONARY FRONT THAT EXTENDS OVER THE NE GULF
OF MEXICO FROM 30N84W TO SE LOUISIANA NEAR 29N90W. THIS FRONTAL
SYSTEM IS BEING SUPPORTED BY A MIDDLE TO UPPER LEVEL TROUGH
ALONG THE E CONUS WITH BASE EXTENDING TO THE NORTHERN YUCATAN
PENINSULA. THE TROUGH ALOFT ALSO SUPPORTS A 1013 MB LOW CENTERED
NEAR 26N87W WITH ASSOCIATED SURFACE TROUGH EXTENDING FROM 28N85W
TO THE LOW CENTER TO 24N92W. SHALLOW MOISTURE BEING ADVECTED
FROM THE CARIBBEAN SEA ALONG WITH A DIFFLUENT ENVIRONMENT ALOFT
SUPPORT SCATTERED SHOWERS AND TSTMS EAST OF 87W. SIMILAR
CONVECTION IS OBSERVED IN THE BAY OF CAMPECHE S OF
19N...REMNANTS OF A FORMER SURFACE TROUGH. STRONG DEEP LAYER
WIND SHEAR AND DRY AIR SUPPORT FAIR WEATHER ELSEWHERE. E-NE WIND
FLOW OF 15 KT IS OVER THE N-NE BASIN...LIGHTER VARIABLE WINDS
ARE OVER THE REMAINDER GULF. LOW PRESSURE WILL DOMINATE ACROSS
THE BASIN THE NEXT TWO DAYS. SURFACE RIDGING WILL START TO BUILD
ACROSS THE GULF FRIDAY.

CARIBBEAN SEA...

SHALLOW MOISTURE ACROSS THE NW CARIBBEAN ALONG WITH A TROUGH
ALOFT SUPPORT SCATTERED SHOWERS AND TSTMS N OF 15N W OF 80W.
ABUNDANT MOISTURE OVER THE SW BASIN AND A DIVERGENT WIND
ENVIRONMENT ALOFT SUPPORT HEAVY SHOWERS AND TSTMS FROM 10N TO
15N W OF 78W. SIMILAR ATMOSPHERIC CONDITIONS OVER THE N-CENTRAL
CARIBBEAN SUPPORT ISOLATED SHOWERS IN THE WINDWARD PASSAGE AND
HAITI SOUTHERN ADJACENT WATERS. A BROAD UPPER LEVEL LOW IS OVER
THE ATLC NE OF PUERTO RICO EXTENDING A TROUGH S ACROSS THE
EASTERN CARIBBEAN TO NORTHERN VENEZUELA...ENHANCING SHOWERS AND
TSTMS ACROSS PUERTO RICO AND COASTAL WATERS. DRY AIR AND STRONG
DEEP LAYER WIND SHEAR INHIBIT CONVECTIVE ACTIVITY OVER THE
REMAINDER S-SE CARIBBEAN. TRADES OF 15 KT DOMINATE OVER THE
CENTRAL BASIN...LIGHTER WINDS ARE ELSEWHERE. NO SIGNIFICANT
CHANGES ARE EXPECTED THE NEXT THREE DAYS.

...HISPANIOLA...

MAINLY CLEAR SKIES ARE ACROSS THE ISLAND BEING INFLUENCED BY DRY
AIR SUBSIDENCE FROM RIDGING ALOFT AND STRONG DEEP LAYER WIND
SHEAR. TO THE W-SW OF THE ISLAND...SHALLOW MOISTURE AND A
DIFFLUENT ENVIRONMENT ALOFT SUPPORT SCATTERED SHOWERS IN THE
WINDWARD PASSAGE AND HAITI SOUTHERN ADJACENT WATERS.
AFTERNOON/EVENING SHOWERS ARE EXPECTED TO DEVELOP THE NEXT
THREE DAYS AS A MOIST AIRMASS MOVES ACROSS THE ISLAND.

ATLANTIC OCEAN...

THE MAIN FEATURE IN THE BASIN IS TROPICAL STORM IDA ALREADY
DISCUSSED IN THE SPECIAL FEATURES SECTION ABOVE. W-NW OF
IDA...AN UPPER LEVEL LOW SUPPORT SCATTERED SHOWERS AND TSTMS
FROM 20N TO 26N BETWEEN 58W AND 67W. OVER THE SW N ATLC...A
MIDDLE TO UPPER LEVEL TROUGH ALONG THE E CONUS WITH BASE
EXTENDING TO THE NORTHERN YUCATAN PENINSULA SUPPORTS A FRONTAL
SYSTEM ANALYZED AS A COLD FRONT FROM AN INVEST AREA ANCHORED BY
A 1008 MB LOW NEAR 34N73W SW TO A 1013 MB LOW NEAR 31N77W TO THE
COAST OF JACKSONVILLE WHERE IT TRANSITIONS TO A STATIONARY FRONT
INTO THE NE GULF OF MEXICO. A SURFACE TROUGH IS ANALYZED AHEAD
OF THE FRONT FROM 30N75W TO 27N78W. NO CONVECTION IS OBSERVED AT
THIS TIME. DIFFLUENCE ALOFT BEING GENERATED BY A SHORT-WAVE
TROUGH OVER THE NW CARIBBEAN AND RIDGING EXTENDING ACROSS THE
CENTRAL BAHAMAS SUPPORT SCATTERED SHOWERS AND TSTMS S OF 25N W
OF 74W. THE REMAINDER BASIN IS BEING INFLUENCED BY A SURFACE
RIDGE CENTERED BY A 1029 MB HIGH NEAR 43N31W.

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

$$
NR
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