[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON SEP 21 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
1715 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM IDA AT 21/1500 UTC IS NEAR 20.6N
48.0W. IDA IS MOVING TOWARD THE NORTH-NORTHWEST...OR 330
DEGREES...AT 6 KNOTS. THE MINIMUM CENTRAL PRESSURE IS 1003 MB.
THE MAXIMUM SUSTAINED WIND SPEEDS ARE 45 KNOTS WITH GUSTS TO 55
KNOTS. NUMEROUS MODERATE CONVECTION IS FROM 16N TO 23N BETWEEN
41W AND 50W. 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.

...TROPICAL WAVES...

A TROPICAL WAVE OVER THE EASTERN ATLC HAS AN AXIS THAT EXTENDS
FROM 17N19W TO 06N20W...MOVING W AT AROUND 10 KT. A POLEWARD
SURGE OF TROPICAL MOISTURE TO AROUND 19N IS NOTED IN SSMI TPW
ALONG THE WAVE. A 700 MB TROUGH IS EVIDENT ON GFS STREAMLINES
BETWEEN 18W AND 27W. SCATTERED MODERATE CONVECTION IS WITHIN 50
NM OF A LINE FROM 17N17W TO 11N22W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA AND RESUMES WEST OF A
TROPICAL WAVE NEAR 10N22W TO 08N35W WHERE THE ITCZ BEGINS AND
CONTINUES TO 08N44W. ISOLATED MODERATE CONVECTION IS WITHIN 50
NM OF EITHER SIDE OF THE MONSOON TROUGH AND ITCZ AXIS.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER RIDGE CENTERED OVER NORTHERN MEXICO HAS AN AXIS THAT
EXTENDS E ACROSS MUCH OF THE GULF BASIN. AN UPPER TROUGH OVER
THE S CENTRAL US IS DIGGING SE OVER THE N CENTRAL GULF THIS
AFTERNOON. THIS UPPER TROUGH SUPPORTS A COLD FRONT THAT ENTERS
THE GULF NEAR 20N87W TO 29N95W. A SURFACE TROUGH EXTENDS OVER
THE EASTERN GULF FROM 27N83W TO A 1013 MB SURFACE LOW NEAR
26N86W TO 25N91W. SCATTERED SHOWERS AND ISOLATED MODERATE
CONVECTION IS FROM 26N TO 20N BETWEEN 82W AND 92W. A DIURNAL
SURFACE TROUGH EXTENDS FROM 22N91W TO 18N93W. NO DEEP CONVECTION
IS NOTED WITH THIS TROUGH. ANOTHER SURFACE TROUGH EXTENDS FROM
LOW PRESSURE OVER THE W ATLC TO THE CENTRAL BAHAMAS TO THE SE
GULF NEAR 24N84W. ISOLATED THUNDERSTORMS ARE WITHIN 30 NM OF THE
TROUGH AXIS. MAINLY GENTLE SURFACE WINDS COVER THE GULF
BASIN...EXCEPT FOR MODERATE N TO NE WINDS N OF THE COLD FRONT.
OVER THE NEXT 24 HOURS THE COLD FRONT WILL BECOME STATIONARY
WHILE THE EASTERN GULF TROUGH SLOWLY DRIFTS S. CONVECTION WILL
REMAIN LIKELY BETWEEN THE COLD FRONT AND SURFACE TROUGH.

CARIBBEAN SEA...
A SURFACE TROUGH IS OVER THE NW CARIBBEAN FROM 22N86W TO 16N88W
SUPPORTING SCATTERED MODERATE CONVECTION FROM 15N TO 20N BETWEEN
83W AND 89W...INCLUDING THE GULF OF HONDURAS. AN UPPER LOW
CENTERED NEAR 15N79W SUPPORTS SCATTERED THUNDERSTORMS AND
ISOLATED MODERATE CONVECTION S OF 15N AND W OF 79W. GENERALLY
FAIR WEATHER IS OVER THE CENTRAL AND EASTERN CARIBBEAN. MODERATE
TO FRESH TRADE WINDS COVER ARE S OF 15N BETWEEN 70W AND 78W OVER
THE S CENTRAL CARIBBEAN. MAINLY GENTLE TO MODERATE TRADE WINDS
ARE ELSEWHERE OVER THE CARIBBEAN. OVER THE NEXT 24 HOURS
CONVECTION WILL CONTINUE OVER THE NW CARIBBEAN AS THE SURFACE
TROUGH REMAINS NEARLY STATIONARY. CONVECTION WILL ALSO CONTINUE
NEAR AND SW OF THE UPPER LOW AS IT SLOWLY MOVES NW.

...HISPANIOLA...
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WILL OCCUR THIS
AFTERNOON AND EVENING IN DAYTIME HEATING. MAINLY FAIR CONDITIONS
ARE EXPECTED OVERNIGHT. A SIMILAR PATTERN IS FORECAST TO REPEAT
ONCE AGAIN ON TUESDAY AND TUESDAY NIGHT.

ATLANTIC OCEAN...
AN UPPER TROUGH EXTENDS FROM AROUND 30N72W SE TO THE CENTRAL
BAHAMAS AND WESTERN CUBA. THIS TROUGH SUPPORTS A SURFACE TROUGH
THAT EXTENDS FROM 31N70W TO 25N75W TO THE FL STRAITS NEAR
24N80W. ISOLATED MODERATE CONVECTION IS WITHIN 130 NM S AND E OF
THE SURFACE TROUGH. A BROAD UPPER LOW IS CENTERED NEAR 23N60W.
ISOLATED THUNDERSTORMS ARE WITHIN A FEW HUNDRED MILES OF THE
UPPER LOW CENTER. RECENT SCATTEROMETER IMAGERY INDICATES THAT A
SURFACE TROUGH HAS DEVELOPED OVER THE CENTRAL ATLC FROM NEAR
29N51W TO 26N56W. SCATTERED MODERATE CONVECTION IS WITHIN 125 NM
OF EITHER SIDE OF THIS NEW TROUGH AXIS. TROPICAL STORM IDA IS
OVER THE CENTRAL ATLC. PLEASE REFER TO THE SPECIAL FEATURES
SECTION FOR MORE DETAILS.  A SURFACE TROUGH EXTENDS FROM 12N47W
TO 06N55W OVER THE CENTRAL TROPICAL ATLC. SCATTERED SHOWERS ARE
WITHIN 160 NM OF THE TROUGH AXIS. A TROPICAL WAVE IS OVER THE
EASTERN ATLC. PLEASE REFER TO THE TROPICAL WAVES SECTION FOR
MORE DETAILS. OVER THE NEXT 24 HOURS EXPECT CONVECTION TO
CONTINUE NEAR THE CENTRAL ATLC SURFACE LOW AND IDA.

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

$$
LATTO
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