[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151754
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 15 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...

A 1012 MB LOW LOCATED MIDWAY BETWEEN THE CAPE VERDE ISLANDS AND
THE LESSER ANTILLES IS CENTERED NEAR 12N42W ALONG A TROPICAL
WAVE THAT EXTENDS FROM 17N42W THROUGH THE LOW TO 08N42W MOVING
NW N NEAR 10 KT. A 30 NM WIDE BAND OF SCATTERED MODERATE
/ISOLATED STRONG CONVECTION IS OBSERVED OVER THE NORTHERN
SEMICIRCLE FROM 13N43W TO 14N41W TO 12N40W. ANOTHER 30 NM WIDE
BAND OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS OVER
THE S SEMICIRCLE OF THE LOW FROM 08N45W TO 09N42W TO 11N41W.
SIMILAR ACTIVITY IS JUST S OF THE LOW WITHIN 45 NM OF 11N42W.
SOME FURTHER DEVELOPMENT OF THIS LOW IS POSSIBLE DURING THE NEXT
COUPLE OF DAYS AFTER WHICH THE UPPER LEVEL WINDS ARE EXPECTED TO
BECOME UNFAVORABLE FOR DEVELOPMENT. THERE IS A HIGH CHANCE OF
TROPICAL FORMATION OVER THE NEXT 48 HOURS.

A 1011 MB BROAD LOW S OF THE CAPE VERDE ISLANDS IS CENTERED NEAR
10N24W ALONG A TROPICAL WAVE THAT EXTENDS FROM 15N24W THROUGH
THE LOW TO 08N24W MOVING WNW NEAR 15 KT. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS WITHIN 30 NM OF LINE FROM 11N24W
TO 12N27W TO 14N30W. SCATTERED MODERATE CONVECTION IS SW OF THE
LOW AND WAVE FROM 08N-09N BETWEEN 25W-29W. THIS ACTIVITY IS
UNDER MID/UPPER LEVEL RIDGING AND CONTINUES TO SHOWS SIGNS OF
ORGANIZATION. ENVIRONMENTAL CONDITIONS ARE EXPECTED TO BE
CONDUCIVE FOR FURTHER DEVELOPMENT OF THIS SYSTEM. THERE IS A
MEDIUM CHANCE OF TROPICAL FORMATION OVER THE NEXT 48 HOURS.

...TROPICAL WAVES...

A RATHER ACTIVE TROPICAL WAVE IS ALONG 64W N OF 11N EXTENDING N
TO NEAR THE VIRGIN ISLANDS. IT IS MOVING W ABOUT 15 KT. THIS
WAVE HAS A WELL DEFINED CLOUD PATTERN ON LATEST SATELLITE
IMAGERY AS WELL AS IN THE 700 MB GFS STREAMLINE ANALYSIS. AS THE
WAVE AXIS PASSED THROUGH THE LESSER ANTILLES YESTERDAY AFTERNOON
AND EVENING SURFACE WINDS SHIFTED FROM NE-E TO SE IN DIRECTION
THERE. THE LATEST SSMI TPW IMAGERY DEPICTS THE WAVE TO BE
EMBEDDED WITHIN A SURGE OF DEEP MOISTURE. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE NOTED WITHIN 60 NM E AND
120 NM W OF THE WAVE N OF 13N. MOISTURE GUIDANCE SUGGESTS THAT
THIS WAVE WILL BE FOLLOWED BY DEEP ATMOSPHERIC MOISTURE AS IT
MOVES ACROSS THE REST OF THE EASTERN CARIBBEAN THROUGH WED.

A TROPICAL WAVE IS ANALYZED OVER THE WESTERN CARIBBEAN ALONG
82W/83W FROM 13N-20N MOVING W 10-15 KT. THE WAVE SIGNATURE IS
ALSO NOTICEABLE AT 700 MB...BUT LESS S OF 15N. DEEP CONVECTION
REMAINS LIMITED WITH THIS WAVE...HOWEVER SMALL CLUSTERS OF
SCATTERED MODERATE CONVECTION ARE MOVING S UNDER NORTHERLY FLOW
OCCURRING ON THE EASTERN PERIPHERY OF UPPER LEVEL RIDGING
LOCATED OVER THAT PORTION OF THE SEA.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH AXIS EXTENDS FROM ACROSS WESTERN AFRICA TO
THE COAST AT 15N17W...AND CONTINUES SW THROUGH THE 1011 MB LOW
ALONG THE EASTERN MOST TROPICAL WAVE ALONG 24W FROM 08N-15N WITH
1011 MB LOW PRESSURE NEAR 10N24W...THEN TO 11N34W AND TO JUST E
OF THE NEXT TROPICAL WAVE ALONG 42W FROM 08N-17N WITH 1012 MB
LOW PRESSURE NEAR 12N42W. THE ITCZ AXIS BEGINS JUST W OF THE
SECOND LOW AND WAVE...AND CONTINUES TO 10N50W TO THE S AMERICAN
COAST NEAR 9N60W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS WITHIN 120 NM N OF THE ITCZ BETWEEN 53W-56W. THE REMAINDER OF
THE CONVECTION IS ASSOCIATED WITH THE TROPICAL WAVES/LOWS
DESCRIBED ABOVE UNDER SPECIAL FEATURES.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH IN THE NW ATLC IS SUPPORTING A COLD FRONT IN THE
NW ATLC AND A STATIONARY FRONT THAT EXTENDS INTO THE DISCUSSION
AREA AND ENTERS THE GULF OF MEXICO FROM NEAR FORT MYERS FLORIDA
SW TO 25N88W AND NW TO 27N92W WHERE IT DISSIPATES. AN UPPER
LEVEL RIDGE EXTENDS FROM OVER MEXICO ALONG 20N COVERING THE GULF
MEXICO AND THE NW CARIBBEAN. THIS RIDGE IN COMBINATION WITH A
SHARP UPPER TROUGH MOVING ACROSS THE NW GULF IS PROVIDING A
DIFFLUENT FLOW ALOFT. SCATTERED MODERATE CONVECTION IS WITHIN 60
NM OF THE FRONT BETWEEN 90W-92W. SCATTERED TO NUMEROUS SHOWERS
AND ISOLATED TSTMS ARE ELSEWHERE N OF THE FRONT W OF 84W...AND S
OF THE FRONT E OF 85W. AS OF 15 UTC...A WEAKENING 1013 MB LOW IS
JUST INLAND THE COAST OF MEXICO AT 23N98W WITH A TROUGH NNE TO
24N97W AND S TO 22N98W. LARGE CLUSTERS OF SCATTERED STRONG
CONVECTION ARE NOTED FROM 20N-25N BETWEEN 92W-97W. THIS ACTIVITY
IS BEING MOSTLY SUSTAINED BY THE UPPER DIFFLUENT PATTERN THERE.
A SURFACE TROUGH...REMNANTS OF GRACE...EXTENDS ALONG THE COAST
OF SE FLORIDA THROUGH THE STRAITS OF FLORIDA TO NEAR 24N81W AND
TO OVER CUBA NEAR 22N81W. IT IS GENERATING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS OVER MUCH OF THE STRAITS OF FLORIDA AND
FLORIDA KEYS. THE FRONT AND 1013 MB LOW ARE FORECAST TO
DISSIPATE TONIGHT. THE SURFACE TROUGH...REMNANTS OF GRACE...
WILL MOVE OVER THE STRAITS OF FLORIDA THROUGH THIS AFTERNOON AND
EVENING...THEN STALL ALONG 88W BY WED NIGHT.

CARIBBEAN SEA...
AN UPPER RIDGE EXTENDS ALONG 20N FROM OVER MEXICO AND THE GULF
OF MEXICO TO 74W COVERING THE WESTERN CARIBBEAN. A SECOND UPPER
RIDGE EXTENDS FROM THE WESTERN ATLC TO OVER THE EASTERN
CARIBBEAN. AN UPPER LOW IS SEEN OVER THE SW CARIBBEAN NEAR
10N78W...AND EXTENDS AN UPPER TROUGH NE ALONG 16N73W TO OVER
HISPANIOLA. AT THE SURFACE...ARE TWO TROPICAL WAVES...PLEASE
REFER TO THE SECTION ABOVE FOR DETAILS. THE UPPER RIDGES ARE
PROVIDING DIFFLUENCE ALOFT TO GENERATE SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS N OF 18N TO CUBA BETWEEN 76W-85W.
CONVECTION OVER THE EASTERN CARIBBEAN UNDER THE SECOND RIDGE IS
MOSTLY ASSOCIATED WITH THE EASTERN CARIBBEAN TROPICAL WAVE
DESCRIBED ABOVE. THE WESTERN CARIBBEAN TROPICAL WAVE WILL REACH
THE YUCATAN PENINSULA BY WED...WHILE THE EASTERN CARIBBEAN
TROPICAL WAVE WILL MOVE ACROSS THE REMAINDER CENTRAL CARIBBEAN
BY WED AND REACH THE WESTERN CARIBBEAN THU.

...HISPANIOLA...
MOSTLY CLEAR SKIES ARE NOTED ACROSS THE ISLAND EARLY THIS
AFTERNOON...WITH THE EXCEPTION OF BUILDING CUMULUS CLOUDS ALONG
THE FAR NORTHERN PORTION...SE AND WESTERN PORTIONS. ISOLATED
SHOWERS ARE POSSIBLE WITH THE MORE MODERATE OF TYPE OF THESE
CLOUDS. A NARROW UPPER TROUGH STRETCHING FROM PANAMA NE TO
15N76W AND TO HAITI WILL REMAIN ABOUT STATIOANRY THROUGH WED...
THEN GRADUALLY SHIFT EASTWARD TO THE FAR NE CARIBBEAN BY LATE
THU. MOISTURE WILL BEGIN TO GRADUALLY INCREASE FROM THE SE THIS
AFTERNOON AND TONIGHT IN ADVANCE OF THE EASTERN CARIBBEAN
TROPICAL WAVE THAT WILL MOVE ACROSS THE ISLAND TONIGHT AND WED.
THE ASSOCIATE MOISTURE AND INSTABILITY WILL LEAD TO SCATTERED
SHOWERS AND THUNDERSTORMS TONIGHT THROUGH WED EVENING.

ATLANTIC OCEAN...
A NARROW UPPER TROUGH IN THE NW ATLC IS SUPPORTING A COLD FRONT
N OF THE AREA WITH A STATIONARY FRONT EXTENDING ALONG 32N68W TO
28N76W...THEN INLAND S FLORIDA NEAR VERO BEACH...AND CONTINUING
FROM THERE TO THE SW FLORIDA COAST NEAR NAPLES AND TO THE GULF
OF MEXICO. AREAS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION ARE SEEN N OF THE FRONT BETWEEN 75W AND THE FLORIDA
COAST...AND ALSO S OF THE FRONT TO THE NW BAHAMAS. A SURFACE
TROUGH...REMNANTS OF GRACE...HAS MOVED JUST INLAND THE SE
FLORIDA COAST...AND EXTENDS S FROM THERE ACROSS THE  STRAITS OF
FLORIDA AND TO THE N CENTRAL COAST OF CUBA NEAR 22N81W. IT IS
GENERATING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF 25N
TO THE CUBAN COAST W OF 79W. A SURFACE TROUGH IS LOCATED OVER
THE W/CENTRAL ATLC FROM 24N60W TO 28N59W. IT IS TO THE SW OF AN
ELONGATED UPPER LOW NEAR 31N56W THAT EXTENDS A NARROW TROUGH SW
TO 25N59W TO 24N68W. THE COMBINED ATMOSPHERIC INSTABILITY OF
THESE FEATURES IS RESULTING IN INCREASING SCATTERED SHOWERS AND
THUNDERSTORMS FROM 23N-28N BETWEEN 60W-68W...AND ALSO N OF 26N
BETWEEN 52W-60W. THE ABOVE SURFACE TROUGH IS A WEAKNESS IN THE
SURFACE RIDGE THAT DOMINATES THE ATLC E OF THE WESTERN ATLC
FRONT...AND IS ANCHORED BY A 1024 MB HIGH N OF THE AREA NEAR
34N38W. THE WESTERN ATLC FRONT N OF 30N WILL SHIFT E OF THE AREA
TONIGHT WHILE THE REMAINDER OF THE FRONT DISSIPATES. THE SURFACE
TROUGH...REMNANTS OF GRACE...WILL MOVE INTO THE GULF OF MEXICO
LATE THIS AFTERNOON AND EVENING. THE EASTERN CARIBBEAN TROPICAL
WAVE WILL REACH THE WINDWARD PASSAGE BY WED NIGHT.

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

$$
AGUIRRE
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