[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 130535
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT THU OCT 13 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0345 UTC.

...TROPICAL WAVES...

FAR E ATLC TROPICAL WAVE ALONG 21W/22W S OF 14N MOVING W 10-15
KT. DUE TO HIGH CLOUDS WAVE AXIS IS NOT READILY SEEN. THE
WAVELENGTH BETWEEN THE ATLC TROPICAL WAVES HAS SHORTENED
CONSIDERABLY...AND THE NEXT WAVE IS ONLY ABOUT 500 NM TO THE W
OF THIS WAVE STILL INLAND OVER AFRICA. SCATTERED MODERATE/STRONG
CONVECTION FROM 5N-14N BETWEEN 22W-26W.

SECOND E ATLC TROPICAL WAVE TILTED N TO SE ALONG 32W/34W S OF
19N MOVING W 10 KT. WAVE LIES ALONG THE LEADING EDGE OF A PLUME
OF AFRICAN DUST AND IS STILL BEING AFFECTED BY STRONG MID-LEVEL
EASTERLIES WHICH ARE GIVING THE WAVE ITS TILT. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 45/60 NM OF LINE
11N33W-13N36W.

CENTRAL ATLC TROPICAL WAVE ALONG 43W S OF 20N DRIFTING W 5-10
KT. THE WAVE'S MOVEMENT HAS DECELERATED PRIMARILY IN RESPONSE TO
A CLOSE UPPER LOW NEAR 16N50W AND THE ADJACENT 60 KT S JET
RETARDING THE MEAN EASTERLY FLOW. ISOLATED SHOWERS/THUNDERSTORMS
FROM 5N9N BETWEEN 40W-47W.

LOW-AMPLITUDE TROPICAL WAVE E OF THE WINDWARD ISLANDS ALONG
54W/55W S OF 14N MOVING W 10 KT. THE UPPER LOW WHICH IS
AFFECTING THE WAVE ALONG 43W IS ALSO PARTLY AFFECTING THIS WAVE
AND IS SLOWING ITS FORWARD MOTION. SCATTERED SHOWERS ARE FROM
7N-10N BETWEEN 52W-57W.

E CARIBBEAN TROPICAL WAVE ALONG 68W S OF 17N MOVING W 10 KT.
WAVE IS EMBEDDED WITHIN BROAD SW UPPER FLOW AND ITS SIGNATURE
CONTINUES TO BE MASKED BY HIGH CLOUDS. SEE CARIBBEAN SECTION
BELOW REGARDING ASSOCIATED CONVECTION.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 14N16W 9N21W...THEN ALONG 7N23W
13N32W...THEN ALONG 10N34W 13N42W...THEN ALONG 12N45W 10N49W
11N53W...THEN ALONG 9N55W 12N61W. WIDELY SCATTERED CLUSTERS OF
SCATTERED MODERATE/STRONG CONVECTION DOT THE AREA FROM 2N-15N
BETWEEN 12W-31W AND FROM 5N-10N BETWEEN 30W-50W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF IS COVERED BY A LARGE UPPER LEVEL RIDGE EXTENDING FROM
S/CENTRAL MEXICO NE TO THE JUST OFF THE CAROLINA COAST...
ANCHORED BY AN UPPER HIGH IN THE SE GULF N OF THE YUCATAN
CHANNEL NEAR 24N85W. EXCEPT FOR A NARROW SWATH OF UPPER MOISTURE
STREAMING FROM NE MEXICO TOWARDS ALABAMA/GEORGIA...THE AREA IS
DOMINATED BY MODERATE/STRONG SUBSIDENCE AND FAIR SKIES. ISOLATED
THUNDERSTORMS MOVING OFF SW FLORIDA INTO FLORIDA BAY AND OFF E
CUBA INTO THE YUCATAN CHANNEL. A WEAK COLD FRONT MAY MOVE OFF
THE N GULF COAST INTO THE WEEKEND...PUSHING SLIGHTLY DRIER AIR
SWD OVER THE AREA...BUT IT IS A LITTLE TOO EARLY TO SAY HOW FAR
S THIS AIR MASS WILL GET.

CARIBBEAN...
THE MAIN PROBLEM OVER THE AREA CONTINUES TO BE THE HEAVY RAIN
PLAGUING PARTS OF THE CENTRAL AND SW CARIBBEAN. FORTUNATELY A
GOOD PORTION OF THE CONVECTIVE CLUSTERS HAVE REMAINED OVER
WATER...BUT ABUNDANT MOISTURE HAS BEEN ADVECTED OVER
HISPANIOLA...PUERTO RICO...AND THE VIRGIN ISLANDS HAS CAUSED
HEAVY RAINFALL ACCUMULATIONS AND FLOODING PROBLEMS. UPPER LEVEL
OUTFLOW HAS INCREASED OVER THE AREA WITH AN UPPER HIGH CENTERED
NEAR 15N75W AND EASTERLY FLOW ALOFT ADVECTING MUCH OF THE
MOISTURE TOWARDS CENTRAL AMERICA. A SURFACE TROUGH EXTENDS
THROUGH THE WINDWARD PASSAGE SW TO 15N70W TO OVER NICARAGUA...
AND MOST OF THE THUNDERSTORMS ARE OCCURRING S AND E OF THIS
BOUNDARY WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION UP
TO 350/400 NM TO THE SE. SOME OF THIS HEAVY ACTIVITY CONTINUES
TO MOVE ACROSS THE DOMINICAN REPUBLIC AND PUERTO RICO. A SECOND
SURFACE TROUGH EXTENDS FROM A 1006 MB LOW OVER THE CAYMAN
ISLANDS NEAR 19N81W W TO 19N86W AND IS TRIGGERING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS OVER THE FAR NW CARIBBEAN. THE
PATTERN IS STILL NOT EXPECTED TO CHANGE MUCH OVER THE NEXT 5
DAYS...WHICH WILL CONTINUE THE THREAT OF HEAVY RAINS AND
FLOODING OVER PUERTO RICO AND HISPANIOLA INTO EARLY NEXT WEEK.

WEST ATLANTIC...
THE SAME WEATHER SYSTEM AFFECTING THE CARIBBEAN CONTINUES
NORTHWARD INTO THE W ATLC WITH A 1006 MB LOW N OF THE REGION
NEAR 33N68W AND A SURFACE TROUGH EXTENDING SE TO A 1005 MB LOW
CENTERED S OF BERMUDA NEAR CONTINUING SSW TO THE WINDWARD
PASSAGE. THESE SURFACE FEATURES ARE COLLOCATED WITH A NARROW
UPPER TROUGH ALONG 32N68W 20N75W WHICH IS ADVECTING THE DEEP
TROPICAL MOISTURE NNE OVER HISPANIOLA AND PUERTO RICO. SCATTERED
MODERATE/STRONG CONVECTION IS LOCATED WITHIN 350/400 NM TO THE E
OF THE SURFACE TROUGH TO 33N. DRY AIR HAS FILTERED IN BEHIND THE
UPPER TROUGH AND IS PRODUCING MAINLY FAIR SKIES W OF 70W TO
FLORIDA.

EAST/CENTRAL ATLANTIC...
A LARGE CUT-OFF UPPER LEVEL LOW IS OVER THE TROPICS ABOUT 700 NM
E OF THE LEEWARD ISLANDS NEAR 16N50W AND HAS DRAGGED A LARGE
AREA OF DRY AIR S BETWEEN IT AND THE LESSER ANTILLES.
ALTHOUGH...THE LOW/TROUGH IS ALSO PULLING TROPICAL MOISTURE NE
INTO THE CENTRAL AND E ATLC WATERS SE OF A LINE FROM 20N49W TO
30N30W. A SHORTWAVE TROUGH IS ALONG 30N30W TO 23N43W AND IS
INTERACTING WITH A SURFACE TROUGH ALONG 26N30W TO 20N42W
PRODUCING WIDELY SCATTERED SHOWERS AND POSSIBLE ISOLATED
THUNDERSTORMS FROM 17N-27N BETWEEN 26W-41W. AN UPPER LEVEL HIGH
IS CENTERED SE OF THE CAPE VERDE ISLANDS NEAR 12N21W AND THE
DIFFLUENT W SIDE OF THIS FEATURE APPEARS TO BE ENHANCING
CONVECTION ASSOCIATED WITH THE TROPICAL WAVE ALONG 22W. THE NE
TRADES HAVE STRENGTHENED OVER THE FAR E PART OF THE AREA AND A
PLUME OF AFRICAN DUST CONTINUES TO MAKE ITS WAY ACROSS THE
ATLC...MAKING IT AS FAR W AS 35W.

$$
WALLACE


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