[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 122338
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED OCT 12 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...TROPICAL WAVES...

FAR EAST ATLANTIC TROPICAL WAVE ALONG 20W S OF 14N MOVING W 10
KT. THE LAST FEW VISIBLE IMAGES FROM METEOSAT-8 PORTRAY A
LOW-AMPLITUDE CIRCULATION EMBEDDED WITHIN THE ITCZ...AND A
CONVECTIVE FLARE-UP IN THE VICINITY JUSTIFIES THIS POSITION. IT
SHOULD BE NOTED THAT 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. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 4N-10N BETWEEN 19W-27W.

SECOND EAST ATLANTIC TROPICAL WAVE TILTED NW/SE ALONG 32W/33W S
OF 19N MOVING W 10-15 KT. THE WAVE LIES ALONG THE LEADING EDGE
OF A PLUME OF SAHARAN DUST AND IS STILL BEING AFFECTED BY STRONG
MID-LEVEL EASTERLIES WHICH ARE GIVING THE WAVE ITS TILT. DEEP
CONVECTION IS MEAGER AT THE MOMENT...WITH SCATTERED MODERATE
CONVECTION MOSTLY CONFINED TO THE ITCZ FROM 4N-7N BETWEEN
31W-37W.

CENTRAL ATLANTIC TROPICAL WAVE ALONG 42W/43W S OF 19N CREEPING W
5-10 KT. THE POSITION MATCHES WELL WITH BUOY 41041 WHICH HAS HAD
LIGHT NELY WINDS AHEAD OF THE AXIS...AND AN ASSORTMENT OF
DRIFTING BUOY/SHIP OBSERVATIONS TO THE E WHICH HAVE HAD SELY
WINDS. THE WAVE'S MOVEMENT HAS DECELERATED PRIMARILY IN RESPONSE
TO A CLOSE UPPER LOW NEAR 17N48W AND THE ADJACENT 60 KT S/SW JET
RETARDING THE MEAN EASTERLY FLOW. ISOLATED SHOWERS/TSTMS NEAR
THE NRN PART OF THE WAVE FROM 15N-20N BETWEEN 37W-44W.

LOW-AMPLITUDE TROPICAL WAVE LOCATED ABOUT 430 NM E OF TRINIDAD
ALONG 53W/54W S OF 13N MOVING W NEAR 10 KT. THE UPPER LOW WHICH
IS AFFECTING THE WAVE ALONG 42W/43W IS ALSO PARTLY AFFECTING
THIS WAVE AND IS SLOWING ITS FORWARD MOTION. A SIGNIFICANT
CLUSTER OF SCATTERED MODERATE CONVECTION HAS FORMED NEAR THE
GREATEST LOW-LEVEL TURNING...FROM 7N-11N BETWEEN 49W-55W.

EAST CARIBBEAN TROPICAL WAVE ALONG 67W S OF 17N MOVING W 15 KT.
THE WAVE IS EMBEDDED WITHIN BROAD W/SW FLOW AND ITS SIGNATURE
CONTINUES TO BE MURKY AT BEST. HOWEVER...IT IS POSSIBLE THAT THE
WAVE MAY HAVE PULLED DRIER AIR FROM THE ATLC WWD ACROSS THE
LEEWARD AND WINDWARD ISLANDS...AND SHIFTED THE HEAVIEST
CARIBBEAN RAINFALL EVER SO SLIGHTLY TO THE W AS COMPARED TO
YESTERDAY. SEE CARIBBEAN SECTION BELOW REGARDING ASSOCIATED
CONVECTION.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 14N10W 12N19W...THEN ALONG 6N20W
13N31W...THEN ALONG 7N32W 14N42W 10N53W. WIDELY SCATTERED
CLUSTERS OF MODERATE/STRONG CONVECTION OVER W AFRICA FROM SIERRA
LEONE NWD TO SENEGAL...AND EWD INTO WRN MALI. SCATTERED
MODERATE/ISOLATED STRONG FROM 4N-12N BETWEEN 19W-27W IN
ASSOCIATION WITH THE TROPICAL WAVE ALONG 20W. WIDELY SCATTERED
MODERATE FROM 10N-13N BETWEEN 26W-29W. WIDELY SCATTERED MODERATE
FROM 4N-9N BETWEEN 32W-44W. SCATTERED MODERATE FROM 7N-10N
BETWEEN 49W-56W IN ASSOCIATION WITH THE TROPICAL WAVE ALONG
53W/54W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF IS COVERED BY A LARGE UPPER LEVEL RIDGE EXTENDING FROM
S/CNTRL MEXICO NEWD TO THE CAROLINA COAST...ANCHORED BY AN UPPER
HIGH W OF FT. MYERS FLORIDA NEAR 26N84W. EXCEPT FOR A NARROW AND
MINOR SWATH OF MOISTURE STREAMING FROM NE MEXICO TOWARDS
ALABAMA...THE AREA IS DOMINATED BY MODERATE/STRONG SUBSIDENCE
AND FAIR SKIES. THE ONLY NOTABLE SHOWER/TSTM ACTIVITY IS
ASSOCIATED WITH THE SEA BREEZE ALONG THE MEXICAN COAST...WITH
ISOLATED TSTMS FROM TAMPICO NWD TO THE U.S. BORDER. ISOLATED
SHOWERS ARE ALSO MOVING FROM THE FAR SE GULF TOWARDS THE YUCATAN
CHANNEL IN THE WAKE OF A SURFACE TROUGH WHICH HAS SWUNG SWD INTO
THE NW CARIBBEAN. 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 THE COPIOUS PLUME OF MOISTURE HAS BEEN ADVECTED OVER
HISPANIOLA...PUERTO RICO...AND THE VIRGIN ISLANDS AND HAS CAUSED
PROLIFIC RAINFALL ACCUMULATIONS AND FLOODING PROBLEMS. RADAR
ESTIMATED RAINFALL AMOUNTS OF OVER 11 INCHES HAVE BEEN OBSERVED
OVER THE PAST 2 DAYS ESPECIALLY ON THE S SIDE OF PUERTO RICO
WHERE THE SWLY FLOW IS IMPINGING ON THE MOUNTAINS. SIMILAR
RAINFALL AMOUNTS HAVE LIKELY OCCURRED ON THE S SIDE OF
HISPANIOLA. UPPER LEVEL OUTFLOW HAS INCREASED OVER THE AREA WITH
AN ANTICYCLONE HAVING FORMED NEAR 15N72W AND EASTERLY FLOW ALOFT
ADVECTING MUCH OF THE MOISTURE TOWARDS CENTRAL AMERICA. A 1004
MB LOW IS CENTERED OVER THE WINDWARD PASSAGE WITH A SURFACE
TROUGH EXTENDING SW TO 14N83W...AND MOST OF THE TSTMS 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 IS CURRENTLY MOVING ACROSS THE
DOMINICAN REPUBLIC AND COULD POSSIBLY SPREAD OVER PUERTO RICO
LATER TONIGHT. A SECOND SURFACE TROUGH IS PINWHEELING SWD FROM
THE LOW WWD ACROSS THE CAYMAN ISLANDS AND IS TRIGGERING ISOLATED
SHOWERS/TSTMS OVER THE FAR NW CARIBBEAN. THE PATTERN IS STILL
NOT EXPECTED TO CHANGE MUCH OVER THE NEXT 5 DAYS...WHICH WILL
CONTINUE TO THREAT FOR HEAVY RAINS AND FLOODING OVER PUERTO RICO
AND HISPANIOLA INTO EARLY NEXT WEEK.

WEST ATLANTIC...
THE SAME WEATHER SYSTEM AFFECTING THE CARIBBEAN CONTINUES NWD
INTO THE W ATLC WITH A 1004 MB LOW CENTERED S OF BERMUDA NEAR
29N65W AND A SURFACE TROUGH EXTENDING SW TO THE WINDWARD
PASSAGE. THESE SURFACE FEATURES ARE COLLOCATED WITH AN UPPER
TROUGH ALONG 32N68W 20N74W WHICH IS ADVECTING THE DEEP TROPICAL
MOISTURE NEWD PAST HISPANIOLA AND PUERTO RICO. SCATTERED
MODERATE/STRONG CONVECTION IS LOCATED E OF THE SURFACE TROUGH
FROM 22N-30N BETWEEN 58W-70W AND NEW CONVECTION IS NOW MOVING
OVER HISPANIOLA TOWARDS THE ADJACENT WATERS. DRY AIR IS
FILTERING IN BEHIND THE UPPER TROUGH AND IS PRODUCING MAINLY
FAIR SKIES W OF 70W INTO FLORIDA.

EAST/CENTRAL ATLANTIC...
A LARGE CUT-OFF UPPER LEVEL LOW HAS DEVELOPED OVER THE TROPICS
ABOUT 750 NM E OF THE LEEWARD ISLANDS NEAR 16N49W AND HAS
DRAGGED A LARGE AREA OF DRY AIR SWD BETWEEN IT AND THE LESSER
ANTILLES. CONVERSELY...THE LOW/TROUGH IS ALSO PULLING TROPICAL
MOISTURE NEWD OVER THE CENTRAL AND E ATLC WATERS SE OF A LINE
FROM TRINIDAD TO 30N26W. A SHORTWAVE TROUGH HAS DIPPED DOWN INTO
THE AREA ALONG 30N30W 24N40W AND IS INTERACTING WITH A SURFACE
TROUGH ALONG 19N42W 25N30W TO PRODUCE WIDELY SCATTERED
SHOWERS/TSTMS FROM 18N-26N BETWEEN 29W-40W. AN UPPER LEVEL
ANTICYCLONE 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 20W. THE NELY
TRADES HAVE STRENGTHENED OVER THE FAR E PART OF THE AREA AND A
PLUME OF SAHARAN DUST HAS BEGUN MAKING ITS WAY ACROSS THE
ATLC...MAKING IT AS FAR W AS 33W AS OF THE LATEST METEOSAT-8
VISIBLE IMAGE (AT 1915 UTC).

$$
BERG


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