[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131723
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE REPOSITIONED ALONG 27W/28W S OF 14N MOVING
W 15 KT.  THIS WAVE HAS GOTTEN SIGNIFICANTLY BETTER-DEFINED
DURING THE PAST 24 HOURS WITH A LARGE AREA OF CONVECTION ON THE
N AND E SIDE.  THERE IS EVEN SOME EVIDENCE OF A BROAD LOW
FORMING NEAR 10N.  SOME INCREASE IN ORGANIZATION SEEMS POSSIBLE
WITH UPPER-LEVEL WINDS NOT ALL THAT UNFAVORABLE... THOUGH IT IS
GETTING LATE TO HAVE SOMETHING FORM IN THE E TROPICAL ATLC.
WIDELY SCATTERED MODERATE CONVECTION FROM 6N-14N BETWEEN
24W-31W.

SECOND E ATLC TROPICAL WAVE TILTED NNW TO SSE FROM 6N35W 17N37W
MOVING W 10 KT. WAVE CONTINUES TO BE NEAR 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.
ISOLATED SHOWERS/TSTMS WITHIN 90 NM OF THE WAVE AXIS.

CENTRAL ATLC TROPICAL WAVE PREVIOUSLY ALONG 43W/44W IS BEING
DROPPED FROM THE ANALYSIS.  IT APPEARS THAT THIS FEATURE IS MORE
ITCZ-RELATED AND NOT A TRUE TROPICAL WAVE.

W-CENTRAL TROPICAL WAVE REPOSITIONED ALONG A SE TO NW LINE 7N53W
18N48W MOVING W 10 KT.  THIS IS A COMPLEX SCENARIO WITH THE WAVE
BECOMING INDISTINGUISHABLE FROM THE MID/UPPER LOW THAT NOW HAS A
SURFACE REFLECTION NEAR THE WAVE.  ISOLATED MODERATE CONVECTION
WITHIN 75 NM OF THE WAVE AXIS.  SOME INCREASE IN SHOWERS IS
LIKELY OVER THE LEEWARD/WINDWARD ISLANDS AS THE WAVE MOVES INTO
THE ISLANDS LATE FRI.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 13N17W 11N29W 8N38W 10N60W.  AN
OUTFLOW BOUNDARY IS KICKING UP SOME TSTMS JUST E OF THE CAPE
VERDES FROM 11N-16N BETWEEN 21W-24W.  ISOLATED MODERATE
CONVECTION WITHIN 75 NM OF AXIS W OF 51W.  WIDELY SCATTERED
MODERATE FROM 4N-9N BETWEEN 30W-41W.

...DISCUSSION...

GULF OF MEXICO...
PERSISTENT MID/UPPER HIGH SITS NEAR 25N85W IN THE E GULF WITH
DRY AIR ALOFT CONTROLLING THE REGION.  ISOLATED SHOWERS/FEW
TSTMS ARE IN THE STRAITS OF FLORIDA... OTHERWISE SKIES ARE
MOSTLY CLEAR EXCEPT FOR CENTRAL AND NE FLORIDA.  TWO VERY WEAK
LOW-LEVEL TROUGHS ARE NOTED IN THE ISOBARIC ANALYSIS.. ONE ALONG
84W AND THE OTHER IN THE BAY OF CAMPECHE NEAR 93W.  AN INCREASE
IN LOW CLOUDS AND A SLIGHT CHANCE OF SHOWERS IS ALL THAT CAN BE
EXPECTED BY THESE FEATURE.  LOW CLOUDS AND ISOLATED SHOWERS ARE
STILL BEHIND A WEAK TROUGH IN THE W ATLC EXTENDING ACROSS
CENTRAL FLORIDA TO ABOUT FT. MYERS.  IN SOME SENSE IT IS A BROAD
DIFFUSE COLD FRONT WITH LONG-LASTING NLY SURFACE WINDS BRINGING
DOWN SLIGHTLY COOLER/DRIER AIR AND CLOUD COVER KEEPING SOME
SMALL TEMPERATURE GRADIENTS.  BY SAT THIS WEATHER WILL SHIFT
SOUTHWARD TO S FLORIDA AND CLEAR OUT NE FLORIDA AS LOW PRESSURE
CAUSES THIS BOUNDARY.. THEN PROBABLY A COLD FRONT... TO MOVE
INTO THE FL STRAITS BY SUN.  OTHER ISOLATED SHOWERS ARE POSSIBLE
IN THE BAY OF CAMPECHE AND ALONG THE NE COAST OF MEXICO IN THE
NEXT FEW DAYS AS SURFACE RIDGING PERSISTS.

CARIBBEAN SEA...
NO BIG CHANGES IN THE CARIBBEAN TODAY.  LOW/MID-LEVEL W TO SW
FLOW DOMINATES WITH ONE TROUGH AXIS FROM NEAR W HAITI TO THE
GULF OF HONDURAS WITH A SMALL 1007 MB LOW NEAR 17.5N82W.  A FEW
TSTMS ARE IN THE GULF OF HONDURAS ON THE W SIDE OF SMALL
LOW-LEVEL DISTURBANCE.  LOW-LEVEL CONVERGENCE ALONG WITH
PLENTIFUL UPPER DIFFLUENCE IS CONTINUING TO PRODUCE A LARGE AREA
OF UNSETTLED WEATHER OVER THE CARIBBEAN SE OF THE TROUGH.
SCATTERED SHOWERS/TSTM COVER THE REGION N OF S AMERICA BETWEEN
70W-81W ORIENTED FROM HISPANIOLA TO JUST OFFSHORE OF COSTA
RICA... JUST SE OF JAMAICA.   STATIONARY UPPER HIGH IS NEAR
15N75W PROVIDING PLENTY OF UPPER DIFFLUENCE FOR NEARBY
SHOWERS/TSTMS.   RAIN IS A LITTLE LIGHTER OVER PUERTO RICO TODAY
WITH THE ACTIVITY NOW FOCUSED NEAR AND OFFSHORE OF HISPANIOLA.
THE THREAT FOR HEAVY RAIN... FLASH FLOODING AND DANGEROUS
MUDSLIDES EXISTS IN THE N CARIBBEAN WITH THIS WEATHER SYSTEM
ESPECIALLY IN HIGHER TERRAIN.   THE HIGHER MOISTURE AXIS
TROPICAL MOISTURE IS EXPECTED TO REMAIN OVER MOST OF THE
CARIBBEAN W OF THE LESSER ANTILLES THROUGH THE WEEKEND WITH AN
ENHANCED CHANCE OF FLOODING ESPECIALLY IN HISPANIOLA.  THE
CHANCE FOR HEAVY RAIN WILL ALSO INCREASE IN JAMAICA TOMORROW
WITH A WEAK LOW PRESSURE AREA TO THE W POSSIBILITY INCREASING
OROGRAPHICALLY-INDUCED RAIN.  OVERALL THE MOISTURE AXIS WILL
STILL BE VERY CLOSE TO PUERTO RICO... PROVIDING AN ENHANCED
CHANCE OF RAIN.

ATLANTIC OCEAN...
ERN PORTION OF THE GULF OF MEXICO MID/UPPER HIGH DOMINATES W OF
75W WITH DRY AIR ALOFT.  A MID/UPPER TROUGH WITH TWO LOWS LIES
FROM THE FIRST LOW NEAR 33N67W CLOSE TO BERMUDA THEN SSW TO A
SECOND LOW CENTER JUST NE OF THE TURKS/CAICOS ISLANDS THEN SW
INTO SE CUBA.  A SURFACE TROUGH AND LOW PRESSURE AREAS ARE
CO-LOCATED BENEATH THE UPPER FEATURES WITH A FEW TSTMS NEAR THE
LOW NE OF THE TURKS/CAICOS.  THERE MAY EVEN BE A LOW NEAR 30N62W
ACCORDING TO THE LATEST VISIBLE PICTURES.  IN ANY EVENT...UPPER
RIDGING FROM PUERTO RICO TO 29N56W IS PROVIDING A VERY DIVERGENT
ENVIRONMENT E OF THE UPPER TROUGH AND PRODUCING WIDELY SCATTERED
MODERATE CONVECTION WITHIN 180 NM OF LINE 21N65W AND 31N59.5W.
COMPUTER MODELS HAVE TRENDED TO MORE OF A NON-TROPICAL LOW NEAR
BERMUDA RATHER THAN SUBTROPICAL WITH LOTS OF WIND SHEAR THOUGH
UNCERTAINTY EXISTS.  UPPER RIDGING LIES OVER THE CENTRAL ATLC
FROM 29N52W EASTWARD TO 31N36W WITH PLENTIFUL HIGH CLOUDS NEAR
AND N OF THE RIDGE AXIS.  PARTLY CLOUDY SKIES ARE GENERALLY N OF
20N NEAR THE RIDGE AXIS SAVE NEAR A WEAK SURFACE TROUGH FROM
31N41W TO 26N46W WITH BROKEN LOW CLOUDS WITHIN 60 NM OF THE
BOUNDARY.  A MID/UPPER LOW IN NEAR 26N31W CAUSING ISOLATED TSTMS
FROM 23N-27N BETWEEN 29W-35W.  OTHERWISE ZONAL FLOW IS IN THE
SUBTROPICAL NE ATLC.  IN THE DEEP TROPICS...WELL-DEFINED
MID/UPPER LOW IS NEAR 16N51.5W CAUSING ISOLATED TSTMS S OF THE
LOW FROM 9N-15N BETWEEN 49W-54W.  UPPER HIGH LIES NEAR 11N26W
RIDGING WNW TO 14N40W.  ITCZ SHOWERS AND CONVECTION WITH THE E
ATLC WAVE IS BEING AIDED BY WIND SHEAR AND UPPER DIVERGENCE.  AT
THE SURFACE... 1025 MB HIGH IS JUST N OF MADEIRA ISLAND RIDGING
SW TO 29N24W THEN 27N39W.

$$
BLAKE

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