[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 051757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE JUL 05 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.

...SPECIAL FEATURES...

TROPICAL STORM CINDY IS CENTERED NEAR 27.6N 90.4W AT 1800 UTC
ABOUT 125 MILES S-SW OF THE MOUTH OF THE MISSISSIPPI RIVER
MOVING NORTH 12 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
1000 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO
60 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT3/WTNT23 KNHC AND/OR MIATCPAT3/WTNT33 KNHC FOR
MORE DETAILS.  SATELLITE IMAGES INDICATE THAT THE CENTER OF
CINDY IS ON THE NW SIDE OF THE DEEP CONVECTION WITH PROMINENT
BANDING FEATURES IN THE E SEMICIRCLE OF THE CYCLONE.  SHIP AND
BUOY OBSERVATIONS SUGGEST THAT THE STORM IS INTENSIFYING AND
UPPER WINDS LOOK FAVORABLE FOR A BIT MORE DEVELOPMENT BEFORE
LANDFALL.  THE SYSTEM IS LIKELY TO SCOOT NORTHWARD TODAY AHEAD
OF A TROUGH DIPPING THRU THE MISSISSIPPI VALLEY ALONG SE TEXAS.
HEAVY RAIN SHOULD BE THE STORM'S MAIN THREAT WITH NUMEROUS
SHOWERS COVERING THE AREA BETWEEN MOBILE AND BATON ROUGE
SOUTHWARD TO THE COAST.  OTHERWISE SCATTERED TSTMS ARE FROM THE
LOUISIANA COAST TO 24N BETWEEN 87W-91W.

TROPICAL DEPRESSION FOUR IS UPGRADED TO TROPICAL STORM DENNIS AT
1500 UTC.  THE CYCLONE IS CENTERED NEAR 13.8N 67.6W AT 1800 UTC
OR 335 MILES SSW OF SAN JUAN PUERTO RICO MOVING WNW 16 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED
WIND SPEED IS 35 KT WITH GUSTS TO 45 KT. SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
AND/OR MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS.  DENNIS HAS AN
IMPRESSIVE SATELLITE PRESENTATION WITH BANDING IN ALL
QUADRANTS... EXCELLENT OUTFLOW AND TSTMS WRAPPING AROUND THE
APPARENT CENTER.  THIS IS ALSO A LARGE SYSTEM WITH 20-25 KT
WINDS STILL OBSERVED 300 MILES E OF THE CENTER AND RARE WLY
WINDS NOTED IN THE ABC ISLANDS.  DENNIS IS TO THE SOUTH OF A
RIDGE OVER THE W ATLC WHICH SHOULD KEEP THE SYSTEM MOVING
GENERALLY WNW FOR THE NEXT SEVERAL DAYS.  UNCERTAINTY EXISTS ON
HOW STRONG THE RIDGE WILL BE FOR LATE WEEK OVER THE GULF OF
MEXICO.  HOW QUICKLY CINDY LEAVES THE PICTURE AND HOW MUCH OF A
WEAKNESS IN THE SUBTROPICAL RIDGE IS LEFT BEHIND ARE STILL
UNKNOWN AND COULD AFFECT THE LONG-RANGE TRACK OF DENNIS.

...TROPICAL WAVES...

E ATLC WAVE IS ALONG 26W/27W S OF 18N MOVING W 15 KT.  THE SAL
SOUNDING FROM THIS MORNING SHOWED SE WINDS IN THE LOW/MIDDLE
LEVELS... AND THE SURFACE WINDS HAVE ALSO GONE SE AT THAT
STATION RECENTLY...INDICATIVE OF THE WAVE'S PASSAGE.  THE WAVE
LOOKS SIMILAR TO YESTERDAY WITH A LARGE CIRCULATION IN THE
LOW/MIDDLE CLOUDS WITHOUT ANY CONVECTION.

WEAK W-CENTRAL ATLC TROPICAL WAVE IS ALONG 55W S OF 16N MOVING W
15-20 KT. WAVE IS NOT WELL-DEFINED WITH LONG-TERM SATELLITE
LOOPS... GLOBAL MODELS... AND QUIKSCAT NOT SHOWING MUCH NEAR THE
WAVE.  IT IS POSSIBLE THAT THE WAVE IS WEAKENING AS IT
APPROACHES THE MUCH LARGER CIRCULATION OF DENNIS.  A SMALL
INCREASE IN MOISTURE IS ALL THAT CAN BE EXPECTED FROM THIS WAVE
IN THE WINDWARD ISLANDS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N16W 7N33W 10N47W.   THE ITCZ IS
NOT WELL-DEFINED W OF 50W.  ISOLATED MODERATE CONVECTION WITHIN
45 NM OF THE AXIS BETWEEN 31W-49W AND FROM 7N-11N BETWEEN
24W-30W.

...DISCUSSION...

GULF OF MEXICO...
OUTSIDE OF WEATHER ASSOCIATED WITH CINDY... THINGS ARE MOSTLY
DRY IN THE REGION.  MODERATE/STRONG SUBSIDENCE COVERS NW TEXAS
WITH VERY DRY ALOFT SUPPRESSING MOST CONVECTION.  MID/UPPER
RIDGING HAS BUILT INTO THE ERN AND SRN GULF WITH MUCH DRIER AIR
THAN AVERAGE OVER FLORIDA.  WIDELY SCATTERED TSTMS SHOULD FORM
OVER SE AND E MEXICO IN THE MOIST SE PORTION OF THE RIDGE.  A
LARGE PUSH OF DRY AIR IN THE MID/UPPER LEVELS FROM THE W ATLC
AND NW CARIBBEAN SHOULD OVERSPREAD MOST OF THE SE AND CENTRAL
GULF BEHIND CINDY DURING THE NEXT COUPLE OF DAYS BEFORE MOISTURE
ASSOCIATED WITH DENNIS BEGINS TO CREEP INTO THE AREA ON FRI.

CARIBBEAN SEA...
STORMY WEATHER COVERS THE LESSER ANTILLES INTO PUERTO RICO
COURTESY OF MOISTURE BEHIND DENNIS AND FAVORABLE SHEARING ALOFT
TO CREATE BANDING FEATURES.  MID/UPPER RIDGING AXIS IS ALONG 16N
E OF 70W WITH DEEP ELY FLOW W OF 75W.  HEAVY RAINS ARE POSSIBLE
IN HISPANIOLA AS BANDS OF TSTMS MOVE OVER THE ISLAND TODAY INTO
TOMORROW.  BY LATE TOMORROW A BIT DRIER AIR SHOULD PUSH INTO THE
LEEWARD ISLANDS... THEN INTO PUERTO RICO ON FRI.  THE WETTEST
AREA SHOULD REMAIN THE WINDWARD ISLANDS AS THE ITCZ SHOULD
REMAIN IN THE VICINITY ALONG WITH FAVORABLE UPPER CONDITIONS FOR
GREATER-THAN-AVERAGE CHANCES OF RAIN THRU THE WEEK.  IF THE
FORECAST TRACK FOR DENNIS IS CORRECT... MOST OF THE HEAVY RAIN
SHOULD AVOID CENTRAL AMERICA EXCEPT FOR MOUNTAINOUS AREAS ON
THE LEEWARD (WESTWARD) SIDE THAT COULD PRODUCE HEAVY RAIN IN SW
FLOW ALOFT.

ATLANTIC OCEAN...
NOT MUCH CHANGE FROM YESTERDAY WITH MID/UPPER RIDGING FROM NE
FLORIDA ACROSS THE W ATLC TO 31N55W.  MID-OCEANIC TROUGH IS
BENEATH THE RIDGE FROM 31N40W TO 21N63W AIDING A FEW TSTMS NEAR
A WEAK SURFACE TROUGH NEAR 27N55W.  MID/UPPER RIDGING DOMINATES
THE NE ATLC AS THE TYPICAL AFRICAN ANTICYCLONE HAS EXPANDED
NORTHWARD.  A SURGE IN MOISTURE IS ASSOCIATED WITH THE NEXT
WAVE... TRIMMING DOWN THE AREA OF DRY AIR ALOFT CONSIDERABLY
WITH THE MOISTURE E OF 30W S OF 23N.  RIDGING EXTENDS FROM THE
CAPE VERDE ISLANDS INTO AN UPPER HIGH NEAR 15N54W WITH STRONG
SUBSIDENCE BETWEEN 30W-50W KEEPING THINGS DRY WITH THE TYPICAL
SCATTERED STRATOCUMULUS CLOUDS N OF THE ITCZ.   WEAK UPPER LOW
IS SEEN NEAR 15N27W... EVIDENCE THAT THE WAVE NEAR THE CAPE
VERDES ISLANDS IS QUITE DEEP.  BELOW AVERAGE SHEAR CONTINUES
THROUGHOUT THE DEEP TROPICS BECAUSE OF THE ENHANCED TROPICAL
RIDGES.  AT THE SURFACE... 1032 MB HIGH NEAR THE AZORES CONTROLS
THE REST OF THE WEATHER WITH TRADES SLACKENING CONSIDERABLY E OF
40W AND NEAR SEASONABLE LEVELS W OF 40W EXCEPT NEAR DENNIS.

$$
BLAKE



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