[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 112340
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU AUG 11 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.

...SPECIAL FEATURE...

TROPICAL STORM IRENE CENTERED NEAR 25.7N 63.9W...OR 825 NM SE OF
CAPE HATTERAS NORTH CAROLINA...AT 11/2100 UTC MOVING WNW 13 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE 1000 MB. MAXIMUM SUSTAINED
WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS. IRENE IS SLOWLY DEVELOPING A MORE
COMPREHENSIVE CONVECTIVE STRUCTURE AND APPEARS TO BE FINALLY
SHAKING THE ILL EFFECTS OF DRY AIR AND SHEAR. UPPER LEVEL
OUTFLOW IS EXPANDING ESPECIALLY TO THE N AND W OF THE SYSTEM
ALTHOUGH SLY UPPER LEVEL FLOW IS STILL IMPINGING A LITTLE SHEAR
OVER THE SRN SEMICIRCLE. THE CONVECTION HAS RESPONDED BY
SHIFTING PRIMARILY TO THE N AND E OF THE CENTER WITH NUMEROUS
MODERATE/STRONG FROM 25N-28.5N BETWEEN 60W-66W.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED ABOUT 100 NM W OF THE AFRICAN COAST ALONG
18W/19W S OF 19N MOVING W 5-10 KT. A 1008 MB LOW IS LOCATED
ALONG THE WAVE ABOUT 70 NM NW OF DAKAR NEAR 15N18.5W BASED ON
WIND AND PRES OBSERVATIONS FROM NEARBY SHIPS AND LAND STATIONS.
THE WAVE IS DEVELOPING A WELL-DEFINED SIGNATURE WITH MID-LEVEL
CLOUDINESS BEGINNING TO "SPILL OVER" THE WAVE AXIS FROM THE
E...AND CONVECTION BEING ORIENTED ALONG A LINE FROM S OF THE
CAPE VERDES NEWD INTO W/CNTRL MAURITANIA. SCATTERED
MODERATE/STRONG INLAND OVER WRN MAURITANIA AND SENEGAL FROM
13N-22N BETWEEN 11W-17W. OTHER DEEP CONVECTION IS FARTHER W
ALONG THE ITCZ. SHOWERS/TSTMS ARE EXPECTED TO MOVE OVER THE CAPE
VERDE ISLANDS ON FRI AND SAT AS THE WAVE PASSES BY.

TROPICAL WAVE ALONG 35W S OF 16N MOVING W 15-20 KT. THE WAVE IS
LOW-AMPLITUDE AND ENSHROUDED BY DRY AIR TO ITS N...BUT A SMALL
CLUSTER OF SHOWERS AND TSTMS HAS BEEN MAINTAINED ALONG THE ITCZ
AND PROGRESSING TO THE W WITH SOME SORT OF MID-LEVEL
CIRCULATION. SCATTERED SHOWERS/TSTMS FROM 8N-13N BETWEEN 35W-41W.

TROPICAL WAVE ALONG 50W S OF 16N MOVING W 15 KT. THIS WAVE IS
NOT VERY WELL-DEFINED AND ACTUALLY APPEARS TO BE ASSOCIATED WITH
AN EASTERLY WIND SURGE...WHOSE LEADING EDGE IS ALONG 10N45W
20N54W. THERE IS NO ASSOCIATED CONVECTION WITH THIS WAVE.

EAST CARIBBEAN TROPICAL WAVE ALONG 65W/66W S OF 20N MOVING W
15-20 KT. THE WAVE IS EMBEDDED WITHIN WEAK FLOW S OF T.S. IRENE
BUT STILL THERE IS AN INVERTED-V SIGNATURE NOTED IN VISIBLE AND
SHORTWAVE INFRARED IMAGERY S OF THE VIRGIN ISLANDS. SCATTERED
MODERATE CLUSTERS OF CONVECTION ARE LOCATED OVER NRN VENEZUELA.

WEST CARIBBEAN TROPICAL WAVE MOVING INLAND OVER CENTRAL AMERICA
ALONG 84W S OF 20N MOVING W 20 KT. INSTABILITY ASSOCIATED WITH
THE WAVE IS INCREASING THE COVERAGE AND INTENSITY OF SEA BREEZE
CONVECTION WHICH HAS DEVELOPED FROM ERN HONDURAS TO NRN COSTA
RICA. NUMEROUS MODERATE/STRONG CONVECTION FROM 9N-16N BETWEEN
83W-86W.

...ITCZ...

ITCZ AXIS CENTERED ALONG 11N19W 11N35W 9N45W 13N65W. SCATTERED
MODERATE CONVECTION WITHIN 75 NM OF THE AXIS BETWEEN 21W-27W.
WIDELY SCATTERED MODERATE WITHIN 90 NM S OF THE AXIS BETWEEN
37W-45W.

...DISCUSSION...

GULF OF MEXICO...
A VIGOROUS CUT-OFF UPPER LOW CONTINUES TO SIT AND SPIN OVER THE
FAR N GULF WATERS...ABOUT 90 NM S OF MOBILE ALABAMA NEAR 29N87W.
A SHARP TROF EXTENDS SW OF THE LOW TO NEAR 22N95W AND THIS IS
PUMPING DEEP TROPICAL MOISTURE FROM SRN MEXICO NEWD ACROSS THE E
GULF WATERS AND FLORIDA. IN ADDITION...A WEAK SFC TROF STRETCHES
FROM THE FLORIDA/GEORGIA BORDER SW TO THE LOUISIANA COAST AND IS
PROVIDING A FOCUS FOR SOME OF THE TSTM ACTIVITY. WIDELY
SCATTERED TSTMS EXTEND FROM S FLORIDA TO THE FL PANHANDLE...THEN
WWD INTO SE LOUISIANA WITH ONLY ISOLATED ACTIVITY OVER THE
NEARSHORE GULF WATERS. MOST OF THE W GULF IS UNDER SUBSIDENCE
PROVIDED BY THE UPPER LOW SO SKIES ARE MAINLY FAIR. SEA BREEZE
TSTMS OVER THE YUCATAN PENINSULA MAY MOVE OFFSHORE THE W COAST
OF THE YUCATAN LATER TONIGHT BUT SHOULD QUICKLY DISSIPATE WITH
THE LOSS OF AFTERNOON HEATING. DEEP MOISTURE WILL BE MOSTLY
LIMITED OVER THE AREA THROUGH THE WEEKEND...SO ANY TSTM
DEVELOPMENT SHOULD BE MAINLY OVER LAND AREAS WHERE HEATING IS
GREATEST.

CARIBBEAN...
AN UPPER LEVEL HIGH OVER THE GULF OF HONDURAS...COUPLED WITH AN
INVERTED TROF STRETCHING FROM THE COAST OF COLOMBIA TO PUERTO
RICO...IS DRIVING 35 KT NORTHERLY FLOW OVER THE W CARIBBEAN. THE
FLOW IS CHARACTERIZED MAINLY BY DRY SUBSIDING AIR TO THE W OF
THE UPPER TROF SO THE WEATHER IS MOSTLY FAIR WHERE THERE IS NO
EFFECTS FROM TSTMS MOVING OFFSHORE THE COASTS OF CUBA AND
JAMAICA. WIDESPREAD TSTMS HAVE DEVELOPED OVER CNTRL AMERICA AND
THE YUCATAN PENINSULA...BUT THIS ACTIVITY WILL CONTINUE
PENETRATING TO THE W ALONG A TROPICAL WAVE. FARTHER E...THE
UPPER FLOW IS MAINLY S/SELY BUT THE ATMOSPHERE IS STILL A LITTLE
TOO DRY TO PRODUCE WIDESPREAD SHOWER ACTIVITY...EVEN ALONG A
TROPICAL WAVE MOVING ACROSS THE E PART OF THE BASIN. HOWEVER...A
CONVERGENCE LINE LOCATED E OF THE ISLANDS IS PRODUCING SCATTERED
TSTMS AT THE MOMENT AND SOME OF THIS ACTIVITY MAY BEGIN TO
SPREAD FROM BARBADOS/ST. VINCENT NWD TO ANTIGUA/MONTSERRAT LATER
TONIGHT. THIS MOISTURE WILL HANG AROUND THE E CARIBBEAN THROUGH
SAT BEFORE ANOTHER SURGE OF DRY AIR ENTERS THE AREA FROM THE NE.

WEST ATLANTIC...
AN UPPER LEVEL RIDGE AXIS EXTENDS FROM A HIGH OVER THE GULF OF
HONDURAS NEWD ACROSS S FLORIDA AND THE FAR WRN ATLC WATERS...TO
ANOTHER UPPER HIGH E OF SAVANNAH GEORGIA NEAR 31N79W. THE RIDGE
LIES ADJACENT TO A WEAKENING UPPER LOW NE OF THE BAHAMAS NEAR
27N73W...BUT THIS FEATURE APPEARS TO BE BEING DROWNED OUT BY THE
EXPANDING OUTFLOW OF T.S. IRENE. IN FACT...THE ENTIRE W ATLC IS
UNDER A FAVORABLY LOW-SHEAR ENVIRONMENT NOW THAT LARGE-SCALE
RIDGING HAS DEVELOPED OVER THE AREA. THE UPPER LOW AND IRENE ARE
JOINING FORCES TO PRODUCE AN AREA OF SUBSIDENCE BETWEEN
THEM...AND SKIES ARE MOSTLY CLEAR BETWEEN 66W-73W. ELSEWHERE
ISOLATED TSTMS ARE LOCATED N OF 30N BETWEEN 75W-79W DUE TO WEAK
TROUGHING ALONG THE CAROLINA COAST.

CENTRAL/EAST ATLANTIC...
A DIGGING UPPER TROF HAS BY-PASSED T.S. IRENE AND IS ALIGNED
ALONG 49W N OF 25N. THE TROF IS PUSHING A WEAK COLD FRONT TO THE
S ALONG 32N33W 30N38W 31N45W...WITH A 1022 MB LOW AT THE END OF
THE FRONT. BROAD SWLY MID/UPPER LEVEL FLOW LIES AHEAD OF THE
TROF OVER THE REMAINDER OF THE SUBTROPICS...WITH DRY AIR E OF
34W TO THE AFRICAN COAST. FARTHER S...AN UPPER LEVEL HIGH IS
LOCATED SE OF T.S. IRENE...AND NE OF THE LEEWARD ISLANDS NEAR
22N55W. A CONVERGENCE LINE EXTENDS SE OF IRENE AND HAS TRIGGERED
SCATTERED MODERATE CONVECTION FROM 12N-20N BETWEEN 56W-61W WHICH
IS SPREADING TOWARDS THE LESSER ANTILLES. DEEP EASTERLY FLOW
EXTENDS ACROSS MOST OF THE TROPICAL ATLC WITH THE EXCEPTION OF
THE FAR E ATLC WHERE A MID/UPPER LEVEL LOW IS DEVELOPING OVER
THE CAPE VERDE ISLANDS. THIS LOW HAS FORCED DRY AIR TO PLUNGE
SWD TO 12N WHILE ALLOWING DEEPER MOISTURE TO EXPAND NWD TO THE
WRN SAHARA/MOROCCO BORDER. THIS SET-UP IS PROVIDING A FAVORABLY
DIVERGENT ENVIRONMENT FOR THE TROPICAL WAVE WHICH RECENTLY MOVED
OFF THE AFRICAN COAST...AND SHEAR VALUES ARE BELOW THRESHOLD
VALUES TO POSSIBLY FOSTER TROPICAL DEVELOPMENT IN THE COMING
DAYS.

$$
BERG


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