[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 120543
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI AUG 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURE...

TROPICAL STORM IRENE IS CENTERED NEAR 26.4N 64.9W...OR 356 NM SE
OF CAPE HATTERAS NORTH CAROLINA...AT 12/0300 UTC MOVING WNW AT
13 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 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. UPPER LEVEL OUTFLOW IS
STRONG IN THE N SEMICIRCLE WITH S SHEAR STILL PRESENT.
THE LOW LEVEL CENTER IS NOT WELL-DEFINED ON INFRARED SATELLITE
IMAGERY. CLOUD TOPS ARE NOT AS COLD AS IT COULD BE LEAVING ONLY
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 25N-29N
BETWEEN 60.5W-66W.

...TROPICAL WAVES...

TROPICAL WAVE IS JUST OFF THE AFRICAN COAST ALONG 19W S OF 22N
MOVING W 5-10 KT WITH A 1011 MB LOW ALONG THE WAVE 17N.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS BEING DRAWN
FROM INLAND OVER AFRICA AROUND THE LOW WITHIN WITHIN 75 NM OF
LINE FROM 19N17W TO INLAND OVER AFRICA AT THE SENEGAL BORDER
NEAR 16N15W. WAVE IS UNDER THE W EDGE OF AN UPPER HIGH THAT IS
INLAND OVER AFRICA...PARTIALLY OBSCURING THE SATELLITE
SIGNATURE.

TROPICAL WAVE IS ALONG 37W S OF 17N MOVING W 15-20 KT. WAVE
PRESENTS A LOW AMPLITUDE LOW LEVEL SIGNATURE. HOWEVER...THE MID
LEVEL FLOW IS BECOMING MORE PRONOUNCED. CLUSTERS OF SCATTERED
MODERATE CONVECTION ARE IN AN INVERTED-V PATTERN WITHIN 60 NM OF
LINE FROM 12N33W PEAKING AT THE WAVE AXIS NEAR 13N37W TO 11N42W.

TROPICAL WAVE IS ALONG 52W/53W S OF 16N MOVING W 15 KT. THIS
WAVE CONTINUES NOT TO BE VERY WELL-DEFINED AND ACTUALLY APPEARS
TO BE ASSOCIATED WITH AN EASTERLY WIND SURGE...WHOSE LEADING
EDGE IS NEAR THE W AXIS. DRY AIR AT ALL LEVELS LENDS THAT THERE
IS NO ASSOCIATED CONVECTION WITH THIS WAVE.

E CARIBBEAN TROPICAL WAVE ALONG 65W/66W S OF 19N MOVING W 10-15
KT. WAVE IS EMBEDDED WITHIN WEAK FLOW S OF T.S. IRENE BUT STILL
THERE IS AN INVERTED-V SIGNATURE NOTED ON THE INFRARED SATELLITE
IMAGERY BETWEEN THE VIRGIN AND ABC ISLANDS. ASSOCIATED DEEP
CONVECTION IS INLAND OVER SOUTH AMERICA.

W CARIBBEAN TROPICAL WAVE IS ALONG 86W S OF 21N MOVING W 15-20
KT. WAVE IS BENEATH AN UPPER HIGH LOCATED OVER NICARAGUA/
HONDURAS WHICH IS ENHANCING SCATTERED MODERATE/ISOLATED STRONG
CONVECTION OVER THE AREA S OF 17N W OF 83W...MOSTLY OVER
HONDURAS. ...ITCZ...

ITCZ AXIS CENTERED ALONG 11N20W 9N28W 10N42W 9N48W 11N62W.
WIDELY SCATTERED CLUSTERS OF SCATTERED MODERATE CONVECTION ARE
WITHIN 150 NM OF THE AXIS FROM 22W-48W.

...DISCUSSION...

GULF OF MEXICO...
CUT-OFF MID/UPPER LOW THAT HAS DOMINATED THE GULF THIS WEEK IS
NOW ALONG THE N GULF COAST NEAR MOBILE ALABAMA WITH A TROUGH
AXIS EXTENDING SSW TO THE COAST OF MEXICO AND THE W BAY OF
CAMPECHE. THIS IS ADVECTING TROPICAL MOISTURE ACROSS S MEXICO NE
ACROSS THE YUCATAN PENINSULA INTO THE SE GULF. IN ADDITION...A
WEAK SURFACE TROUGH STRETCHES FROM THE FLORIDA PANHANDLE NEAR
PANAMA CITY SW TO THE W GULF NEAR 26N92W. PORTION OF THE W GULF
IS UNDER MODERATE SUBSIDENCE PROVIDED BY THE UPPER LOW SO SKIES
ARE MAINLY FAIR. THUNDERSTORMS OVER THE YUCATAN PENINSULA ARE
MOVING WITHIN W WITHIN 45 NM ALONG THE COAST IN THE BAY OF
CAMPECHE E OF 96W. DEEP MOISTURE WILL BE MOSTLY LIMITED OVER THE
AREA THROUGH THE WEEKEND...SO ANY THUNDERSTORM ACTIVITY SHOULD
BE MAINLY OVER LAND AREAS WHERE HEATING IS GREATEST.

CARIBBEAN...
MID/UPPER LEVEL HIGH IS OVER THE HONDURAS/NICARAGUA BORDER
PRODUCING W TO S FLOW OVER THE W CARIBBEAN W OF 79W. THIS
COUPLED WITH AN INVERTED UPPER TROUGH STRETCHING FROM COLOMBIA
TO HAITI IS GIVING W CARIBBEAN DRY SUBSIDING AIR FROM 75W-82W
AND MOSTLY FAIR TO THE DEEP CARIBBEAN WATERS. THUNDERSTORMS ARE
MOVING OFFSHORE THE COASTS OF CUBA AND HAITI. MID/UPPER HIGH
OVER THE CENTRAL ATLC EXTENDS INTO THE E CARIBBEAN N OF 12N E OF
67W WHICH IS DRYING THE UPPER AIR OVER MOST OF THE AREA EXCEPT
OVER THE THE LESSER ANTILLES WERE SCATTERED THUNDERSTORMS ARE
FROM 11N-17N BETWEEN 57W-63W. THIS MOISTURE WILL HANG AROUND THE
E CARIBBEAN THROUGH SAT BEFORE ANOTHER SURGE OF DRY AIR ENTERS
THE AREA FROM THE NE.

WEST ATLANTIC...
MID/UPPER LEVEL HIGH ANCHORED OVER THE W ATLC NEAR 32N78W IS
EXTENDING A SHARP UPPER RIDGE AXIS S TO OVER CUBA AND THE RIDGE
OVER THE W CARIBBEAN. THIS RIDGE LIES ADJACENT TO A WEAK UPPER
LOW NE OF THE BAHAMAS NEAR 26N74W...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 MODERATE SUBSIDENCE BETWEEN THEM...AND SKIES ARE MOSTLY
CLEAR BETWEEN 69W-80W WITH SOME SCATTERED HIGH CLOUDS BETWEEN
74W-77W. ELSEWHERE ISOLATED THUNDERSTORMS ARE LOCATED N OF 30N
ALONG THE GEORGIA COAST.

CENTRAL/EAST ATLANTIC...
A DIGGING DEEP LAYERED TROUGH IS TO THE E OF T.S. IRENE WITH THE
AXIS EXTENDING THROUGH 32N37W SW ALONG 27N46W TO A BASE NEAR
22N52W. THE UPPER TROUGH IS PUSHING A WEAK COLD FRONT TO THE SE
ALONG 32N31W 30N37W 31N43W TO A 1021 MB LOW AT THE END OF THE
FRONT NEAR 30N45W. BROAD SW MID/UPPER LEVEL FLOW IS AHEAD OF THE
TROUGH OVER THE REMAINDER OF THE SUBTROPICS...WITH DRY AIR E OF
40W TO THE AFRICAN COAST. FARTHER S...MID/UPPER LEVEL HIGH IS
LOCATED SE OF T.S. IRENE...AND NE OF THE LEEWARD ISLANDS NEAR
22N58W. A CONVERGENCE LINE EXTENDS SE OF IRENE AND HAS TRIGGERED
SCATTERED MODERATE CONVECTION FROM 11N-17N BETWEEN 57W-63W. DEEP
EASTERLY FLOW EXTENDS ACROSS MOST OF THE TROPICAL ATLC WITH THE
EXCEPTION OF THE FAR E ATLC WHERE A WEAK MID/UPPER LEVEL LOW IS
JUST S OF THE CAPE VERDE ISLANDS. THIS LOW HAS FORCED DRY AIR
TO PLUNGE S TO 12N WHILE ALLOWING DEEPER MOISTURE TO EXPAND
N TO THE W SAHARA/MOROCCO BORDER. THIS SET-UP IS PROVIDING A
FAVORABLY DIVERGENT ENVIRONMENT OF THE TROPICAL WAVE WHICH
RECENTLY MOVED OFF THE AFRICAN COAST.

$$
WALLACE


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