[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121751
TWDAT

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

...SPECIAL FEATURE...

TROPICAL STORM OPHELIA CENTERED NEAR 31.8N 77.3W...OR 150 NM ESE
OF CHARLESTON SOUTH CAROLINA AND 220 NM SSW OF CAPE HATTERAS
NORTH CAROLINA...AT 12/1800 UTC MOVING NW 3 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 989 MB. MAXIMUM SUSTAINED WIND SPEED
IS 60 KT WITH GUSTS TO 75 KT. SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC AND THE PUBLIC
ADVISORY UNDER HEADERS MIATCPAT1/WTNT31 KNHC FOR MORE DETAILS.
OPHELIA HAS BEEN SITUATED OVER THE SAME WATERS FOR THE PAST
SEVERAL DAYS AND THE RESULTANT UPWELLING HAS COOLED SEA SURFACE
TEMPERATURES BELOW 80F IN SPOTS. THE COOLER WATERS AND THE
ENTRAINMENT OF DRY AIR FROM OFF THE CONTINENT HAS CAUSED THE
DEEP CONVECTION NEAR THE CENTER TO DIE AND THE WIND FIELD TO
EXPAND. DURING THE MORNING HOWEVER...DEEP CONVECTION HAS ONCE
AGAIN BEGUN TO DEVELOP IN SPIRAL BANDS THAT EXTEND UP TO 150 NM
FROM THE CENTER. SCATTERED MODERATE CONVECTION FROM 30N-34N
BETWEEN 74W-81W. WIDELY SCATTERED MODERATE ALSO FROM 29N-33N
BETWEEN 70W-73W.

...TROPICAL WAVES...

CENTRAL ATLANTIC TROPICAL WAVE TILTED ALONG 10N45W 16N44W 23N40W
MOVING W 10-15 KT. THE WAVE IS PUSHED BACK A BIT BASED ON A
WELL-DEFINED CIRCULATION OBSERVED IN METEOSAT-8 VISIBLE IMAGERY.
THE WAVE CONTINUES TO BE SURROUNDED BY DRY SAHARAN AIR WITH A
SMALL PATCH OF EMBEDDED MOISTURE FROM 10N-23N BETWEEN 40W-48W.
ISOLATED SHOWERS ARE LOCATED WITHIN THIS AREA...BUT ALL DEEP
CONVECTION IS LOCATED ABOUT 400 NM TO THE E NEAR THE ITCZ.

CENTRAL CARIBBEAN TROPICAL WAVE ALONG 74W S OF 24N MOVING W
15-20 KT. THE WAVE IS COLLOCATED WITH AN INVERTED UPPER LEVEL
TROUGH WHICH IS MOVING WWD ACROSS HAITI AND THE WINDWARD
PASSAGE...BUT THE LOW-LEVEL CIRCULATION IS WEAK AND HARD TO
DISTINGUISH. SLIGHT CURVATURE IS NOTED OVER THE SRN BAHAMAS N OF
THE WINDWARD PASSAGE. WIDELY SCATTERED SHOWERS/TSTMS FROM
19N-23N BETWEEN 66W-72W WHERE SELY FLOW BEHIND THE WAVE IS
CONVERGING WITH NLY FLOW BEHIND A CENTRAL ATLC COLD FRONT.

TROPICAL WAVE OVER THE YUCATAN PENINSULA AND GUATEMALA ALONG
89W/90W S OF 22N MOVING W 15-20 KT. AN APEX TO THE LOW-LEVEL
FLOW IS OBSERVED N OF THE YUCATAN COAST BUT ALL DEEP CONVECTION
IS LAGGING THE AXIS PRIMARILY OVER THE GULF OF HONDURAS.
SCATTERED MODERATE CONVECTION FROM 15N-21N BETWEEN 83W-88W WITH
SOME ACTIVITY MOVING NWD OVER COZUMEL AND CANCUN...AND FARTHER S
OVER BELIZE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N12W 6N25W 11N43W...THEN ALONG
9N46W 6N57W...THEN ALONG 10N75W 9N84W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IN A SQUALL LINE OVER W
AFRICA FROM 8N-13N BETWEEN 6W-13W. SCATTERED MODERATE FROM 4N-8N
BETWEEN 22W-29W. WIDELY SCATTERED TSTMS FROM 8N-14N BETWEEN
30W-43W. NUMEROUS MODERATE/STRONG S OF 11N BETWEEN 77W-83W WITH
HEAVY TSTMS MOVING OVER PARTS OF PANAMA.

...DISCUSSION...

GULF OF MEXICO...
TROPICAL STORM OPHELIA CONTINUES TO MEANDER JUST OFF THE
SOUTHEAST COAST OF THE UNITED STATES AND HAS BEEN BRINGING DRIER
CONTINENTAL AIR SWD OVER FLORIDA AND THE NE GULF WATERS.
MOISTURE IS A LITTLE BIT MORE CONCENTRATED OVER THE SRN AND WRN
GULF BUT STILL THE SHOWER/TSTM ACTIVITY IS QUITE LIMITED AT THE
MOMENT. AN UPPER LOW WITH A STRONGLY SUBSIDENT ENVIRONMENT IS
CENTERED NEAR 26N93W MOVING W 5-10 KT TOWARDS THE TEXAS
COAST...AND ISOLATED SHOWERS/TSTMS ARE E OF THE FEATURE S OF 26N
BETWEEN 87W-91W WHERE TROPICAL MOISTURE IS BEING PULLED NWD.
ISOLATED SHOWERS ARE ALSO FROM 20N-26N W OF 94W TOWARDS THE
MEXICAN COAST. MOISTURE AND SHOWERS WILL REMAIN FOCUSED OVER THE
S/W GULF OVER THE NEXT FEW DAYS...AND THE NE GULF WILL REMAIN
POSITIONED IN THE DRY REGIME SW OF OPHELIA.

CARIBBEAN...
AN UPPER LEVEL HIGH IS CENTERED NEAR THE YUCATAN CHANNEL WITH A
SHARP RIDGE AXIS EXTENDING SWD TO THE COAST OF NICARAGUA. UPPER
DIFFLUENCE IS LOCATED ON THE W SIDE OF THE HIGH AND IS PRODUCING
SCATTERED CLUSTERS OF MODERATE CONVECTION FROM CANCUN SEWD TO NE
HONDURAS. THE NELY FLOW ON THE E SIDE OF THE HIGH IS DRIVING
DRIER AIR SWD ACROSS CUBA AND JAMAICA INTO THE SW CARIBBEAN AND
HAS PUSHED THE STRONGEST CONVECTION S OF 11N PRIMARILY OVER
PANAMA AND COSTA RICA. AN UPPER TROUGH EXTENDS FROM THIS AREA OF
CONVECTION NEWD TO THE DOMINICAN REPUBLIC WITH EASTERLY FLOW
FEEDING INTO THE TROUGH BRINGING MORE DRY AIR IN FROM THE ATLC
WATERS. A SMALL PATCH OF WIDELY SCATTERED SHOWERS ARE LOCATED
ABOUT 120-400 NM E OF THE LESSER ANTILLES AND SOME OF THIS
ACTIVITY MAY SKIRT ACROSS THE CENTRAL ISLANDS LATER THIS
EVENING/TONIGHT.

WEST ATLANTIC...
TROPICAL STORM OPHELIA IS CENTERED JUST N OF THE AREA NEAR THE
SOUTH CAROLINA COAST AND IS DRAGGING DRY AIR SWD OVER FLORIDA
AND JUST N OF THE BAHAMAS. A SURFACE TROUGH EXTENDS S OF OPHELIA
FROM 30N72W TO ANDROS ISLAND AND GENERALLY MARKS THE
DIFFERENTIATION OF MOIST AIR OVER THE ATLC FROM RELATIVELY DRY
AIR OVER FLORIDA. ISOLATED SHOWERS/TSTMS HAVE BEEN FORMING ALONG
THIS BAND BUT ARE GENERALLY NOW LIMITED TO N OF 28N. A STRONG
UPPER LEVEL TROUGH IS DIGGING SWD TO THE E OF OPHELIA AND HAS
REACHED 25N BETWEEN 44W-60W. THIS HAS PUSHED A COLD/STATIONARY
FRONT INTO THE AREA ALONG 32N46W 26N56W 30N68W WITH SCATTERED
MODERATE CONVECTION WITHIN 75 NM OF THE BOUNDARY BETWEEN 24N-28N.

CENTRAL/EAST ATLANTIC...
A STATIONARY FRONT LIES ALONG 31N33W 24N48W...AHEAD OF THE COLD
FRONT WHICH IS SINKING SWD OVER THE CENTRAL ATLC. SCATTERED
SHOWERS/TSTMS ARE WITHIN 45 NM OF THE FRONT BUT THERE IS A LACK
OF UPPER LEVEL SUPPORT AND THIS ACTIVITY WILL BECOME ABSORBED BY
THE APPROACHING COLD FRONT. A MID/UPPER LEVEL LOW IS LOCATED
OVER THE CENTRAL TRPCL ATLC NEAR 19N46W AND IS PUTTING MODERATE
SWLY SHEAR OVER THE TROPICAL WAVE NEAR 45W...PUSHING ALL THE
SHOWER ACTIVITY FARTHER E. FARTHER E...A STATIONARY UPPER TROUGH
IS DIGGING SWD PAST SPAIN/PORTUGAL DOWN TO THE CANARY ISLANDS
WITH A JET RACING NE ACROSS MOROCCO INTO THE MEDITERRANEAN SEA.
AN UPPER LEVEL RIDGE HAS BUILT IN FROM N TO S ALONG 37W AND IS
PUSHING DRIER AIR SWD ACROSS THE CAPE VERDE ISLANDS...VIRTUALLY
LIMITING DEEP CONVECTION TO IMMEDIATELY NEAR THE ITCZ.

$$
BERG


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