[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 182351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT 18 SEP 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
SECTIONS OF SOUTH AMERICA...AND ATLC 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 FEATURES...

TROPICAL STORM JEANNE IS CENTERED NEAR 22.2N 72.3W...OR BETWEEN
MAYAGUANA ISLAND AND THE CAICOS ISLANDS...AT 19/0000 UTC MOVING
N 5 KT. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50
KT. MINIMUM CENTRAL PRESSURE REPORTED BY THE HURRICANE HUNTER IS
1002 MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/
WTNT21 KNHC FOR MORE DETAILS. A LOW-LEVEL SWIRL RACED WWD AWAY
FROM THE CONVECTION OF JEANNE EARLIER THIS AFTERNOON BUT THEN
THE HURRICANE HUNTERS FLEW INTO THE STORM AND FOUND A SECOND
CIRCULATION UNDER THE CLOUD/TSTM CANOPY. THE CONVECTION IS
POORLY ORGANIZED AND SEEMS TO BE LIMITED TO THE DIFFLUENT SIDE
OF A MID/UPPER LOW CENTERED OVER E CUBA NEAR 20N75W. SCATTERED
MODERATE CONVECTION FROM 19N-24N BETWEEN 69W-73W. SINCE JEANNE
IS MOVING SO SLOWLY...VERY HEAVY RAINFALL WILL CONTINUE TO COME
IN SPURTS OVER THE TURKS AND CAICOS ISLANDS AND SE BAHAMAS.

HURRICANE KARL IS CENTERED NEAR 15.9N 40.2W...OR ABOUT 1075
MILES W OF THE CAPE VERDE ISLANDS...AT 18/2100 UTC MOVING WNW 10
KT. MAXIMUM SUSTAINED WIND SPEED IS 95 KT WITH GUSTS TO 115 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 965 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. KARL HAS A VERY SMALL PINHOLE EYE...PROBABLY
ABOUT 5 NM WIDE...WHICH IS EMBEDDED WITHIN A NEARLY CIRCULAR
AREA OF STRONG CONVECTION. THE HURRICANE HAS SEVERAL SPIRAL
BANDS IN ALMOST EVERY QUADRANT AND GOOD OUTFLOW IN ALL
DIRECTIONS. IN PARTICULAR...A OUTFLOW JET APPEARS TO EXTEND TO
THE NE OF KARL DUE TO AN UPPER LOW LOCATED ABOUT 700 NM NE OF
KARL. NUMEROUS STRONG CONVECTION WITHIN 65 NM OF THE EYE.
SCATTERED MODERATE ELSEWHERE FROM 13N-21N BETWEEN 36W-44W.

A STRONG TROPICAL WAVE IS LOCATED JUST W OF THE CAPE VERDE
ISLANDS ALONG 27W S OF 19N MOVING W 10-15 KT. THERE HAS NOT YET
BEEN SUFFICIENT EVIDENCE THAT A SFC LOW HAS FORMED ALONG THE
WAVE...BUT SATELLITE IMAGERY DOES SEEM TO SHOW AT LEAST A
MID-LEVEL CIRCULATION NEAR 13N28W. THE CONVECTION AROUND THIS
FEATURE HAS CONSOLIDATED INTO ONE BAND TO THE N...WITH SCATTERED
MODERATE/STRONG FROM 13N-15.5N BETWEEN 26W-30W. THE SYSTEM IS
BECOMING BETTER ORGANIZED AND TROPICAL CYCLONE DEVELOPMENT IS
POSSIBLE WITHIN THE NEXT 36 HRS.

...TROPICAL WAVES...

TROPICAL WAVE NEAR THE LESSER ANTILLES HAS BEEN NUDGED A BIT TO
THE E ALONG 59W S OF 21N...AND IS MOVING W ABOUT 10 KT. NONE OF
THE ISLANDS IN THE LEEWARD/WINDWARD CHAIN HAVE INDICATED THAT A
WAVE HAS PASSED...AND SATELLITE IMAGERY WOULD ARGUE THAT THE
WAVE IS JUST E OF THE ISLANDS ALONG AN AREA OF SHOWERS/TSTMS. A
WEAK LOW-LEVEL SWIRL IS LOCATED ABOUT 65 NM N OF BARBADOS...AND
THIS IS WHERE THE WAVE IS PLACED. MOST OF THE SHOWERS/TSTMS HAVE
DISSIPATED WITH ONLY ISOLATED LIGHT SHOWERS FROM 16N-22N BETWEEN
56W-60W.

TROPICAL WAVE HAS MOVED OVER MEXICO ALONG 100W/101W S OF 22N
MOVING W 15 KT. SCATTERED MODERATE CONVECTION HAS DEVELOPED JUST
N OF THE WAVE ALONG THE MEXICAN COAST...AND BENEATH AN UPPER
LEVEL HIGH CENTERED NEAR 25N98W...FROM 18N-27N BETWEEN 96W-100W.

...ITCZ...

ITCZ AXIS EXTENDS FROM GUINEA-BISSAU ALONG 13N16W TO
14N24W...THEN ALONG 6N28W 10N39W 7N52W...THEN ALONG 6N60W 7N80W.
THE ITCZ IS ILL-DEFINED BETWEEN AFRICA AND THE TROPICAL WAVE AT
27W AND THERE IS A LARGE AREA OF CONVECTION S OF THE OUTLINED
AXIS. WIDELY SCATTERED MODERATE FROM 2N-11N BETWEEN 10W-23W.
WIDELY SCATTERED MODERATE FROM 4N-10N BETWEEN 23W-32W. SCATTERED
MODERATE OVER GUYANA...THE PERIPHERY OF VENEZUELA...AND E
COLOMBIA.

...DISCUSSION...

GULF OF MEXICO...
ONE OF THE FIRST COLD FRONTS OF THIS LATE SUMMER/EARLY FALL HAS
PUSHED ITS WAY INTO THE GULF OF MEXICO...EXTENDING FROM THE W
ATLC ACROSS CNTRL FLORIDA TO 27N90W THEN TO NEAR HOUSTON TEXAS.
THE FRONT WAS PROBABLY HELPED ALONG BY THE CIRCULATION
ASSOCIATED WITH EX-HURRICANE IVAN...NOW OFF THE DELMARVA
PENINSULA...BUT REGARDLESS IT HAS BROUGHT IN MUCH DRIER AIR
BEHIND IT WITH DEWPOINTS FALLING INTO THE UPPER 50S F OVER THE
FLORIDA PANHANDLE. AN UPPER LEVEL TROF IS ALSO SITUATED ALONG
THE EASTERN SEABOARD...TRAILING INTO THE NE GULF...AND THIS HAS
BROUGHT STRONG SUBSIDENCE OVER THE AREA IN THE MID/UPPER LEVELS.
FARTHER W...AN UPPER LEVEL HIGH IS CENTERED JUST S OF
BROWNSVILLE TEXAS AND IT APPEARS THAT THE ASSOCIATED UPPER LEVEL
DIVERGENCE IS TRIGGERING SOME TSTMS ALONG THE NE MEXICO COAST
JUST TO THE N OF A TROPICAL WAVE.

CARIBBEAN...
THE NORMAL EASTERLY TRADES ARE PRETTY MUCH NON-EXISTENT ACROSS
THE CARIBBEAN FOR THE SECOND STRAIGHT DAY DUE TO THE WEAKENED
GRADIENT CAUSED BY T.S. JEANNE. WITHOUT THE COOLING BREEZE...THE
ISLAND OF CURACAO REACHED 96F/36C YESTERDAY AND MUCH OF THE AREA
WAS SWELTERING IN THE HEAT AGAIN TODAY. A SFC TROF HAS DEVELOPED
TO THE SW OF JEANNE THAT EXTENDS FROM HAITI WWD ACROSS JAMAICA
TO 17N83W...AND WIDELY SCATTERED SHOWERS/TSTMS HAVE BEEN FORMING
AROUND THIS AXIS FROM 12N-20N BETWEEN 75W-82W. IN ADDITION...THE
BAND OF CONVECTION THAT HAD BEEN TO THE SE OF JEANNE HAS BEEN
DISSIPATING WITH ONLY ISOLATED SHOWERS/TSTMS NOW EXTENDING FROM
ARUBA TO PUERTO RICO AND THE VIRGIN ISLANDS. ELSEWHERE...AN
INVERTED MID-LEVEL TROF EXTENDS ACROSS HONDURAS AND THE GULF OF
HONDURAS...AND SCATTERED MODERATE CONVECTION HAS DEVELOPED TO
THE S OVER LAND FROM E HONDURAS TO W PANAMA.

SUBTROPICAL ATLANTIC...
STRONG RIDGING CONTINUES OVER THE W ATLC AND THE EXPANDING
ANTICYCLONIC OUTFLOW OF T.S. JEANNE IS REINFORCING THIS FEATURE.
BROAD WLY FLOW EXTENDS TO THE E OF JEANNE WITH ABUNDANT UPPER
LEVEL MOISTURE FROM 20N-26N BETWEEN 45W-75W. THIS FLOW IS
FEEDING IN TO THE E SIDE OF A WELL-DEFINED MID/UPPER LOW
CENTERED NEAR 32N56W...AND WIDELY SCATTERED MODERATE CONVECTION
HAS DEVELOPED FROM 26N-32N BETWEEN 49W-53W. AN UPPER RIDGE LIES
TO THE E OF THE LOW ALONG 20N50W 32N40W AND TWO MID/UPPER LOWS
CONTINUE TO SWIRL OVER THE E ATLC NEAR 25N32W AND 30N16W. THE
EASTERNMOST LOW IS BRINGING DRIER AIR OVER THE CANARY ISLANDS
BUT A FEW SHOWERS MAY BE EMBEDDED WITHIN THE MID/UPPER LEVEL
CLOUDINESS OVER W SAHARA...MOROCCO...AND THE ADJACENT WATERS.

TROPICAL ATLANTIC...
AN UPPER LEVEL RIDGE AND UPPER LEVEL MOISTURE IS SITUATED OVER
THE LEEWARD ISLANDS EXTENDING NEWD INTO THE SUBTROPICAL WATERS
BUT DRIER AIR IS MOVING IN FROM THE E BETWEEN 45W-56W ALONG AN
INVERTED TROF ALONG 11N54W 20N47W. A SECOND UPPER RIDGE EXTENDS
TO THE E OF HURRICANE KARL ALONG 14N WITH STRONG WLY
FLOW...PROBABLY AN OUTFLOW JET...JUST TO THE N BETWEEN 19N-24N.
AN AREA OF SPEED DIVERGENCE EXTENDS ALONG A LINE 12N31W
4N17W...AND THIS HAS INCREASED CONVECTIVE ACTIVITY WELL S OF THE
ITCZ.

$$
BERG


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