[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181146
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM 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 0600 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 1115 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION JEANNE WAS UPGRADED AGAIN TO TROPICAL STORM
AT 18/0300 UTC. THE CENTER OF T.S. JEANNE AT 8 AM EDT...1200Z...
WAS NEAR 21.2N 72.8W OR NEAR THE EASTERN TIP OF GREAT INAGUA
ISLAND...DRIFTING WEST-NORTHWEST. MAXIMUM SUSTAINED WIND SPEED
40 KT GUSTS 50 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 1000 MB.
SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. THE LOW LEVEL CENTER REMAINS PARTIALLY EXPOSED
JUST OFF OF THE EAST COAST OF GREAT INAGUA IN THE BAHAMAS.
SCATTERED MODERATE/ ISOLATED STRONG CONVECTION IS OVER THE TURKS
AND CAICOS WITHIN 60 NM OF 22N FROM 70W-73W. THE LOW LEVEL
CENTER IS AT THE SW END OF AN UPPER LEVEL TROF THAT EXTENDS FROM
THE CENTRAL ATLANTIC TO CUBA AND THE WINDWARD PASSAGE. AN AREA
OF MODERATE SUBSIDENCE/ DRY AIR EXTENDS ACROSS THE W ATLC ACROSS
THE BAHAMAS TO THE N COAST OF CUBA AND HAITI. THE MODELS VARY ON
DIRECTION THAT JEANNE WILL TAKE BUT THE INTENSIFICATION WILL BE
LIMITED TO TROPICAL STORM STRENGTH.

TROPICAL STORM KARL WAS UPGRADED TO HURRICANE AT 18/0900 UTC.
HURRICANE KARL IS CENTERED NEAR 14.9N 38.6W...OR ABOUT 850 NM
WEST OF THE CAPE VERDE ISLANDS...AT 18/0900 UTC MOVING NORTHWEST
13 KT. MAXIMUM SUSTAINED WIND SPEED 75 KT WITH GUSTS 90 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE 981 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. INFRARED SATELLITE IMAGERY NOW SHOWS THAT KARL
HAS DEVELOPED A SMALL BUT DISTINCT EYE. THE UPPER LEVEL OUTFLOW
REMAINS IMPRESSIVE TO THE N AND W OF THE SYSTEM BUT STILL HAS
NOT IMPROVED TO THE S. KARL IS LAGGING TO THE E OF A LARGE AREA
OF DRY SAHARAN AIR...BUT WITH ITS FORECAST TRACK TURNING IT TO
THE N OVER THE ATLC IT WILL PROBABLY BE ABLE TO ESCAPE THE BRUNT
OF THE UNFAVORABLE ENVIRONMENT. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 12N-17N BETWEEN 36W-41W. SCATTERED
CLUSTERS OF SIMILAR CONVECTION COVER THE REMAINDER OF THE AREA
FROM 11N-19N BETWEEN 34W-43W.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE CAPE VERDE ISLANDS IS ALONG 24W S OF 18N
MOVING W 10-15 KT. A LOWER TO MID LEVEL LOW CENTER...BUT NOT ON
THE SURFACE...IS OBSERVED ON INFRARED AND VISIBLE SATELLITE
IMAGERY NEAR 13N. CLUSTERS OF SCATTERED MODERATE/STRONG
CONVECTION ARE WITHIN 90 NM OF 14N FROM 22W-29W.

TROPICAL WAVE E OF THE LESSER ANTILLES IS ALONG 59W S OF 23N
MOVING W 10-15 KT. WELL DEFINED SIGNATURE CURVATURE OF AN
INVERTED V IS OBSERVED IN THE INFRARED SATELLITE IMAGERY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS ALONG THE
CENTER OF THE WAVE WITHIN 75 NM OF LINE FROM 15N57W-18N58W.
AT THE UPPER LEVELS...THE WAVE IS EMBEDDED WITH MODERATE/STRONG
SUBSIDENCE AND IS ALONG THE LEADING EDGE OF THE SAHARAN DUST
THAT STRETCHES ACROSS THE ATLC. THEREFORE...FURTHER DEVELOPMENT
IS NOT EXPECTED.

TROPICAL WAVE LOCATED OVER S MEXICO AND THE BAY OF CAMPECHE IS
ALONG 97W S OF 21N MOVING W 10-15 KT. WAVE POSITION IS BASED
PURELY ON EXTRAPOLATION. THIS WAVE IS MOVING OUT OF THE ATLANTIC
REGION. NO ASSOCIATED DEEP CONVECTION.

...ITCZ...

ITCZ AXIS EXTENDS ALONG 13N10W 14N22W 10N26W 16N34W 11N38W
9N60W. THIS AXIS IS DISTORTED BY A TROPICAL WAVE AND HURRICANE
KARL. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
3N-10N BETWEEN 9W-16W. CLUSTERS OF SIMILAR CONVECTION ARE FROM
2N-13N BETWEEN 16W-35W.

...DISCUSSION...

GULF OF MEXICO...
GULF IS DOMINATED BY A LARGE MID/UPPER LEVEL HIGH ALONG THE
COAST OF MEXICO CENTERED NEAR 25N97W WITH THE ANTICYCLONIC FLOW
COVERING ALL BUT THE NE GULF. BROAD DIFFLUENCE TO THE IMMEDIATE
S HAS TRIGGERED A FEW SHOWERS/THUNDERSTORMS OVER THE FAR SW
GULF. THE MID/UPPER LEVEL TROUGH OVER THE E UNITED STATES
CONTINUES MOVE NE OVER NEW ENGLAND WITH THE REMNANTS OF IVAN.
MODERATE/STRONG SUBSIDENCE COVERS THE NE GULF INCLUDING MOST OF
FLORIDA AND THE SE STATES.

CARIBBEAN...
OVER THE NW CARIBBEAN IS MID/UPPER LEVEL NE FLOW THAT IS A
RESULT OF THE HIGH OVER THE GULF OF MEXICO. THE REMAINDER OF THE
CARIBBEAN IS DOMINATED BY A MID/UPPER LEVEL HIGH CENTERED S OF
HAITI NEAR 14N79W. THIS IS INFLUENCING T.S. JEANNE WHICH IS
CENTERED NEAR THE BAHAMAS. THE RESULTING ANTICYCLONIC FLOW IS
RESPONSIBLE FOR THE DISPLACEMENT OF THE CONVECTION E OF THE LOW
LEVEL CENTER OF JEANNE. MODERATE SUBSIDENCE/DRY AIR EXTENDS
ACROSS CUBA INTO THE CARIBBEAN N OF 17N FROM 80W-85W AND IS
ASSOCIATED WITH AN INDUCED TROF BETWEEN THE ANTICYCLONIC FLOWS.

SUBTROPICAL ATLANTIC....
N OF THE REGION...UPPER LEVEL RIDGING CONTINUES TO BUILD TO THE
E OF THE REMNANTS OF IVAN. RIDGE AXIS EXTENDS FROM THE STRAITS
OF FLORIDA NEAR 24N80W NE TO BEYOND 32N71W. NARROW SWATH OF
UPPER LEVEL MOISTURE EXTENDS TO THE W OF THE RIDGE AXIS ACROSS
THE W ATLC TO THE STRAITS OF FLORIDA WITH ISOLATED SHOWERS.
MID/UPPER LEVEL TROF EXTENDS S INTO THE CENTRAL ATLC N OF 28N
FROM 47W-67W WITH A SHEAR AXIS EXTENDING SW ALONG 28N67W TO THE
WINDWARD PASSAGE. THIS SHEAR AXIS IS FUNNELING STRONG
SUBSIDENCE/DRY AIR OVER THE W ATLC TO CUBA AND HAITI EXPOSING
THE LOW LEVEL CENTER OF JEANNE. AN EMBEDDED UPPER LEVEL LOW IS
CENTERED NEAR 30N52W AND IS MOVING N. AT THE SURFACE IS A WEAK
1016 MB LOW JUST N OF THE AREA NEAR 34N53W. RIDGE AXIS EXTENDS
FROM 20N65W E 24N55W THEN NE TO BEYOND 32N43W BROAD WITH
DIFFLUENCE TO THE W OF THE AXIS IS DEVELOPING CLUSTERS SCATTERED
MODERATE/ISOLATED STRONG CONVECTION N OF 22N FROM 44W-56W. THE E
ATLC IS DOMINATE BY AN UPPER LEVEL TROF N OF 24N E OF 38W WITH A
WEAK EMBEDDED UPPER LOW NEAR 27N33W AND A STRONG MID/UPPER LOW
OVER THE CANARY ISLANDS NEAR 28N18W. STRONG SUBSIDENCE/DRY AIR
COVERS THE SAME AREA.

TROPICAL ATLANTIC...
MID/UPPER RIDGE AXIS EXTENDS ACROSS THE TROPICAL ATLC WITH A
UPPER LEVEL HIGH NEAR 16N27W W TO A STRONGER UPPER LEVEL HIGH
ASSOCIATED WITH T.S. KARL TO OVER THE LESSER ANTILLES NEAR
16N62W. AN INDUCED TROF IS BETWEEN KARL AND THE CARIBBEAN
ISLANDS ALONG 48W/50W.

$$
WALLACE



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