[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 151153
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED 15 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...

HURRICANE IVAN IS CENTERED NEAR 26.7 87.9W OR 180 MILES SSE OF
THE MOUTH OF THE MISSISSIPPI RIVER AT 15/1200 UTC MOVING NNW AT
11 KT. MAXIMUM SUSTAINED WIND SPEED IS 120 KT WITH GUSTS TO 145
KT MAKING IVAN A DANGEROUS CATEGORY 4 HURRICANE ON THE
SAFFIR-SIMPSON SCALE. ESTIMATED MINIMUM CENTRAL PRESSURE IS 939
MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC OR MIATCMAT4/
WTNT24 KNHC FOR MORE DETAILS. THE CLOUD TOP TEMPERATURES HAVE
MAINTAINED IN THE -75 DEG C RANGE OVERNIGHT. VERTICAL SHEAR HAS
RELAXED OVER THE LAST 6 HOURS ALLOWING THE UPPER LEVEL OUTFLOW
TO BECOME MORE SYMMETRICAL IN ALL QUADRANTS. IVAN IS A STRONG
CATEGORY 4 STROM AT PRESENT ALTHOUGH INTENSITY COULD FLUCTUATE
OVER NEXT 24 HOURS...REGARDLESS IVAN WILL MAKE LANDFALL AS A
MAJOR HURRICANE. THIS IS AN EXTREMELY LARGE AND DANGEROUS
HURRICANE WITH DAMAGING WINDS...STORM SURGE..AND HEAVY RAINFALL
EXPECTED TO COVER MOST OF THE N GULF COAST. BECAUSE OF THE SIZE
OF IVAN...IT IS EXPECTED TO REMAIN HURRICANE STRENGTH WELL
INLAND AFTER LANDFALL. SHOWERS/THUNDERSTORMS HAVE ALREADY MOVE
ONSHORE OVER THE FLORIDA PENINSULA AND INTO THE FLORIDA
PANHANDLE AND WILL BE MOVING ONSHORE OVER THE REMAINDER OF THE N
GULF COAST IN THE NEXT FEW HOURS. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION COVERS A LARGE AREA WITHIN 175/200 NM OF A
LINE FROM 24N90W TO OVER FLORIDA NEAR 30N83W. CONDITIONS WILL BE
IMPROVING OVER CUBA AND THE YUCATAN PENINSULA DURING THE DAY
TODAY.

TROPICAL STORM JEANNE IS CENTERED NEAR 17.2N 64.8W OR 35 MILES S
OF ST. CROIX AT 15/0600 UTC MOVING WNW AT 7 KT. MAXIMUM
SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 996 MB. ON THE CURRENT TRACK AND
SPEED JEANNE WILL CROSS OVER PUERTO RICO THIS EVENING. SEE
LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS.

JEANNE IS AGAIN BECOMING MORE ORGANIZED WITH PUERTO RICO RADAR
INDICATING A LOW LEVEL CENTER JUST SW OF ST CROIX. OUTFLOW IS
GOOD EXCEPT TO THE W WHERE IT IS UNDERGOING SHEAR FROM THE RIDGE
TO THE E OF HURRICANE IVAN. NUMEROUS STRONG CONVECTION IS WITHIN
30/45 NM OF 64W FROM 15N-17N. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS COVERS THE REMAINDER OF THE AREA FROM 14-21N
BETWEEN 61W-66W.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED S OF THE CAPE VERDE ISLANDS IS ALONG
23W/24W MOVING W 15-20 KT WITH A 1009 MB SURFACE LOW ALONG THE
WAVE NEAR 11N. SYSTEM APPEARS MORE ORGANIZED THIS MORNING.
SCATTERED MODERATE/STRONG CONVECTION IS FROM 8N-13N BETWEEN
22W-28W.

TROPICAL WAVE OVER THE CENTRAL ATLC IS ALONG 6N41W-21N45W MOVING
W 10-15 KT. THE WAVE WAS BEING TRACKED ALONG A WEAK INVERTED-V
SIGNATURE WHICH IS LEADING EDGE OF THE SAHARAN DUST. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF LINE FROM
13N43W-18N42W.

TROPICAL WAVE IN THE W CARIBBEAN IS ALONG 82W/83W S OF 21N
MOVING W 10-15 KT. THIS IS A WEAK WAVE WITH LITTLE OR NO
SIGNATURE CURVATURE AND IS POSITIONED IS AN EXTRAPOLATION.
NO ASSOCIATED DEEP CONVECTION.

...ITCZ...

ITCZ AXIS IS ALONG 15N10W 13N19W 8N27W 10N40W 17N60W. CLUSTERS
OF SCATTERED MODERATE/STRONG CONVECTION ARE FROM 7N-11N BETWEEN
27W-34W. CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION ARE FROM 3N-8N BETWEEN 8W-23W. CLUSTERS OF SCATTERED
MODERATE CONVECTION ARE WITHIN 150 NM OF LINE FROM 6N38W-12N57W.

...DISCUSSION...

GULF OF MEXICO...
E OF 90W...THE BIGGEST PROBLEM TODAY AND TOMORROW IS OBVIOUSLY
ASSOCIATED WITH HURRICANE IVAN. IVAN CONTINUES TO MOVE N TOWARDS
THE N GULF COAST...SANDWICHED BETWEEN A RIDGE TO THE E AND A
RIDGE WHICH EXTENDS FROM HURRICANE JAVIER IN THE E PACIFIC
ACROSS CNTRL MEXICO TO OVER THE W GULF. HURRICANE IVAN HAS
CREATED ITS OWN UPPER LEVEL ENVIRONMENT...WITH BROAD UPPER
RIDGING AND OUTFLOW TO THE E TO OVER THE SE UNITED STATES S TO
OVER THE CARIBBEAN. THE OUTFLOW IS MORE RESTRICTED TO THE W
BECAUSE OF DRY AIR AND MODERATE/STRONG SUBSIDENCE BORDERING IVAN
W OF 91W AND BEING DRAWN INTO THE FLOW OF IVAN S OF 23N W OF
87W. A VIGOROUS SHORTWAVE CONTINUES TO PULL AWAY FROM IVAN
HEADING INTO THE NE UNITED STATES. IN THE NEXT FEW DAYS...THE
LONGWAVE TROF NOW DIGGING ACROSS THE ROCKY MOUNTAINS WILL
CONTINUE TO DRAW IVAN TO THE N...BUT THE INCREASING SHEAR WILL
BE TOO LATE TO WEAKEN THE STORM BEFORE LANDFALL.

CARIBBEAN...
NOW THAT IVAN HAS LEFT THE CARIBBEAN WE HAVE TO DEAL WITH
INTENSIFYING T.S. JEANNE. SHOWERS/THUNDERSTORMS ARE EXPANDING W
OVER PUERTO RICO AND E OVER THE LEEWARD ISLANDS. UPPER LEVEL
OUTFLOW IS EXPANDING TO THE S AND E OF THE SYSTEM OVER MUCH OF
THE LESSER ANTILLES AND W TROPICAL ATLANTIC. A SMALL TROF
INDUCED BY THE FLOW BETWEEN JEANNE AND THE OUTFLOW OF IVAN
EXTENDING FROM S OF THE DOMINICAN REPUBLIC TO 22N67W. REMAINDER
OF THE CARIBBEAN IS DOMINATED BY ANTICYCLONIC FLOW FROM IVAN
PRODUCING S TO SE WINDS ACROSS THE AREA.

WEST ATLANTIC...
OUTFLOW FROM HURRICANE IVAN IS EXPANDING ACROSS THE SE UNITED
STATES OVER S CAROLINA INTO THE W ATLC AND CARIBBEAN...
GENERALLY W OF 69W...AND OUTFLOW FROM T.S. JEANNE IS EXPANDING
NE TO 26N BETWEEN 53W-66W. IN BETWEEN THESE TWO INDUCED
RIDGES...A LEFTOVER MID/UPPER LEVEL TROF N OF 26N FROM 54W-69W
WITH ASSOCIATED STRONG SUBSIDENCE/DRY AIR N OF 27N. A SURFACE
TROF IS ASSOCIATED WITH THE THIS UPPER LEVEL TROF EXTENDS FROM A
COLD FRONT NEAR 30N54W TO 25N65W. SCATTERED SHOWERS/
THUNDERSTORMS ARE WITHIN 75/90 NM OF LINE FROM 26N56W TO BEYOND
32N50W.

CENTRAL/EASTERN ATLANTIC...
W OF 55W...MID/UPPER LEVEL RIDGE AXIS EXTENDS FROM NE OF JEANNE
NEAR 23N54W TO BEYOND 32N45W. A DEPARTING MID/UPPER LOW NOW
LOCATED WELL N OF THE REGION HAS A TRAILING TROF EXTENDING SW
INTO THE TROPICS NEAR 15N49W. A STRONG UPPER LEVEL HIGH IS
CENTERED NEAR 19N36W AND IS PUMPING MOISTURE FROM THE TROPICS N
BETWEEN 30W-43W. FARTHER DOWNSTREAM...A BROAD LONGWAVE TROF IS
CENTERED WELL N OF THE REGION OVER SPAIN EXTENDING SW ALONG THE
NW COAST OF AFRICA. CYCLONIC FLOW IS N OF 20N E OF 25W.

TROPICAL ATLC...
A WEAK MID/UPPER LEVEL HIGH IS CENTERED JUST E OF T.S. JEANNE
NEAR 15N60W WITH BROAD N FLOW EXTENDING S TO 10N W OF 50W. THE
AREA BETWEEN 45W-50W LIES BETWEEN THE MID/UPPER LEVEL HIGH AND A
STRONG UPPER LEVEL HIGH TO THE E...AND THIS IS MOSTLY AN
EXTENSION OF TROUGHING N OF 20N. MODERATE/STRONG SUBSIDENCE
EXTENDS N OF 13N BETWEEN 45W-56W. ELSEWHERE S OF 10N...THE UPPER
FLOW IS PREDOMINANTLY EASTERLY.

$$
WALLACE


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