[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 150557
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0345 UTC.

...SPECIAL FEATURES...

HURRICANE IVAN IS CENTERED NEAR 25.6N 87.4W OR 265 MILES SSE OF
THE MOUTH OF THE MISSISSIPPI RIVER AT 15/0600 UTC MOVING NNW AT
10 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 934
MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT4/WTNT34 KNHC OR MIATCMAT4/
WTNT24 KNHC FOR MORE DETAILS. IVAN HAS MAINTAINED THE RELATIVE
SMALL EYE BUT THE CLOUD TOP TEMPERATURES HAVE WARMED A BIT OVER
THE LAST 6 HOURS. VERTICAL SHEAR MAY BE LESSENING A BIT AS UPPER
LEVEL OUTFLOW BECOMES MORE ESTABLISHED ON THE NW QUADRANT AND
THIS COULD ALLOW SLIGHT STRENGTHENING AS THE HURRICANE
APPROACHES THE N GULF COAST. THIS IS AN EXTREMELY LARGE AND
DANGEROUS HURRICANE...AND RESIDENTS AND TOURISTS WITHIN THE
WARNING AREAS ARE URGED TO FOLLOW THE DIRECTION OF LOCAL
EMERGENCY MANAGERS TO TAKE THE PROPER PRECAUTIONS BEFORE THE
STORM MAKES LANDFALL. BECAUSE OF THE SIZE OF IVAN...IT IS
EXPECTED TO REMAIN HURRICANE STRENGTH FOR 12 HOURS AFTER
LANDFALL. SCATTERED MODERATE/STRONG CONVECTION COVERS A LARGE
AREA FROM 23N-29N BETWEEN 81W-89W INCLUDING PORTIONS OF THE
FLORIDA PENINSULA AND THE FLORIDA KEYS. AN OUTER RAINBAND DOES
EXTEND ACROSS W CUBA THROUGH THE YUCATAN CHANNEL TO OFF THE
COAST OF BELIZE.

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. 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 NOT AS ORGANIZED AS IT WAS YESTERDAY. PUERTO RICO
RADAR INDICATES A LOW LEVEL CENTER CLOSE TO AN AREA OF
STRONGEST CONVECTION. THIS COULD BE A NEW CENTER IS TRYING TO
DEVELOP. ALTHOUGH IT IS UNDER SOME VERTICAL SHEAR SOME MODELS
ARE PREDICTING THAT JEANNE WILL BECOME A HURRICANE OVER THE NEXT
DAY OR TWO. NUMEROUS STRONG CONVECTION IS WITHIN A 45 NM RADIUS
OF 17.5N64.5W WHICH IS 35 NM SW OF ST.CROIX. SCATTERED MODERATE/
STRONG CONVECTION IS WITHIN 90/120 NM OF LINE FROM 14N62W TO
20N64W INCLUDING THE LEEWARD ISLANDS N OF DOMINICA AND ALL OF
THE VIRGIN ISLANDS. SCATTERED SHOWERS/WIDELY ISOLATED
THUNDERSTORMS ARE FROM 12N-23N BETWEEN 58W-68W.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED BETWEEN AFRICA AND THE CAPE VERDE ISLANDS
IS ALONG 20W. WITH A 1012 MB SURFACE LOW ALONG THE WAVE NEAR
11N. ALTHOUGH THE WAVE AXIS HAS APPEARED TO BE ONLY MOVING 5-10
KT OVER THE PAST 6 HOURS...THE WAVE HAS BROADEN AND THE LEADING
EDGE HAS A FORWARD SPEED 15-20 KT. THEREFORE THE CONVECTION NOW
APPEARS W OF THE WAVE AXIS FROM 0000 UTC POSITION. SCATTERED
MODERATE/STRONG CONVECTION IS FROM 9N-14N BETWEEN 22W-26W.

TROPICAL WAVE OVER THE CENTRAL ATLC IS ALONG 6N39W-20N42W MOVING
W 15-20 KT. THE WAVE WAS BEING TRACKED ALONG A WEAK INVERTED-V
SIGNATURE WHICH IS LEADING EDGE OF THE SAHARAN DUST. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION WITHIN 90 NM OF
LINE FROM 13N40W-17N42W.

TROPICAL WAVE IN THE W CARIBBEAN IS ALONG 81W/82W S OF 20N
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 11N10W 11N18W 9N23W 9N41W TO 17N60W. CLUSTERS
OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 4N-11N
BETWEEN 20W 41W.

...DISCUSSION...

GULF OF MEXICO...
E OF 90W...THE BIGGEST PROBLEM TODAY INTO 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 FROM 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
90W AND BEING DRAWN INTO THE FLOW OF IVAN S OF 23N W OF 88W. 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 MAY BE TOO LATE TO
WEAKEN THE STORM MUCH BEFORE LANDFALL. REGARDLESS OF THE EXACT
TIMING...IVAN IS EXPECTED TO MAKE LANDFALL ALONG THE N GULF
COAST BETWEEN LOUISIANA AND THE FLORIDA PANHANDLE AS A MAJOR
HURRICANE.

CARIBBEAN...
JUST AS IVAN HAS LEFT THE AREA...NOW WE HAVE TO DEAL WITH
INTENSIFYING T.S. JEANNE. THE CENTER OF CIRCULATION IS PASSING
OVER THE SOUTHERN MOST OF THE VIRGINS ISLANDS WITH SHOWERS/
THUNDERSTORMS EXPANDING W OVER PUERTO RICO AND THE ADJACENT
WATERS. UPPER LEVEL OUTFLOW IS EXPANDING TO THE S AND E OF THE
SYSTEM OVER MUCH OF THE LESSER ANTILLES. A SMALL TROF IS TO THE
NW OF JEANNE EXTENDING FROM S OF HISPANIOLA TO 23N65W. 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 S OF THE CAROLINAS INTO THE W ATLC AND CARIBBEAN...
GENERALLY W OF 70W...AND OUTFLOW FROM T.S. JEANNE IS EXPANDING
NE TO 26N BETWEEN 55W-63W. IN BETWEEN THESE TWO INDUCED
RIDGES...A LEFTOVER MID/UPPER LEVEL TROF N OF 26N FROM 57W-67W
WITH ASSOCIATED STRONG SUBSIDENCE/DRY AIR N OF 28N. A SURFACE
TROF IS ASSOCIATED WITH THE THIS TROF EXTENDS FROM A COLD FRONT
NEAR 31N57W ALONG 27N62W TO 25N68W. SCATTERED SHOWERS/
THUNDERSTORMS ARE WITHIN 60 NM OF 26N FROM 64W-69W AND WITHIN 90
NM OF LINE FROM 27N56W TO BEYOND 32N51W.

CENTRAL/EASTERN ATLANTIC...
W OF 55W...MID/UPPER LEVEL RIDGE AXIS EXTENDS FROM NE OF JEANNE
NEAR 23N57W TO BEYOND 32N47W. 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-40W. 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 15N61W WITH BROAD N FLOW EXTENDING S TO 10N W OF 55W. THE
AREA BETWEEN 45W-55W 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 12N BETWEEN 43W-55W. ELSEWHERE S OF 10N...THE UPPER
FLOW IS PREDOMINANTLY EASTERLY.

$$
WALLACE


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