[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 150000
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE 14 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...

HURRICANE IVAN IS CENTERED NEAR 24.7N 87.0W OR 325 MILES SSE OF
THE MOUTH OF THE MISSISSIPPI RIVER AT 14/0000 UTC MOVING NNW 9
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. LATEST MINIMUM CENTRAL PRESSURE MEASURED
BY A NOAA AIRCRAFT IS 929 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 PRETTY
MUCH MAINTAINED ITS STRUCTURE OVER THE PAST 6 HOURS BUT THE MOST
NOTABLE CHANGE IS THAT THE EYE HAS WIDENED TO ABOUT 26 NM.
STRONG CONVECTION IS STILL WRAPPED COMPLETELY AROUND THE CENTER
AND THE COLDEST CLOUD TOPS...ABOUT -76C...ARE OVER THE ERN
SEMICIRCLE WITHIN 60-120 NM FROM THE EYEWALL. THE STRONGEST
SPIRAL BANDS ARE OVER THE NRN SEMICIRCLE AND SE QUADRANT...WHICH
IS CONFIRMED BY THE KEY WEST AND TAMPA BAY RADARS WHICH SHOW
BANDS OF RAIN JUST OFFSHORE. 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. NUMEROUS MODERATE/STRONG CONVECTION
WITHIN 200 NM E SEMICIRCLE AND 100 NM W SEMICIRCLE WITH
SCATTERED MODERATE IS SPIRAL BANDS ELSEWHERE FROM 21N-28N
BETWEEN 82W-87W. WIDELY SCATTERED SHOWERS/TSTMS ALSO EXTEND SWD
ALONG A FEEDER BAND FROM W CUBA TO THE GULF OF HONDURAS...ALONG
WITH INCREASING RAINFALL COVERAGE ACROSS MUCH OF N FLORIDA.

TROPICAL STORM JEANNE IS CENTERED NEAR 17.0N 64.1W OR 65 MILES
SE OF ST. CROIX AT 14/0000 UTC MOVING WNW 9 KT. MAXIMUM
SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 998 MB. SEE LATEST NHC PUBLIC
ADVISORY OR NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.
VERY STRONG CONVECTION HAS DEVELOPED PRIMARILY S AND E OF THE
LOW-LEVEL CIRCULATION OF JEANNE...AND THE SYSTEM HAS BEEN
STRENGTHENING QUITE WELL DURING THE DAY GIVEN THE BIT OF NWLY
SHEAR ASSOCIATED WITH A MID/UPPER TROF N OF PUERTO RICO. THE SAN
JUAN RADAR VAGUELY SHOWS THE LOW-LEVEL CENTER COMING INTO VIEW
ABOUT 60 NM SE OF ST. CROIX BUT SO FAR THE RADAR ONLY SHOWS
WIDELY SCATTERED SHOWERS/TSTMS MOVING ACROSS THE VIRGIN ISLANDS
AND PUERTO RICO. THE STRONGEST CONVECTION IS LAGGING TO THE E
AND IS CURRENTLY AFFECTING THE NORTHERN LEEWARD ISLANDS BETWEEN
DOMINICA AND ANGUILLA. NUMEROUS MODERATE/STRONG CONVECTION IS
FROM 13.5N-18.5N BETWEEN 61W-65.5W. WIDELY SCATTERED MODERATE IS
ELSEWHERE FROM 13N-20N BETWEEN 57W-68W. GIVEN THE SLOW MOVEMENT
OF JEANNE...RAINFALL TOTALS ACROSS PARTS OF THE NORTHERN LEEWARD
ISLANDS...VIRGIN ISLANDS...AND PUERTO RICO MAY BE AS HIGH AS
10"...ESPECIALLY IN THE MORE MOUNTAINOUS AREAS.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED BETWEEN AFRICA AND THE CAPE VERDE ISLANDS
ALONG 19W/20W MOVING W 10-15 KT. THERE IS A BROAD MID-LEVEL
CIRCULATION NOTED ALONG THE WAVE BUT THERE HAS BEEN NO EVIDENCE
THAT A SURFACE LOW HAS DEVELOPED. WIDELY SCATTERED MODERATE
CONVECTION IS PRIMARILY W OF THE AXIS FROM 6N-13N BETWEEN
19W-24W.

TROPICAL WAVE OVER THE CENTRAL ATLC IS RE-POSITIONED ALONG 8N37W
21N40W MOVING W 10-15 KT. THE WAVE WAS BEING TRACKED ALONG A
WEAK INVERTED-V SIGNATURE A LITTLE FARTHER W...WHICH APPEARS TO
BE THE LEADING EDGE OF A WEAKENING SAHARAN AIR LAYER BOUNDARY. A
MORE WELL-DEFINED LOW-LEVEL CIRCULATION...WHICH HAPPENS TO BE
COLLOCATED WITH CONVECTION...IS CROSSING 40W AND APPEARS TO BE A
MORE APPROPRIATE LOCATION FOR THE WAVE. HOVMOELLER DIAGRAMS ALSO
SHOWS A DISTINCT AND CONTINUOUS CLOUD MASS WITH THE WAVE MOVING
ACROSS THE E ATLC OVER THE PAST FEW DAYS WHICH IS NOW NEAR 40W.
WIDELY SCATTERED MODERATE CONVECTION FROM 11N-14N BETWEEN
38W-42W. ISOLATED SHOWERS/TSTMS FROM 14N-20N BETWEEN 40W-43W.

WEST CARIBBEAN TROPICAL WAVE ALONG 80W S OF 20N MOVING W 10-15
KT. THE WAVE IS SUFFERING FROM STRONG SLY INFLOW INTO HURRICANE
IVAN IN THE GULF OF MEXICO...AND SEEMS TO BE ORIENTED ALONG A
CONVERGENCE LINE S OF GRAND CAYMAN. SCATTERED MODERATE
CONVECTION FROM 10N-13.5N BETWEEN 80W-84W.

...ITCZ...

ITCZ AXIS EMERGES JUST OFFSHORE THE COAST OF GUINEA-BISSAU...
THEN REFORMS ALONG 8N20W 8N24W 12N36W 10N39W 15N57W...THEN ALONG
9N64W 9N70W 7N80W. WIDELY SCATTERED MODERATE CONVECTION 200 NM S
OF THE AXIS BETWEEN 23W-37W. SCATTERED MODERATE OVER GUYANA AND
ERN VENEZUELA...AS WELL AS ALONG THE COLOMBIAN COAST NEAR THE
GUAJIRA PENINSULA.

...DISCUSSION...

GULF OF MEXICO...
EAST OF 90W...THE BIGGEST PROBLEMS THIS EVENING ARE OBVIOUSLY
ASSOCIATED WITH HURRICANE IVAN. THE HURRICANE CONTINUES TO MOVE
NWD TOWARDS THE N GULF COAST...SANDWICHED BETWEEN AN
EWD-RETREATING ATLC RIDGE AND A RIDGE WHICH EXTENDS FROM THE
PACIFIC ACROSS CNTRL MEXICO INTO THE W GULF. THE HURRICANE HAS
CREATED ITS OWN UPPER LEVEL ENVIRONMENT...WITH BROAD UPPER
RIDGING AND OUTFLOW TO THE E FROM N FLORIDA SWD TO CNTRL CUBA.
THE OUTFLOW IS MORE RESTRICTED TO THE W...WITH DRY AIR AND
MODERATE/STRONG SUBSIDENCE BORDERING IVAN W OF 90W. A VIGOROUS
SHORTWAVE CONTINUES TO PULL AWAY FROM IVAN HEADING INTO THE
NORTHEAST U.S...AND THE LESSENING SHEAR SHOULD PREVENT THE DRY
AIR FROM BECOMING ENTRAINED INTO THE CIRCULATION. 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 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
JUST SE OF THE VIRGINS ISLANDS WITH SHOWERS/TSTMS EXPANDING WWD
OVER PUERTO RICO AND THE ADJACENT WATERS. UPPER LEVEL OUTFLOW IS
EXPANDING TO THE S OF THE SYSTEM OVER MUCH OF THE E
CARIBBEAN...AND IN FACT BROAD NELY UPPER FLOW COVERS ALMOST THE
ENTIRE BASIN DUE TO THE OUTFLOW OF HURRICANE IVAN. A WEAK RIDGE
EXTENDS FROM HONDURAS NEWD ACROSS THE CAYMAN ISLAND TO
CUBA...WHICH IS ENHANCING THE ADVECTION OF DRY AIR WITH PATCHES
OF MOISTURE FROM THE W ATLC INTO THE CARIBBEAN BASIN.

WEST ATLANTIC...
OUTFLOW FROM HURRICANE IVAN IS EXPANDING ACROSS FLORIDA INTO THE
W ATLC...GENERALLY W OF 70W...AND OUTFLOW FROM T.S. JEANNE IS
EXPANDING NEWD TO 26N BETWEEN 50W-65W. IN BETWEEN THESE TWO
INDUCED RIDGES...A LEFTOVER MID-LEVEL TROF STRETCHES N OF PUERTO
RICO ALONG 18N67W 25N63W WITH DRY AIR UP TO 450 NM W OF THE AXIS
TO THE SRN BAHAMAS. THE FEATURE IS BECOMING INCORPORATED INTO A
DIGGING SHORTWAVE TROF WHICH IS DROPPING SWD FROM THE NW ATLC N
OF 27N BETWEEN 58W-67W. A SFC TROF IS ASSOCIATED WITH THE UPPER
TROF...EXTENDING ALONG 32N54W 23N69W WITH WIDELY SCATTERED
MODERATE UP TO 180 NM AHEAD OF THE AXIS N OF 28N.

REMAINDER OF SUBTROPICAL ATLC...
W OF 50W...A DEPARTING MID/UPPER LOW NOW LOCATED NEAR 36N40W HAS
A TRAILING TROF EXTENDING SWWD INTO THE TROPICS BEYOND 20N46W. A
STRONG UPPER LEVEL ANTICYCLONE IS CENTERED NEAR 20N33W AND IS
PUMPING MOISTURE FROM THE TROPICS NWD BETWEEN 35W-43W. ISOLATED
SHOWERS/TSTMS ARE PROPAGATING NWD AWAY FROM THE CNTRL ATLC
TROPICAL WAVE FROM 20N-27N BETWEEN 37W-42W. WIDELY SCATTERED
MODERATE CONVECTION IS ALSO N OF 30N BETWEEN 32W-35W. FARTHER
DOWNSTREAM...A BROAD LONGWAVE TROF IS CENTERED OFF THE IBERIAN
PENINSULA AND EXTENDS SWD TO 20N E OF 27W...INCLUDING ACROSS THE
CANARY ISLANDS. THE TROF IS ACTUALLY INDUCING THE DEVELOPMENT OF
WIDELY SCATTERED SHOWERS/TSTMS ALONG THE PEAKS OF THE ATLAS MTNS
OVER WESTERN SAHARA AND MOROCCO.

TROPICAL ATLC...
A WEAK MID/UPPER LEVEL ANTICYCLONE IS CENTERED JUST E OF T.S.
JEANNE NEAR 15N60W WITH BROAD NLY FLOW EXTENDING SWD TO 11N W OF
50W. THE AREA BETWEEN 44W-50W LIES BETWEEN THE ANTICYCLONE AND A
STRONG ANTICYCLONE 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 16N...THE UPPER FLOW IS
PREDOMINANTLY ELY WITH WEAK DIFFLUENCE PRODUCING AREAS OF WIDELY
SCATTERED CONVECTION NEAR THE ITCZ E OF 38W. SOME DRY AIR HAS
MADE IT ALL THE WAY S TO THE LATITUDE OF THE CAPE VERDE
ISLANDS...BUT THERE IS PLENTY OF MOISTURE S OF 13N TO SUPPORT
CONVECTION ALONG THE TROPICAL WAVE NEAR 20W.

$$
BERG


This weather bulletin was brought to you by:
www.nashvilleweather.net