[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 112359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT 11 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 FEATURE...
HURRICANE IVAN HAS INTENSIFIED THIS AFTERNOON AND HAS NOW
REGAINED CATEGORY 5 STATUS.  IT IS CENTERED NEAR 18.2N 79.7W OR
130 MILES/205 KM SE OF GRAND CAYMAN AT 12/0000 UTC MOVING SLOWLY
W BUT EXPECTED TO MOVE WNW 8 KT. MAXIMUM SUSTAINED WIND SPEED IS
145 KT WITH GUSTS TO 175 KT. ESTIMATED MINIMUM CENTRAL PRESSURE
IS 912 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 HURRICANE HAS THE
6TH LOWEST CENTRAL PRESSURE RECORDED IN THE ATLC BASIN HISTORY
BETWEEN MITCH 1998/CAMILLE 1969 (905 MB) AND JANET OF 1955 (914
MB).  DURING THE DAY IVAN HAS BECOME MORE SYMMETRIC WITH OUTFLOW
IMPROVING ON THE NW SIDE AND A BETTER-DEFINED EYE...APPEARING TO
COMPLETE AN EYEWALL CYCLE WITH THE PLANE NO LONGER REPORTING
CONCENTRIC EYEWALLS.  NUMEROUS STRONG WITHIN 90 NM OF THE CENTER
WITH WIDELY SCATTERED RAINBANDS OUT 150 NM W AND 200 NM E
SEMICIRCLE.  IVAN STILL HAS ABOUT 36 HOURS OVER THE CARIBBEAN
AND HAS THE POTENTIAL TO POSSIBLY BECOME EVEN A LITTLE STRONGER
GIVEN LIGHT SHEAR FORECAST AND WARM PLUS DEEP CARIBBEAN WATERS.

...TROPICAL WAVES...
E ATLC TROPICAL WAVE ALONG 29W/30W S OF 21N MOVING W 15 KT.
BROAD ROTATION IS NOTED ON NIGHT-TIME SATELLITE PICTURES WITH
THIS HIGH-AMPLITUDE WAVE.  THERE IS NO CONCENTRATION OF
CONVECTION WITH THE WAVE AND ANY SIGNIFICANT TSTM ACTIVITY IS
LIMITED TO THE ITCZ.

CENTRAL ATLC TROPICAL WAVE IS ALONG 49W/50W S OF 18N MOVING W 15
KT.  THIS IS A BROAD BUT DISORGANIZED WAVE THAT IS FORECAST TO
AFFECT THE LEEWARD/WINDWARD ISLANDS ABOUT THIS TIME TOMORROW
WITH AN INCREASE IN WINDS/RAIN.  UPPER LEVEL WINDS ARE KEEPING
THE SYSTEM FROM DEVELOPING... WHICH ACTUALLY EXTENDS FROM
HURRICANE IVAN IN THE W CARIBBEAN.  ISOLATED MODERATE FROM
9N-18N BETWEEN 48W-53W.

TROPICAL WAVE IS LOCATED OVER THE LEEWARD/WINDWARD ISLANDS ALONG
62W/63W S OF 20N MOVING W 10-15 KT. A 1009 MB LOW IS ALONG THE
WAVE NEAR 17N61W.  THIS IS A WEAK LOW WITH ONLY ISOLATED
MODERATE WITHIN 45 NM TO ITS S.  SOME INCREASE IN RAIN IS
FORECAST OVER THE VIRGIN ISLANDS INTO PUERTO RICO OVERNIGHT INTO
TOMORROW AS THE WAVE PASSES.

...ITCZ...
ITCZ AXIS EXTENDS ALONG 11N15W 6N20W 8N30W 7N42W 11N53W.  WIDELY
SCATTERED MODERATE FROM 7N-9.5N BETWEEN 30W-35W.  ISOLATED
MODERATE WITHIN 60 NM OF AXIS BETWEEN 20W-30W AND FROM 6N-12N
BETWEEN 45W-55W.

...DISCUSSION...
GULF OF MEXICO...
DEEP LAYERED TROUGH EXTENDS FROM THE FLORIDA PANHANDLE TO 25N93W
CONTINUING S INTO THE BAY OF CAMPECHE.  THIS TROUGH IS A
DIVIDING LINE BETWEEN VERY DRY MID/UPPER LEVEL AIR OVER THE NW
GULF N OF 25N AND WETTER CONDITIONS E OF THE TROUGH AXIS.  THIS
FEATURE HAS BEEN SLOWLY MIGRATING WESTWARD WITH ISOLATED
MODERATE WITHIN 90 NM E OF THE TROUGH AXIS.  MID/UPPER HIGH IS
NW OF IVAN NEAR 24N85W... A BIT STRONGER THAN ORIGINALLY
FORECAST.  THERE ARE ISOLATED TO WIDELY SCATTERED SHOWERS OVER
THE FLORIDA PENINSULA TODAY WITH LOW-LEVEL ELYS INCREASING DUE
TO IVAN MOVING A BIT CLOSER.  ALL EYES ARE TO THE SE IVAN...
FORECAST TO MOVE INTO GULF WATERS MON.

CARIBBEAN...
OUTSIDE OF THE HURRICANE... THE WEATHER IS FAIRLY QUIET.
ANTICYCLONIC FLOW BASICALLY IS OVER THE ENTIRE AREA WITH SOME
WLY SHEAR ENHANCING SHOWERS OVER THE LEEWARD ISLANDS.  MID/UPPER
LEVEL DRY AIR IS PRESENT E OF 70W AND NW OF THE CAYMANS...
SOMEWHAT FORCED BY LARGE-SCALE SUBSIDENCE FROM THE HURRICANE.

SUBTROPICAL ATLANTIC...
WEAKENING UPPER TROUGH IS OVER THE NW BAHAMAS WITH PLENTY OF DRY
AIR ALOFT.  THE MAIN FEATURE IS A POWERFUL MID/UPPER LOW NEAR
28N65W ABOUT 240 NM S OF BERMUDA.  THIS LOW IS ASSISTING A LARGE
AREA OF WIDELY SCATTERED WEAK/MODERATE CONVECTION NEAR AND E OF
THE CENTER FROM 52W-63W N OF 24N.  IN ADDITION... A 50 KT JET IS
PRESENT S OF THE LOW... PART OF THE OUTFLOW FROM IVAN... WHICH
IS INTERACTING WITH DEEP LAYERED MOISTURE TO PRODUCE SCATTERED
MODERATE WITHIN 75 NM OF 55.5W FROM 20N25N.  RIDGE AXIS IS ALONG
46W WITH A TROUGH PRESENT FROM THE AZORES SSW TO 23N33W.  THE
WEATHER IS BENIGN BETWEEN AFRICA AND 45W WITH NO SIGNIFICANT
CONVECTION. WEAK HIGH PRESSURE CONTROLS THE AREA OUTSIDE OF
SURFACE TROUGH ALONG 31W N OF 25N.

TROPICAL ATLANTIC...
UPPER RIDGE AXIS IS PRESENT ALONG 16NW OF 35W HEADING ENE TO
18N15W IN THE E ATLC.  WEAK TROUGHS ARE PRESENT ALONG 54W N OF
15N AND 32W N OF 16N.  THE WESTERNMOST TROUGH IS JUST W OF A
TROPICAL WAVE WITH SOME LIFT/WLY SHEAR ASSISTING A BIT OF
CONVECTION ON THE N SIDE OF THE WAVE.  RELATIVELY DRY AIR IN THE
MID/UPPER LEVELS IS FROM 30W-45W WITH AN INCREASE IN MOISTURE
NOTED E OF 30W TO W AFRICA.

$$
BLAKE

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