[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 122355
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN 12 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 IS CENTERED NEAR 19.5N 82.8W OR 210 MILES SE OF
THE WESTERN TIP OF CUBA AT 13/0000 UTC MOVING WNW 9 KT. MAXIMUM
SUSTAINED WIND SPEED IS 130 KT WITH GUSTS TO 160 KT. MINIMUM
CENTRAL PRESSURE IS 915 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 HAD MULTIPLE EYEWALLS DURING THE DAY WITH AN EXPANDING WIND
FIELD.  CIMSS ANALYSES INDICATE A LOW-SHEAR ENVIRONMENT WHICH
COULD BE FAVORABLE FOR SOME ADDITIONAL STRENGTHENING.  WATER
VAPOR PICTURES SHOW A WEAKENING MID/UPPER HIGH NEAR 22N87W WHICH
IS BEING ERODED FROM THE N BY A SHORTWAVE OVER W TENNESSEE.  THE
STRENGTH OF THIS RIDGE AND THE AMOUNT OF RIDGING DEVELOPING
AFTER THE SHORTWAVE EXITS SEEM TO BE THE CONTROLLING FACTORS FOR
THE FUTURE PATH OF THE CYCLONE.  SCATTERED STRONG WITHIN 120 NM
OF THE CENTER WITH RAINBANDS TO THE E OUT 275 NM.

...TROPICAL WAVES...
TROPICAL WAVE OVER THE E ATLC ALONG 35W S OF 21N MOVING W 15-20
KT.  V-SHAPE IS EVIDENT IN SATELLITE PICTURES THOUGH ANY
CONVECTION IS QUITE DISORGANIZED.  ISOLATED MODERATE WITHIN 90
NM OF THE WAVE AXIS BETWEEN 9N-21N.

TROPICAL WAVE ALONG 56W S OF 19N MOVING W 15 KT.  THE WAVE HAS
GOTTEN A BIT BETTER ORGANIZED SINCE YESTERDAY BUT LACKS ANY
SURFACE CIRCULATION.  SATELLITE PICTURES SUGGEST THAT A BROAD
CENTER COULD BE FORMING ALONG 15N BUT THE IMAGES ARE FAR FROM
CONCLUSIVE.  UPPER-LEVEL CONDITIONS ARE MARGINAL FOR DEVELOPMENT
BUT THE GFS ALSO INDICATES THAT THIS IS THE NEXT AREA TO WATCH.
SHOWERS AND THUNDERSTORMS SHOULD SPREAD ACROSS THE LESSER
ANTILLES OVERNIGHT INTO TOMORROW.  WIDELY SCATTERED MODERATE
FROM 11N-18N BETWEEN 51W-59W.

TROPICAL WAVE IN THE E CARIBBEAN ALONG 67W S OF 22N MOVING W
10-15 KT.  THIS WAVE HAS WEAKENING IN STRUCTURE SINCE YESTERDAY
WITH THE LOW DISSIPATING AND ONLY A FEW SHOWERS NEAR THE AXIS.
ISOLATED MODERATE WITHIN 90 NM OF PUERTO RICO AND THE US VIRGIN
ISLANDS.

...ITCZ...
ITCZ AXIS EXTENDS ALONG 11N14W 8N26W 9N56W.  WIDELY SCATTERED
MODERATE WITHIN 60 NM OF THE AXIS FROM 35W-47W.  SCATTERED
MODERATE FROM 6N-9N BETWEEN 26W-32W.

...DISCUSSION...
GULF OF MEXICO...
MID/UPPER TROUGH IS DIPPING INTO THE NORTHERN GULF FROM WESTERN
TENNESSEE SOUTHWARD THRU NEW ORLEANS TO 25N91W.  WLY FLOW COVERS
THE GULF N OF 23N WITH A SMALL MID/UPPER HIGH NEAR 22N88W.  THE
ZONAL FLOW IS ENHANCING TSTMS ALONG A SURFACE TROUGH FROM THE
BAY OF CAMPECHE NNE TO NEAR LAKE CHARLES LOUISIANA.  ISOLATED
MODERATE NW OF A LINE FROM 20N95W TO 30N86W.  OUTFLOW FROM IVAN
IS BEGINNING TO IMPINGE UPON THE SE GULF WITH CIRRUS COVERING
THE NW CUBA EDGING INTO S FLORIDA.  SUBSIDENCE... PROBABLY
FORCED SOMEWHAT BY THE HURRICANE... IS LEADING TO VERY LITTLE
DIURNAL CONVECTION OVER THE EXTREME S FLORIDA AND THE YUCATAN.
SWELL FROM IVAN SHOULD MAKE ITS WAY INTO THE GULF OVERNIGHT.

CARIBBEAN...
IVAN REMAINS THE STORY WITH TWO OUTFLOW JETS...NE AND SW
QUADRANTS.  OTHERWISE ANTICYCLONIC FLOW CONTROLS THE AREA WITH A
RIDGE AXIS JUST S OF CUBA THRU HAITI TO 15N63W.   STRONG WLY
FLOW OVER THE LEEWARD ISLANDS COMBINING WITH A DEEP MOISTURE
FROM A TROPICAL WAVE TO PRODUCE WIDELY SCATTERED SHOWERS E OF
PUERTO RICO N OF GUADELOUPE.  DRY AIR IN NOTED IN THE MID/UPPER
LEVELS E OF 73W.  NEXT TROPICAL WAVE IS MOVING INTO THE AREA
TOMORROW WHICH SHOULD SIGNIFICANTLY INCREASE THE RAIN COVERAGE
IN THE LESSER ANTILLES.

SUBTROPICAL ATLANTIC...
LARGER FEATURES DOMINATE THIS AREA WITH A TROUGH-RIDGE-TROUGH
PATTERN ACROSS MUCH OF THE SUBTROPICAL ATLC.  SLOW-MOVING
MID/UPPER LEVEL LOW IS JUST S OF BERMUDA... FORCING A LARGE AREA
OVER SCATTERED MODERATE CONVECTION FROM 22N-28N BETWEEN 56W-62W.
ASSOCIATED UPSTREAM SUBSIDENCE AND DRY AIR COVERS THE AREA W OF
65W LIMITING SIGNIFICANT CLOUDS/CONVECTION.  MID-UPPER LEVEL
RIDGE EXISTS OVER THE CENTRAL ATLC ALONG 54W WITH THE E ATLC
TROUGH ALONG 31N32W TO 23N42W. SCATTERED SHOWERS/THUNDERSTORMS
ARE OCCURRING WITH THE TROUGH FROM 24N-27N BETWEEN 30W-33W. OVER
THE FAR E ATLC...A WELL DEFINED MIDDLE TO UPPER LEVEL RIDGE
EXTENDS WESTWARD FROM AFRICA ALONG 17N/18N TO 30W.

TROPICAL ATLANTIC...
MID/UPPER INVERTED TROUGH IS JUST E OF THE LESSER ANTILLES...
BRINGING A SLUG OF MOISTURE ASSOCIATED WITH A TROPICAL WAVE NEAR
THE E CARIBBEAN.  SOME DIVERGENCE NEAR THE WAVE AXIS SEEMS TO
ENHANCING CONVECTION.  OTHERWISE MOST OF THE TROPICAL ATLC IS
UNDER THE INFLUENCE OF A MID/UPPER RIDGE AXIS EXTENDING FROM
AFRICA NEAR 17N WSW INTO A HIGH CENTER NEAR 16N51W NW TO
20N60W.  WEAK TROUGH SPLITS THE RIDGE NEAR 35W RESULTING IN
ENHANCED ITCZ CONVECTION WITHIN 5 DEG TO THE EAST AND SUPPRESSED
ITCZ CONVECTION WITHIN 5 DEG TO THE WEST. ELSEWHERE...DEEP
LAYERED ELY FLOW PREVAILS.

$$
BLAKE

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