[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 141819 RRA
TWDAT

TROPICAL WEATHER DISCUSSION...DELAYED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE 14 SEP 2004

...DELAYED FOR LATEST INFORMATION....

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
HURRICANE IVAN IS CENTERED NEAR 23.7N 86.5W OR 405 MILES SSE OF
THE MOUTH OF THE MISSISSIPPI AT 13/1800 UTC MOVING NNW AT 8 KT.
MAXIMUM SUSTAINED WIND SPEED IS 120 KT WITH HIGHER GUSTS MAKING
IVAN A DANGEROUS CATEGORY 4 HURRICANE ON THE SAFFIR-SIMPSON
SCALE. MINIMUM CENTRAL PRESSURE HAS RISEN TO 931 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 BECOME MORE SYMMETRIC OVER THE PAST FEW HOURS AS
CONVECTION ON THE WESTERN SIDE HAS EXPANDED/FILLED IN AND
PRESENTLY EXTENDS ABOUT 120 NM FROM CENTER...EXCEPT ABOUT 80 TO
100 NM IN THE NW QUADRANT. THE EYE... WHILE WELL DEFINED ON IR
AND WV SATELLITE IS CLOUDED OVER IN THE VISIBLE. CONVECTION HAS
SPREAD OUT...MAINLY TO THE S AND E OVER THE PAST SEVERAL HOURS.
THE MOST INTENSE CONVECTION HAS BEEN TRANSIENT...BUT IS
PRESENTLY LOCATED IN THE SW QUADRANT. MOTION CONTINUES TO THE NW.
OUTER RAINBANDS EXTEND N OVER THE W HALF OF CUBA AND ARE
PRIMARILY W OF 82W...THOUGH SOME SHOWERS ACTIVITY PRESENTLY
EXTENDS ACROSS THE CENTRAL PART OF THE SUNSHINE STATE. TO THE
CONVECTION IS SPREADING N PAST 27N AND E OF 90W. RAINBANDS ALSO
EXTEND SWD TO THE GULF OF HONDURAS...THE FAR NE TIP OF THE
YUCATAN PENINSULA AND THEN COAST OF NICARAGUA. CONVECTION S OF
18N BECOMES WIDELY SCATTERED. TROPICAL STORM FORCE AND VERY
HEAVY RAIN CAN BE EXPECTED WITHIN THESE RAINBANDS. IN THE UPPER
LEVELS...IVAN IS FLANKED BY A WEAKENING SHORTWAVE TROUGH TO THE
NORTHWEST WITH A SHORTWAVE RIDGE RECENTLY DEVELOPED JUST INLAND
OF THE SE TEXAS COAST AND MAY EXTEND S ALONG THE NE MEXICAN
COAST. A STRONG MIDDLE TO UPPER LEVEL RIDGE TO THE EAST OF IVAN.
THIS PATTERN CONTINUES TO SUPPORT EXCELLENT OUTFLOW IN ALL BUT
THE W QUADRANT WHERE SOME WLY FLOW OVER THE CENTRAL GLFMEX IS
IMPINGING UPON THE THE SYSTEM. OUTFLOW APPEARS TO BE EXPANDING
TO THE N AND NE WHERE A SHORTWAVE TROUGH OVER THE SE U.S. IS
MOVING OFF TO THE E. OTHERWISE...THE ATMOSPHERE LOOKS GENERALLY
FAVORABLE AND IVAN SHOULD REMAIN A MAJOR HURRICANE AS IT MOVES
TOWARD THE N OVER THE GULF OF MEXICO THIS AFTERNOON AND
TONIGHT.

TROPICAL DEPRESSION ELEVEN WAS UPGRADED TO TROPICAL STORM JEANNE
AT 1500 UTC THIS MORNING. CONVECTION IS EXPANDING...MAINLY TO
THE SOUTH OF THE CENTER AND HAS EXPANDED TO NEARLY 200 NM S OF
THE CENTER AND 120 NM TO THE EAST AND WEST. MODERATE SHEAR
APPEARS TO IMPINGING ON THE WEST SIDE OF JEANNE WITH THE LOW
LEVEL CENTER CLOSE TO BECOMING EXPOSED THIS MORNING.
HOWEVER...CONVENTION HAS BECOME INTENSE OVER THE PAST FEW HOURS
NEAR THE CENTER AND SCATTERED CONVECTION IS DEVELOPING TO THE N
UNDER IMPROVING OUTFLOW. VISIBLE SATELLITE NICELY SHOWS CLOUD
TOPS TO THE W OF THE CENTER BEING BLOWN OFF TO THE NORTH AND
NORTHEAST. IN THE LOW LEVELS...A GOOD SUPPLY OF MOISTURE
CONTINUES TO BE ADVECTED INTO THE S AND E OF JEANNE WHILE TO THE
WEST...LOW LEVEL CLOUDS CONTINUE TO PULL AWAY FROM JEANNE E OF
65W. THE ENVIRONMENT IS BECOMING FAVORABLE AS A MID/UPPER LEVEL
LOW HAS DEVELOPED NEAR 25N 65W. THIS LOW IS FAR ENOUGH TO AWAY
FROM JEANNE TO MAINTAIN A LOW SHEAR AND DIVERGENT PATTERN.

...TROPICAL WAVES...
NEW TROPICAL WAVE INTRODUCED OFF THE COAST OF AFRICA ALONG
19W/20W MOVING 15-20 KT. THIS IS BASED ON NEARBY SURFACE REPORTS
AND LATEST VISIBLE SATELLITE IMAGERY.  ASSOCIATED CONVECTION IS
CONFINED WITHIN THE ITCZ.

WELL-DEFINED TROPICAL WAVE OVER THE E ATLC ALONG 44/45W S OF
21N MOVING W 15 KT. THE WAVE CONTINUES TO DEMONSTRATE A CLASSIC
SIGNATURE IN SATELLITE IMAGERY. HOWEVER...THE SYSTEM REMAINS
ELONGATED AND CONVECTION SCATTERED ALONG A THIN AREA W OF THE
WAVE.

TROPICAL WAVE OVER THE CENTRAL CARIBBEAN ALONG 79W S OF 22N
MOVING W 10-15 KT. THE WAVE HAS VIRTUALLY NO SATELLITE SIGNATURE
AND THE PERTURBATION IN NEARBY SOUNDINGS HAS BECOME QUITE WEAK.
THE CURRENT POSITION IS BASED PRIMARILY UPON EXTRAPOLATED
MOTION.  NO SIGNIFICANT CONVECTION.

...ITCZ...
ITCZ AXIS SNAKES E TO W ALONG 10N13W 14N35W 10N50W 17N556W...
THEN WEAKLY ALONG COAST OF VENEZUELA AND COLUMBIA...AND OVER
CENTRAL AMERICA OVER PANAMA AND COSTA RICA. SCATTERED MODERATE
CONVECTION FROM 3N-12N E OF 35W...FROM 10N TO 15N BETWEEN 32W
AND 42W AND ALSO OVER THE SW CARIBBEAN.

...DISCUSSION...

GULF OF MEXICO...
VIGOROUS SHORTWAVE TROUGH IS NOW LIFTING OVER MIDDLE ATLANTIC
STATES AS THE WESTERN EXTENSION OF SUBTROPICAL RIDGE RETREATS
FROM THE EAST GULF BACK TO THE EAST. IVAN IS MOVING N/NW AND
FILLING THIS VOID AND IS THE DOMINATE FEATURE FOR THE GULF.
SHORTWAVE RIDGE NEAR 100W IS HELPING TO PRODUCE SOME WIDELY
SCATTERED CONVECTION OVER THE NW GULF IN A SMALL AREA OF
DIFLUENT NE OF THE RIDGE AXIS. WATER VAPOR IMAGERY SHOWS SOME
DRYING BEING PULLED INTO THE WESTERN GULF W OF IVAN...AS ALSO
INDICATED BY THE LIMITED OUTFLOW ON TH E W SIDE OF IVAN.
CONVECTION ASSOCIATED WITH IVAN SHOULD TO CONTINUE TO GRADUALLY
SPREAD UNIMPEDED TO THE NORTH ALONG WITH THIS HURRICANE. HEAVY
RAIN AND GUSTY WINDS TO TROPICAL STORM FORCE WILL ACCOMPANY
THESE WINDS AND CONDITIONS WILL DETERIORATE RAPIDLY OVER THE
NEXT 12-24 HOURS AS POWERFUL HURRICANE IVAN MOVES INTO THE
CENTRAL GLFMEX.

CARIBBEAN...
AS IVAN PULLS AWAY TO THE N...SCATTERED CONVECTION CONTINUES S
OF IVAN...MAINLY W OF 82W WITH A  ONE OUTER RAINBAND OF NOTE
PERSISTING NE FROM NEAR 17N 85W TO THE ISLE OF YOUTH THEN N ITO
THE GULF OF MEXICO. IN THE EASTERN CARIBBEAN...TROPICAL STORM
JEANNE IS DEVELOPING NICELY WITH THE CENTER SW OF SAINT KITTS.
LATEST SATELLITE SHOWS JEANNE CONTINUING ON A WESTERLY COURSE.
CONVECTION HAS RECENTLY BLOSSOMED OVER PUERTO RICO AND EXTENDS
SE ALONG A BAND TO NEAR 16N 65W THEN E TO NEAR 15N 62W. SHOWERS
AND TSTMS ALONG THIS BAND HAVE INCREASED GREATLY OVER THE PAST
FEW HOURS. THIS ACTIVITY WILL LIKELY CONTINUE TO AFFECT THE NE
PORTION OF THE E CARIBBEAN THIS AFTERNOON AND TONIGHT.
ELSEWHERE...MIDDLE TO UPPER LEVEL RIDGING INDUCED BY OUTFLOW
FROM IVAN DOMINATES THE CENTRAL CARIBBEAN WITH ASSOCIATED
SUBSIDENCE PRODUCING RATHER TRANQUIL/DRY WEATHER.

SUBTROPICAL ATLANTIC...
A TROUGH-RIDGE-TROUGH PATTERN PREVAILS ACROSS THE SUBTROPICAL
ATLC. THE SHORT WAVE TROUGH ALONG/NEAR 65 W SPILT...LEAVING A
CUT OFF CIRCULATION NEAR 22N 65W WHILE THE NORTHERN END SHEARS
OFF TO THE EAST. SCATTERED CONVECTION IS NOTED NEAR THIS LOW AND
EXTENDS NE 32N 54W AND BEYOND IN THE DIFLUENT FLOW LEADING INTO
UPPER RIDGE E OF THIS CENTER. THIS RIDGE HAS BECOME MORE SW TO
NE ORIENTED WITH AN ASSOCIATED LARGE AREA OF DRY CONDITIONS
BETWEEN 45W AND 50W. A SECOND UPPER TROF HAS ALSO BEGIN TO FORM
AN UPPER LEVEL LOW...NEAR 22N 44W WITH A BROAD UPPER RIDGE ALONG
33N TO THE EAST. WIDELY SCATTERED CONVECTION IS SEEN BETWEEN 35W
AND 40W. AT THE SURFACE...SUBTROPICAL RIDGE REMAINS DISRUPTED BY
THE SW TO NE SURFACE TROF NEAR 60W.

TROPICAL ATLANTIC...
A WELL DEFINED MIDDLE TO UPPER LEVEL RIDGE AXIS EXTENDS WESTWARD
FROM AFRICA ALONG 17N/18N TO 40W. THE RIDGE HAS BEEN SLOWLY
BUILDING WESTWARD ALLOWING DEEP LAYERED ELY FLOW TO RETURN TO
THE E ATLC.  THIS IS GENERALLY A FAVORABLE REGIME FROM TROPICAL
WAVE DEVELOPMENT.  MID-OCEANIC TROUGH DIPS INTO THE TROPICAL
ATLC WATERS BETWEEN 45W-55W. THIS PATTERN IS PRODUCING ENHANCED
ITCZ CONVECTION FROM 30-45W AND SUPPRESSING ITCZ ACTIVITY
BETWEEN 45W-60W.

$$
PROSISE/RHOME


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