[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 141211
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1145 UTC.

...SPECIAL FEATURE...
HURRICANE IVAN IS CENTERED NEAR 23.1N 86.1W OR 55 MILES NW OF
THE W TIP OF CUBA AT 14/1200 UTC MOVING NNW AT 9 KT. MAXIMUM
SUSTAINED WIND SPEED IS 135 KT WITH GUSTS 165 KT. THIS MAKES
IVAN A DANGEROUS CATEGORY 4 HURRICANE ON THE SAFFIR-SIMPSON
SCALE. MINIMUM CENTRAL PRESSURE IS 925 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 APPEARS LESS ORGANIZED THAN OVER THE LAST FEW DAYS WITH THE
DEEP CONVECTION LIMITED ON THE W SIDE. THIS IS MOST LIKELY DUE
TO THE INTERACTION WITH THE YUCATAN PENINSULA AND THE SHORTWAVE
TROUGH THAT HAS BEEN OVER THE W GULF. NUMEROUS STRONG CONVECTION
ONLY WITHIN 90 NM OF THE CENTER IN THE E SEMICIRCLE. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION COVERS A LARGE AREA FROM
19N-27N BETWEEN 81W-87W. OUTER RAINBANDS EXTEND OVER S FLORIDA
AND THE FLORIDA KEYS AND W CUBA BUT ARE LIMITED TO THE W TO
ALONG THE IMMEDIATE COAST OF THE YUCATAN PENINSULA. IN THE UPPER
LEVELS...IVAN IS FLANKED BY A SHORTWAVE TROUGH TO THE WEST THAT
IS DIGGING FURTHER S AND ADVECTION MODERATE SUBSIDENCE/DRY AIR N
OF 21N FROM 90W-94W. STRONG MID/UPPER LEVEL RIDGING IS TO THE
EAST OF IVAN. THE OUTFLOW IS GOOD IN ALL BUT THE SW QUADRANT
WHERE SOME DRY AIR IS BEING ADVECTED INTO THE SYSTEM.
OTHERWISE...THE ATMOSPHERE LOOKS GENERALLY FAVORABLE AND IVAN
WILL CONTINUE TO BE A MAJOR HURRICANE AS IT MOVES ACROSS THE
GULF.

TROPICAL DEPRESSION ELEVEN IS CENTERED NEAR 16.6 62.5W AT
14/1200 UTC OR 165 MILES ESE OF SAINT CROIX IN THE U.S. VIRGIN
ISLANDS DRIFTING WESTWARD. MAXIMUM SUSTAINED WIND SPEED IS 35 KT
WITH HIGHER GUSTS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009
MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/
WTNT21 KNHC FOR MORE DETAILS.

SATELLITE IMAGERY INDICATES THAT T.D. ELEVEN IS DEVELOPING AND
COULD BECOME A TROPICAL STORM TODAY. NUMEROUS STRONG CONVECTION
IS W OF THE LEEWARD ISLANDS WITHIN A 45 NM RADIUS OF 16N62W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERS THE AREA
FROM 14N-18N BETWEEN 60W AND 64W. AT THE UPPER LEVELS...THE
RIDGING FROM IVAN IS TO THE IMMEDIATE WEST OF THE T.D. ELEVEN
AND A RIDGE AXIS TO THE E EXTENDS FROM AN UPPER HIGH JUST E NEAR
17N58W. THE ENVIRONMENT CONTINUES TO APPEAR FAVORABLE FOR
ADDITIONAL DEVELOPMENT FRO THE NEXT 48 HOURS WHEN A VERTICAL
SHEAR FROM IVAN WILL BEGIN TO IMPACT T.D. ELEVEN.

...TROPICAL WAVES...
TROPICAL WAVE IN THE MID ATLC ALONG 42W/43W S OF 27N MOVING W
10-15 KT. THE WAVE CONTINUES DISPLAY THE CLASSIC SIGNATURE ON
SATELLITE IMAGERY WITH THE ASSOCIATED DEEP CONVECTION TO THE E
OF THE WAVE AXIS. THIS LARGE AMPLITUDE WAY IS ELONGATED WITH NO
ORGANIZED OF THE CONVECTION. CLUSTERS OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION ARE FROM 12N-26N BETWEEN 38W-43W.

TROPICAL WAVE IN THE CENTRAL CARIBBEAN ALONG 77W/78W S OF 23N
MOVING W 15-20 KT. THE WAVE SIGNATURE IS OBSCURED BY HIGH CLOUDS
FROM HURRICANE IVAN. THE CURRENT POSITION IS BASED PRIMARILY
UPON EXTRAPOLATED MOTION. NUMEROUS STRONG CONVECTION IS S OF 10N
E OF 79W TO INLAND OVER COLOMBIA AND PANAMA.

...ITCZ...
ITCZ AXIS EXTENDS ALONG 19N10W 7N24W 13N38W 10N48W 11N62W. LARGE
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 3N-15N BETWEEN 15W-36W WITH SMALL CLUSTERS N OF 3N TO
INLAND OVER AFRICA BETWEEN 10W-15W AND FROM 7N12N BETWEEN
48W-54W.

...DISCUSSION...

GULF OF MEXICO...
BIG WEATHER MAKER IN THE GULF IS HURRICANE IVAN. SEE SPECIAL
FEATURES ABOVE. TROUGH CONTINUES TO MOVE SLOWLY TO OVER THE E
UNITED STATES WITH A WELL DEFINED UPPER LEVEL LOW MOVING NE
ACROSS KENTUCKY. WATER VAPOR IMAGERY SHOWS THAT BASE OF THE
TROUGH AMPLIFIED INTO THE CENTRAL GULF WITH ASSOCIATED
SUBSIDENCE AND DRY AIR NOW AFFECTING MOST OF THE N GULF COAST
FROM THE FLORIDA PANHANDLE TO TEXAS. A SHORTWAVE TROUGH EXTENDS
S OVER THE CENTRAL GULF AHEAD OF HURRICANE IVAN.
ELSEWHERE...MODERATE SUBSIDENCE AND DRY AIR AHEAD OF HURRICANE
IVAN PREVAILS OVER THE W GULF CREATING A TEMPORARY PERIOD OF
TRANQUIL CONDITIONS EXCEPT ALONG THE IMMEDIATE TEXAS COAST WHERE
ISOLATED SHOWERS PREVAIL FROM CORPUS CHRISTI TO GALVESTON.

CARIBBEAN...
EVEN THOUGH IVAN IS OUT OF THE CARIBBEAN INTO THE GULF MEXICO
BROAD RIDGING IS STILL COVERING THE W TWO-THIRDS OF THE
CARIBBEAN. AN OUTER RAINBAND ASSOCIATED WITH IVAN EXTENDS S
ACROSS W CUBA INTO THE GULF OF HONDURAS. TROUGH IN THE
CENTRAL/WESTERN ATLC EXTENDS INTO THE CARIBBEAN FROM THE VIRGIN
ISLANDS TO HISPANIOLA. TO THE E...T.D. ELEVEN IS NEAR THE
LEEWARD ISLANDS. SEE SPECIAL FEATURES ABOVE.

SUBTROPICAL ATLANTIC...
THE TROUGH-RIDGE-TROUGH-RIDGE PATTERN CONTINUES ACROSS THE
SUBTROPICAL ATLC. THE PATTERN IS COMPRISED OF A MID/UPPER LEVEL
LOW MOVING NE AWAY FROM BERMUDA WITH A TRAILING TROUGH EXTENDING
THROUGH 32N63W S TO 18N68W. ASSOCIATED SUBSIDENCE AND DRY AIR
COVERS THE AREA N OF 20N FROM 62W-72W LIMITING SIGNIFICANT
CLOUDS/CONVECTION SAVE SOME UPPER LEVEL HIGH CLOUDINESS FROM
IVAN OVER THE BAHAMAS. E OF THE MID/UPPER LOW/TROUGH...DIFFLUENT
FLOW IN THE MID-UPPER LEVELS IS PRODUCING A LARGE AREA OF
CLOUDINESS AND SCATTERED SHOWERS/THUNDERSTORMS WITHIN 140 NM OF
LINE FROM 22N65W TO BEYOND 32N55W. A MID-UPPER LEVEL RIDGE
EXISTS OVER THE CENTRAL ATLC ALONG 53W/54W AND A TROUGH TO THE E
EXTENDING FROM A UPPER LOW NEAR 31N41W S INTO THE TROPICAL ATLC
14N47W. DIFFLUENT FLOW IN THE MID-UPPER LEVELS AND THE CLOSE
PROXIMITY OF THE MID-ATLC TROPICAL WAVE ARE PRODUCING A LARGE
AREA OF CLOUDINESS AND SCATTERED SHOWERS/THUNDERSTORMS. SEE
TROPICAL WAVES ABOVE. MID/UPPER LEVEL RIDGE IN THE E ATLC
EXTENDS ALONG 29W N OF 20N.

TROPICAL ATLANTIC...
A WELL DEFINED MID/UPPER LEVEL RIDGE AXIS EXTENDS WEST FROM OVER
AFRICA ALONG 14N TO 15N40W. 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. CENTRAL ATLC TROUGH DIPS INTO THE TROPICAL ATLC
WATERS BETWEEN 50W-60W. THIS PATTERN IS PRODUCING ENHANCED ITCZ
CONVECTION FROM 35-45W AND SUPPRESSING ITCZ ACTIVITY BETWEEN
45W-55W.

$$
WALLACE



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