[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 130102 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 12 2008

...CORRECTED SURFACE ANALYSIS SYNOPTIC AND SATELLITE IMAGERY
TIME...

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

AT 13/0000Z...THE CENTER OF LARGE HURRICANE IKE WAS ESTIMATED BY
NOAA DOPPLER WEATHER RADARS...AND AIR FORCE RESERVE AND NOAA
RECONNAISSANCE AIRCRAFT...TO BE NEAR 28.3N AND 94.0W OR ABOUT 75
NM SOUTHEAST OF GALVESTON TEXAS OR ABOUT 85 NM SOUTH OF BEAUMONT
TEXAS. IKE HAS BEEN MOVING BETWEEN THE WEST-NORTHWEST AND
NORTHWEST NEAR 13 MPH...20 KM/HR. A NORTHWEST MOTION IS EXPECTED
TO CONTINUE TONIGHT WITH A TURN TOWARD THE NORTH EXPECTED ON
SATURDAY.  ON THE FORECAST TRACK...THE CENTER OF IKE WILL BE
VERY NEAR THE UPPER TEXAS COAST BY LATER THIS EVENING OR EARLY
SATURDAY MORNING. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 954
MB. IKE HAS STRENGTHENED SOME. THE MAXIMUM SUSTAINED WIND SPEEDS
ARE NOW 95 KT WITH HIGHER GUSTS. THIS MAKES IKE A STRONG
CATEGORY TWO HURRICANE ON THE SAFFIR-SIMPSON SCALE BUT COULD
REACH THE COAST AS A CATEGORY THREE...MAJOR HURRICANE. STRONGER
WINDS...ESPECIALLY IN STRONGER GUSTS...ARE LIKELY ON HIGH RISE
BUILDINGS. PLEASE READ THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY
UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. COASTAL STORM
SURGE FLOODING OF UP TO 20 FEET...WITH A FEW SPOTS TO NEAR 25
FEET...ABOVE NORMAL TIDES ALONG WITH LARGE AND DANGEROUS
BATTERING WAVES...CAN BE EXPECTED NEAR AND TO THE EAST OF WHERE
THE CENTER OF IKE MAKES LANDFALL. THE SURGE EXTENDS A GREATER
THAN USUAL DISTANCE FROM THE CENTER DUE TO THE LARGE SIZE OF THE
CYCLONE. IKE IS EXPECTED TO PRODUCE RAINFALL AMOUNTS OF 5 TO 10
INCHES OVER EASTERN TEXAS AND EXTREME SOUTHWESTERN
LOUISIANA...WITH ISOLATED AMOUNTS OF 15 INCHES POSSIBLE.
ISOLATED TORNADOES ARE ALSO POSSIBLE TONIGHT OVER PORTIONS OF
SOUTHERN LOUISIANA AND SOUTHEASTERN TEXAS.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 18W SOUTH OF 14N MOVING WEST NEAR 20
KT. SOME CYCLONIC TURNING IS ALONG THE WAVE AXIS NEAR 6N. THE
WAVE IS GENERATING A LARGE CLOUD MASS WITH EMBEDDED SHOWERS FROM
FROM 4N-11N BETWEEN 16W-20W. DEVELOPMENT...IF ANY...OF THIS
SYSTEM IS EXPECTED TO BE SLOW TO OCCUR.

A TROPICAL WAVE IS ALONG 41W/42W SOUTH OF 20N MOVING WEST NEAR
10 KT. CYCLONIC TURNING IS NOTED ON THE WAVE AXIS NEAR 15NW. AN
EARLIER ASCAT PASS INDICATED NE WINDS OF 15-20 KT JUST AHEAD OF
THE WAVE AXIS FROM 12N-16N. ISOLATED MODERATE CONVECTION IS
WITHIN 100 NM E OF WAVE LINE FROM 14N-17N.

A TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES. ITS AXIS IS
ALONG 58W SOUTH OF 20N MOVING WEST 15 KT. AN INVERTED-V
SIGNATURE IS NOTED ON VIS SATELLITE IMAGERY. SCATTRED MODERATE
CONVECTION IS WITHIN 120 NM EITHER SIDE OF AXIS FROM 12N-18N.
MOISTURE FROM THIS TROPICAL WAVE WILL REACH THE LESSER ANTILLES
LATE TONIGHT OR EARLY SATURDAY INCREASING THE LIKELIHOOD OF
SHOWERS. BARBADOS IS ALREADY REPORTING MAINLY LIGHT SHOWERS AND
TSTMS.

A TROPICAL WAVE IS OVER THE CARIBBEAN SEA ALONG 68W/69W SOUTH OF
19N MOVING WEST 10-15 KT. SCATTERED SHOWERS AND ISOLATED TSTMS
ARE BEHIND THE WAVE AXIS JUST SOUTH OF PUERTO RICO.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 8N13W 6N25W 8N38W 8N50W 9N62W.
BESIDES THE CONVECTION MENTIONED IN THE TROPICAL WAVE SECTION...
A CLUSTER OF MODERATE TO STRONG CONVECTION IS NEAR 7N24W.
SCATTERED MODERATE CONVECTION IS FROM 5N-8N BETWEEN 45W-48W.

...DISCUSSION...

THE GULF OF MEXICO...
ALL THE ATTENTION REMAINS FOCUSED ON POWERFUL HURRICANE IKE
THAT COULD REACH THE UPPER TEXAS COAST AS A MAJOR HURRICANE LATE
TONIGHT OR EARLY SATURDAY...THEN WILL WEAKEN AFTER LANDFALL...
AND IT IS FORECAST TO BECOME EXTRATROPICAL BY 48 HOURS...AND
MERGE WITH A FRONTAL SYSTEM BY 72 HOURS. CONDITIONS ARE
DETERIORATING RAPIDLY ALONG THE COAST. HURRICANE FORCE WINDS
EXTEND OUTWARD UP TO 105 NM FROM THE CENTER OF IKE...AND
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 240 NM. OUTER
RAINBANDS ASSOCIATED WITH THE LARGE CIRCULATION OF THIS TROPICAL
CYCLONE ARE MOVING ONSHORE ALONG THE UPPER TEXAS COAST AND SW
LOUISIANA. RISING WATER LEVELS AND BATTERING WAVES ARE ALSO
AFFECTING THE AREA. SEE SPECIAL FEATURES FOR MORE DETAILS.
ELSEWHERE...A SURFACE RIDGE FROM THE SE CONUS EXTENDS INTO THE
FAR EASTERN GULF COVERING THE STATE OF FLORIDA. PRES GRADIENT
BETWEEN IKE AND THE RIDGE IS PRODUCING 20-30 KT OVER THE EASTERN
GULF. IN THE UPPER LEVELS...ANTICYCLONIC FLOW ASSOCIATED WITH AN
UPPER-LEVEL HIGH LOCATED OVER EASTERN TEXAS DOMINATES MUCH OF
THE GULF REGION.

THE CARIBBEAN SEA...
A TROPICAL WAVE EXTENDS FROM THE EASTERN PORTION OF DOMINICAN
REPUBLIC TO WESTERN VENEZUELA ALONG 68W/69W...AND ANOTHER ONE IS
APPROACHING THE LESSER ANTILLES. SEE ABOVE. NLY UPPER-LEVEL
WINDS ASSOCIATED WITH THE LARGE RIDGE THAT ALSO COVERS THE GULF
OF MEXICO ARE NOTED ACROSS CUBA...THE NW CARIBBEAN AND NORTHERN
CENTRAL AMERICA. THESE WINDS ARE ENHANCING SOME CONVECTIVE
ACTIVITY OVER HONDURAS AND NICARAGUA...AND ARE ALSO TRANSPORTING
SOUTH THE HIGH CLOUDINESS RELATED TO THE OUTFLOW OF IKE. AN
UPPER-LEVEL LOW SPINNING BETWEEN THE SE BAHAMAS AND EASTERN CUBA
HAS A TROUGH EXTENDING SWD TO ANOTHER UPPER-LOW OVER THE SW
CARIBBEAN. ISOLATED SHOWERS ARE ASSOCIATED WITH THESE
UPPER-LEVEL LOWS. THE EASTERN CARIBBEAN IS UNDER THE INFLUENCE
OF A RIDGE ANCHORED ON AN UPPER-LEVEL HIGH LOCATED NEAR 19N55W.
SLY FLOW BETWEEN THESE UPPER LEVEL FEATURES IS ADVECTING UPPER
LEVEL MOISTURE FROM SOUTH AMERICA THROUGH THE E CARIBBEAN INTO
PUERTO RICO AND THE VIRGIN ISLANDS.

THE ATLANTIC OCEAN...
AN AREA OF DISTURBED WEATHER...INCLUDING SOME OF THE REMNANTS OF
TROPICAL STORM JOSEPHINE...IS LOCATED A COUPLE HUNDRED MILES
NORTHEAST OF THE SOUTHEASTERN BAHAMAS. A SFC TROUGH IS ANALYZED
IN THIS AREA AND RUNS FROM 26N70W TO JUST N OF HISPANIOLA NEAR
20N71W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
200 NM E OF THE TROUGH AXIS FROM 22N-26N ENHANCED BY A DIFFLUENT
PATTERN ALOFT. SOME SLOW DEVELOPMENT OF THIS SYSTEM IS POSSIBLE
OVER THE NEXT COUPLE OF DAYS AS IT MOVES SLOWLY W-NW. SOME OF
THE COMPUTER MODELS BRING THIS AREA OF DISTURBED WEATHER OVER
SOUTH-CENTRAL FLORIDA ON SUNDAY. THREE TROPICAL WAVES ARE
BETWEEN WEST AFRICA AND THE LESSER ANTILLES. SEE TROPICAL WAVE
SECTION. OTHERWISE...AN UPPER-LEVEL LOW IS CENTERED NEAR 29N51W
WHILE ANOTHER ONE IS NEAR 26N34W. A BROAD UPPER-LEVEL HIGH IS
SITUATED JUST WEST OF THE CAPE VERDE ISLANDS NEAR 16N28W
EXTENDING A RIDGE ACROSS THE DEEP TROPICS TO 45W. JUST WEST OF
THIS RIDGE...AN INVERTED TROUGH IS GENERATING SOME CONVECTIVE
ACTIVITY FROM 12N-18N BETWEEN 47W-50W. AS PREVIOUSLY MENTIONED
ANOTHER UPPER-LEVEL HIGH IS NEAR 19N55W. AT THE SURFACE...A HIGH
PRESSURE CENTER LOCATED E OF THE AZORES EXTENDS A RIDGE ACROSS
THE FORECAST AREA MAINLY N OF 20N AND EAST OF 60W.

$$
GR







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