[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 151749 CCA
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT SEP 15 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION INGRID...CENTERED 16.4N 53.7W...OR ABOUT 510
NM/820 KM E OF THE LESSER ANTILLES...MOVING WEST-NORTHWEST 9 KT.
THE MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. PLEASE
READ THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT3/WTNT23 KNHC OR THE PUBLIC ADVISORY MIATCPAT3/WTNT33
KNHC FOR MORE DETAILS. NUMEROUS MODERATE AND ISOLATED STRONG
SHOWERS AND THUNDERSTORMS ARE FLARING WITHIN 120 NM IN THE
SOUTHEAST QUADRANT. THE DEPRESSION REMAINS IN AN AREA OF STRONG
UPPER-LEVEL WINDS THAT ARE NOT CONDUCIVE FOR DEVELOPMENT...AND
THE DEPRESSION IS EXPECTED TO WEAKEN FURTHER OVERNIGHT.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 35W SOUTH OF 18N MOVING
WEST 10 TO 15 KT. CONVECTION AROUND WAVE IS MORE PROLIFIC THAN
24 HOURS AGO AS IT INTERACTS WITH UPPER DIVERGENT FLOW ALOFT.
SSMI/AMSRE-DERIVED PRECIPITABLE WATER VALUES SHOW A DISTINCT
PLUME ASSOCIATED WITH THIS WAVE. VISIBLE IMAGERY HINTS THAT THE
WAVE MAY BE SLIGHTLY ORIENTED SW-NE.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 45W/46W SOUTH OF 17N
MOVING WEST 10 TO 15 KT. ANIMATED SATELLITE IMAGERY SHOWS MID
LEVEL ROTATION ASSOCIATED WITH THIS WAVE NEAR 9N ALONG THE ITCZ.
ONLY WEAK CONVECTION IS NOTED CURRENTLY NEAR THE WAVE.
HOWEVER...AS IT CONTINUES IN AN AREA OF LIGHT WIND SHEAR...SOME
DEVELOPMENT IS POSSIBLE.

AN EASTERN CARIBBEAN TROPICAL WAVE IS ALONG 68W SOUTH OF 18N
MOVING WEST 10 TO 15 KT. THE WAVE IS DEPICTED WELL ON BOTH
HOVMOLLER ANALYSIS AND PRECIPITABLE WATER IMAGERY. THE WAVE IS
IN AN AREA OF MODERATE TO STRONG WLY SHEAR...BETWEEN A BROAD
UPPER LOW CENTERED N OF HISPANIOLA...AND UPPER RIDGING OVER THE
SW CARIBBEAN. AS SUCH...ONLY ISOLATED MODERATE CONVECTION IS
NOTED E OF THE WAVE...FROM 12N TO 16N BETWEEN 65W AND 68W.

A TROPICAL WAVE EXTENDS ALONG 94W FROM THE SOUTHWESTERN GULF OF
MEXICO ACROSS THE ISTHMUS OF TEHUANTEPEC MEXICO AND INTO THE
EASTERN PACIFIC OCEAN...WEST 10 TO 15 KT. AN UPPER LEVEL LOW IS
CENTERED E OF THE WAVE NEAR 21N90W. THE SUBSIDENCE...DRY
AIR..AND NELY SHEAR ASSOCIATED WITH THE UPPER LOW IS SUPPRESSING
CONVECTIVE DEVELOPMENT NEAR THE NORTHERN PORTION OF THE WAVE
OVER THE GULF OF MEXICO.

...THE ITCZ...
AXIS IS ALONG 12N17W 14N25W 9N41W 16N52W 10N63W. SCATTERED
MODERATE CONVECTION WITHIN 150 NM N OF AXIS BETWEEN 34W AND 38W.

DISCUSSION...

THE GULF OF MEXICO...
A WEAK SURFACE TROUGH OVER THE NE GULF WILL MOVE E AND DISSIPATE
TODAY AHEAD OF A COLD FRONT ENTERING THE NORTHERN GULF WATERS
TONIGHT. THE FRONT WILL BE FOLLOWED BY SLIGHTLY INCREASED WINDS
AND SEAS THROUGH SUN OVER NRN WATERS. AN UPPER LOW OVER THE
YUCATAN WILL SHIFT W AHEAD OF A AN UPPER ANTICYCLONE CENTERED
OVER THE NE GULF...WHICH IN TURN WILL MOVE W AHEAD OF AN UPPER
TROUGH DIGGING THROUGH THE SOUTHEAST STATES. AT THE SURFACE A
WEDGE OF HIGH PRES WILL SETTLE OVER THE SOUTHEAST STATES BEHIND
THE FRONT...PROVIDING MODERATE ELY FLOW OVER MUCH OF THE GULF
WATERS THROUGH MON.

THE CARIBBEAN SEA...
MAIN INFLUENCE CONTINUES TO BE NWLY SHEAR ACROSS THE CARIBBEAN
BASIN. THIS IS THE RESULT UPPER LEVEL TROUGHING FROM THE BAHAMAS
THROUGH THE YUCATAN PENINSULA...AND AN UPPER ANTICYCLONE OVER
THE SW CARIBBEAN. THIS IS GENERALLY SUPPRESSING CONVECTIVE
DEVELOPMENT OVER THE MOST OF THE CARIBBEAN. HOWEVER...THE LIGHT
SHEAR AND UPPER EXHAUST PROVIDED BY THE UPPER ANTICYCLONE IS
ENHANCING SCATTERED MODERATE CONVECTION OVER SW CARIBBEAN WATERS
FROM COLOMBIA TO NICARAGUA. GLOBAL MODELS ARE DEPICTING THE
DEVELOPMENT OF A LOW PRES CENTER IN THIS AREA EARLY NEXT WEEK AS
THE NEXT TROPICAL WAVE APPROACHES FROM THE EASTERN
CARIBBEAN...ALTHOUGH THE TIMING AND INTENSITY OF THE LOW REMAIN
UNCERTAIN.

THE ATLANTIC OCEAN...
MID/UPPER RIDGE EXTENDS ACROSS THE EASTERN ATLC FROM THE AFRICAN
COAST TO 20N31W TO 14N46W. DIVERGENCE ALOFT ON THE SRN EDGE OF
THE RIDGE AXIS IS SUPPORTING CONVECTION ALONG THE ITCZ AS
MENTIONED ABOVE...AS WELL AS ADDING UPPER SUPPORT TO THE
TROPICAL WAVE AT 46N. AN UPPER LOW IS CENTERED NEAR 25N56W. SWLY
FLOW ALOFT BETWEEN THE RIDGE AND THIS UPPER LOW IS PROVIDING
UPPER EXHAUST FOR T.D. INGRID TO THE S. FURTHER E...ANOTHER
UPPER LOW IS CENTERED NEAR 23N70W. ISOLATED MODERATE CONVECTION
IS NOTED NEAR THE UNSTABLE CENTER OF THE LOW N OF
HISPANIOLA...FROM 22N TO 24N BETWEEN 67W AND 69W. SOME MID LEVEL
TURNING IS EVIDENT...BUT LOW LEVEL CUMULUS STREAKS SHOW
GENERALLY SELY FLOW...WITH LITTLE EVIDENCE OF A LOW LEVEL
ROTATION AT THIS TIME.

$$
CHRISTENSEN


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