[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 040004
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU SEP 03 2009

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
2115 UTC.

...SPECIAL FEATURES...

TROPICAL DEPRESSION ERIKA IS CENTERED NEAR 16.7N 65.3W AT
03/2100 UTC OR ABOUT 130 MILES...205 KM...SOUTH-SOUTHEAST OF SAN
JUAN PUERTO RICO AND ABOUT 325 MILES...525 KM...EAST-SOUTHEAST
OF SANTO DOMINGO IN THE DOMINICAN REPUBLIC MOVING W AT 10 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED
WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. SCATTERED MODERATE TO
STRONG CONVECTION IS FROM 15N-17N BETWEEN 64W-65W. WIDELY
SCATTERED MODERATE CONVECTION IS ALSO E OF THE CENTER FROM
14N-17N BETWEEN 60W-63W. SEE LATEST NHC INTERMEDIATE PUBLIC
ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC AND THE
FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21
KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 18W S OF 17N MOVING W NEAR 10 KT. A 1009
MB LOW IS ALONG THE WAVE AXIS NEAR 11N18W. SATELLITE IMAGERY AND
CIMSS WAVETRAK MODEL GUIDANCE SHOW BROAD CYCLONIC TURNING ALONG
THE WAVE AXIS BETWEEN 13W-27W. SCATTERED MODERATE TO ISOLATED
STRONG CONVECTION IS FROM 14N-16N BETWEEN 18W-21W. SCATTERED
SHOWERS COVERS A LARGE AREA FROM 8N-17N BETWEEN 17W-25W.

TROPICAL WAVE IS ALONG 32W S OF 20N MOVING W NEAR 10 KT. A 1013
MB LOW IS ALONG THE WAVE AXIS NEAR 14N32W. THE WAVE COINCIDES
WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL
PRECIPITABLE WATER IMAGERY...HOWEVER...VISIBLE SATELLITE IMAGERY
INDICATES A DRY SAHARAN AIR LAYER SURROUNDING THE WAVE...THUS
INHIBITING ANY SIGNIFICANT DEEP CONVECTION. MOST SCATTERED
SHOWERS AND WIDELY SCATTERED MODERATE CONVECTION ARE EMBEDDED
WITHIN THE ITCZ FROM 5N-11N BETWEEN 26W-36W.

TROPICAL WAVE IS ALONG 49W S OF 17N MOVING W 10 KT. THE WAVE
REMAINS LOW-AMPLITUDE AND EMBEDDED WITHIN THE ITCZ AT THE
LEADING EDGE OF A MOISTURE MAXIMUM AS INDICATED BY THE TPW
IMAGERY. CONVECTION IS LIMITED TO ISOLATED SHOWERS FROM 11N-14N
BETWEEN 45W-49W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 11N32W 9N50W 10N61W.
ASIDE FROM THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...SCATTERED MODERATE CONVECTION IS FROM 7N-9N BETWEEN
24W-26W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...A 1011 MB SURFACE LOW IS CENTERED IN THE E GULF
NEAR 27N85W. A SURFACE TROUGH EXTENDS NE ACROSS CENTRAL FLORIDA
TO 29N80W. ANOTHER SURFACE TROUGH EXTENDS S FROM THE LOW TO THE
YUCATAN CHANNEL NEAR 22N86W. WIDELY SCATTERED MODERATE
CONVECTION IS OVER THE SE GULF...S FLORIDA...W CUBA...AND THE
YUCATAN PENINSULA. ELSEWHERE...ISOLATED MODERATE CONVECTION IS
OVER THE SW GULF S OF 23N AND W OF 94W. THE REMAINDER OF THE
GULF HAS FAIR SKIES WITH LIGHT WINDS. IN THE UPPER LEVELS...A
LARGE UPPER LEVEL TROUGH IS OVER THE GULF WITH AXIS ALONG 89W
EXTENDING TO THE YUCATAN PENINSULA. EXPECT...AN UPPER LEVEL LOW
TO FORM OVER THE E GULF...AND AN UPPER LEVEL RIDGE TO MOVE OVER
THE W GULF...IN 24 HOURS. ALSO EXPECT...CONVECTION TO PERSIST
OVER THE SAME AREAS MENTIONED ABOVE FOR THE NEXT 24 HOURS.

CARIBBEAN SEA...
SEE TROPICAL DEPRESSION ERIKA ABOVE. IN ADDITION...THE
CONVECTION ASSOCIATED WITH ERIKA IS SUPPORTED ALOFT BY UPPER
LEVEL ANTICYCLONIC CIRCULATION CENTERED NEAR 13N65W.
ELSEWHERE... SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS
OVER THE SW CARIBBEAN S OF 11N AND W OF 75W. EXPECT...MORE
CONVECTION OVER THE LESSER ANTILLES...THE SW CARIBBEAN...AND
CENTRAL AMERICA OVER THE NEXT 24 HOURS.

THE ATLANTIC OCEAN...
A 1010 MB LOW IS CENTERED IN THE W ATLC NEAR 33N76W WITH A
SURFACE TROUGH EXTENDING SW TO COCOA BEACH FLORIDA. SCATTERED
SHOWERS ARE WITHIN 90 NM EITHER SIDE OF THE SURFACE TROUGH.
ANOTHER SURFACE TROUGH EXTENDS FROM 31N75W TO THE N BAHAMAS AT
25N77W. SCATTERED SHOWERS AND TSTMS ARE FROM 22N-32N BETWEEN
72W-79W. STRONG MIDDLE TO UPPER LEVEL MOIST SLY FLOW ALOFT AND
UPPER DIFFLUENCE IS FURTHER ENHANCING THE CONVECTION ACROSS THE
W ATLC. TO THE EAST OF THIS ACTIVITY...A BROAD UPPER LEVEL RIDGE
COVERS THE REMAINDER OF THE W ATLC ANCHORED NEAR 31N69W. A UPPER
LEVEL LOW IS CENTERED NEAR 26N60W. UPPER LEVEL DIFFLUENCE E OF
THE UPPER LOW IS GENERATING SCATTERED SHOWERS FROM 24N-29N
BETWEEN 50W-56W. THE REMAINDER OF THE CENTRAL AND ERN ATLC IS
DOMINATED BY RATHER BENIGN UPPER LEVEL FEATURES AND A BROAD
SURFACE RIDGE N OF 22N W OF 70W. THIS SURFACE RIDGE IS ANCHORED
BY A 1025 MB HIGH N OF THE REGION CENTERED NEAR 33N42W.

$$
FORMOSA





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