[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 230014
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED AUG 22 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURE...
TROPICAL STORM DEAN CONTINUES TO PUSH FURTHER INLAND OVER MEXICO
AND HAS WEAKENED QUITE RAPIDLY OVER THE HIGH TERRAIN OF MEXICO.
AS OF 0000 UTC DEAN WAS CENTERED NEAR 20.5N 99.0W...OR ABOUT 75
MILES NORTH OF MEXICO CITY MEXICO...MOVING W AT 17 MPH. MAXIMUM
SUSTAINED WIND SPEEDS HAVE DECREASED TO 45 MPH WITH HIGHER GUSTS
OVER THE ELEVATED TERRAIN OF THE SIERRA MADRE. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 996 MB. PLEASE SEE THE LATEST NHC FORECAST
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE
LATEST PUBLIC ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR MORE
DETAILS. DEAN RETAINS A WELL ORGANIZED CONVECTIVE CLOUD PATTERN
AT THE MID AND UPPER LEVELS DESPITE THE TREK OVER THE HIGH
TERRAIN...HOWEVER AT THE LOW LEVELS SURFACE OBSERVATIONS
INDICATE THAT THE SYSTEM HAS BEEN ESSENTIALLY SHREDDED OVER THE
MEXICAN TERRAIN. SCATTERED MODERATE ISOLATED STRONG CONVECTION
IS OCCURRING OVER CENTRAL MEXICO WITH OVERCAST MID AND HIGH
LEVEL CLOUD DEBRIS EXTENDING OVER THE WRN BAY OF CAMPECHE AND
GULF OF MEXICO. CONTINUED WEAKENING IS EXPECTED UNTIL DEAN
DISSIPATES OVER THE MOUNTAINS OF CENTRAL MEXICO OVERNIGHT. DEAN
IS  EXPECTED TO PRODUCE STORM TOTAL RAINFALL OF 5 TO 10 INCHES
OVER PARTS OF SOUTHERN AND CENTRAL MEXICO...WITH MAXIMUM AMOUNTS
OF UP TO 20 INCHES. THESE RAINS COULD CAUSE LIFE-THREATENING
FLASH FLOODS AND MUDSLIDES.

...TROPICAL WAVES...
TROPICAL WAVE IS TILTED ALONG 22N60W TO THE SOUTH AMERICAN COAST
AT 8N59W MOVING W 15 KT. SHORTWAVE INFRARED SATELLITE IMAGERY
SHOWS AN ELONGATED AND NARROW ZONE OF LOW LEVEL CYCLONIC TURNING
IN ASSOCIATION WITH THIS WAVE JUST E OF THE LESSER ANTILLES. IN
ADDITION...THE WAVE SHOWS UP WELL IN THE UW-CIMSS TPW PRODUCT AS
A SECONDARY SURGE OF MOISTURE BEHIND THE LARGER WAVE TO ITS W.
DEEP CONVECTION IS MINIMAL AND DISORGANIZED WITH THIS WAVE...
THOUGH A FEW ISOLATED TSTMS ARE NEAR THE SRN PORTION OF THE AXIS
S OF 14N OVER THE SRN WINDWARD ISLANDS GENERALLY BETWEEN
60W-63W.

A VERY HIGH AMPLITUDE TROPICAL WAVE IS ALONG 75W/76W S OF 29N
MOVING W AT A BRISK 15-20 KT. SATELLITE IMAGERY STILL SHOWS THAT
THE FOCUS OF THE LOW LEVEL TURNING IS JUST E OF THE CENTRAL
BAHAMAS WITH A WELL DEFINED LOW LEVEL CENTER NOTED NEAR 25N76W.
BAHAMAS METAR DATA TO THE S OF THIS TURNING STILL INDICATE LIGHT
NE WINDS...THUS THE FEATURE DOES NOT APPEARS TO BE CLOSED AT THE
SURFACE AT THIS TIME. THE ASSOCIATED SCATTERED SHOWERS AND
ISOLATED TSTMS ARE RATHER SPARSE AND NOT ORGANIZED AND NOW
EXTEND NWD FROM ERN CUBA ACROSS THE NW BAHAMAS. THE WAVE IS
EXPECTED TO BRING SHOWERS AND THUNDERSTORMS TO THE FLORIDA
PENINSULA OVER THE NEXT DAY OR SO. HOWEVER...UPPER-LEVEL WINDS
ARE NOT FAVORABLE FOR TROPICAL CYCLONE FORMATION AS THE WAVE IS
SITUATED OVER THE NORTHERN EXTENT OF A AN UPPER LEVEL LOW OVER
THE NW CARIBBEAN. CONVECTION NOTED EARLIER WITH THE CARIBBEAN
PORTION OF THE WAVE BETWEEN 73W-77W HAS ALL BUT DISSIPATED.
THIS SRN BRANCH OF THE WAVE IS EXPECTED TO BRING MOISTURE
ADDITIONAL SHOWERS TO CENTRAL AMERICA AND THE YUCATAN OVER THE
SECOND PART OF THE WEEK.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N16W 9N30W 10N42W 9N58W. THE ITCZ
REMAINS HIGHLY ZONAL FOR LATE AUGUST WITH SCATTERED MODERATE
ISOLATED CONVECTION WITHIN 120 NM OF THE AXIS BETWEEN 22W AND
36W. UW CIMSS SAHARAN AIR LAYER ANALYSES AND BACKWARD
EXTRAPOLATION OF A WAVE PASSAGE OFF THE AFRICAN COAST ON AUG 19
INDICATE A LOW AMPLITUDE TROPICAL WAVE ALONG 40W. THIS WAVE
WILL BE ADDED ON THE 0000 UTC SFC ANALYSIS.

DISCUSSION...

GULF OF MEXICO...
THE MAIN FOCUS THIS EVENING REMAINS WEAKENING TROPICAL STORM
DEAN THAT DESPITE MOVING FURTHER INLAND OVER MEXICO NEAR THE
TOWN OF TECOLUTLA...SEE SPECIAL FEATURES ABOVE. DEAN IS BEING
STEERED WWD BY A DEEP LAYER RIDGE TO ITS N/NE. TROPICAL MOISTURE
FROM DEAN IS ROUNDING THIS RIDGE AND MOVING THROUGH TEXAS.
DRY/STABLE AIR IS OVER THE ERN GULF KEEPING WEATHER MOSTLY
FAIR...THOUGH MOISTURE/SHOWERS EXPECTED TO INCREASE THROUGH THU
IN THE SE PORTION WITH THE APPROACHING TROPICAL WAVE AND MID TO
UPPER LOW. SFC RIDGING WILL REMAIN QUASI STATIONARY OVER THE N
GULF OVER THE NEXT FEW DAYS.

CARIBBEAN SEA...
THE MOST SIGNIFICANT AREA OF WEATHER IN THE CARIBBEAN IS IN THE
SW PORTION...WITH SCATTERED SHOWERS AND TSTMS S OF 15N BETWEEN
73 AND 78W. THE CONVECTION IN THIS VICINITY IS IN PART DUE TO
THE TROPICAL WAVE ALONG 75W/76W AS DESCRIBED ABOVE...BUT IS ALSO
BEING SUPPORTED BY DIFFLUENT FLOW ALOFT. MOISTURE WITH THIS
WAVE...AND THE WAVE NEARING THE WINDWARD ISLANDS...WILL PUSH W
THROUGH THE BASIN OVER THE NEXT COUPLE OF DAYS. ELSEWHERE AT THE
SFC LIGHT TO MODERATE TRADES ARE IN PLACE AND GENERALLY EXPECTED
TO PERSIST THROUGH THU. THE UPPER PATTERN IS DOMINATED BY THE
LARGE AND ELONGATED UPPER LOW JUST S OF CUBA...AND THE SRN
PERIPHERY OF AN UPPER RIDGE OVER THE ERN PORTION. LIFT WITH THE
UPPER LOW IS ALSO SUPPORTING SCATTERED SHOWERS/ISOLATED TSTMS
OVER THE NW CARIBBEAN N OF 15N BETWEEN 79W-84W.

ATLANTIC OCEAN...
SHOWERS AND TSTMS ARE MOVING THROUGH THE WRN ATLC WITH THE
TROPICAL WAVE ALONG 75W/76W AS DESCRIBED ABOVE. TROUGHING IS
VERTICALLY STACKED IN THIS VICINITY...EXTENDING N FROM AN UPPER
LOW JUST S OF CUBA. AN UPPER HIGH IS NEAR 30N60W THAT HAS
RIDGING EXTENDING S TO THE ERN CARIBBEAN. THIS IS SUPPORTING A
FEW ISOLATED TSTMS BETWEEN 65W-70W. BENIGN UPPER LOWS ARE NOTED
NEAR 23N52W AND 32N36W...WHILE THE REMAINDER OF THE FAR ERN ATLC
AREA IS DOMINATED BY TYPICAL UPPER RIDGING. ELSEWHERE AT THE SFC
A 1021 MB HIGH IS NEAR 30N56W...EXPECTED TO SLIDE SW IN ADVANCE
OF THE FRONTAL SYSTEM N OF THE AREA. LIGHT TO MODERATE TRADE
WINDS AND FAIR WEATHER AROUND THIS RIDGING DOMINATE MUCH OF THE
AREA N OF 13N E OF 50W.

$$
COBB




This weather bulletin was brought to you by:
www.nashvilleweather.net