[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 221806
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURE...
HURRICANE DEAN IS NOW INLAND OVER MEXICO AND BEGINNING TO
WEAKEN...CENTERED NEAR 20.5N 97.3W...OR VERY NEAR POZA RICA
MEXICO...AT 22/1800 UTC MOVING WNW AT 19 MPH. MAXIMUM SUSTAINED
WIND SPEEDS HAVE DECREASED TO 85 MPH WITH HIGHER GUSTS.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 982 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 INCLUDING THE LATEST
WATCH AND WARNING INFORMATION. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS OVER THE WRN BAY OF CAMPECHE AND INLAND
OVER MEXICO S OF 25N W OF 94W. CONTINUED WEAKENING IS EXPECTED
UNTIL DEAN DISSIPATES OVER THE MOUNTAINS OF CENTRAL MEXICO
TONIGHT. 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 22N59W 6N56W MOVING W 15-20 KT.
VISIBLE 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 OVERALL
MINIMAL AND DISORGANIZED WITH THIS WAVE...THOUGH A FEW ISOLATED
TSTMS ARE NEAR THE NRN PORTION OF THE AXIS FROM 16N-20N BETWEEN
56W-60W. SCATTERED MODERATE CONVECTION IS ALSO FURTHER
S...BEGINNING TO MOVE THROUGH TRINIDAD AND TOBAGO...WITHIN 120
NM EITHER SIDE OF THE AXIS FROM 10N-13N.

TROPICAL WAVE IS ALONG 73W/74W S OF 30N MOVING W 15-20 KT. THIS
WAVE HAS SHOWED UP WELL IN RECENT QUIKSCAT AND ASCAT PASSES.
SATELLITE IMAGERY STILL SHOWS THAT THE FOCUS OF THE LOW LEVEL
TURNING IS JUST E OF THE CENTRAL BAHAMAS FROM 23N-27N BETWEEN
71W-78W. BAHAMAS METAR DATA TO THE S OF THIS TURNING ARE STILL
SHOWING LIGHT NE TO E WINDS...SO AM STILL NOT CONVINCED THERE IS
A CLOSED SURFACE LOW WITH THIS FEATURE. THE ASSOCIATED SCATTERED
SHOWERS AND ISOLATED TSTMS ARE A BIT LESS CONCENTRATED THAN THEY
WERE EARLY THIS MORNING...AND NOW EXTEND NE FROM WRN CUBA ACROSS
THE NW BAHAMAS AND INTO THE ATLC FOR A FEW HUNDRED NM. 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. SCATTERED
MODERATE CONVECTION HAS ALSO PERSISTED WITH THE CARIBBEAN
PORTION OF THE WAVE BETWEEN 73W-77W. THIS SRN BRANCH OF THE WAVE
IS EXPECTED TO BRING MOISTURE/SHOWERS TO CENTRAL AMERICA AND THE
YUCATAN AS WE MOVE THROUGH THE SECOND PART OF THE WEEK.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N16W 9N30W 10N40W 9N47W 6N56W.
THERE IS A LITTLE MORE CONVECTION ALONG THE AXIS TODAY BUT THE
ITCZ REMAINS HIGHLY ZONAL ACROSS THE TROPICAL ATLC. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS NEAR THE COAST OF AFRICA
FROM 8N-13N E OF 17W. NUMEROUS MODERATE/ISOLATED STRONG IS
WITHIN 120 NM S OF THE AXIS BETWEEN 20W-28W. SCATTERED MODERATE
IS WITHIN 90 NM S AND 120 NM N OF THE AXIS BETWEEN 29W-44W.
SIMILAR ACTIVITY IS FROM 9N-11N BETWEEN 41W-55W.

DISCUSSION...

GULF OF MEXICO...
THE MAIN FOCUS TODAY REMAINS WEAKENING HURRICANE DEAN THAT
RECENTLY MADE LANDFALL IN 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 W OF 73W.
THE CONVECTION IN THIS VICINITY IS IN PART DUE TO THE TROPICAL
WAVE ALONG 74W 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 74W 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 30N68W 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 22N50W AND 32N36W...WHILE THE REMAINDER OF THE FAR ERN ATLC
AREA IS DOMINATED BY TYPICAL UPPER RIDGING. ELSEWHERE AT THE SFC
A 1023 MB HIGH IS NEAR 30N50W...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.

$$
WILLIS


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