[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 031800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON SEP 03 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 FEATURES...

HURRICANE FELIX HAS WEAKENED BUT IS STILL EXTREMELY DANGEROUS
AND COULD RESTRENGTHEN. FELIX IS CENTERED NEAR 14.2N 78.7W AT
03/1800 UTC OR ABOUT 265 NM EAST OF CABO GRACIAS A DIOS ON THE
NICARAGUA/HONDURAS BORDER...MOVING W AT 18 KT. THE MINIMUM
CENTRAL PRESSURE ESTIMATED FROM AIR FORCE HURRICANE HUNTER
AIRCRAFT DATA IS 950 MB. MAXIMUM SUSTAINED WIND SPEED IS 125 KT
WITH GUSTS TO 155 KT. THIS MAKES FELIX A CATEGORY FOUR HURRICANE
ON THE SAFFIR-SIMPSON SCALE. 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 INCLUDING THE LATEST WATCH AND WARNING
INFORMATION. FELIX CONTINUES ON A RATHER QUICK WNW PATH STEERED
BY A STRONG RIDGE TO ITS N. IR SATELLITE IMAGES DEPICT SOME
STRUCTURAL CHANGES TO THE SHAPE AND SIZE OF THE CONVECTIVE
PATTERN OVER TIME WITH THE EYEWALL NOT QUITE AS SYMMETRIC AS
EARLIER. NUMEROUS MODERATE TO STRONG IS WITHIN 90 NM E AND 45 NM
W SEMICIRCLES. A VERY STRONG BAND...CONTAINING SIMILAR
CONVECTION...IS IN THE NW SEMICIRCLE WITHIN 175 NM OF THE
CENTER.

AN AREA OF LOW PRES...ANALYZED 1012 MB...IS CENTERED NEAR
11N40W. THIS LOW PRES SYSTEM HAS BEEN ON A VERY SLOW SW DRIFT
OVER THE PAST FEW DAYS AND HAS GENERALLY CHANGED LITTLE. THE LOW
LEVEL CIRCULATION REMAINS WELL DEFINED BUT SHOWER ACTIVITY IS
DISORGANIZED. DESPITE THE LACK OF IMPROVEMENT IN STRUCTURE THERE
STILL IS SOME POTENTIAL FOR THIS SYSTEM TO BECOME A TROPICAL
DEPRESSION DURING THE NEXT COUPLE OF DAYS.

A LOW PRES AREA IS OFF THE GEORGIA COASTLINE CENTERED NEAR
31N79W...ESTIMATED TO BE 1013 MB. VISIBLE SATELLITE IMAGERY
SHOWS SOME IMPROVEMENT IN ORGANIZATION WITH LOW-LEVEL TURNING
EASILY APPARENT. AT THE MOMENT...THIS LOW IS STILL SOMEWHAT
FRONTAL IN NATURE WITH A SHIELD OF LOW CLOUDS LINEARLY SHAPED TO
THE E OF THE CIRCULATION. HOWEVER...THERE IS SOME POTENTIAL FOR
SLOW TROPICAL DEVELOPMENT AS IT DRIFTS EASTWARD DURING THE NEXT
COUPLE OF DAYS. DISORGANIZED SHOWERS AND TSTMS ARE WITHIN 180 NM
MOSTLY TO THE E OF THE LOW-LEVEL CENTER.


...TROPICAL WAVES...

LARGE TROPICAL WAVE IS ALONG 25W/26W S OF 22N MOVING W 15 KT.
THIS WAVE IS EMBEDDED WITHIN A STRETCHED GYRE COVERING CLOSE TO
A 15 DEG E-W AREA. A FEW SURROUNDING SHIP/BUOY OBSERVATIONS AND
A PARTIAL QSCAT PASS SUGGEST THAT THIS CYCLONIC TURNING IS AT
THE SFC. THE LATEST VISIBLE IMAGES SHOW ROTATION CONCENTRATED
ALONG THE WAVE AXIS NEAR 14N...AND A LOW WILL LIKELY BE ADDED TO
THE NEXT SYNOPTIC MAP TO REFLECT THIS. EVEN THOUGH THE WAVE
STRUCTURE HAS IMPROVED A BIT...SHOWER ACTIVITY REMAINS VERY
LIMITED LIKELY SUPPRESSED BY THE STABLE LOW TO MID LEVEL AIR
SURROUNDING THIS FEATURE.

TROPICAL WAVE IS ALONG 56W S OF 22N MOVING W 10 KT. SATELLITE
IMAGERY SHOWS A CLASSIC INVERTED V-SHAPE TO THE LOW CLOUD FIELD.
SFC OBSERVATIONS MATCH THE SATELLITE SIGNATURE WITH LOWER
PRESSURES CLOSER TO THE WAVE AXIS AND WINDS TURNING
CYCLONICALLY. SHOWER ACTIVITY REMAINS MINIMAL AND CONFINED TO
THE INTERSECTION OF THE ITCZ FROM 10N-12N BETWEEN
54W-58W...SUPPRESSED BY SINKING AIR PRODUCED BY AN UPPER TROUGH.

TROPICAL WAVE IS OVER PORTIONS OF CENTRAL AMERICA ALONG 87W/88W
MOVING W 10-15 KT. THIS ONCE ACTIVE WAVE IS NO LONGER EASILY
DISCERNIBLE IN ANY OF THE AVAILABLE DATA...THEREFORE THE CURRENT
POSITION IS BASED ON FORWARD EXTRAPOLATION. SHOWERS AND TSTMS
ARE ISOLATED AT BEST IN THE REGION.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 16N17W 12N27W 10N42W 12N52W 10N63W.
SCATTERED SHOWERS AND TSTMS COVER A LARGE AREA ROUGHLY FROM
6N-10N E OF 38W ASSOCIATED WITH CROSS EQUATORIAL SWLY FLOW.

DISCUSSION...

GULF OF MEXICO...
THE WRN CORNER OF THE GULF...ROUGHLY W OF 96W...IS EXPERIENCING
SCATTERED SHOWERS AND TSTMS. THIS ACTIVITY IS PRIMARILY
ASSOCIATED WITH UPPER DIFFLUENCE BETWEEN AN ELONGATED UPPER
RIDGE OVER THE SE STATES AND AN UPPER LOW OVER SW TEXAS AND N
MEXICO. SEA LEVEL PRES ANALYSIS DOES SHOW DECENT TROUGHING...SO
THE COMBINATION BETWEEN SELY LOW-LEVEL RETURN FLOW AND SOME
CONVERGENCE IS LIKELY A CONTRIBUTING FACTOR TO THIS PERSISTENT
AREA OF UNSETTLED WEATHER. THE TAIL END OF A SFC BOUNDARY
EXTENDS ACROSS N CENTRAL FL TO 28N85W. THIS TROUGH IS ASSOCIATED
WITH A BROAD LOW PRES LOCATED OFF THE GEORGIA COAST. DOPPLER
RADAR IS DETECTING ISOLATED SHOWERS NEAR THE BOUNDARY BUT NOT
MUCH TO TALK ABOUT. MUCH OF THE REMAINDER OF THE GULF IS
RELATIVELY QUIET WITH A 1020 MB HIGH PARKED ACROSS THE MIDDLE
GULF NEAR 27N89W. THIS IS ALLOWING WINDS TO BE VERY LIGHT ACROSS
THE E AND CENTRAL GULF.

CARIBBEAN SEA...
EXTREMELY DANGEROUS HURRICANE FELIX IS THE FOCUS AS IT MOVES
ACROSS THE WESTERN CARIBBEAN. FELIX IS EXPECTED TO PRODUCE 5 TO
8 INCHES ACROSS NORTHERN HONDURAS AND NORTHEASTERN NICARAGUA
...WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 12 INCHES. THESE
RAINS COULD PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD
SLIDES. SEVERAL WATCHES AND WARNINGS ARE IN EFFECT. FOR DETAILS
AND REFERENCES SEE SPECIAL FEATURE SECTION ABOVE. SINKING AIR
DRAWN S FROM THE ATLC AND PARTIALLY ENHANCED BY THE STRONG
CIRCULATION OF FELIX LIES ACROSS MUCH OF THE AREA E OF 70W
...PRODUCING A FAIR WEATHER DAY ACROSS THIS AREA. WINDS AND SEAS
HAVE ALSO DECREASED HERE WITH THE HURRICANE NOW WELL TO THE W.

ATLANTIC OCEAN...
A STALLED FRONT LIES ACROSS OUR NRN BORDER EXTENDING FROM 29N69W
TO A LOW PRES SYSTEM CENTERED OFF THE GEORGIA COAST NEAR 31N79W.
A SFC TROUGH HANGS SW FROM THE LOW TO CENTRAL FLORIDA. SCATTERED
SHOWERS AND TSTMS ARE MOST CONCENTRATED WITHIN 180 NM OF THE
LOW AND WITHIN 60 NM OF THE TROUGH AXIS N OF 28N. ISOLATED
SHOWERS AND TSTMS ARE ELSEWHERE WITHIN 120 NM OF THE FRONT. FOR
MORE DETAILS REFER TO THE SPECIAL FEATURE SECTION ABOVE. HIGH
LEVEL CLOUDINESS ORIGINATING FROM THIS ACTIVITY SPREADS MUCH
FARTHER S DRIVEN BY STRONG NLY FLOW BETWEEN AN UPPER HIGH
CENTERED NEAR 24N68W AND AN UPPER LOW NEAR 25N53W. BOTH OF THESE
UPPER FEATURES HAVE BEEN SLOW TO MOVE OVER THE PAST COUPLE OF
DAYS. A WEAK SFC TROUGH...LIKELY LINKED TO A MID LEVEL LOW...IS
OVER THE BAHAMAS GENERATING A FEW SHOWERS. ANOTHER WEAK AREA OF
LOW PRES IS CENTERED FARTHER E NEAR 30N57W. THIS WEAK LOW IS
ATTACHED TO A COLD FRONT WHICH EXTENDS VERY FAR N. ELSEWHERE AT
THE SFC...A 1020 MB HIGH IS NEAR 25N69W...WHILE MODERATE RIDGING
DOMINATES THE E ATLC S OF A 1030 MB HIGH NEAR 47N20W. THIS
PATTERN HAS ALLOWED TRADES TO REMAIN LIGHT TO MODERATE ACROSS
MOST OF THE AREA. IN THE E ATLC...A DOMINATING UPPER HIGH
REMAINS PARKED ACROSS THE AREA CENTERED NEAR 24N20W. ABUNDANT
DRY AIR ALOFT IS EMBEDDED WITHIN THIS RIDGE. STRONG E TO SELY
FLOW NEAR THE SW PERIPHERY OF THIS HIGH IS SHEARING THE SPECIAL
FEATURE NEAR 11N40W.

$$
CANGIALOSI






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