[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 051750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 05 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...

A NON-TROPICAL AREA OF LOW PRES LOCATED ABOUT 350 NM
WEST-SOUTHWEST OF BERMUDA NEAR 29N71W...ANALYZED 1008 MB...HAS
GENERALLY CHANGED LITTLE IN STRUCTURE TODAY. VISIBLE IMAGES SHOW
AN EXPOSED LOW-LEVEL CENTER WITH MOST OF THE SHOWER AND TSTMS
ACTIVITY STRETCHED OUT TO THE NE OF THE LOW FROM 29N-32N BETWEEN
68W-71W AND ALONG THE TRAILING TROUGH AXIS. A NEW BURST OF
CONVECTION HAS FORMED NEAR THE CENTER. A QSCAT PASS AROUND 11Z
DEPICTED STRONG WINDS TO THE E OF THE CIRCULATION ALTHOUGH
SEVERAL OF THE WIND BARBS WHERE RAIN FLAGGED...HOWEVER IT IS
LIKELY THAT NEAR GALE FORCE WINDS ARE OCCURRING AS THERE IS
SEVERAL 20-25 KT UNCONTAMINATED VECTORS. THIS LOW HAS BEEN
MOVING SLOWLY EWD OR JUST S OF E OVER THE PAST 24-48 HOURS BUT
LITTLE MOVEMENT IS EXPECTED DURING THE NEXT DAY OR SO. AN AIR
FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS EN ROUTE TO
INVESTIGATE THE SYSTEM THIS AFTERNOON. STAY TUNED.

...TROPICAL WAVES...

LONG WAVELENGTH TROPICAL WAVE IS ALONG 37W/38W S OF 23N MOVING W
NEAR 20 KT OVER THE PAST 24 HOURS. THIS WAVE HAS CHANGED LITTLE
IN STRUCTURE SINCE MOVING OFF THE AFRICAN COAST WITH ABOUT A 15
DEG LONGITUDE AREA OF LOW-LEVEL CYCLONIC TURNING. THE WEAK LOW
THAT WAS STATIONARY ALONG 40W FOR THE PAST FEW DAYS HAS BEEN
DRAWN E INTO THE WAVE'S ROTATION AND IS CURRENTLY CENTERED ALONG
THE WAVE AXIS NEAR 12N...ANALYZED 1013 MB. WHILE THE SATELLITE
PRESENTATION OF THIS WAVE IS IMPRESSIVELY LARGE AND WELL
DEFINED...DEEP SHOWER ACTIVITY IS VERY LIMITED AND CONFINED TO
THE INTERSECTION OF THE ITCZ.

LOW AMPLITUDE TROPICAL WAVE IS ALONG 68W S OF 17N MOVING W 15
KT. THE UW-CIMSS TPW ANIMATION TELLS THE STORY BEST...SHOWING
THIS WEAK WAVE (WHICH APPEARED TO HAVE SOME ROTATION) SPLITTING
YESTERDAY JUST PAST 60W. THE NRN PART OF THE WAVE IS ROTATING
NWD AROUND THE ATLC SUBTROPICAL RIDGE AND DISSIPATING. THE SRN
PORTION CONTINUES ITS WWD MOVEMENT BUT IS VERY WEAK AND NOT
PRODUCING ANY SENSIBLE WEATHER.


...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N14W 8N22W 13N35W 10N40W 8N55W
10N62W. SCATTERED SHOWERS AND TSTMS COVER A LARGE AREA FROM
5N-13N E OF 20W PARTIALLY ASSOCIATED WITH THE NEXT TROPICAL WAVE
STILL INLAND OVER AFRICA. SCATTERED SHOWERS AND ISOLATED TSTMS
ARE WITHIN 180 NM S OF THE AXIS BETWEEN 20W-36W.

DISCUSSION...

GULF OF MEXICO...
THE PATTERN HAS CHANGED LITTLE ACROSS THE GULF OVER THE
PAST FEW DAYS. AN ELONGATED UPPER HIGH HAS DRIFTED S A BIT
CENTERED NEAR THE S COAST OF LOUISIANA. SOME DIFFLUENCE ALOFT
BETWEEN THIS RIDGE AND DEEP LAYER TROUGHING OVER THE W ATLC HAS
SPARKED ISOLATED TO SCATTERED TSTMS ACROSS PARTS OF THE E GULF
ROUGHLY FROM 25N-28N BETWEEN THE FL COAST AND 87W. THIS ACTIVITY
IS GENERALLY MOVING S-SW DRIVEN BY THE UPPER FLOW. ENHANCED
CONFLUENCE BETWEEN THE STRETCHED HIGH AND AN INVERTED TROUGH
OVER THE BAY OF CAMPECHE IS DRYING OUT THE AIR IN THE MID AND
UPPER LEVELS...PROVIDING MOSTLY FAIR WEATHER ACROSS MUCH OF THE
CENTRAL AND SW GULF. AT THE SFC...A WEAK 1016 MB HIGH HAS BEEN
QUASI-STATIONARY NEAR 28N91W. THIS WEAK HIGH IS ALLOWING WINDS
TO BE LIGHT AND ANTICYCLONIC ACROSS THE REGION.

CARIBBEAN SEA...
THE REMNANTS OF ONCE CATEGORY FIVE HURRICANE FELIX IS NOW WELL
INLAND NEAR THE BORDER OF NORTHEASTERN GUATEMALA AND
NORTHWESTERN HONDURAS. EVEN THOUGH STRONG WINDS ARE NO LONGER A
CONCERN HEAVY RAINFALL OVER PORTIONS OF CENTRAL AMERICA COULD
RESULT IN LIFE-THREATENING FLASH FLOODS AND MUD SLIDES. RAINFALL
REPORTS FOR THE HONDURAS WEATHER SERVICE INDICATE SEVERAL
STATIONS WITH OVER 4 INCHES OF RAIN. THE MAXIMUM ACCUMULATION
REPORTED WAS IN LA CEIBA WHERE 6.2 INCHES OF RAIN FELL.
THE REMNANT CIRCULATION OF FELIX AND BROAD SELY FLOW OVER THE S
CARIB IS DRAWING AMPLE MOISTURE FROM THE ITCZ ACROSS THE SW
CARIB AND INTO LIKELY ALREADY SATURATED ERN NICARAGUA ...ROUGHLY
SE OF A LINE ALONG 15N84W 12N73W. LESS ORGANIZED SCATTERED
SHOWERS AND TSTMS ARE OVER PORTIONS OF THE NW CARIB FROM 17N-20N
BETWEEN 78W-84W. THIS ACTIVITY IS ASSOCIATED WITH INSTABILITY
NEAR AN UPPER LOW. IN THE E CARIB...A SLOW MOVING UPPER LOW IS
CENTERED NEAR 15N67W. OVERALL...THIS FEATURE IS ADVECTING DRIER
AIR INTO THE E CARIB E OF 72W THOUGH THERE IS A NARROW SWATH OF
CLOUDINESS AND ISOLATED SHOWERS ON IT'S ERN SIDE JUST W OF THE
WINDWARD ISLANDS.

ATLANTIC OCEAN...
THE MAIN FEATURE OF INTEREST IN THE ATLC DISCUSSION IS THE LOW
PRES SYSTEM LOCATED ABOUT 350 NM WEST-SOUTHWEST OF BERMUDA. FOR
DETAILS ON THIS SYSTEM REFER TO THE SPECIAL FEATURE SECTION
ABOVE. OTHERWISE...THE ATLC DISCUSSION AREA IS FAIRLY QUIET WITH
A 1023 MB HIGH CENTERED NEAR 29N30W CONTROLLING THE SFC PATTERN.
THIS HIGH IS PRODUCING LIGHT TO MODERATE WINDS ACROSS MUCH OF
THE AREA...EXCEPT STRONGER WINDS NEAR THE LARGE TROPICAL WAVE IN
THE E ATLC AS SUGGESTED BY THE TIGHTENED PRES PATTERN ANALYZED.

ALOFT...A RIDGE IS STRETCHED OUT ACROSS THE SUBTROPICS WITH A
ROUGH AXIS RUNNING ALONG 24N BETWEEN 25W-65W WITH SEVERAL
EMBEDDED ANTICYCLONES. THE MAIN ANTICYCLONE IS CENTERED NEAR
23N38W. OVERALL...DRY STABLE AIR IS ASSOCIATED WITH THIS RIDGE.
THERE IS AN AN AREA OF SCATTERED SHOWERS AND ISOLATED TSTMS NEAR
OUR NRN BORDER N OF 28N BETWEEN 45W-52W ASSOCIATED WITH
INSTABILITY NEAR A RETREATING SHORTWAVE TROUGH. UPPER TROUGHING
ALSO COVERS THE E ATLC TO THE S OF A LARGE UPPER LOW N OF THE
MADEIRA ISLANDS. THERE IS AN ASSOCIATED SHIELD OF HIGH
CLOUDINESS N OF 29N BUT NOT MUCH WEATHER TO TALK ABOUT.

$$
CANGIALOSI





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