[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 061738
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU SEP 06 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 LOW PRES SYSTEM IS LOCATED BETWEEN BERMUDA AND
THE BAHAMAS CENTERED NEAR 29N69W...ANALYZED 1009 MB. THE LOW HAS
BEEN NEARLY STATIONARY THIS MORNING...BUT IS EXPECTED TO MOVE
GENERALLY TOWARD THE NORTHWEST OVER THE NEXT DAY OR SO.
SATELLITE IMAGES SHOW THIS LOW HIGHLY ELONGATED AND STRETCHED
NE-SW ALONG A TROUGH AXIS...WHICH EXTENDS FROM THE LOW
SOUTHWESTWARD ACROSS THE CENTRAL BAHAMAS TO 23N78W. IR IMAGES
AND LIGHTNING DATA SUGGEST THAT SCATTERED SHOWERS AND TSTMS ARE
WITHIN 210 NM E OF THE LOW AND WITHIN 90 NM E OF THE TRAILING
TROUGH AXIS. WATER VAPOR IMAGERY DEPICTS ABUNDANT DRY AIR TO THE
W OF THE LOW/TROUGH. THE INTERACTION WITH THIS UPPER LOW HAS
GENERALLY MADE THIS SYSTEM LESS ORGANIZED TODAY. HOWEVER...THE
UPPER PATTERN COULD BECOME MORE FAVORABLE OVER THE NEXT COUPLE
OF DAYS...AND THERE IS STILL SOME POTENTIAL FOR THIS SYSTEM TO
BECOME A TROPICAL CYCLONE.

...TROPICAL WAVES...

TROPICAL WAVE IS INTRODUCED ON THE 12Z ANALYSIS NEAR THE COAST
OF W AFRICA ALONG 17W S OF 17N ESTIMATED TO BE MOVING W 10-15
KT. THIS WAVE HAS GOOD WWD CONTINUITY OVER THE CONTINENT WHEN
LOOKING AT MET-9 SATELLITE HOVMOLLER DIAGRAMS. IN ADDITION...THE
UW-CIMSS TPW ANIMATION DEPICTS MOISTENING NEAR THE AFRICAN COAST
ASSOCIATED WITH THIS ANALYZED FEATURE. VISIBLE IMAGES SHOW A
FAIR AMOUNT OF BROAD CYCLONIC LOW-LEVEL TURNING...WHICH WAS
MOSTLY USED TO PLACE THE AXIS. THIS WAVE IS ALSO MORE
ACTIVE...IN TERMS OF CONVECTION...THAN THE OTHERS CURRENTLY IN
THE ATLC BASIN. HOWEVER...THIS CONVECTION IS FAIRLY LINEAR IN
STRUCTURE ALIGNED IN THE ITCZ FROM 5N-8N E OF 29W. SCATTERED
SHOWERS AND TSTMS ARE ELSEWHERE WITHIN 180 NM EITHER SIDE OF
THE WAVE AXIS.

LARGE TROPICAL WAVE IS TITLED ALONG 24N41W 16N44W 6N43W MOVING W
15 KT. THE LOW-LEVEL SWIRL...FORMERLY AN INVEST AREA...WHICH WAS
NEAR THE LONGITUDE OF THE WAVE AXIS YESTERDAY AT THIS TIME HAS
ACTUALLY TRACKED E WITHIN THE WAVE'S ROTATION NOW CENTERED WELL
E NEAR 12N35W. ANOTHER WEAK SWIRL HAS FORMED CLOSER TO THE WAVE
AXIS LONGITUDE NEAR 14N42W. BOTH OF THESE LOWS ARE VERY WEAK AND
ARE NOT PRODUCING MUCH WEATHER. THE WAVE ITSELF REMAINS VERY
WELL DEFINED WITH A LARGE AREA OF PRONOUNCED TURNING IN THE LOW
LEVELS. DESPITE THE CONTINUED IMPRESSIVE APPEARANCE...SHOWER
ACTIVITY IS VERY LIMITED LIKELY SUPPRESSED BY THE DRY STABLE
ENVIRONMENT IT IS EMBEDDED IN.

TROPICAL WAVE IS ALONG 74W S OF 17N MOVING W 15 KT. SINCE THE
SPLITTING OF THIS WAVE A COUPLE OF DAYS AGO IT HAS BEEN
DIFFICULT TO TRACK WITH THE CURRENT POSITION BASED MOSTLY ON
EXTRAPOLATION. THERE IS SOME CLOUDINESS NEAR THE WAVE BUT THIS
IS LIKELY MORE ASSOCIATED WITH AN UPPER LOW IN THE REGION.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N17W 6N25W 7N32W 10N46W 10N62W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE E ATLC TROPICAL
WAVE...THERE IS NO SIGNIFICANT CONVECTION.

DISCUSSION...

GULF OF MEXICO...
A NE-SW ELONGATED UPPER RIDGE REMAINS THE PRIMARY FEATURE ALOFT
IN THE AREA. PRONOUNCED DIFFLUENCE BETWEEN THE HIGH AND DEEP
LAYER TROUGHING ACROSS THE W ATLC IS AIDING IN THE DEVELOPMENT
OF SCATTERED SHOWER AND TSTM ACTIVITY IN THE E GULF...WHICH HAS
BEEN THE CASE OVER THE PAST COUPLE OF DAYS. HOWEVER...THIS
ACTIVITY IS A LITTLE MORE CONCENTRATED TODAY LIKELY DUE TO A
LOW-LEVEL TROUGH DEFINED BY WEAK CONVERGENCE IN THE SHIP/BUOY
DATA. CURRENTLY...SCATTERED SHOWERS AND TSTMS ARE WITHIN 120 NM
SW OF A LINE FROM THE WRN FL PANHANDLE TO THE WRN FL
KEYS...31N87W 24N82W. CLUSTERS OF SCATTERED MODERATE CONVECTION
ARE IN THE S BAY OF CAMPECHE S OF 19N BETWEEN 93W AND 95W
ASSOCIATED WITH THE REMNANTS OF FELIX. THE REMAINDER OF THE
REGION IS RELATIVELY TRANQUIL UNDER MODERATE DRY AIR ALOFT. SFC
WINDS REMAIN FAIRLY LIGHT AND GENERALLY OUT OF THE E TO SE NEAR
THE SW PERIPHERY OF A W ATLC RIDGE...EXCEPT FOR THE SHIFTING
WINDS CLOSE TO THE AFOREMENTIONED SFC TROUGH.

CARIBBEAN SEA...
WITH THE REMNANTS OF FELIX DISSIPATING WELL INLAND OVER S
MEXICO...MUCH OF THE CARIB BASIN HAS BECOME MUCH QUIETER. MID TO
HIGH LEVEL CLOUDS ARE ADVECTED ACROSS THE W CARIB BY NLY FLOW ON
THE E PERIPHERY OF A RIDGE CENTERED TO THE NW OF THE REGION. A
FEW POCKETS OF SHOWERS ARE BEGINNING TO DEVELOP ACROSS CUBA AND
W OF JAMAICA NEAR A WEAK SMALL UPPER LOW OR INVERTED TROUGH. A
LARGER WWD MOVING UPPER LOW IS CENTERED ABOVE THE CENTRAL CARIB
NEAR 17N72W. THIS FEATURE IS EMBEDDED WITHIN A DRY AIRMASS BUT
IS STILL GENERATING A FEW CLOUDS IN ITS VICINITY. THE E CARIB IS
VERY STABLE WITH ABUNDANT DRY AIR ALOFT ADVECTED IN FROM THE
TROPICAL ATLC. THIS IS PROVIDING FAIR WEATHER ACROSS THE ERN
ISLANDS. TRADE WINDS ARE FAIRLY LIGHT ACROSS THE REGION WITH
WINDS TO 20 KT CONFINED TO NEAR THE COLOMBIAN COAST.

ATLANTIC OCEAN...
THE MAIN FEATURE OF INTEREST IN THE ATLC DISCUSSION IS THE
NON-TROPICAL LOW PRES SYSTEM LOCATED BETWEEN BERMUDA AND THE
BAHAMAS. FOR DETAILS ON THIS SYSTEM REFER TO THE SPECIAL FEATURE
SECTION ABOVE.  OTHERWISE...THE ATLC DISCUSSION AREA IS FAIRLY
QUIET WITH A PAIR OF 1022 MB HIGHS CENTERED NEAR 26N29W AND
28N44W CONTROLLING THE SFC PATTERN. THIS HIGH PRES RIDGE IS
PRODUCING LIGHT TO MODERATE WINDS ACROSS MUCH OF THE
AREA...EXCEPT STRONGER 15-20 KT NELY WINDS NEAR THE LARGE
TROPICAL WAVE...FROM 19N-23N BETWEEN 41W-48W...AS DEPICTED ON A
9Z QSCAT PASS.

ALOFT...A RIDGE IS STRETCHED OUT ACROSS THE SUBTROPICS WITH A
MEAN AXIS RUNNING E-W ALONG 25N BETWEEN 25W-65W WITH SEVERAL
EMBEDDED ANTICYCLONES. THE MAIN ANTICYCLONE IS CENTERED NEAR
27N55W. OVERALL...DRY STABLE AIR IS ASSOCIATED WITH THIS RIDGE.
THERE IS AN AREA OF SCATTERED SHOWERS NEAR OUR NRN BORDER N OF
29N BETWEEN 48W AND THE SPECIAL FEATURE ASSOCIATED WITH DEBRIS
MOISTURE SPREAD OUT BY A WLY JET BETWEEN THE SUBTROPICAL RIDGING
AND HIGH LATITUDE TROUGHS. 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 AND ISOLATED
SHOWERS N OF 28N E OF 34W ENHANCED BY A WEAK SFC TROUGH OF LOW
PRES.

$$
CANGIALOSI




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