[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 081040
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON OCT 08 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1030 UTC.

...SPECIAL FEATURE...

A BROAD AREA OF LOW PRES IS CENTERED IN THE NW CARIB NEAR
18.5N85W...ANALYZED 1003 MB AT 09Z. THIS LOW SITS ALONG A SFC
TROUGH WHICH RUNS ENE FROM THE LOW TOWARD CUBA NEAR 20N79W AND
WNW OF THE LOW ACROSS THE YUCATAN PENINSULA AND INTO THE SW
GULF. SYNOPTIC 24-HOUR PRESSURE TENDENCIES ONLY INDICATE SLIGHT
DEEPENING SINCE YESTERDAY AT THIS TIME. SATELLITE IMAGES
CONTINUE TO SHOW A RATHER BROAD AREA OF LOW TO MID LEVEL
TURNING. A 0230Z ASCAT OVERPASS CONFIRMED THE SATELLITE
APPEARANCE REVEALING AN ELONGATED CIRCULATION WITH LIGHT WINDS.
CONVECTION HAS INCREASED SOME OVERNIGHT...BUT STILL REMAINS
STRETCHED OUT ALONG THE TROUGH AXIS FROM 17N-19N BETWEEN
84W-88W. UPPER-LEVEL WINDS ARE FAVORABLE FOR DEVELOPMENT OF THIS
SYSTEM DURING THE NEXT COUPLE OF DAYS AS IT MOVES VERY SLOWLY
WESTWARD OR NORTHWESTWARD. AN AIR FORCE HURRICANE HUNTER
AIRCRAFT IS SCHEDULED TO INVESTIGATE THIS SYSTEM LATER
TODAY...IF NECESSARY.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 38W/39W S OF 13N ESTIMATED TO BE MOVING
W 15 KT. THIS LOW AMPLITUDE WAVE HAS BEEN DIFFICULT TO SEE SINCE
EMERGING OFF THE AFRICAN COAST...LIKELY A FEW DAYS AGO...AS IT
HAS BEEN EMBEDDED WITHIN THE LINEAR ITCZ CLOUDINESS. THE WAVE IS
MORE VISIBLE ON THIS MORNING'S IMAGERY WITH THE ASSOCIATED DEEP
CLOUDINESS REACHING A POLEWARD CREST ALONG THE ANALYZED AXIS.
THE MIMIC TPW ANIMATION SHOWS A NARROW RATHER QUICK WWD MOVING
MOISTURE BUMP PERTURBING THE ITCZ...RELATED TO THIS WEAK
FEATURE. SCATTERED SHOWERS AND TSTMS ARE WITHIN 210 NM EITHER
SIDE OF THE AXIS.

TROPICAL WAVE IS ALONG 56W S OF 20N MOVING W TO NW NEAR 10 KT. A
1010 MB LOW IS LOCATED ALONG THE WAVE AXIS NEAR 18N. THIS LOW
ONLY CONSISTS OF LOW-LEVEL CLOUDS...AND IN FACT MAY BE OPENING
UP. WEAKENING SCATTERED MODERATE CONVECTION IS WELL REMOVED TO
THE E OF THE WAVE FROM 16N-18N BETWEEN 51W-53W...SHEARED OFF BY
STRONG UPPER SWLY FLOW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N16W 7N29W 9N37W 8N43W 10N62W. THE
AXIS REMAINS ACTIVE TONIGHT. IN ADDITION TO THE CONVECTION
ASSOCIATED WITH THE TROPICAL WAVES...SCATTERED MODERATE IS
WITHIN 180 NM N AND 210 NM S OF THE AXIS BETWEEN 24W-50W.
SIMILAR CONVECTION IS FROM 4N-6N E OF 19W.

DISCUSSION...

THE GULF OF MEXICO...
QUITE BREEZY WEATHER CONTINUES OVER THE CENTRAL AND EASTERN GULF
WATERS THIS MORNING. DATA FROM SHIPS...BUOYS AND A RECENT ASCAT
PASS REVEAL ELY WINDS MAINLY IN THE 15-20 KT RANGE E OF A SFC
TROUGH AXIS ALONG 20N90W 26N95W. THIS MODERATE TO FRESH FLOW IS
ASSOCIATED WITH A TIGHTENED PATTERN BETWEEN A BROAD LOW PRES
AREA IN THE NW CARIB AND A HIGH PRES RIDGE PARKED OVER THE
MID-ATLANTIC STATES. THIS STIFF FLOW IS PICKING UP STREAMS OF
SHALLOW QUICK MOVING SHOWERS FROM THE ATLC AND STEERING THEM
ACROSS FLA AND THE GULF WATERS. SLIGHTLY DEEPER MOISTURE IS IN
PLACE ACROSS THE CENTRAL GULF...ROUGHLY S OF 27N BETWEEN
85W-93W...ASSOCIATED WITH DEEP LAYER INVERTED TROUGHING RELATED
TO THE NW CARIB LOW. CURRENTLY...IR IMAGES ARE NOT INDICATING
MUCH IN THE WAY OF ORGANIZED TSTM ACTIVITY EXCEPT FOR A SMALL
PATCH FROM 24N-26N BETWEEN 86W-88W. THE WEATHER ACROSS THE FAR
W/SW CORNER REMAINS TRANQUIL...SITUATED TO THE W OF THE INVERTED
TROUGHING...WITH FAIR TO MOSTLY CLEAR SKIES AND RATHER LIGHT SFC
FLOW .

THE CARIBBEAN SEA...
THE SLOW MOVING BROAD AREA OF LOW PRES IN THE NW CARIB BETWEEN
BELIZE... HONDURAS...AND THE CAYMAN ISLANDS IS THE MAIN FEATURE
OF INTEREST THIS MORNING. FOR DETAILS REFER TO THE SPECIAL
FEATURE SECTION ABOVE. ELSEWHERE...SCATTERED MODERATE CONVECTION
HAS MOVED LITTLE OVER THE PAST SEVERAL HOURS N OF 15N BETWEEN
74W-78W...WHICH INCLUDES PORTIONS OF JAMAICA...ERN CUBA AND THE
WINDWARD PASSAGE. THIS ACTIVITY IS ASSOCIATED WITH MOIST SLY
LOW-LEVEL FLOW AND SOME CONVERGENCE IN THE LOW-LEVELS TO THE S
OF AN ATLC SFC TROUGH. UPPER-LEVEL FLOW IS ALSO DIFFLUENT OVER
THIS REGION BETWEEN TROUGHING OVER THE BAHAMAS AND RIDGING OVER
THE CENTRAL CARIBBEAN. THIS UPPER PATTERN IS HELPING TO GENERATE
AND SPREAD WIDESPREAD HIGH LEVEL CLOUDINESS ACROSS THE ENTIRE
REGION. THE SFC TRADE WIND FLOW HAS BEEN GREATLY INTERRUPTED
OVER THE PAST COUPLE OF DAYS ESP W OF 70W...DUE TO THE BROAD LOW
PRES TROUGH. THIS IS EXPECTED TO CONTINUE TO BE THE CASE FOR A
COUPLE MORE DAYS AS THE LOW MOVES VERY SLOWLY. E OF 70W...TRADES
ARE FAIRLY LIGHT BUT THEY MAY INCREASE SLIGHTLY BY MID-WEEK AS
THE SUBTROPICAL ATLC HIGH RIDGES FURTHER W.

THE ATLANTIC OCEAN...
AN ELONGATED SFC TROUGH PERSISTS ACROSS MUCH OF THE SW AND
CENTRAL ATLC EXTENDING FROM THE SE BAHAMAS NEWARD ALONG 22N77W
23N60W 32N48W. A WEAK LOW...ANALYZED 1010 MB...HAS FORMED ALONG
THE TROUGH AXIS NEAR 27N52W. A MID TO UPPER-LEVEL TROUGH WITH A
SERIES OF EMBEDDED SHORTWAVES ARE SUPPORTING THIS LONG STRETCHED
OUT SURFACE FEATURE. THERE ARE A COUPLE OF AREAS ALONG THE
TROUGH WHERE LOW TO MID-LEVEL VORTICITY APPEARS TO BE MAXIMIZED.
ONE IS LOCATED SEVERAL HUNDRED MILES NORTH OF PUERTO RICO
..WHERE THERE IS A CLUSTER OF SCATTERED MODERATE CONVECTION FROM
22N-25N BETWEEN 65W-68W. THE SECOND VORT MAX IS STRONGLY SHEARED
LOCATED TO THE E OF THE WEAK SFC LOW GENERATING SCATTERED
MODERATE CONVECTION FROM 24N-29N BETWEEN 45W-51W. UPPER-LEVEL
WINDS REMAIN STRONG WHICH ARE INHIBITING ANY TROPICAL
DEVELOPMENT OF THESE SYSTEMS. N AND W OF THE TROUGH AXIS...ELY
SFC WINDS REMAIN MODERATE TO FRESH DUE TO THE TIGHTENED GRADIENT
BETWEEN THE TROUGH AND HIGH PRES OVER THE MID ATLC STATES.

MUCH QUIETER WEATHER EXISTS E OF 40W UNDER THE INFLUENCE OF A
SFC RIDGE EXTENDING SW FROM A 1027 MB HIGH E OF THE AZORES NEAR
39N17W. THIS IS KEEPING WINDS LIGHT IN THE SUBTROPICS AND
MODERATE IN THE TROPICS...EXCEPT SLIGHTLY STRONGER 20-25 KT NLY
WINDS OFF THE COAST OF NW AFRICA WHERE THE GRADIENT REMAINS
TIGHTER PER USUAL. THE MAIN MID TO UPPER LEVEL FEATURE OVER THE
TROPICS IS AN UPPER HIGH LOCATED NEAR 12N39W. THE UPPER-LEVEL
FLOW IS QUITE STRONG OUT OF THE W TO SW ON THE NORTHERN SIDE OF
THE TROPICAL RIDGE WHICH IS SPREADING SOME HIGH DEBRIS
CLOUDINESS...FROM ITCZ CONVECTION...S OF 20N BETWEEN 30W-45W. A
SHARP UPPER TROUGH IS BEGINNING TO CUT OFF JUST TO THE NE
OF THE MADEIRA ISLANDS. THIS FEATURE IS GENERATING SOME
CLOUDINESS AND SHOWERS OVER THOSE ISLANDS AND NE TOWARD SRN
PORTUGAL WITH A TAIL OF MOISTURE PASSING THROUGH THE CANARY
ISLANDS.

$$
CANGIALOSI




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