[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 311046
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT MON JUL 30 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 FEATURES...

TROPICAL DEPRESSION THREE CENTERED NEAR 37.8N 64.9W AT 31/0900
UTC OR 330 NM NORTH OF BERMUDA AND ABOUT 330 NM SOUTHEAST
OF CHATHAM MASSACHUSETTS MOVING NNE 18 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1007 MB. MAXIMUM SUSTAINED WINDS ARE 30 KT
WITH GUSTS TO 40 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR ADDITIONAL DETAILS.
THE SYSTEM REMAINS IN A SHEARED ENVIRONMENT WITH THE DEEP
CONVECTION CONFINED TO WITHIN 120-150 NM NORTHEAST OF THE
PARTIALLY EXPOSED LOW LEVEL CENTER. ALTHOUGH THE SYSTEM IS
EXPECTED TO REMAIN IN THIS ENVIRONMENT UNTIL IT TRANSITIONS TO
AN EXTRATROPICAL SYSTEM WITHIN 24 HOURS...THERE IS THE POTENTIAL
FOR THE DEPRESSION TO REACH STORM STRENGTH WITHIN THAT TIME.

1010 MB LOW NEAR 10N50W POSSIBLY SPAWNED BY THE RE-LOCATED
TROPICAL WAVE ALONG 58W WAS LOCATED ABOUT 650 NM E OF THE
WINDWARD ISLANDS IS FAIRLY WELL ORGANIZED WITH A BAND OF
SCATTERED MODERATE TO STRONG CONVECTION DEVELOPING WITHIN
120-150 NM OF THE WELL DEFINED LOW LEVEL CENTER. THIS SYSTEM IS
IN A FAVORABLE ENVIRONMENTAL FOR DEVELOPMENT AND COULD BECOME A
TROPICAL DEPRESSION OVER THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...
TROPICAL WAVE RE-LOCATED TO ALONG 34W/35W S OF 20N WITH A
TRAILING 1010 MB LOW NEAR 12N29W. THE WAVE WAS MOVING W AT 10-15
KT WHILE THE LOW WAS DRIFTING WWD. BROAD CYCLONIC TURNING IN THE
STRATOCUMULUS FIELD WAS NOTED ALONG THE WAVE AXIS WITH
ADDITIONAL TURNING NOTED IN THE VICINITY OF THE TRAILING LOW.
A FEW EMBEDDED SHOWERS WERE NOTED IN THE W SEMICIRCLE OF THE
LOW. SCATTERED MODERATE THUNDERSTORMS WERE NOTED MAINLY
WITHIN 90 NM OF THE INTERSECTION OF THE WAVE AND ITCZ BETWEEN
29W AND 38W.

RE-LOCATED TROPICAL WAVE ALONG 58W S OF 18N WAS MOVING W 15 KT.
THE WAVE WAS RELOCATED BASED ON SSMI DERIVED TOTAL PRECIPITABLE
WATER (TPW) IMAGERY WHICH CLEARLY SHOWED THE AXIS OF THE WAVE
FURTHER W AND SEPARATING FROM THE LOW PRESSURE AREA NEAR 10N50W.
BROKEN TO OVERCAST MULTILAYERED CLOUDS WITH WIDELY SCATTERED
SHOWERS AND THUNDERSTORMS WERE SPREADING WWD OVER THE WINDWARD
ISLANDS.

TROPICAL WAVE IN THE E-CENTRAL CARIBBEAN AND SW N ATLANTIC IS
TILTED FROM 23N67W THROUGH 15N69W TO INLAND OVER SOUTH AMERICA
NEAR 5N69W MOVING W 10-15 KT. BROAD LOW LEVEL INVERTED-V
SIGNATURE NOTED IN TRADE WIND CUMULUS FIELD GENERALLY IN THE ARE
BETWEEN 66W-76W. WIDELY SCATTERED THUNDERSTORMS WERE OCCURRING
AT THE NORTHERN END OF THE WAVE AXIS JUST NORTH OF PUERTO RICO
AND HISPANIOLA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N16W 13N23W 8N34W 11N44W 9N55W
8N60W. EXCEPT AS NOTED ABOVE...SCATTERED MODERATE/STRONG
CONVECTION IS MOVING OFF W AFRICA WITHIN 120 NM OF THE COAST
FROM 9N-16N. CLUSTERS OF SCATTERED MODERATE CONVECTION ARE
WITHIN 90 NM OF THE COAST OF SOUTH AMERICA BETWEEN 54W AND 59W.

...DISCUSSION...
GULF OF MEXICO...
LARGE MID TO UPPER LEVEL ANTICYCLONE WITH CENTERS OVER THE TEXAS
BIG BEND AND E-CENTRAL TEXAS APPEARS TO BE RETROGRADING TO THE W
WITH THE ASSOCIATED RIDGE EXTENDED ESEWD ACROSS THE NE GULF TO
CENTRAL FLORIDA. AS A RESULT ANTICYCLONIC FLOW ALOFT PREVAILED
OVER MOST OF THE GULF OF MEXICO. A SMALL CYCLONIC CIRCULATION
NEAR 24N99W WAS UNDERCUTTING THE RIDGE AS IT MOVED INTO NE
MEXICO. MODERATE BUT SOMEWHAT DIFLUENT NELY UPPER LEVEL FLOW WAS
ADVECTING HIGH LEVEL CLOUD DEBRIS ACROSS THE ERN HALF OF THE
GULF AND ALSO MAINTAINING WIDELY SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS IN THE AREA. A MORE SUBSTANTIAL LINE OF
THUNDERSTORMS WAS NOTED OFF THE ALABAMA...MISSISSIPPI AND
LOUISIANA COASTS. AT THE SURFACE...WEAK RIDGE EXTENDS FROM THE W
ATLC ACROSS THE STRAITS OF FLORIDA TO A 1015 MB HIGH OVER THE
CENTRAL GULF NEAR 26N90W. THIS OVERALL PATTERN IS EXPECTED TO
REMAIN IN PLACE FOR THE NEXT SEVERAL DAYS OR SO. THE PRESENCE OF
DIFLUENT FLOW SE OF THE ANTICYCLONE AND AN APPROACHING UPPER
LEVEL TROUGH/ASSOCIATED FRONTAL SYSTEM OVER THE DEEP SOUTH HOLDS
THE POTENTIAL FOR ADDITIONAL SCATTERED THUNDERSTORMS OVER THE NE
GULF AND NORTH FLORIDA LATER TODAY.

CARIBBEAN...
AN UPPER RIDGE EXTENDS FROM NW COLOMBIA NEAR 9N78W NW TO THE
YUCATAN PENINSULA NEAR BELIZE. WEAK UPPER LEVEL INVERTED TROUGH
COUPLED WITH DRY STABLE AIR DOMINATES THE REMAINDER OF THE
CARIBBEAN W OF 67W. WIDELY SCATTERED TRADE WIND SHOWERS AND A
FEW THUNDERSTORMS WERE NOTED IN THE EASTERN CARIBBEAN PER SAN
JUAN WSR-88D DATA...AND ALSO MOVING INTO THE CENTRAL WINDWARD
ISLANDS IN ADVANCE OF THE TROPICAL WAVE ALONG 58W.

ATLANTIC...
SEE SPECIAL FEATURES FOR TROPICAL DEPRESSION THREE. VERY
AMPLIFIED PATTERN IN PLACE OVER THE N ATLANTIC WITH SHORT TERM
IMPLICATIONS FOR THE TROPICAL DEPRESSION. BROAD TROUGH COMPLEX
OVER THE NW ATLANTIC WITH FIRST NEGATIVELY TILTED SHORTWAVE
EXTENDING FROM NEW ENGLAND SEWD THROUGH 38N67W TO 35N64W. UPPER
LEVEL DIFFLUENCE E OF THE TROUGH AXIS IS ALLOWING DEEP
CONVECTION TO PERSIST IN THE VICINITY OF THE LOW LEVEL CENTER OF
THE DEPRESSION. A SECOND POTENT SHORTWAVE TROUGH SWINGING IN
FROM THE NW AND CUTTING ACROSS THE MID-ATLANTIC STATES INTO THE
CAROLINAS HAS ALLOWED SCATTERED STRONG THUNDERSTORMS TO PERSIST
AHEAD OF ANOTHER AREA OF LOW PRESSURE NEAR 32N76W AND A SURFACE
TROUGH EXTENDING SWD TO NEAR 29N79W. THE FLOW IS STRONGLY
DIFLUENT AS WELL IN THIS AREA AND SHOULD CONTRIBUTE TO OVERALL
INTENSIFICATION OF THIS AREA OF LOW PRESSURE OVER THE NEXT 24
HOURS.

FURTHER S...AN ELONGATED RIDGE AXIS FROM 31N57W SWWD TO
THE WRN BAHAMAS WITH SOME MODERATE SUBSIDENCE NOTED S OF THE
RIDGE. CYCLONIC CIRCULATION NEAR 30N51W MOVING WWD 10 KT HAS
ASSOCIATED SHEAR AXIS EXTENDING SWWD TO A SMALL CYCLONIC
CIRCULATION NEAR 20N65W. ANTICYCLONES NEAR 16N48W AND 26N27W
AND ASSOCIATED FLOW PREVAIL OVER THE REMAINDER OF THE ATLANTIC
WITH DEEP EASTERLY FLOW IN PLACE OVER THE AREA. UW CIMSS SAL
ANALYSIS INDICATES SAHARAN DUST CONTINUES OVER THE ATLANTIC E OF
45W THOUGH THE COVERAGE IS NOT AS EXTENSIVE AS PREVIOUS DAYS.
AT THE SURFACE...DRY STABLE AIR E OF 60W AND A SURFACE RIDGE
ANCHORED BY A 1027 MB HIGH WELL N OF THE REGION NEAR 41N41W
DOMINATE THE ATLC GIVING THE AREA FAIR CONDITIONS TONIGHT.

$$
COBB






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