[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 140005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON AUG 13 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2330 UTC.

...SPECIAL FEATURE...

TROPICAL DEPRESSION FOUR WAS NEAR 11.9N 32.3W AT 13/2100 UTC
MOVING WEST 17 KT. MINIMUM CENTRAL PRESSURE IS 1005 MB WITH
MAXIMUM SUSTAINED WINDS 30 KT GUSTING TO 40 KT. THE ASSOCIATED
DEEP CONVECTION REMAINS DISPLACED TO THE W OF THE CENTER DUE TO
EASTERLY SHEAR OVER THE SYSTEM. SCATTERED MODERATE IS FROM
10N-13N BETWEEN 33W-37W. A CONTINUED BRISK AND GENERALLY
WESTWARD MOTION SHOULD CONTINUE DURING THE NEXT COUPLE OF DAYS
WHILE THE CYCLONE MOVES ALONG THE SOUTHERN PERIPHERY OF A DEEP
LAYER RIDGE. SOME STRENGTHENING IS FORECAST...AND THE DEPRESSION
COULD BECOME A TROPICAL STORM TONIGHT OR ON TUESDAY. PLEASE
REFER TO THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC ADVISORY UNDER
MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS.

A 1009 MB LOW IS NEAR 22N87W...OR JUST N OF THE NE TIP OF THE
YUCATAN PENINSULA. THE SYSTEM IS INTERACTING WITH AN UPPER LOW
MOVING INTO THE WRN GULF TO PRODUCE WIDESPREAD CLOUDINESS AND
DISORGANIZED SHOWERS ESPECIALLY OVER THE SE GULF...S OF 27N E OF
92W. UPPER-LEVEL WINDS ARE GRADUALLY BECOMING MORE FAVORABLE FOR
DEVELOPMENT OF THIS SYSTEM...AND A TROPICAL DEPRESSION COULD
FORM TONIGHT OR TOMORROW AS THE LOW MOVES TO THE WEST-NORTHWEST
AT 10 TO 15 MPH.  INTERESTS IN THE WESTERN GULF OF MEXICO SHOULD
MONITOR THE PROGRESS OF THIS SYSTEM.  AN AIR FORCE RESERVE
RECONNASSIANCE PLANE IS SCHEDULED TO INVESTIGATE THIS SYSTEM
TOMORROW AFTERNOON...IF NECESSARY.

...TROPICAL WAVES...
A TROPICAL WAVE WAS ADDED ALONG 19/20W ESTIMATED TO BE MOVING W
NEAR 15 KT. A 1009 MB LOW IS ALONG THE WAVE NEAR 15N...WHICH
SHOWED UP WELL IN A RECENT QUIKSCAT PASS. THE WAVE PASSAGE WAS
VERY EVIDENT IN THE DAKAR SOUNDING DATA FROM LAST NIGHT TO THIS
MORNING. DEEP CONVECTION IS MINIMAL THOUGH THE ASSOCIATED
CLOUDINESS IS BEGINNING TO SPREAD THROUGH THE CAPE VERDE
ISLANDS.

TROPICAL WAVE IS ALONG 45/46W S OF 15N MOVING W NEAR 10 KT.
CYCLONIC TURNING IS EVIDENT IN THE SURROUNDING LOW TO MID LEVEL
CLOUDS...AND THE WAVE SHOWS UP AS A LOW AMPLITUDE SURGE OF
MOISTURE IN THE UW-CIMSS TPW PRODUCT. REGARDLESS...DEEP
CONVECTION IS MINIMAL WITH ASSOCIATED SHOWER ACTIVITY MOSTLY
EMBEDDED IN THE ITCZ.

A TROPICAL WAVE WAS ADDED ON THE INTERMEDIATE 13/1500 UTC
ANALYSIS ALONG THE SPECIAL FEATURE IN THE SRN GULF. SEE DETAILS
ABOVE.

...THE ITCZ...
AXIS CENTERED ALONG 15N23W 14N29W 11N37W 11N43W 9N48W 8N61W.
OUTSIDE OF THE CONVECTION OUTLINED ABOVE TO THE W OF TROPICAL
DEPRESSION 4...VERY LITTLE DEEP CONVECTION IS NOTED NEAR THE
ITCZ THIS EVENING.

DISCUSSION...

THE GULF OF MEXICO...
THE HIGHLIGHT CONTINUES TO BE THE SPECIAL FEATURE JUST N OF THE
YUCATAN AS DESCRIBED ABOVE. A MID TO UPPER LOW IS SPINNING NEAR
25N92W. UPPER DIFFLUENCE BETWEEN THIS FEATURE AND AN UPPER
ANTICYCLONE CENTERED NEAR THE COLORADO/KANSAS BORDER IS
SUPPORTING SCATTERED SHOWERS/ISOLATED TSTMS WITHIN 60NM EITHER
SIDE OF A TAMPICO TO LAKE CHARLES LINE. A SFC TROUGH REMAINS
ANALYZED TO THE W OF THE SPECIAL FEATURE EXTENDING N FROM
CENTRAL BAY OF CAMPECHE TO NEAR THE LOUISIANA COAST. THIS
FEATURE SEEMS TO BE LESS PRONOUNCED THAN IT WAS...AND IS HARD TO
FIND WITH THE FLOW AROUND THE SPECIAL FEATURE TAKING OVER.
THUS...THE TROUGH WILL LIKELY BE REMOVED FROM THE 14/0000 UTC
MAP.

THE CARIBBEAN SEA...
WIDESPREAD CLOUDINESS...SCATTERED SHOWERS AND ISOLATED TSTMS
COVER MUCH OF THE WRN CARIB MAINLY W OF 78W. IN ADDITION A FEW
CLUSTERS OF MODERATE CONVECTION ARE OFF THE COAST OF
COLOMBIA/PANAMA S OF 14N BETWEEN 72W-78W. THIS WEATHER IS IN
RESPONSE TO THE SPECIAL FEATURE MOVING N OF THE YUCATAN INTO THE
GULF...A SFC TROUGH NOW ANALYZED IN THE SW CARIB ALONG 15N82W
19N79W...AND WIDELY UPPER DIFFLUENT FLOW BETWEEN THE RIDGING IN
THE NW CARIB AND AN UPPER LOW JUST S OF PUERTO RICO. THE
REMAINDER OF THE CENTRAL AND ERN CARIB IS MOSTLY QUIET WITH
FAIRLY DRY/STABLE MID TO UPPER AIR IN PLACE. MODERATE TRADES E
OF 80W BEND MORE SE IN THE NW CARIB AHEAD OF THE SPECIAL
FEATURE.

THE ATLANTIC OCEAN...
A LINGERING FRONTAL BOUNDARY IS MOSTLY N OF THE WRN ATLC AREA
EXTENDING THROUGH BERMUDA W TO ABOUT 250 NM OFF THE
GEORGIA/NORTH FLORIDA COAST. LIFT AHEAD OF THIS BOUNDARY
CONTINUES TO PRODUCE BROKEN TO OVERCAST MULTILAYERED
CLOUDINESS...SCATTERED SHOWERS AND ISOLATED TSTMS MAINLY N OF
26N BETWEEN 60W-75W. THIS ACTIVITY ALSO BEING SUPPORTING BY
UPPER DIFFLUENT FLOW BETWEEN TROUGHING OFF THE SOUTHEAST U.S.
COAST AND AND UPPER RIDGING THAT EXTENDS ENE FROM THE NRN
BAHAMAS TO NEAR 32N60W. AN UPPER LOW IS NEAR 30N49W BUT IS NOT
GENERATING ANY SENSIBLE WEATHER AS IT IS SURROUNDED BY FAIRLY
DRY AIR. A LARGE MID TO UPPER HIGH IS NEAR 22N40W. THE ELY FLOW
S OF THIS HIGH IS PRODUCING SHEAR OVER TROPICAL DEPRESSION 4.
ANOTHER UPPER LOW IS IN THE NE PART OF THE AREA NEAR
30N19W...THAT IS PRODUCING MAINLY HIGH CLOUDS N OF 29N BETWEEN
22W-26W. THE REMAINDER OF THE SFC PATTERN IS DOMINATED BY A 1024
MB HIGH NEAR 33N33W. THIS HAS AN ELONGATED RIDGE STRETCHING SW
TO NEAR THE CENTRAL BAHAMAS. OVERALL MOSTLY FAIR WEATHER AND
MODERATE TRADES RULE N OF 15N E OF 45W.

$$
MW/MT




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