[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 161809
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT MON JUL 16 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.

...TROPICAL WAVES...

CENTRAL ATLANTIC TROPICAL WAVE IS TILTED ALONG AXIS 18N40W
2N45W...MOVING WEST 20 KT. THIS REMAINS A VERY LARGE AMPLITUDE
WAVE WITH VISIBLE SATELLITE IMAGERY INDICATING BROAD TURNING IN
THE STRATOCUMULUS FIELD BETWEEN 35W AND 50W. THE WAVE IS
PRECEDED BY A LARGE AREA OF SAHARAN DUST AS INDICATED BY
CIMSS ANALYSES. SURFACE OBSERVATIONS FROM MARTINIQUE AND
DOMINICA INDICATED HAZE AS WELL. THIS DUST WAS INHIBITING DEEP
CONVECTION WITH THE EXCEPTION OF SCATTERED MODERATE CONVECTION
NEAR THE INTERSECTION OF THE WAVE AXIS AND ITCZ FROM 4N TO 6N
BETWEEN 45W AND 51W.

TILTED TROPICAL WAVE OVER THE FAR SW ATLANTIC AND EAST-CENTRAL
CARIBBEAN ALONG 22N64W 11N70W MOVING WEST 15 KT. THE 1200 UTC
RAOB FROM SAN JUAN SUGGESTED THE WAVE HAD JUST PASSED TO THE
WEST OF THE STATION WITH INCREASED LOW LEVEL WINDS. IN ADDITION
PRECIPITABLE WATER VALUES HAVE INCREASED TO 2.12 INCHES. THE
WAVE IS UNDER THE INFLUENCE OF AN UPPER LEVEL TROUGH OVER THE
SOUTHWEST NORTH ATLANTIC WITH DIFLUENT FLOW E OF THE TROUGH AXIS
MAINTAINING SCATTERED MODERATE ISOLATED STRONG CONVECTION WITHIN
120 NM EITHER SIDE OF THE WAVE AXIS AND NORTH OF 16N. SHOWER AND
THUNDERSTORM ACTIVITY HAS ALSO SPREAD TO PORTIONS OF THE
DOMINICAN REPUBLIC AS WELL.

THE NORTHERN EXTENSION OF AN EAST PACIFIC TROPICAL WAVE ALONG
96W IS OVER THE EXTREME SOUTHERN BAY OF CAMPECHE AND WAS
TRIGGERING SCATTERED SHOWER AND ISOLATED THUNDERSTORM ACTIVITY
OVER THE BAY OF CAMPECHE. THE PORTION OF THE WAVE WHICH EXTENDED
INTO THE EAST PACIFIC WAS MORE ACTIVE WITH WELL DEFINED TURNING
IN THE LOW AND MID LEVEL CLOUDS JUST TO THE SOUTHWEST OF THE
GULF OF TEHUANTEPEC.

...THE ITCZ...
AXIS OF THE ITCZ IS ALONG 11N16W 9N25W 11N41W 5N53W. OTHER THAN
THE CONVECTION DESCRIBED IN ASSOCIATION WITH THE TILTED WAVE
ALONG 18N40W 2N46W...SCATTERED MODERATE THUNDERSTORMS WERE NOTED
ELSEWHERE WITHIN 90-120 NM OF THE WAVE AXIS BETWEEN 26W AND
42W.

...DISCUSSION...
THE GULF OF MEXICO...
EXTENSION OF AN ATLANTIC SURFACE RIDGE IS FROM SOUTH
FLORIDA/FLORIDA STRAITS THROUGH 24N90W TO THE EAST CENTRAL COAST
OF MEXICO NEAR TAMPICO. HIGHLY AMPLIFIED FLOW REMAINS OVER THE
CONUS WITH THE AXIS OF A SHARP UPPER LEVEL RIDGE ALONG 110W
WITH THE DOWNSTREAM TROUGH EXTENDING FROM THE SOUTHERN ILLINOIS
SOUTHWARD ALONG THE TEXAS COAST TO NEAR 23N95W. A DEVELOPING
CYCLONIC CIRCULATION WAS NOTED OVER SOUTHEAST TEXAS. THE
ASSOCIATED SOUTHWESTERLY UPPER LEVEL FLOW AND UPPER DIFFLUENCE
COVERED THE NORTHWESTERN HALF OF THE GULF OF MEXICO. AS A RESULT
SCATTRED MODERATE TO STRONG THUNDERSTORMS CONTINUED ALONG A
SURFACE TROUGH WHICH EXTENDED FROM JUST EAST OF BROWNSVILLE
TEXAS TO SOUTHEAST LOUISIANA COAST. THE LIGHTNING DATA HAS
REMAINED ACTIVE OVER THE PAST SEVERAL HOURS. A NARROW RIDGE AXIS
BETWEEN ANTICYCLONES OVER THE ISTHMUS OF TEHUANTEPEC AND THE
NORTH CENTRAL ATLANTIC WAS OVER SOUTH FLORIDA...THE FLORIDA
STRAITS AND EXTREME SE GULF.

THE CARIBBEAN SEA...
A RATHER LARGE MID TO UPPER LEVEL ANTICYCLONE OVER THE ISTHMUS
OF TEHUANTEPEC DOMINATED THE FLOW OVER THE CARIBBEAN WEST OF
85W. THIS ANTICYCLONE WAS SEPARATING FROM A MUCH LARGER
ANTICYCLONE OVER THE CONNECTED TO THE ANTICYCLONE OVER THE
WESTERN ATLANTIC OCEAN. THE BASE OF A MID TO UPPER LEVEL TROUGH
WAS SPREADING WESTWARD OVER THE CARIBBEAN AND ENTERED THE BASIN
OVER EXTREME EASTERN CUBA AND EXTENDED SOUTHWARD TO 12N81W WITH
A FAIRLY LARGE CYCLONIC CIRCULATION NOTED OVER THE WINDWARD
PASSAGE NEAR 20N74W. A BROAD SWATH OF AMPLIFYING SOUTHERLY
FLOW AT THE MID AND UPPER LEVELS COVERS THE AREA SOUTHEAST OF
THE UPPER TROUGH AND 73W. THIS DIFLUENT FLOW REGIME WAS
ENHANCING SCATTERED MODERATE TO STRONG CONVECTION ALONG THE
TROPICAL WAVE OVER THE EAST CENTRAL CARIBBEAN. AN EASTERLY SURGE
IN THE WAKE OF THE TROPICAL WAVE WAS MOVING INTO THE FAR EASTERN
CARIBBEAN AND WAS ACCOMPANIED BY SOME SAHARAN DUST. SCATTERED
MODERATE THUNDERSTORMS WERE OCCURRING OVER THE EXTREME SOUTHWEST
CARIBBEAN SOUTH OF 10N TO THE COAST OF PANAMA. ELSEWHERE ONLY
LOW TOPPED SHOWERS AND ISOLATED THUNDERSTORMS WERE NOTED OVER
THE CARIBBEAN.

THE ATLANTIC OCEAN...
A PERSISTENT POSITIVELY TILTED MID TO UPPER LEVEL TROUGH EXTENDS
FROM A MIDDLE TO UPPER LEVEL CYCLONIC CIRCULATION CENTER NEAR
30N59W THROUGH 26N65W TO A SECOND CYCLONIC CENTER OVER THE
WINDWARD PASSAGE. WIDELY SCATTERED MODERATE CONVECTION IS NOTED
IN ASSOCIATION WITH THE SECOND CYCLONIC CIRCULATION OVER CUBA.
AN EXPANDING ANTICYCLONE WAS NOTED OVER THE TROPICAL ATLANTIC
NEAR 18N50W WITH A SMALLER ANTICYCLONE NEAR 18N30W. BOTH
FEATURES DOMINATED THE AREA BETWEEN THE AFRICAN COAST AND
60W. A SHEARED EASTERN ATLANTIC MIDDLE TO UPPER LEVEL TROUGH
EXTENDS FROM 32N10W TO 27N27W 27N35W. SURFACE ANTICYCLONIC FLOW
IS NORTH OF 20N BETWEEN AFRICA AND 80W.

$$
COBB


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