[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121749
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU JUL 12 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...
A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 37W/38W S OF 17N MOVING
W 15-20 KT. BROAD LOW LEVEL INVERTED-V SHAPE PATTERN IS OBSERVED
ON SATELLITE IMAGERY...AND IN ADDITION THE HOVMOLLER DIAGRAM
DEPICTS ITS QUICK WESTWARD MOVEMENT VERY WELL. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS ASSOCIATED WITH THE WAVE
FROM 6N-14N BETWEEN 36W-42W. A LARGE AREA OF AFRICAN DUST IS
BEHIND AND AHEAD OF THE WAVE AXIS. CURRENTLY...AND ACCORDING TO
THE GFS MODEL...MOISTURE FROM THIS WAVE SHOULD BEGIN TO REACH
THE WINDWARD ISLANDS LATE SATURDAY.

THE TROPICAL WAVE THAT WAS PREVIOUSLY ALONG 62W/63W IS RELOCATED
FURTHER WEST BASED ON SATELLITE IMAGERY...SFC OBSERVATIONS AND
THE HOVMOLLER DIAGRAM THAT CLEARLY SHOWS THE WESTWARD
PROPAGATION OF THE WAVE. THE WAVE IS MOVING W NEAR 20 KT AND IS
GENERATING SOME SHOWER AND TSTMS ACTIVITY AS WELL AS GUSTY WINDS
OVER THE ABC ISLANDS. THIS MORNING AT 11Z BONAIRE REPORTED A
WIND GUST TO 35 KT...AND ONE HOUR LATER CURACAO REPORTED A GUSTY
WIND OF 30 KT. THE SAHARAN AIR LAYER FROM CIMSS IS SHOWING A
PATCH OF AFRICAN DUST BEHIND THE WAVE AXIS COVERING THE EASTERN
CARIBBEAN AND THE LESSER ANTILLES WITH HAZY CONDITIONS.

THE TROPICAL WAVE THAT WAS PREVIOUSLY LOCATED ALONG 74W/75W IS
ALSO ADJUSTED AHEAD ALONG 80W BASED ON SATELLITE IMAGERY AND THE
SSMI-DERIVED TROPICAL PRECIPITABLE WATER. THERE IS WEAK CYCLONIC
TURNING ALONG THE WAVE AXIS NEAR 11N. THE WAVE...COUPLED WITH
THE EPAC ITCZ IS PRODUCING CLUSTERS OF MODERATE TO ISOLATED
STRONG CONVECTION OVER THE SW CARIBBEAN MAINLY FROM 9N-13N WEST
OF 80W. PART OF THIS CONVECTIVE ACTIVITY IS AFFECTING THE
CARIBBEAN PLAINS OF NICARAGUA.

THE NORTHERN PART OF A TROPICAL WAVE ALONG 91W/92W IS GENERATING
SCATTERED SHOWERS OVER GUATEMALA.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 11N15W 7N25W 10N35W 7N45W 7N60W.
BESIDES FOR CONVECTION ASSOCIATED WITH THE TROPICAL WAVE...
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 5N-11N
EAST OF 21W TO THE AFRICAN COAST. SIMILAR CONVECTION IS WITHIN
40-60 NM OF THE AXIS BETWEEN 42W-48W.

...DISCUSSION...
GULF OF MEXICO...
BROAD UPPER RIDGE COVERS MUCH OF THE GULF WITH THE UPPER HIGH
OFF THE COAST OF LOUISIANA NEAR 27N92W EXTENDING FROM TEXAS TO
ACROSS FLORIDA INTO THE W ATLC. AN UPPER HIGH IS OVER NW MEXICO
EXTENDING A RIDGE OVER TEXAS. AN INVERTED TROUGH IS OVER CENTRAL
MEXICO DRAWING SCATTERED SHOWERS AND ISOLATED TSTM ALONG THE
MEXICAN COAST FROM 19N-23N W OF 94W TO INLAND OVER MEXICO. A
DEEP LAYERED TROUGH IS INLAND OVER THE E US TO THE N GULF COAST
WITH THE ASSOCIATED FRONTAL BOUNDARY OVER SOUTHERN GEORGIA AND
ALABAMA. A PRE-FRONTAL TROUGH IS ANALYZED ON THE 15Z MAP FROM
31N83W TO 28N86W.  A LINE OF SHOWERS WITH EMBEDDED TSTMS IS
ASSOCIATED WITH THIS TROUGH OVER THE NE CORNER OF THE GULF.
SURFACE RIDGE REMAINS EXTENDING FROM THE W ATLC AND COVERS THE
ENTIRE GULF WITH A 1022 MB HIGH IN THE CENTRAL GULF NEAR 27N90W.
THIS FEATURE WILL REMAIN NEARLY STATIONARY GIVING THE ARE MAINLY
LIGHT AND VARIABLE WINDS. NARROW LINES OF SCATTERED SHOWERS AND
ISOLATED TSTMS ARE OVER THE EASTERN GULF INCLUDING THE FLORIDA
KEYS.

CARIBBEAN SEA...
ONCE AGAIN...THE MOST ACTIVE WEATHER ACROSS THE BASIN IS FOUND
OVER THE SW CARIBBEAN DUE TO A COMBINATION OF THE CLOSE
PROXIMITY OF THE ITCZ IN THE E PACIFIC REGION...TROPICAL
WAVES...AND THE SEMI-PERMANENT COLOMBIAN LOW. SEE TROPICAL WAVE
SECTION. IN THE UPPER LEVELS...BROAD UPPER RIDGE OVER THE W ATLC
AND THE GULF OF MEXICO EXTENDS OVER THE N CARIBBEAN N OF 18N W
OF 77W. A SECOND UPPER RIDGE IS OVER THE TROPICAL ATLC AND
EXTENDS OVER THE E CARIBBEAN E OF 73W INDUCING AN ELONGATED
UPPER LOW FROM THE WINDWARD PASSAGE TO OVER HONDURAS. UPPER
DIFFLUENCE IS ENHANCING SCATTERED SHOWERS OVER HISPANIOLA. DRY
STABLE UPPER AIR COVERS THE NW CARIBBEAN WHILE ABUNDANT UPPER
LEVEL MOISTURE COVERS THE REMAINDER OF THE REGION. MODERATE TO
STRONG EASTERLY TRADE WINDS OF 20 TO 25 KT CONTINUE ACROSS THE
AREA. THESE WINDS ARE EXPECTED TO PERSIST DURING THE UPCOMING
WEEKEND. WAVES ACROSS THE CARIBBEAN BASIN ARE MOVING PRETTY FAST
DUE TO THE STRONG TRADE WINDS.

ATLANTIC OCEAN...
UPPER HIGH ANCHORED IN THE GULF OF MEXICO EXTENDS INTO THE W
ATLC W OF 65W. THE REMAINDER OF THE FORECAST AREA IS DOMINATED
BY RATHER BENIGN FEATURES...SUCH AS A WEAK UPPER LOW NEAR 27N54W
AND AN UPPER RIDGE-TROUGH  OVER THE REMAINDER OF THE ATLC. AT
THE SURFACE...A RIDGE DOMINATES THE ENTIRE ATLC FORECAST AREA
WITH A 1029 MB HIGH NEAR 34N47W. MOSTLY FAIR WEATHER AND
MODERATE TRADE WINDS ARE OBSERVED UNDER THE INFLUENCE OF THIS
RIDGE. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE OVER THE
EXTREME NW PORTION OF THE AREA AHEAD OF A COLD FRONT THAT LIES
ACROSS THE SE U.S.

$$
GR






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