[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 312358
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU JUL 31 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND 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
2315 UTC.

...TROPICAL WAVES...

A LARGE TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 29W
SOUTH OF 22N. THE CLOUD PATTERN IS EXHIBITING A WELL DEFINED
CYCLONIC CIRCULATION ABOUT TWO DEGREES IN DIAMETER WITH THE LOW
LEVEL CENTER ON THE WAVE AXIS NEAR 18N. SCATTERED SHOWERS AND
ISOLATED TSTMS ARE WITHIN 125 NM NW QUADRANT OF CENTER.
CONDITIONS ARE NOT CONDUCIVE FOR SIGNIFICANT DEVELOPMENT DURING
THE NEXT COUPLE OF DAYS DUE PRIMARILY TO COOLER SEA SURFACE
TEMPERATURES.

SERIES OF PICTURES OVER THE PAST SEVERAL HOURS INDICATE THAT THE
TROPICAL WAVE LOCATED OVER THE E CARIBBEAN ALONG 64W AT 18Z IS
NOW FURTHER WEST ALONG 68W S OF 19N. THE SAN JUAN DOPPLER RADAR
AND VIS SAT IMAGERY SHOW A LARGE BAND OF SHOWERS WITH EMBEDDED
TSTMS WITHIN 125 NM E OF THE WAVE AXIS. UPPER DIFFLUENT IS
HELPING TO INDUCE THIS CONVECTIVE ACTIVITY. MOISTURE ASSOCIATED
WITH THIS WAVE WILL CONTINUE TO AFFECT PUERTO RICO AND
HISPANIOLA TONIGHT REACHING JAMAICA TOMORROW.

A TROPICAL WAVE IS OVER THE YUCATAN PENINSULA AND N CENTRAL
AMERICA ALONG 88W AT 21Z. THE WAVE IS ENHANCING SOME SHOWER AND
TSTM ACTIVITY MAINLY OVER PARTS OF COSTA RICA AND GUATEMALA.
THIS SYSTEM WILL CONTINUE TO MOVE WWD WITH AN INCREASE IN
MOISTURE OVER SE MEXICO AND THE BAY OF CAMPECHE THIS FRIDAY.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 13N17W 16N26W 10N34W 9N46W
11N61W. A CLUSTER OF MODERATE TO STRONG CONVECTION COVERS THE
AREA FROM 7N-11N BETWEEN 51W-54W. SIMILAR CONVECTION IS OVER NE
VENEZUELA. SCATTERED SHOWERS AND ISOLATED TSTMS ARE NEAR THE
INTERSECTION OF THE WAVE ALONG 29W AND THE ITCZ.

...DISCUSSION...

THE GULF OF MEXICO...
AS TYPICAL FOR THIS TIME OF THE YEAR...THE AZORES HIGH EXTENDS A
RIDGE WWD ENVELOPING THE SE CONUS AND THE GULF OF MEXICO. THIS
FEATURE IS GIVING THE W HALF OF THE GULF SLY WINDS OF 10 TO 15
KT WHILE MOSTLY LIGHT AND VARIABLE WINDS PREVAIL OVER THE E HALF
OF THE GULF REGION DUE TO A WEAK 1016 MB SFC HIGH EMBEDDED IN
THE RIDGE NEAR 25N84W AT 21Z. SCATTERED SHOWERS AND ISOLATED
TSTMS ARE OVER THE NORTHERN GULF WATERS. THIS ACTIVITY HAS
PERSISTED DURING THE LAST THREE DAYS LIKELY DUE TO PRESENCE OF
AN UPPER-LEVEL HIGH OVER THE SE CONUS WHICH IS PRODUCING UPPER
DIFFLUENCE ACROSS THE AREA. NE TO E UPPER-LEVEL WIND FLOW COVERS
MOST OF THE GULF OF MEXICO. MODERATE TO STRONG SUBSIDENCE IS
NOTED OVER THE BAY OF CAMPECHE WHERE THERE IS AN UPPER-LEVEL
TROUGH EXTENDING WWD FROM AN UPPER LOW OVER E CUBA. THE HIGH
PRES RIDGE WILL REMAIN ACROSS THE CENTRAL GULF DURING THE NEXT
FEW DAYS DRIFTING TO THE NORTHERN GULF WATERS SUN.

THE CARIBBEAN SEA...
AN ACTIVE TROPICAL WAVE IS MOVING WWD ACROSS THE E CARIBBEAN. A
SECOND TROPICAL WAVE IS GENERATING SOME SHOWERS AND TSTMS OVER
CENTRAL AMERICA. SEE TROPICAL WAVE SECTION FOR DETAILS. FRESH
TRADE WINDS COVERS THE CARIBBEAN SEA. AN EARLIER QSCAT PASS
SHOWED ELY WINDS OF 20 TO 25 KT JUST OFF THE COLOMBIAN COAST.
ALOFT...AN UPPER LEVEL LOW CENTERED OVER THE PROVINCE OF
CAMAGUEY CUBA IS GENERATING SCATTRED SHOWERS AND TSTMS OVER THE
E PORTION OF CUBA...JAMAICA AND HAITI. UPPER DIFFLUENCE BETWEEN
THIS LOW AND THE UPPER-LEVEL HIGH OVER THE SE U.S. SI SUPPORTING
THE DEVELOPMENT OF SOME CONVECTIVE ACTIVITY OVER WESTERN CUBA
WHERE LIGHTNING DATA DEPICTS SCATTERED TSTMS. CONVECTION HAS
ALSO FLARE UP OVER W VENEZUELA AND N COLOMBIA. T

THE ATLANTIC OCEAN...
AS PREVIOUSLY MENTIONED...THE BERMUDA-AZORES HIGH CENTERED NEAR
37N27W WITH 1025 MB EXTENDS A RIDGE ACROSS THE DISCUSSION AREA
TO THE STRAITS OF FLORIDA PRODUCING MOSTLY FAIR WEATHER AND
MODERATE TRADE WINDS. WINDS ARE STRONGEST...IN THE 20-25 KT
RANGE WITHIN 250 NM N SEMICIRCLE OF THE SFC LOW ALONG THE
TROPICAL WAVE OVER E ATLC...AND BETWEEN THE MADEIRA AND THE
CANARY ISLANDS LIKELY DUE A TIGHT PRES GRADIENT BETWEEN THE
AZORES HIGH AND LOWER PRES INLAND OVER W AFRICA. ALOFT...AN
UPPER-LEVEL LOW IS SPINNING OVER E CUBA AND THE BAHAMAS. THE
UPPER-LEVEL HIGH OVER THE SE U.S. EXTENDS A RIDGE OVER THE
REMAINDER OF THE W ATLC. ANOTHER UPPER-LEVEL LOW IS NEAR 26N51W
AND THE THIRD ONE IS NEAR 34N39W WITH A TROUGH EXTENDING SWD
INTO THE FORECAST AREA ALONG 39W/40W. AN UPPER-LEVEL HIGH
CENTERED OVER THE TROPICS NEAR 16N42W IS ENHANCING CONVECTION
ALONG THE ITCZ W OF 50W.

$$
GR






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