[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 072355
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU AUG 07 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 LOW AMPLITUDE TROPICAL WAVE IS JUST SOUTH OF THE CAPE VERDE
ISLANDS ALONG 25W/26W WITH A 1009 MB LOW ALONG THE WAVE AXIS
NEAR 12N MOVING W 10-15 KT. 850 MB SATELLITE DERIVED VORTICITY
AND THE MIMIC-TPW FROM CIMSS ALSO SUPPORT THE WAVE POSITION.
SCATTERED MODERATE CONVECTION IS MAINLY AHEAD OF THE WAVE AND
NEAR THE INTERSECTION OF THE WAVE AND THE ITCZ FROM 8N-10N
BETWEEN 26W-32W. SCATTERED SHOWERS ARE AROUND THE LOW CENTER.

A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 44W/45W FROM 12N-25N
MOVING W NEAR 15 KT. THE WAVE CONTINUES TO SHOW A WELL DEFINED
INVERTED-V CURVATURE ON SATELLITE IMAGERY. NO DEEP CONVECTION IS
ASSOCIATED WITH THIS FEATURE. MAINLY LOW/MID CLOUDS AND ISOLATED
SHOWERS ARE EITHER SIDE OF THE WAVE AXIS.

THE TROPICAL WAVE PREVIOUSLY LOCATED ALONG 59W IS RELOCATED
FURTHER E ALONG 55W S OF 13N BASED ON OBSERVATIONS...THE TPW
PRODUCT AND 850 MB SATELLITE DERIVED VORTICITY. THIS IS A LOW
AMPLITUDE TROPICAL WAVE. THE GFS MODEL SHOWS AN INCREASE IN
MOISTURE ASSOCIATED WITH THE WAVE AS IT MOVES WWD ACROSS THE
WINDWARD ISLANDS TOMORROW. MOISTURE WILL CONTINUE TO BUILD UP AS
THE WAVE CROSSES THE E CARIBBEAN ON SAT. SCATTERED SHOWERS ARE
NEAR THE INTERSECTION OF THE WAVE AN THE ITCZ. THE WAVE IS ALSO
ENHANCING SOME SHOWER ACTIVITY OVER THE GUYANAS.

TROPICAL WAVE IS ALONG 78W/79W S OF 20N MOVING W 10-15 KT. THE
SAHARAN AIR LAYER FROM CIMSS REVEALS THAT THE WAVE IS AT THE
LEADING EDGE OF A SURGE OF AFRICAN DUST WHICH COVERS THE E
CARIBBEAN AND N OF THE GREATER ANTILLES MOVING INTO THE TURKS
AND CAICOS. THE WAVE COUPLED WITH UPPER DIFFLUENCE IS ENHANCING
CONVECTION OVER E CUBA...JAMAICA AND THE SW CARIBBEAN.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N16W 13N24W 10N30W 10N46W 8N58W.
BESIDES THE CONVECTION MENTIONED ON THE TROPICAL WAVE SECTION...
A CLUSTER OF MODERATE CONVECTION IS MOVING OFF THE AFRICAN COAST
BETWEEN 13N-16N. SIMILAR CONVECTION IS FROM 5N-9N BETWEEN
45W-50W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER-LEVEL RIDGE ANCHORED OVER THE FOUR CORNER REGION
DOMINATES THE N GULF WATERS WHILE AN UPPER-LEVEL TROUGH IS
AMPLIFYING OVER THE EASTERN US. THIS TROUGH IS SUPPORTING A COLD
FRONT THAT IS FORECAST TO REACH THE GULF COAST ON SATURDAY AND
STALL SUN BEFORE DISSIPATING MON. THE SE GULF IS DOMINATED BY AN
UPPER-LEVEL LOW CENTERED OVER THE WESTERN TIP OF CUBA. UPPER
DIFFLUENCE BETWEEN THESE UPPER LEVEL FEATURES IS SUPPORTING THE
DEVELOPMENT OF SCATTERED SHOWERS AND TSTMS OVER THE EASTERN
PORTION OF THE GULF MAINLY S OF 26N AND OVER THE YUCATAN
PENINSULA. SHOWERS AND TSTMS ARE ALSO AFFECTING THE SE U.S.
AHEAD OF THE AFOREMENTIONED COLD FRONT THAT CURRENTLY EXTENDS
ACROSS THE CAROLINAS AND THE TENNESSEE VALLEY. AT THE SURFACE...
A RIDGE CENTERED ON A 1017 MB HIGH NEAR 28N93W AT 2100 UTC
DOMINATES THE ENTIRE GULF REGION. AS THE FRONTAL BOUNDARY DIPS
INTO THE SE U.S. LATE TONIGHT/FRI MORNING THE SURFACE RIDGE WILL
WEAKEN AND MOVE S ACROSS THE CENTRAL GULF DURING THE UPCOMING
WEEKEND.

CARIBBEAN SEA...
AN UPPER-LEVEL LOW IS SPINNING OVER WESTERN CUBA COVERING THE SE
GULF AND THE NW CARIBBEAN. BROAD UPPER-LEVEL HIGH IS CENTERED
JUST SOUTH OF HISPANIOLA WHILE ANOTHER UPPER-LEVEL LOW IS NE OF
THE LEEWARD ISLANDS NEAR 19N56W. THE CYCLONIC FLOW ASSOCIATED
WITH THIS SECOND UPPER LOW REACHES THE FAR E CARIBBEAN.
UPPER LEVEL DIFFLUENCE COUPLED WITH THE CLOSE PROXIMITY OF THE
EPAC ITCZ IS GENERATING SCATTERED SHOWERS AND THUNDERSTORMS OVER
THE SW CARIBBEAN S OF 13N W OF 80W TO INLAND OVER COSTA RICA
AND NICARAGUA. CONVECTION HAS FLARED UP OVER CUBA DUE TO THE
PRESENCE OF THE ABOVE MENTIONED UPPER LOW. A DRIER AIR MASS
COVERS THE E CARIBBEAN. MODERATE TO STRONG EASTERLY TRADE WINDS
ARE BLOWING ACROSS THE BASIN. A TROPICAL WAVE NOW ALONG 55W WILL
MOVE ACROSS THE WINDWARD ISLANDS TOMORROW BRINGING AN INCREASE
IN THE LIKELIHOOD OF RAIN.

ATLANTIC OCEAN...
A WEAK 1015 MB LOW HAS DEVELOPED OVER THE CENTRAL BAHAMAS NEAR
25N76W ALONG THE SURFACE TROUGH THAT EXTENDS FROM 27N75W TO
24N78W. THIS LOW IS GENERATING SCATTERED SHOWERS AND ISOLATED
TSTMS OVER THAT AREA. ALOFT...THERE IS AN UPPER-LEVEL LOW OVER
THE BAHAMAS COVERING THE W ATLC W OF 70W. A SECOND UPPER-LEVEL
LOW IS CENTERED NEAR 19N56W. A BAND OF MULTILAYERED CLOUDS WITH
POSSIBLE SHOWERS IS ON THE WESTERN SIDE OF THE LOW. THIS BAND OF
MOISTURE MAY REACH THE N LEEWARD ISLANDS TOMORROW. A THIRD UPPER
LOW IS OVER THE CENTRAL ATLC NEAR 27N44W. AN UPPER-LEVEL HIGH
SITUATED NEAR 19N40W DOMINATES THE TROPICS AND IS SUPPORTING
SOME CONVECTION ALONG THE ITCZ. OTHERWISE..THE ATLC IS DOMINATED
BY MODERATE/STRONG SUBSIDENCE AND DRY SOMEWHAT STABLE AIR WITH A
SURFACE RIDGE EXTENDING SW FROM A 1024 MB HIGH LOCATED NE OF THE
AZORES. THE COMBINATION OF THE RIDGE AND LOWER PRES OVER AFRICA
IS PRODUCING A SWATH OF NELY WINDS OF 20-25 KT BETWEEN THE
MADEIRA/CANARY ISLANDS AND THE AFRICAN COAST.

$$
GR




This weather bulletin was brought to you by:
www.nashvilleweather.net