[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 181804
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED 18 AUG 2004

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURES...

TROPICAL STORM DANIELLE IS CENTERED NEAR 28.5N 39.5W AT 18/1500
UTC MOVING NORTH AT 10 KT.  MAXIMUM SUSTAINED WIND SPEED HAS
DECREASED TO 55 KT WITH GUSTS TO 65 KT AND THE ESTIMATED MINIMUM
CENTRAL PRESSURE IS 994 MB.  SEE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.
DANIELLE CONTINUES TO EXPERIENCE STRONG SW SHEAR AND THE LOW
LEVEL CIRCULATION IS NOW PARTIALLY EXPOSED.  THE CLOUD/
CONVECTIVE PATTERN HAS BECOME VERY ASYMMETRIC AND CLOUD TOP
TEMPERATURES CONTINUE TO WARM. DANIELLE IS EXPECTED TO CONTINUE
WEAKENING OVER THE NEXT FEW DAYS AS IT TURNS EWD AROUND THE N
PERIPHERY OF MID-LEVEL RIDGE OVER THE E ATLC. SCATTERED MODERATE
CONVECTION FROM 28N-30N BETWEEN 36W-39W.

...TROPICAL WAVES...

TROPICAL WAVE OVER THE C ATLC PREVIOUSLY ALONG 35W/36W S OF 17N
MOVING W NEAR 20 KT HAS BEEN RELOCATED TO 38W/39W BASED ON
VISIBLE SATELLITE DATA...  WHICH SHOWS A LOW TO MID-LEVEL
CIRCULATION NEAR 10N ALONG THE AXIS.  AN AREA OF SCATTERED
MODERATE CONVECTION IS WITHIN 300 NM OF THE WAVE AXIS.

TROPICAL WAVE APPROXIMATELY 300 NM E OF THE BARBADOS 54W/55W S
OF 15N MOVING W NEAR 15-20 KT. ONLY WIDELY SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ACCOMPANY THE WAVE FROM 9N-15N BETWEEN
52W-60W.  BANDS OF CIRRUS ARE MOVING NORTHWARD OVER THE WAVE ON
THE E SIDE OF THE MID/UPPER LEVEL TROUGH OVER THE CARIBBEAN.

TROPICAL WAVE...REMNANTS OF T.S. EARL...OVER HONDURAS/NICARAGUA
ALONG 87W/88W S OF 20N MOVING W 20 TO 25 KT.  ASSOCIATED
CONVECTION IS MAINLY ALONG THE CARIBBEAN COAST OF
HONDURAS/NICARAGUA. SCATTERED MODERATE CONVECTION FROM 11N-18N
BETWEEN 82W-88W.

...ITCZ...
ITCZ AXIS ALONG 13N14W 7N40W 9N69W.  SCATTERED MODERATE
CONVECTION FROM 6N-15N BETWEEN 11W-19W... 01N-11N BETWEEN
35W-46W. VERY LITTLE CONVECTION ALONG THE AXIS EXCEPT NEAR
TROPICAL WAVES.

...DISCUSSION...
GULF OF MEXICO...
MID/UPPER LEVEL RIDGE IS BEGINNING TO WEAKEN OVER THE NORTHERN
GLFMEX BUT STILL EXTENDS FROM THE BAY OF CAMPECHE NEWD ACROSS
THE STRAITS OF FLORIDA INTO THE WESTERN ATLANTIC TO NEAR 31N76W.
LONG WAVE TROUGH IS CENTERED OVER WESTERN TEXAS AND IS BEGINNING
TO PUSH EAST INTO THE GULF CAUSING DEEP EASTERLY FLOW RESULTING
IN WIDELY SCATTERED SHOWERS/THUNDERSTORMS AHEAD OF THE TROUGH
OVER THE NORTHERN GULF.  ELSEWHERE...  TROPICAL WAVE MAKING ITS
WAY ACROSS SE MEXICO NEAR 98W IS PRODUCING SCATTERED MODERATE
CONVECTION OVER THE BAY OF CAMPECHE SOUTH OF 21N W OF 94W.
MID/UPPER LOW OVER THE NW CARIBBEAN IS UNDERCUTTING THE RIDGE
REMAINS OVER THE SE GULF... BUT SHOWERS/THUNDERSTORMS ARE VERY
LIMITED OVER THE SE GLFMEX AND FLORIDA STRAITS. THE UPPER LOW
MAY CONTINUE TO SPARK CLOUDS/CONVECTION AS IT SLOWLY WEAKENS
OVER THE SE GLFMEX DURING THE NEXT 24 HOURS.

CARIBBEAN SEA...
THE PRIMARY FEATURE OVER THE CARIBBEAN IS A STRONG TROPICAL WAVE
MOVING OVER CENTRAL AMERICA ALONG 87W/88W. THE WAVE IS
INTERACTING WITH A MID/UPPER LEVEL LOW OVER THE NW CARIBBEAN AND
IS PRODUCING SCATTERED MODERATE/STRONG CONVECTION OVER PORTIONS
OF CENTRAL AMERICA FROM PANAMA NORTH TO HONDURAS... AND OFF THE
NORTHERN PANAMA COAST. OVER THE E CARIBBEAN... SUBSIDENCE AND
VERY DRY MIDDLE TO UPPER LEVEL AIR DOMINATES E OF 81W PRODUCING
AN UNUSUAL ABSENCE OF CLOUDS/CONVECTION.

SUBTROPICAL ATLANTIC...
THERE HAS BEEN LITTLE CHANGE IN THE OVERALL MID-UPPER LEVEL
PATTERN DURING THE LAST 24 HOURS.  THE BLOCKING PATTERN IS
COMPRISED OF A RIDGE OVER THE W ATLC EXTENDING FROM THE BAHAMAS
NEWD OVER BERMUDA CONTINUING EWD OVER THE CENTRAL ATLC POLEWARD
OF A LARGE MID/UPPER LEVEL LOW NEAR 31N47W. E OF THE UPPER
LOW...A MID/UPPER LEVEL RIDGE EXTENDS N/S ALONG 32W.  MOST OF
THE UPSTREAM DYNAMICS AND MOISTURE IS RIDING UP AND OVER THE W
ATLC RIDGE LEAVING DRY AIR AND TRANQUIL WEATHER OVER THE W HALF
OF THE ATLC. THE EXCEPTION IS ALONG THE E COAST OF FLORIDA
WHERE  SCATTERED MODERATED/ ISOLATED STRONG CONVECTION IS
OCCURRING OVER THE GULF STREAM.  THE FLOW BECOMES MORE CONFLUENT
S OF THE UPPER LOW PRODUCING STRONG SUBSIDENCE AND VERY DRY AIR
IN THE MIDDLE AND UPPER LEVELS S OF 24N BETWEEN 40-70W. OVER THE
E ATLC...TROPICAL STORM  DANIELLE CONTINUES TO LIFT NEWD AROUND
THE W PERIPHERY OF A MID-UPPER LEVEL RIDGE ALONG 32W.
HOWEVER...THE TROPICAL STORM IS NOW UNDER THE INFLUENCE OF
STRONG SW SHEAR AND IS RAPIDLY WEAKENING. FURTHER E...A
SHORTWAVE TROUGH IS DIGGING SEWD OVER THE CANARY ISLANDS INTO NW
AFRICA. ASSOCIATED SUBSIDENCE AND DRY AIR PREVAILS E OF 22W.  AT
THE SURFACE...DANIELLE IS DISRUPTING THE E PORTION OF THE
SUBTROPICAL RIDGE WITH THE W EXTENT ENTERING THE AREA ALONG
32N50W AND EXTENDING SW TO N FLORIDA.

TROPICAL ATLANTIC...
MID/UPPER LEVEL TROUGH OVER THE CENTRAL SUBTROPICAL ATLC DROPS
SWD INTO THE TROPICAL ATLC THROUGH 20N50W TO THE SE CARIBBEAN.
ASSOCIATED STRONG SUBSIDENCE CONTINUES TO BLANKET A LARGE
PORTION OF THE AREA N OF THE ITCZ BETWEEN 45W-60W. FURTHER
E...MID-UPPER LEVEL RIDGE EXTENDS SWD THROUGH 21N37W 12N54W INTO
S AMERICA NEAR E VENEZUELA.  THIS REGIME IS PRODUCING DEEP ELY
FLOW OVER THE TROPICAL REGIONS E OF 45W.  HOWEVER...CONFLUENT
FLOW AND SUBSIDENCE ASSOCIATED WITH A SHORTWAVE TROUGH ALONG THE
NW COAST OF AFRICA APPEARS TO BE LIMITING SIGNIFICANT TROPICAL
WAVE DEVELOPMENT.

$$
JP/RK




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