[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 171734
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE 17 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
1715 UTC.

...SPECIAL FEATURES...

HURRICANE DANIELLE IS CENTERED NEAR 24.0N 40.2W AT 17/1500 UTC
MOVING NORTH NORTHWEST AT 14 KT.  MAXIMUM SUSTAINED WIND SPEED
IS 90 KT WITH GUSTS TO 110 KT AND THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 970 MB.  SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.  EVEN
THOUGH AN INTERMITTENT RAGGED EYE REMAINS EVIDENT IN IR
SATELLITE IMAGERY...DANIELLE APPEARS TO BE EXPERIENCING SOME SW
SHEAR. THE CONVECTIVE PATTERN IS BECOMING LESS SYMMETRIC AND
UPPER LEVEL OUTFLOW IS NOW RESTRICTED OVER THE W SEMICIRCLE.
INCREASING SHEAR IS EXPECTED TO WEAKEN DANIELLE OVER THE NEXT
FEW DAYS AS IT MOVES AROUND THE W PERIPHERY OF MID-LEVEL RIDGE
ALONG 20N. NUMEROUS STRONG CONVECTION IS WITHIN 75 NM OF THE
CENTER OVER THE SW...SE...AND NE QUADRANTS.  NUMEROUS MODERATE
CONVECTION IS WITHIN 150 NM OVER THE NW QUADRANT.

...TROPICAL WAVES...

TROPICAL WAVE 220 NM W OF THE CAPE VERDE ISLANDS ALONG 28W S OF
16N MOVING W NEAR 20 KT. LATEST IR SATELLITE IMAGERY CONTINUES
TO SHOW A LOWER TO MID-LEVEL CIRCULATION NEAR 10N BUT CONVECTION
IS ISOLATED MAINLY CONFINED TO THE ITCZ.  MODERATE ACTIVITY
CONVECTION IS NOTED WITHIN 60 NM RADIUS OF 9N32W.

TROPICAL WAVE APPROXIMATELY 660 NM E OF BARBADOS ALONG 48W S OF
15N MOVING W NEAR 20 KT. ITCZ CONVECTION IN THE VICINITY OF THE
WAVE HAS INCREASED OVERNIGHT WITH SCATTERED MODERATE ACTIVITY
NOTED FROM 7N-10N BETWEEN 41W-51W.

TROPICAL WAVE...REMNANTS OF T.S. EARL... OVER THE CENTRAL
CARIBBEAN ALONG 77W/78W S OF 18N MOVING W 25 KT WAS RELOCATED
TO 80W/81W BASED ON VISIBLE SATELLITE DATA. A EARLIER NEARBY
SHIP OBSERVATION AT 1600 UTC INDICATED THAT THE WAVE CONTINUES
TO PRODUCE STRONG WINDS TO NEAR GALE FORCE.  ASSOCIATED
CONVECTION HAS INCREASED BUT REMAINS UNORGANIZED. SCATTERED
MODERATE CONVECTION IS OCCURRING FROM 14N-16N BETWEEN 77W-83W.
GIVEN THE LACK OF ORGANIZATION AND THE RATHER FAST MOTION OF
THIS
WAVE...SIGNIFICANT RAINFALL AMOUNTS ARE UNLIKELY.
HOWEVER...GUSTY WINDS DUE TO PASSING SHOWERS/TSTMS WILL AFFECT
THE CAYMAN ISLAND.

TROPICAL WAVE OVER GUATEMALA ALONG 91W/92W S OF 17N MOVING W
20-25 KT.  THE SATELLITE SIGNATURE ASSOCIATED WITH THIS WAVE IS
CURRENTLY POOR AND THE POSITION IS BASED PRIMARILY ON
EXTRAPOLATION. SMALL AREA OF SCATTERED MODERATE CONVECTION ALONG
THE W COAST OF GUATEMALA.

...ITCZ...
ITCZ AXIS IS ALONG 13N10W 6N20W 10N30W 9N35W 5N60W 9N70W. WIDELY
SCATTERED CONVECTION WITH IN 90 NM OF ITCZ AXIS BETWEEN 10W-14W.
MODERATE ACTIVITY CONVECTION IS NOTED WITHIN 60 NM RADIOS OF
9N32W.  WIDELY SCATTERED MODERATE CONVECTION WITHIN 160 NM
EITHER SIDE OF AXIS FROM 40W-60W.

...DISCUSSION...
GULF OF MEXICO...
A MID/UPPER LEVEL RIDGE...FROM S FLORIDA TO THE BAY OF
CAMPECHE...WILL REMAIN IN CONTROL OVER MOST OF THE GLFMEX
THROUGH MID-WEEK. THE NEARLY STATIONARY RIDGE WILL KEEP UPSTREAM
DISTURBANCES N OF THE AREA WITH A SERIES OF SHORTWAVE TROUGHS
BYPASSING THE AREA OVER THE CENTRAL AND E UNITED STATES.  DEEP
CONVECTION CONTINUES TO BE SPARSE WITH THE ONLY ACTIVITY OF NOTE
BEING A LINE OF NORTHWESTWARD MODERATE CONVECTION OVER THE BAY
OF CAMPECHE. ISOLATED SHOWERS/THUNDERSTORMS ARE NOTED ALONG A
REMNANT FRONTAL BOUNDARY EXTENDING FROM THE FLORIDA PANHANDLE TO
THE S TIP OF TEXAS. THE AIRMASS N OF THE BOUNDARY IS STILL
FAIRLY DRY SUPPRESSING CONVECTION ALONG THE N GULF COAST.
ELSEWHERE...A SECOND TROUGH OVER THE W ATLC EXTENDS ACROSS S
FLORIDA INTO THE SE GLFMEX.  ISOLATED SHOWERS/THUNDERSTORMS ARE
LOCATED JUST W OF THE FLORIDA KEYS.

CARIBBEAN SEA...
THE PRIMARY WEATHER MAKER OVER THE CARIBBEAN IS THE REMNANTS OF
T.S. EARL WHICH DEGENERATED INTO A TROPICAL WAVE ON MONDAY. THE
WAVE CONTINUES TO PRODUCE STRONG GUSTY WINDS AND SCATTERED
MODERATE CONVECTION FROM 14N-16N BETWEEN 77W-83W AS IT MARCHES
RAPIDLY WESTWARD AT 25 KT.  TYPICAL LOW LEVEL CONVERGENCE LINE
FROM E PANAMA TO CENTRAL NICARAGUA IS BECOMING MORE CONVECTIVE.
OVER THE E CARIBBEAN... SUBSIDENCE AND VERY DRY MIDDLE TO UPPER
LEVEL AIR HAS MOVED INTO THE AREA FROM THE ATLC AND IS
SUPPRESSING CONVECTIVE ACTIVITY E OF 73W. THIS DRY AIRMASS WILL
MARCH WESTWARD ACROSS THE CARIBBEAN LIMITING CONVECTION UNTIL
THE NEXT WAVE APPROACHES WED.

SUBTROPICAL ATLANTIC...
A SHORTWAVE RIDGE-TROUGH PATTERN PREVAILS OVER THE W ATLC WITH A
MID-UPPER LEVEL RIDGE EXTENDING FROM THE N BAHAMAS NEWD TO
BEYOND 33N66W AND A MID-UPPER LEVEL TROUGH EXTENDING FROM
BERMUDA SWD OVER THE S BAHAMAS NEAR 21N72W. FURTHER
E...MID-OCEANIC TROUGH HAS SPLIT FORMING A LARGE MID-UPPER LEVEL
LOW OVER THE CENTRAL ATLC NEAR 31N47W MOVING WNW 15 KT. THERE IS
JUST ENOUGH INSTABILITY ASSOCIATED WITH THE COLD CORE LOW TO
PRODUCE AN AREA OF SCATTERED SHOWERS/ISOLATED MODERATE
CONVECTION FROM FROM 24N-33N BETWEEN 44W-51W.  HOWEVER...THE
FLOW BECOME CONFLUENT S OF THE UPPER LOW PRODUCING STRONG
SUBSIDENCE S OF 24N BETWEEN 40-66W. OVER THE E ATLC...HURRICANE
DANIELLE CONTINUES TO LIFT NWD AROUND THE W PERIPHERY OF A
MID-UPPER LEVEL RIDGE ALONG 24N E OF 42W.  THE HURRICANE IS NOW
ENCOUNTERING AN INCREASINGLY HOSTILE ENVIRONMENT AND SHOULD
WEAKEN OVER THE NEXT FEW DAYS.  AT THE SURFACE...SUBTROPICAL
RIDGE EXTENDS FROM A STATIONARY 1025 MB HIGH OVER THE CENTRAL
ATLC NEAR 36N52W SW TO THE BAHAMAS. THE RIDGE IS DISRUPTED OVER
FLORIDA BY A WEAK LOW LEVEL TROUGH EXTENDING FROM 29N73W THROUGH
FLORIDA NEAR LAKE OKEECHOBEE DISSIPATING IN THE GULF JUST WEST
OF KEY WEST.

TROPICAL ATLANTIC...
STRONG SUBSIDENCE OVER THE CENTRAL ATLC W OF HURRICANE DANIELLE
EXTENDS WELL INTO THE TROPICAL ATLC PRODUCING VERY DRY AIR AND
GENERALLY TRANQUIL WEATHER N OF THE ITCZ.  FURTHER E...E/W
ORIENTED MID-UPPER LEVEL RIDGE POSITIONED JUST N OF THE CAPE
VERDE ISLANDS IS PRODUCING DEEP ELY FLOW E OF HURRICANE
DANIELLE.  THIS REGIME IS GENERALLY FAVORABLE FOR ITCZ/WAVE
RELATED CONVECTION BUT NEITHER ARE CURRENTLY PRODUCING
SIGNIFICANT ACTIVITY.

$$
JP/JA







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