[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 202358
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...
TROPICAL STORM DANIELLE HAS BEEN DOWNGRADED TO A DEPRESSION AND
IS LOCATED NEAR 31.0N 37.7W AT 20/2100 UTC. IT IS MOVING NW 3 KT
WITH MAXIMUM SUSTAINED WINDS OF 30 KT GUSTS 40 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1009 MB. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC FOR MORE
DETAILS.  STRONG SW SHEAR CONTINUES WITH INTERMITTENT PUFFS OF
DEEP CONVECTION NEAR AND NE OF THE CENTER.

...TROPICAL WAVES...
TROPICAL WAVE JUST W OF THE CAPE VERDE ISLANDS ALONG 27W S OF
22N MOVING W 10 KT.  1010 MB LOW PRESSURE CENTER IS ALONG THE
WAVE NEAR 16N.  THIS WAVE HAS BEEN CREEPING WESTWARD VERY SLOWLY
AS IT IS STUCK IN THE SW MONSOON FLOW OFF W AFRICA.  HOWEVER IT
IS EXPECTED TO ACCELERATE IN THE NEXT DAY OR TWO AS IT
ENCOUNTERS MORE OF A STEERING COMPONENT FROM THE AZORES HIGH.
NO SIGNIFICANT CONVECTION.

TROPICAL WAVE PREVIOUSLY ALONG 54W/55W IS RELOCATED ALONG
61W/62W IN THE LESSER ANTILLES S OF 15N MOVING W 20-25 KT.
LONG-TERM SATELLITE LOOPS INDICATE THIS WAVE IS SCREAMING
WESTWARD WITH MOST OF THE INCREASED SHOWERS CONFINED TO AND W OF
THE WINDWARD ISLANDS.  WIDELY SCATTERED MODERATE FROM 11N-14N
BETWEEN 59W-65W.

TROPICAL WAVE PREVIOUSLY ALONG 69W IS RELOCATED ALONG 73W SOUTH
OF 17N MOVING W 20 KT.  THIS POSITION BEST FITS EXTRAPOLATED
MOTION AND CLOUD STREAMERS IN THE CENTRAL CARIBBEAN.

...ITCZ...
ITCZ AXIS IS ALONG 9N13W 10N23W 8N37W 10N61W.  WIDELY SCATTERED
MODERATE WITHIN 60 NM OF AXIS FROM 35W-40W AND 42W-45W.
ISOLATED MODERATE FROM 8N-11N E OF 23W.

...DISCUSSION...
GULF OF MEXICO AND SUBTROPICAL ATLC W OF 75W...
PRETTY QUIET WEATHER PATTERN IN THE W GULF WITH UPPER RIDGING IN
PLACE AND MODERATE SUBSIDENCE.  SHORTWAVE ROTATING AROUND THE
RIDGE OVER E OKLAHOMA IS CAUSING A LARGE AREA OF TSTMS INLAND
OVER LOUISIANA/MISSISSIPPI/ALABAMA THIS EVENING.  UPPER TROUGH
RUNS FROM THE OUTER BANKS OF N CAROLINA SSW TO THE FLORIDA KEYS
INTO NW CUBA.  THIS TROUGH DID NOT AFFECT THE WEATHER IN THE
PENINSULA MUCH TODAY WITH TYPICAL SHOWERS FORMING INLAND AND
MOVING WESTWARD.  THE TSTMS OVER THE SE USA ARE EXPECTED TO FORM
A LITTLE CLOSER TO THE GULF TOMORROW AND A BIT FARTHER E WITH N
FLORIDA LIKELY TO GET MORE RAIN THAN TODAY.

CARIBBEAN SEA...
LITTLE CHANGE FROM YESTERDAY WITH THE MID-OCEANIC TROUGH IN
PLACE FROM E HISPANIOLA WSW TO E NICARAGUA.  MODERATE/STRONG
SUBSIDENCE WITHIN 90 NM OF THE TROUGH AXIS LIMITING SIGNIFICANT
CONVECTION.  A FEW MORE SHOWERS ARE IN THE NW CARIBBEAN TODAY AS
A RESULT OF THE TROUGH OVER FLORIDA DIPPING INTO THAT AREA.  A
TROPICAL WAVE OVER THE LESSER ANTILLES HAS INCREASED
MOISTURE/RAIN... FUELED IN PART BY UPPER DIVERGENCE NEAR AND S
OF AN UPPER RIDGE AXIS ALONG 13N E OF 66W.  A HIGHER-THAN-
AVERAGE CHANCE OF RAIN IS LIKELY FOR THE ISLANDS N OF VENEZUELA
TOMORROW INCLUDING THE ABC ISLANDS.  TRANSIENT ISOLATED MODERATE
ITCZ CONVECTION IS S OF 11N W OF 80W.

SUBTROPICAL ATLANTIC E OF 75W...
SURFACE TROUGH IS ALONG 31N62W TO 27N75W.  EARLIER TSTMS NEAR
THE TROUGH AXIS HAVE DIED DOWN WITH ONLY ISOLATED SHOWERS
PRESENT FROM 25N-30N BETWEEN 60W-70W.  UPPER HIGH NEAR 24N71W IS
HELPING TO ENHANCE SHOWERS NEAR AND NW OF THE HIGH'S CENTER.
HOWEVER AN UPPER LOW NEAR 22N63W HAS VIRTUALLY NO WEATHER
ASSOCIATED WITH IT... ALONG THE REST OF THE FEATURES IN THE
SUBTROPICAL ATLC.  ANOTHER UPPER HIGH IS NEAR 21N53W WITH
TROUGHING CONTROLLING THE CENTRAL ATLC BETWEEN 30W-45W WITH AXIS
ALONG 32N35W 22N42W.  THIS IS THE TROUGH THAT CONTINUES TO SHEAR
DANIELLE WITH THE FEATURE BASICALLY ON TOP OF THE TROPICAL
CYCLONE.  UPPER RIDGING IS PRESENT OVER THE REST OF THE ATLC
SAVE A SMALL UPPER LOW JUST E OF THE CANARY ISLANDS.  THE AZORES
RIDGE IS A BIT TATTERED TONIGHT WITH DANIELLE BREAKING THE RIDGE
ALONG WITH THE SURFACE TROUGH NEAR FLORIDA.

TROPICAL ATLANTIC...
STRONG MID/UPPER SUBSIDENCE IS PUTTING A LID ON CONVECTION
OUTSIDE OF THE ITCZ THIS EVENING.  DRY AIR STRETCHES ACROSS THE
ENTIRE AREA ESPECIALLY W OF A TROUGH AXIS FROM 20N32W 11N39W.
SHEAR IS GENERALLY LIGHT BUT THE WATER VAPOR PICTURES LOOK MORE
LIKE MID-JULY THAN LATE AUGUST.  OTHERWISE THE LOW-LEVEL SW
MONSOON FLOW STRETCHES FARTHER W THAN AVERAGE... ALL THE WAY TO
~40W ALONG ABOUT 8N.  TSTMS FROM THE NEXT WAVE ARE ABOUT TO
EMERGE IN THE E ATLC OFF W AFRICA BETWEEN 10N AND DAKAR.

$$
BLAKE


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