[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 071050
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN AUG 07 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA... GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN
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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES..
THE CENTER OF TROPICAL STORM HARVEY AT 07/0900 UTC WAS NEAR
35.4N 54.6W MOVING NE 10 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 997 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 50 KT
WITH GUSTS TO 60 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC OR MIATCPAT3/WTNT33 KNHC
FOR MORE DETAILS.  RECENT MICROWAVE IMAGES SUGGEST THE CENTER OF
HARVEY IS A LITTLE TO THE W OF A LARGE EXPLOSION OF TSTMS.  THE
STORM WILL BE CROSSING THE 26C ISOTHERM LATER TODAY WHICH SHOULD
START TO WEAKEN THE SYSTEM... AND THEN BE FINISHED OFF BY A
MID-LATITUDE TROUGH QUICKLY APPROACHING FROM THE WEST.  COMPUTER
MODELS SUGGEST THAT THE REMNANTS OF HARVEY COULD BECOME A LARGE
POWERFUL EXTRATROPICAL STORM NEAR OR W OF THE AZORES IN A FEW
DAYS.  SCATTERED MODERATE CONVECTION IS WITHIN 90 NM OF THE
CENTER IN THE E SEMICIRCLE.

THE CENTER OF TROPICAL DEPRESSION NINE AT 07/0900 UTC WAS NEAR
19.6N 44.7W MOVING WNW 9 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1007 MB. THE MAXIMUM SUSTAINED WIND SPEED IS 30 KT
WITH GUSTS TO 40 KT. SEE THE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC OR MIATCPAT4/ WTNT34
KNHC FOR MORE DETAILS.  THE DEPRESSION IS VERY CLOSE TO TROPICAL
STORM INTENSITY WITH CURVED CONVECTION CLOSE TO THE CENTER FOR
THE FIRST TIME.  A LARGE UPPER LOW/TROUGH HAS BEEN SHEARING THE
SYSTEM BUT ITS INFLUENCE SEEMS TO BE WANING AS THE DEPRESSION
HAS PASSED THE TROUGH AXIS.  COMPUTER MODELS ARE SPLIT ON
WHETHER THE SHEAR WILL CONTINUE AT MODERATE LEVELS DUE TO THE
UPPER TROUGH SPLITTING AND MOVING WESTWARD WITH THE DEPRESSION
OR ABATE DUE TO UPPER RIDGING BUILDING IN THE CENTRAL ATLC.
SCATTERED MODERATE CONVECTION IS IN THE ERN SEMICIRCLE OF THE
DEPRESSION FROM 18.5N-21.5N BETWEEN 41.5W-44.5W.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS NEAR THE CAPE VERDE ISLANDS ALONG 24W S
OF 16N MOVING W 15 KT.  COMPLEX WAVE SITUATION AS THE MID-LEVEL
PORTION OF THE WAVE APPEARS TO BE APPROACHING 30W.  THE WAVE
POSITION IS A COMPROMISE BETWEEN THE MID-LEVEL SIGNATURE ON
OVERNIGHT SATELLITE PICTURES... TSTMS IN THE ITCZ.. AND 24 HOUR
PRESSURE CHANGES NEAR ZERO IN THE CAPE VERDES.. INDICATING THE
WAVE SHOULD BE CLOSE.   THE GFS SUGGESTS THE WAVE WILL
ACCELERATE WESTWARD DURING THE NEXT FEW DAYS.

W-CENTRAL ATLANTIC TROPICAL WAVE IS TILTED FROM SSW TO NNE NEAR
SURINAME TO 18N54W MOVING W 10-15 KT.  SATELLITE IMAGES SHOWS
TWO ENERGY CENTERS WITH THE WAVE.. ONE AT THE NORTHERN END NEAR
16N AND OTHER ONE NEAR THE ITCZ S OF 10.5N.  MOISTURE ASSOCIATED
WITH THE NORTHERN PART OF THE WAVE SHOULD ENTER THE SOUTHERN
LEEWARD ISLANDS LATE TODAY AT ABOUT THE LATITUDE OF GUADELOUPE.
THE SOUTHERN PORTION OF THE WAVE IS EXPECTED TO IMPACT THE
WINDWARD ISLANDS OVERNIGHT WITH SCATTERED SHOWERS/TSTMS EXPECTED
OVER THAT AREA THROUGH MON.  THE GFS EVEN SUGGESTS A WEAK LOW
COULD SPIN UP IN THE S PORTION OF THE WAVE BY THE EARLY PART OF
THE WEEK.  SCATTERED SHOWERS AND A FEW TSTMS ARE FROM
15.5N-17.5N BETWEEN 52W-58W WITH WIDELY SCATTERED TSTMS FROM
8N-11N BETWEEN 51W-58W.

CENTRAL AMERICAN TROPICAL WAVE IS ALONG 91W S OF 19N MOVING W 15
KT.  LARGE TSTMS THAT FORMED OVER HONDURAS AND NICARAGUA AND
CONTINUED INTO THE BAY OF CAMPECHE WERE PROBABLY ENHANCED BY THE
WAVE AXIS.  THE GFS SUGGESTS THAT A STRONG LOW-LEVEL WIND
MAXIMUM RESIDES BEHIND THE WAVE IN THE SW CARIBBEAN... WHICH
COULD CREATE ENHANCED WINDS IN THE GULF OF PAPAGAYO TOMORROW.
ISOLATED MODERATE CONVECTION IS WITHIN 90 NM OF 20N94.5W.

...ITCZ...

ITCZ IS CENTERED ALONG 14N16W 9N27W 8N40W 12N50W 8N60W.  WIDELY
SCATTERED MODERATE CONVECTION WITHIN 75 NM OF AXIS BETWEEN
32W-40W AND WITHIN 60 NM OF LINE 10N51W 9N55W 7N58W.  ISOLATED
MODERATE WITHIN 90 NM OF AXIS E OF 29W.

...DISCUSSION...

GULF OF MEXICO...
WEAK LOW LIES S OF THE AL/FL STATE LINE NEAR 29.5N87.5W WITH A
NARROW LINE OF SHOWERS/TSTMS AHEAD OF THE FEATURE WITHIN 45 NM
OF LINE 26N87W 31N84.5W.  WEAK SURFACE TROUGH EXTENDS WSW TO
28N92W... INDICATED BY SURFACE OBSERVATIONS AND A NARROW CU LINE
ON SATELLITE.  NEARLY STATIONARY INVERTED TROUGH LIES FROM THE
YUCATAN CHANNEL CUBA TO 26N87W AND IS RESPONSIBLE FOR A VERY
DIVERGENT PATTERN ALOFT WHICH SHOULD CREATE MORE TSTMS NEAR
26N86W LATER TODAY.  WEAK 1017 MB SURFACE HIGH PRESSURE LIES
OVER THE W GULF NEAR BUOY 42002 WITH MOST WINDS 10 KT OR LESS IN
THE GULF SAVE THE NE PART NEAR THE LOW.  IN THE UPPER LEVELS...
SLOW-MOVING UPPER LOW IS S OF BIRMINGHAM WITH TROUGHING S TO
27N88W.  THE GFS INDICATES THAT THE LOW WILL DRIFT NE DURING THE
NEXT 24 HOURS... WITH ANOTHER ACTIVE TSTM DAY LIKELY FROM THE NE
GULF OF MEXICO TO 88W NORTHWARD THRU THE TENNESSEE VALLEY WITH
OTHER TYPICAL DAILY STORMS OVER THE FLORIDA PENINSULA.

CARIBBEAN SEA...
PAIR OF MID/UPPER LOWS DOMINATE THE WEATHER PICTURE... THE FIRST
BEING OVER THE NW CARIBBEAN ELONGATED FROM NW TO SE NEAR 20N84W
AND THE OTHER DEPARTING THE CARIBBEAN N OF DOMINICAN REPUBLIC E
OF TURKS/CAICOS ISLAND AT 22N71W.  STRONG NW CHANGING TO SW
WINDS AT 75W COVER THE AREA W OF 67W WITH UPPER DIVERGENCE
CAUSING WIDELY SCATTERED TSTMS S OF SAN ANDRES W OF 80W.
MODERATE SUBSIDENCE IS KEEPING MOST SIGNIFICANT CONVECTION TO A
MINIMUM WITH ONLY ISOLATED DIURNAL ACTIVITY EXPECTED OVER THE
GREATER ANTILLES TODAY.  MOISTURE SHOULD GENERALLY BE INCREASING
THIS WEEK WITH THE LARGE AREA OF SHOWERS ASSOCIATED WITH A
TROPICAL WAVE AND A SURGE OF MOISTURE POSITIONED W OF 40W S OF
15N STILL E OF THE CARIBBEAN.  MUCH WETTER CONDITIONS WILL
OVERSPREAD THE SE CARIBBEAN BY MON.. EVEN AS FAR W AS THE ABC
ISLANDS BY LATE TUE...THOUGH KEEPING THE LEEWARD ISLANDS OUT OF
MOST OF THE ENHANCED RAIN.  CONTINUED STORMY WEATHER IS LIKELY
OVER CENTRAL AMERICA ESPECIALLY S OF NICARAGUA AS UPPER
TROUGHING REMAINS WITH PLENTY OF DIVERGENCE AIDING AFTERNOON
CONVECTION.

ATLANTIC OCEAN...
MID/UPPER HIGH IS NEARLY STATIONARY NEAR 31N74W RIDGING WESTWARD
TO SE GEORGIA.  A MUCH MORE SIGNIFICANT FEATURE IS BARRELLING
NNW THRU THE W ATLC...A POWERFUL MID/UPPER LOW NEAR 22N71W
MOVING NNW 15 KT.  COMPUTER MODELS SUGGEST THIS LOW WILL
CONTINUE DEEPENING THROUGHOUT THE ATMOSPHERE WITH A SURFACE
TROUGH NOW EVIDENT W OF THE LOW FROM HAITI TO 25N74W.  HOWEVER
NO DEVELOPMENT IS LIKELY DUE TO THE STRONG MID/UPPER LOW'S
PROXIMITY.  COLD-AIR INSTABILITY ALOFT CLOSER TO THE LOW ALONG
WITH AN OLD TROUGH IS FUELING ISOLATED MODERATE CONVECTION FROM
23N-28N BETWEEN 69W-75W.  FARTHER E... LARGE MID/UPPER HIGH IS
NEAR 24N57W WITH MODERATE/STRONG SUBSIDENCE N OF 13N BETWEEN
48W-65W.  THE MUCH-DISCUSSED TROUGH THAT IS SHEARING T.D. NINE
IS ALIGNED FROM 16N44W TO 30N39W WITH LIGHT TO MODERATE WLY
WINDS ALOFT OVER THE DEPRESSION.  IN THE DEEP TROPICS... UPPER
RIDGING IS ALONG 15N W OF 35W..BROKEN BY AN INVERTED TROUGH IN
THE MID/UPPER LEVELS S OF 20N ALONG 31W.  OTHERWISE THE AFRICAN
ANTICYCLONE CONTROLS THE REST OF THE AREA E OF THE CAPE VERDES.
AT THE SURFACE... 1023 MB HIGH IS NEAR 31N36W WITH WEAKER THAN
AVERAGE TRADES COVERING MOST OF THE DEEP TROPICS EXCEPT NEAR THE
NORTHERN SEMICIRCLE OF THE DEPRESSION.

$$
BLAKE

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