[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210004
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL.
805 PM EDT WED JUL 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURE...

TROPICAL STORM EMILY IS CENTERED INLAND NEAR 25.0N 99.7W...OR
ABOUT 50 NM SSE OF MONTERREY MEXICO AND 105 NM SW OF MCALLEN
TEXAS...AT 21/0000 UTC MOVING W 10 KT. MAXIMUM SUSTAINED WIND
SPEED IS 45 KT WITH GUSTS TO 55 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 995 MB. SEE THE LATEST FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC AND THE PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT5/WTNT35 KNHC FOR MORE DETAILS.
VISIBLE IMAGERY CONTINUES TO SHOW A NEARLY CIRCULAR CLOUD
PATTERN MOVING METHODICALLY WWD OVER NE MEXICO AND LIFTING ONTO
THE MEXICAN PLATEAU. BOTH SATELLITE AND RADAR IMAGERY CLEARLY
SHOW THE CENTER OF EMILY NOW ALONG THE ERN SLOPES OF THE SIERRA
MADRE OCCIDENTALS...WHICH RISE ABRUPTLY FROM ABOUT 1000 FT TO
8000 FT OVER A DISTANCE OF ABOUT 40 NM TO THE S OF MONTERREY.
BECAUSE OF THIS...THE LOW-LEVEL CENTER WILL LIKELY BECOME
TRAPPED E OF THE MTNS AND DISINTEGRATE WHILE THE MID-LEVEL
CIRCULATION CONTINUES W OVER THE PLATEAU. VERY HEAVY RAINFALL
WILL CONTINUE TO FALL OVER NE MEXICO AS EMILY WINDS
DOWN...ESPECIALLY TO THE N OF THE CENTER OVER NUEVO LEON AND
COAHUILA STATES WHERE UPSLOPE FLOW IS OCCURRING. NUMEROUS
MODERATE/STRONG CONVECTION IS FROM 23N-28N BETWEEN 98W-101W...AS
WELL AS SCATTERED MODERATE UP TO 200 NM INLAND OVER SE TEXAS.

...TROPICAL WAVES...

EAST ATLANTIC TROPICAL WAVE ALONG 26N19W 18N22W 6N23W MOVING W
10-15 KT WITH A 1009 MB LOW ALONG THE AXIS NEAR 18N22W. THE WAVE
IS ACCOMPANIED BY AN EXPANSIVE CIRCULATION THAT REACHES FROM THE
ITCZ NWD TO THE CANARY ISLANDS...BETWEEN COASTAL AFRICA AND 40W.
THE SFC LOW IS LOCATED AT THE CENTER OF THIS CIRCULATION VERY
NEAR THE NE CAPE VERDE ISLANDS AND IS SURROUNDED BY A THICK
PLUME OF SAHARAN DUST...REDUCING VISIBILITY TO ABOUT 6 MILES AT
SAL. BROAD S/SW FLOW TO THE E OF THE WAVE AXIS IS TRANSPORTING
LARGE AMOUNTS OF MOISTURE NWD OVER W AFRICA...WHICH HAS BEEN
SUPPORTING DEEP CONVECTION WELL INTO WRN SAHARA AND MAURITANIA.
SCATTERED MODERATE/STRONG CONVECTION IS CURRENTLY FOCUSED OVER
SENEGAL AND GAMBIA FROM 11N-19N BETWEEN 13W-19W. THE LOW IS
EXPECTED TO MOVE QUICKLY TO THE SW AND DISSIPATE...BUT THE WAVE
ITSELF WILL BE ABLE TO MAINTAIN A WELL-DEFINED SIGNATURE. DEEP
TROPICAL MOISTURE WILL BE DRAWN NWD BEHIND THE WAVE WITH THE
POSSIBILITY OF SHOWERS/TSTMS DEVELOPING OVER THE CAPE VERDES
LATE THU AND FRI.

CENTRAL ATLANTIC TROPICAL WAVE ALONG 43W/44W S OF 22N MOVING W
15 KT. MET-8 VISIBLE IMAGERY SHOWS A SHARP INVERTED-V SIGNATURE
IN THE LOW-LEVEL CLOUD FIELD AND THE LEADING EDGE OF THE SURGE
OF SAHARAN DUST (HIGHER UP IN THE MID-LEVELS). THE ATMOSPHERE IS
TOO DRY TO SUPPORT DEEP CONVECTION EXCEPT FOR AN OCCASIONAL TSTM
ALONG THE ITCZ.

WEAK TROPICAL WAVE LOCATED OVER THE SRN WINDWARD ISLANDS AND ERN
VENEZUELA ALONG 62W S OF 12N MOVING W 10-15 KT. THIS WAVE
REMAINS WEAK AND LOW-LATITUDE...BUT THERE WERE INDICATIONS IN
THE 12Z TRINIDAD SOUNDING THAT THE AXIS MAY HAVE BEEN JUST
APPROACHING THE ISLAND. SINCE TRINIDAD ONLY RELEASES A
RADIOSONDE ONCE A DAY...THIS MAY NOT BE CONFIRMED UNTIL TOMORROW
MORNING WHEN IT CAN BE DETERMINED IF THE LOW-LEVEL WIND SHIFTED
TO SE. SCATTERED/NUMEROUS MODERATE CONVECTION IS STRUNG FROM
PARTS OF SURINAME NW THROUGH CNTRL VENEZUELA.

AMPLIFIED CENTRAL CARIBBEAN TROPICAL WAVE ALONG 73W REACHES
ACROSS HISPANIOLA TO NEAR THE TURKS AND CAICOS ISLANDS...MOVING
W/NW 10-15 KT. HEAVY SHOWERS/TSTMS CONTINUE TO FORM NEAR THE NRN
END OF THE WAVE OVER HISPANIOLA AND THE TURKS AND CAICOS
ISLANDS...FORCED BY A SHARP MID/UPPER TROF ALONG THE S COAST OF
CUBA. SATELLITE IMAGERY SEEMS TO SUGGEST A FAINT MID-LEVEL
CIRCULATION...AND MOST OF THE NUMERICAL MODELS DEVELOP A WEAK
SFC LOW/SHARP TROF NEAR THE BAHAMAS IN THE COMING DAYS...SO THIS
AREA WILL BE WATCHED FOR ANY SIGNS OF DEVELOPMENT. FOR
NOW...NUMEROUS MODERATE CONVECTION IS FROM 17N-24N BETWEEN
68W-73W AND COULD CAUSE FLASH FLOODING OVER PARTS OF HISPANIOLA
THROUGH TONIGHT AND EARLY THU.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 17N17W 9N29W 15N42W 9N50W 8N60W
...THEN OVER THE SW CARIBBEAN ALONG 12N74W 10N83W. ISOLATED
SHOWERS/TSTMS FROM 5N-9N BETWEEN 33W-37W. SCATTERED MODERATE
WITHIN 75 NM OF THE AXIS BETWEEN 52W-58W. SCATTERED MODERATE
OVER PARTS OF NRN COLOMBIA AND PANAMA.

...DISCUSSION...

GULF OF MEXICO...
THE WEATHER IS QUICKLY IMPROVING OVER THE GULF WATERS AS THE ERN
EDGE OF THE CLOUD ENVELOPE ASSOCIATED WITH TROPICAL STORM EMILY
ONLY EXTENDS 100 NM OFFSHORE...AND SHOULD MOVE TOTALLY INLAND
THROUGH THE NIGHT. THE UPPER LEVEL ANTICYCLONE LOCATED OVER THE
SYSTEM CONTINUES TO PUMP HIGH CLOUDINESS OVER THE WRN GULF BUT
THIS TOO SHOULD BEGIN TO MOVE OUT OF THE AREA AS STRONGER NE/E
FLOW DEVELOPS WITH THE APPROACH OF A SHARP TROF OVER CUBA. THE
LOW-LEVEL AIR MASS IS LARGELY DRY AT THE MOMENT SO EXCEPT FOR A
FEW TSTMS WHICH ARE MOVING OFF THE CUBA AND FLORIDA
COASTS...THERE WILL BE VERY LITTLE SHOWER ACTIVITY UNTIL
MOISTURE INCREASES AGAIN LATE FRI OVER THE SE GULF AHEAD OF A
TRPCL WAVE. ELSEWHERE...SCATTERED TSTMS OVER THE YUCATAN
PENINSULA HAVE SPAWNED OUTFLOW BOUNDARIES WHICH ARE MOVING INTO
THE BAY OF CAMPECHE S OF 21N E OF 93W.

CARIBBEAN...
MOST OF THE ENERGY AND DYNAMICS ASSOCIATED WITH THE TRPCL WAVE
OVER THE CNTRL CARIBBEAN IS LOCATED NEAR THE SRN BAHAMAS SO
EXCEPT FOR THE CONTINUOUS HEAVY RAINS OCCURRING OVER HISPANIOLA
THERE IS VERY LITTLE GOING ON FARTHER S OVER THE CNTRL CARIBBEAN
WATERS. WHAT IS MORE IMPRESSIVE IS A LARGE BATCH OF SCATTERED
MODERATE/STRONG CONVECTION OVER THE SW CARIBBEAN S OF 16N
BETWEEN 78W-84W WHICH HAS DEVELOPED DUE TO STRONG UPPER
DIFFLUENCE AND A WEAK SFC TROF LYING OFF THE COAST OF NICARAGUA
AND COSTA RICA. THE DIFFLUENCE LIES E OF AN UPPER LOW LOCATED
OVER THE SW GULF OF HONDURAS...AND S OF AN UPPER TROF WHICH
EXTENDS FROM THE LOW TO THE CAYMAN ISLANDS AND S CUBA. THE UPPER
LEVEL ANTICYCLONE IS EXPECTED TO BEGIN SHIFTING NW AFTER 24
HRS...AS WELL AS THE DEEPEST TRPCL MOISTURE...SO ROUNDS OF
CONTINUOUS SHOWERS/TSTMS CAN BE EXPECTED OVER THE SW CARIBBEAN
THROUGH THU NIGHT...AND SHOULD EXPAND OVER THE NW CARIBBEAN AS
WELL. FARTHER E...DEEP DRY AIR HAS MOVED IN BEHIND THE CNTRL
CARIBBEAN TRPCL WAVE TO PRODUCE FAIR WEATHER E OF
67W...REINFORCED BY A SWATH OF UPPER LEVEL SUBSIDENCE NOW
SPREADING OVER THE CNTRL LESSER ANTILLES.

ATLANTIC...
1022 MB HIGH PRES IS CENTERED SE OF BERMUDA NEAR 28N61W WITH A
RIDGE MORE OR LESS ALIGNED ALONG 30N W OF 55W. AN UPPER HIGH IS
LOCATED NE OF THE VIRGIN ISLANDS NEAR 21N63W WITH A SHARP RIDGE
EXTENDING NW TO 27N73W...PROVIDING A DIFFLUENT ENVIRONMENT FOR
THE DEVELOPMENT OF SCATTERED SHOWERS/TSTMS NEAR THE TURKS AND
CAICOS ISLANDS AND HISPANIOLA. FARTHER E...A TIGHTLY-WOUND UPPER
LOW IS LOCATED NEAR 32N43W WITH A TROF EXTENDING SW TO 24N56W
AND THIS HAS SERVED TO CUT THE SUBTROPICAL RIDGE IN HALF NEAR
50W. THE E ATLC IS DOMINATED BY A DEEP-LAYERED CYCLONIC
CIRCULATION ASSOCIATED WITH A STRONG TROPICAL WAVE WHICH MOVED
OFF THE AFRICAN COAST YESTERDAY...AND THIS HAS PROPELLED AN
EXTENSIVE SURGE OF AFRICAN DUST OVER THE OPEN WATERS OF THE ATLC
E OF 46W. AN UPPER LEVEL HIGH IS CENTERED OVER THIS AREA NEAR
20N30W BUT IS FOLLOWED BY THE UPPER LEVEL SIGNATURE OF THE TRPCL
WAVE NEAR THE CAPE VERDE ISLANDS.

$$
BERG





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