[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 292359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU MAY 29 2008

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

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURE...

TROPICAL STORM ALMA MADE LANDFALL ALONG THE PACIFIC COAST OF
NICARAGUA THIS AFTERNOON AND IS NOW LOCATED NEAR 12.9N 87.1W...
OR NEAR THE HONDURAS/NICARAGUA BORDER ABOUT 115 NM S OF
TEGUCIGALPA...AT 30/0000 UTC MOVING N 8 KT. MAXIMUM SUSTAINED
WIND SPEED HAS DIMINISHED TO 45 KT WITH GUSTS TO 55 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 998 MB. ALMA IS EXPECTED
TO CONTINUE MOVING INLAND ACROSS NORTHERN SECTIONS OF CENTRAL
AMERICA WITH SQUALLY WEATHER SPREADING ACROSS THE FAR WESTERN
CARIBBEAN OVER THE NEXT 24-36 HRS. ALTHOUGH THE WINDS WILL
WEAKEN DUE TO ITS INTERACTION WITH LAND...HEAVY RAINFALL WILL
CONTINUE OVER PORTIONS OF COSTA RICA...NICARAGUA...HONDURAS...EL
SALVADOR...GUATEMALA...AND BELIZE AS A STEADY STREAM OF TROPICAL
MOISTURE LIFTS N FROM THE PACIFIC. TOTAL RAINFALL ACCUMULATIONS
OF 10-15" ARE POSSIBLE WITH ISOLATED AMOUNTS UP TO 20"...
ESPECIALLY OVER THE HIGHER TERRAIN...INCREASING THE LIKELIHOOD
OF DEVASTATING FLASH FLOODS.

SOME REPORTED 48 HOUR RAINFALL TOTALS INCLUDE
PANAMA CITY PANAMA          1.97"
SANTIAGO PANAMA             5.55"
DAVID PANAMA                5.75"
SAN JOSE COSTA RICA         3.07"

SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPEP1/WTPZ31 KNHC AND THE FULL FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMEP1/WTPZ21 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE HAS MOVED PAST THE CAPE VERDE ISLANDS ALONG 31W S
OF 15N MOVING W 15 KT. TPW PRODUCTS CONTINUE TO SHOW A
WELL-DEFINED DEEP-LAYERED MOISTURE SURGE EXTENDING FROM THE
TROPICS NWD TO ABOUT 21N EVEN THOUGH THERE IS VERY LITTLE
SIGNATURE IN CONVECTIONAL SATELLITE IMAGERY. A SMALL INFLECTION
IS NOTED WITHIN THE ITCZ AND ALL ASSOCIATED CONVECTION IS
CONCENTRATED ALONG THE ITCZ AXIS ITSELF.

LOW-LATITUDE TROPICAL WAVE ALONG 44W/45W S OF 8N...ABOUT 450 NM
E OF FRENCH GUIANA...MOVING W 15 KT. THIS WAVE HAS CONTINUED TO
BECOME MORE WELL-DEFINED OVER THE PAST SEVERAL
DAYS...SPECIFICALLY ASSOCIATED WITH THE MOISTURE FIELD. IT IS
EXPECTED TO REACH THE COAST OF SOUTH AMERICA BY THIS TIME
TOMORROW AND WILL LIKELY INCREASE TSTM COVERAGE OVER THE GUIANAS
OVER THE NEXT 2-3 DAYS. ALL ASSOCIATED CONVECTION IS CURRENTLY
WITHIN THE ITCZ.

TROPICAL WAVE LOCATED OVER THE CENTRAL CARIBBEAN NEAR 73W S OF
21N MOVING W 15-20 KT. ODDLY ENOUGH...THIS WAVE HAS MARKED THE
LEADING EDGE OF A DRY SURGE ACROSS THE EASTERN CARIBBEAN AS IT
RUNS INTO THE EXTREMELY MOIST ENVIRONMENT OVER THE WESTERN
CARIBBEAN. THE AXIS HAS BECOME DIFFICULT TO LOCATED NOW THAT IT
IS MOVING INTO A LARGE-SCALE CYCLONIC GYRE YET MIMIC-TPW PLACES
IT NICELY NEAR THE GUAJIRA PENINSULA OF COLOMBIA. SCATTERED
MODERATE CONVECTION EXTENDS FROM 15N-22N BETWEEN 67W-78W
ALTHOUGH THIS IS LIKELY ALSO ASSOCIATED WITH A BROAD SURFACE
TROUGH EXTENDING NE OF CENTRAL AMERICA. SCATTERED
MODERATE/ISOLATED STRONG IS ALSO OVER NW VENEZUELA AND NORTHERN
COLOMBIA.

TROPICAL WAVE OVER THE GULF OF HONDURAS ALONG 85W S OF 20N
MOVING W 10 KT. THE WAVE HAS BECOME WRAPPED INTO THE CIRCULATION
OF T.S. ALMA OVER WESTERN NICARAGUA AND IS BECOMING INCREASINGLY
INDISTINGUISHABLE FROM THE LARGE-SCALE PATTERN. IN FACT...A MORE
WELL-DEFINED SURFACE TROUGH EXTENDS FROM HONDURAS TO NEAR
JAMAICA WITH AN E/W LINE OF SCATTERED MODERATE CONVECTION
LIFTING NWD FROM 15N-21N W OF 78W. THE WAVE AXIS WILL BE DROPPED
FROM THE 30/0000 UTC ANALYSIS IN FAVOR OF THE TROUGH.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 12N10W 5N20W 6N31W 1N55W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION OFF THE COAST OF AFRICA S OF
10N BETWEEN 8W-15W. SCATTERED MODERATE/STRONG FROM 00N-5N
BETWEEN 20W-30W. ISOLATED MODERATE WITHIN 120 NM OF AXIS W OF
31W INTO SOUTH AMERICA...WHERE COVERAGE BECOMES MORE NUMEROUS.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL HIGH REMAINS CENTERED ALONG THE PACIFIC COAST OF
MEXICO NEAR MAZATLAN BUT THE RIDGE AXIS HAS SHIFTED W SINCE
YESTERDAY...NOW EXTENDING NE ACROSS TEXAS. A SHARP UPPER TROUGH
AXIS NOW STRETCHES ACROSS THE GULF FROM N FLORIDA TO 26N90W THEN
TO THE ISTHMUS OF TEHUANTEPEC. MODERATE/STRONG SUBSIDENCE LIES W
OF THE TROUGH AXIS WHILE DEEPER MOISTURE IS INCREASING TO THE
E...CREEPING N FROM THE NW CARIBBEAN. A FEW PATCHES OF SHOWER
ACTIVITY ARE MOVING W ACROSS THE CENTRAL GULF AND SW GULF BUT
OTHERWISE MUCH OF THE AREA IS EXPERIENCING FAIR WEATHER.
HOWEVER...TSTMS WHICH HAVE FORMED ACROSS THE YUCATAN PENINSULA
AND CUBA COULD MOVE OFFSHORE WITHIN THE NEXT FEW HRS DUE TO THE
SOUTHEASTERLY STEERING FLOW.

CARIBBEAN...
T.S. ALMA HAS MADE LANDFALL OVER WESTERN NICARAGUA AND IS
ADVECTING DEEP TROPICAL MOISTURE FROM THE FAR EASTERN PACIFIC
NWD ACROSS MUCH OF THE WESTERN CARIBBEAN W OF 75W. UPPER LEVEL
OUTFLOW IS SPREADING AWAY FROM ALMA WITH AN UPPER HIGH CENTERED
NEAR 17N81W...AND THE CIRRUS FLOWING E/SE TOWARDS THE EASTERN
CARIBBEAN. ASIDE FROM CONVECTION DESCRIBED WITH THE TROPICAL
WAVES...NUMEROUS MODERATE/STRONG CONVECTION HAS ALSO FLARED OVER
EASTERN HONDURAS...NICARAGUA...AND THE ADJACENT WATERS FROM
10N-18N BETWEEN 82W-86W. THE CLEAREST SKIES EXTEND OVER THE SE
CARIBBEAN ACROSS THE ABC ISLANDS...THE COAST OF VENEZUELA...AND
THE WINDWARD ISLANDS DUE TO A DRYING ATMOSPHERE.

ATLANTIC...
THE SUBTROPICAL RIDGE REMAINS BROKEN OVER THE W ATLANTIC WITH
SEVERAL SURFACE TROUGHS STILL STRUNG THROUGH THE AREA. ONE
TROUGH OVER THE BAHAMAS IS PRODUCING SCATTERED SHOWERS/TSTMS
OVER THE BAHAMAS FROM 23N-28N BETWEEN 73W-78W AND THE ASSOCIATED
MOISTURE IS EXPECTED TO MOVE W ACROSS S FLORIDA BY FRI EVENING.
ANOTHER SURFACE TROUGH EXTENDS FROM 31N58W TO 24N63W IS
PRODUCING ISOLATED SHOWERS/TSTMS WITHIN 120 NM OF THE
AXIS...ESPECIALLY IN THE VICINITY OF AN UPPER LOW NEAR 23N63W.
FARTHER E...A SPRAWLING 1026 MB HIGH IS CENTERED NEAR 32N39W
WITH LITTLE ACTIVE WEATHER ACROSS THE EASTERN/CENTRAL ATLANTIC.
A LONGWAVE TROUGH AXIS EXTENDS FROM MADEIRA ISLAND SW TO 25N43W
WITH 70-75 KT WESTERLY FLOW STRETCHING ACROSS THE CANARY ISLANDS
INTO NW AFRICA. AN UPPER HIGH IS LOCATED FARTHER S NEAR THE CAPE
VERDE ISLANDS AND IS PULLING SOME UPPER LEVEL MOISTURE FROM THE
TROPICS BACK TOWARDS AFRICA. HOWEVER...DEEP MOISTURE REMAINS
SCANT E OF 60W AND THUS ALL DEEP CONVECTION IS LIMITED TO THE
ITCZ.

$$
BERG



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