[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 050004
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT AUG 04 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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.

...TROPICAL WAVES...
HIGH AMPLITUDE TROPICAL WAVE EXTENDS ACROSS THE WRN CAPE VERDE
ISLANDS ALONG 25W S OF 23N MOVING W NEAR 15 KT. THIS WAVE
CONTINUES TO EXHIBIT A LARGE WELL DEFINED AREA OF CYCLONIC
TURNING IN THE LOW AND MID LEVEL CLOUDS. THE MOST PRONOUNCED
ROTATION IS NOW PUSHING JUST W OF THE CAPE VERDE ISLANDS. DEEP
CONVECTION REMAINS MINIMAL NEAR THIS ROTATION THOUGH. THE MORE
PERSISTENT SCATTERED SHOWER/TSTM ACTIVITY HAS BEEN ACROSS THE
SRN PORTION OF THE WAVE AND THE INTERSECTION OF THE ITCZ FROM
7N-12N BETWEEN 22W-30W.

TROPICAL WAVE IS ALONG 42W S OF 18N MOVING W NEAR 15 KT. THIS
WEAK WAVE REMAINS DIFFICULT TO LOCATE AS IT IS EMBEDDED IN THE
FLOW OF THE LARGER WAVES TO IT'S E AND W. STABLE AIR AND BROKEN
STRATOCUMULUS CLOUDS SURROUND THIS FEATURE. ISOLATED SHOWERS AND
TSTMS NEAR THE AXIS S OF 12N ARE MORE LIKELY ASSOCIATED WITH THE
ITCZ.

HIGH AMPLITUDE TROPICAL WAVE IS ALONG 57W/58W MOVING W 15-20 KT.
THIS LARGE-SCALE WAVE REMAINS FAIRLY EASILY SEEN WITH A
PRONOUNCED INVERTED-V SHAPE NOTED IN THE LOW AND MID LEVEL CLOUD
FIELD. ALTHOUGH DEEP CONVECTION REMAINS MINIMAL WITH THIS
WAVE...THE FEATURE HAS GAINED MOISTURE COMPARED TO YESTERDAY AS
IT IS INTERACTING WITH AN UPPER LOW NEAR 21N59W. THIS IS
PRODUCING WIDESPREAD CLOUDINESS WITH SCATTERED SHOWERS N OF 15N
WITHIN 250NM EITHER SIDE OF THE AXIS.

STRONG TROPICAL WAVE IS MOVING THROUGH THE W CARIBBEAN AND
CENTRAL AMERICA ALONG 85W S OF 24N MOVING W NEAR 20 KT. SINCE
THE WAVE IS MOVING INLAND OVER CENTRAL AMERICA FURTHER
DEVELOPMENT IS NOT ANTICIPATED.  HOWEVER...THE WAVE IS EXPECTED
TO BRING LOCALLY HEAVY RAINFALL AND GUSTY WINDS OVER PORTIONS OF
CENTRAL AMERICA AND THE YUCATAN PENINSULA TONIGHT AND SUNDAY.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS CURRENTLY FROM
13N-22N W OF 79W. A RECENT FLARE UP OF MODERATE TO STRONG
CONVECTION IS ALSO OVER THE GUANACASTE REGION OF COSTA RICA.

THE NRN PORTION OF A TROPICAL WAVE ALONG 95W EXTENDS ACROSS THE
BAY OF CAMPECHE S OF 21N MOVING W 15-20 KT. THIS WAVE REMAINS
WEAK WITH THE CURRENT PSN BASED MOSTLY ON A MODEST WWD SURGE OF
MOISTURE NOTED ON THE UW-CIMSS TPW PRODUCT. SOME OF THE MOISTURE
APPEARS TO BE ROTATING MORE NW AROUND THE RIDGING OVER THE GULF.
SHOWERS AND TSTMS ARE OVERALL MINIMAL.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 16N15W 11N26W 10N40W 16N56W.
BESIDES FOR THE CONVECTION DISCUSSED WITH THE TROPICAL
WAVES...SCATTERED MODERATE TO STRONG CONVECTION IS NEAR THE
COAST OF AFRICA FROM 11N-14N E OF 19W. SCATTERED MODERATE IS
WITHIN 120NM N/150NM S OF THE AXIS BETWEEN 30W-40W. ISOLATED
MODERATE IS FROM 8N-11N BETWEEN 46W-55W.

...DISCUSSION...
THE GULF OF MEXICO...
THE GULF IS FAIRLY QUIET THIS EVENING WITH A 1022 MB SFC HIGH S
OF MOBILE NEAR 27N88W. ISOLATED SHOWERS STILL LINGER WITHIN 120
NM EITHER SIDE OF A BROWNSVILLE TO FLORIDA BIG BEND LINE BUT
HAVE GENERALLY DIMINISHED OVER THE LAST SEVERAL HOURS. A SWATH
OF UPPER MOISTURE NOTED IN THIS VICINITY AS WELL. VERY DRY MID
TO UPPER AIR IS OVER THE GULF FROM 24N-28N E OF 90W THROUGH
SOUTHERN FLORIDA...CONTRIBUTING TO THE NICE WEATHER THERE.
INCREASING MOISTURE...CLOUDINESS...AND SHOWERS ARE NOW AFFECTING
THE FAR ERN BAY OF CAMPECHE AND THE SRN GULF S OF 23N BETWEEN
84W-92W. THIS IS ASSOCIATED WITH THE NRN EXTENT OF THE STRONG
TROPICAL WAVE MOVING THROUGH THE NW CARIBBEAN. THIS MOISTURE IS
EXPECTED TO CONTINUE SPREADING INTO THE BAY OF CAMPECHE LATE
TONIGHT AND TOMORROW AS THE WAVE CONTINUES W. HI PRES OVER THE
NE GULF WILL KEEP WINDS LIGHT TO MODERATE OTHERWISE.

THE CARIBBEAN SEA...
THE MAIN FEATURE IN THE CARIB IS THE ACTIVE TROPICAL WAVE MOVING
OVER THE NW PORTION AND CENTRAL AMERICA. FOR DETAILS REFER TO
THE TROPICAL WAVES SECTION ABOVE. OTHERWISE...THIS REGION
REMAINS RATHER TRANQUIL WITH UPPER NELY FLOW DRAWING DRIER AIR
INTO MUCH OF THE CENTRAL AND ERN PORTIONS. THE ATMOSPHERE IS A
LITTLE MORE MOIST ACROSS THE NRN LEEWARD ISLANDS AND PUERTO
RICO...CLOSER TO AN UPPER LOW CENTER. RADAR DATA FROM SAN JUAN
SHOWS QUICK MOVING STREAMS OF SHOWERS MOVING THROUGH THE AREA
FROM THE ENE...LIKELY ASSOCIATED IN PART WITH LIFT FROM THE
UPPER LOW IN ADDITION TO NORMAL LOW LEVEL TRADE WIND MOISTURE.
AN INCREASE IN MOISTURE IS LIKELY OVER THE ERN CARIB OVER NEXT
COUPLE OF DAYS AS THE LARGE TROPICAL WAVE IN THE TROPICAL ATLC
APPROACHES. OTHERWISE MODERATE TO FRESH TRADES ARE IN PLACE AND
EXPECTED TO PERSIST OVER THE NEXT COUPLE OF DAYS.

THE ATLANTIC OCEAN...
ON THE LARGE SCALE THE WRN ATLC IS QUIET THIS EVENING IN
RESPONSE TO VERTICALLY STACKED RIDGING. A THIN CONVERGENCE LINE
OF SHOWERS BETWEEN 27N79W AND 31N76W HAS MOSTLY DIMINISHED...BUT
ANOTHER SIMILAR FEATURE HAS DEVELOPED FROM JUST OFFSHORE ST.
AUGUSTINE TO NEAR 31N76W. THESE SHOWERS ARE DEVELOPING WITH
CONFLUENT FLOW AHEAD OF THE WEAK SFC LOW PUSHING E FROM THE
SOUTH CAROLINA COAST. DEEP MOISTURE HAS PERSISTED OVER THE ATLC
BETWEEN 53W-69W. SOME OF THIS IS STILL ASSOCIATED WITH NLY UPPER
FLOW DRAWING MOISTURE DOWN FROM AN OLD FRONTAL BOUNDARY N OF THE
AREA...THOUGH THE LARGE AMPLITUDE TROPICAL WAVE ALONG 58W IS
INCREASING THE MOISTURE IN THE VICINITY AS IT INTERACTS WITH THE
UPPER LOW NE OF THE LEEWARD ISLANDS NEAR 21N59W. A WEAK 1016 MB
SFC LOW IS S OF THE OLD FRONTAL BOUNDARY NEAR 31N62W. SCATTERED
MODERATE CONVECTION IS JUST AHEAD OF THIS FEATURE FROM 30N-32N
BETWEEN 58W-61W.

THE REMAINDER OF THE UPPER PATTERN IS RATHER BENIGN WITH OVERALL
LITTLE SIGNIFICANT MOISTURE BEING PRODUCED. OUTSIDE OF THE LARGE
TROPICAL WAVES...THE REMAINDER OF THE SFC PATTERN IS DOMINATED
BY A RIDGE EXTENDING FROM A 1027 MB HIGH NEAR 35N37W TO A 1020
MB CENTER NEAR 26N70W CONTINUING W INTO THE GULF. THE
COMBINATION OF THIS HIGH PRES AND A LARGE AREA OF STABLE AIR
ALOFT IS PRODUCING WIDESPREAD FAIR WEATHER N OF 18N E OF 50W.
TYPICAL STABLE SCATTERED STRATOCUMULUS ARE THE MAIN SOURCE OF
CLOUD COVER ACROSS THIS REGION. TRADES ARE MODERATE...EXCEPT
NEAR THE CARIB ISLANDS AND THE COAST OF NW AFRICA WHERE THE
TIGHTENED PRES GRAD IS PRODUCING SLIGHTLY STRONGER WINDS.

$$
WILLIS




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