[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041035
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI JUL 04 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURE....

TROPICAL STORM BERTHA CENTERED NEAR 14.2N 28.3W AT 0900 UTC OR
ABOUT 275 NM WSW OF THE CAPE VERDE ISLANDS MOVING WNW AT 12 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. MAXIMUM SUSTAINED
WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT42 KNHC
FOR MORE DETAILS. BERTHA IS PULLING AWAY FROM THE CAPE VERDE
ISLANDS. LITTLE IMPACT WAS AFFECTED NEAR SAL ON THU AS SFC
REPORTS SHOW MAX WINDS JUST OVER 20 KT...A PRESSURE OF 1012 MB
AND VERY LITTLE RAINFALL. MORE OF AN IMPACT WAS LIKELY FELT OVER
THE SOUTHERN ISLANDS CLOSER TO THE CORE OF COMPACT BERTHA.
A LARGE BURST OF CONVECTION FORMED EARLIER THIS MORNING BUT IT
HAS SINCE DECREASED SOME WITH THE ESTIMATED LOW-LEVEL CENTER
NEAR THE S PORTION OF THE BLOW-UP. STILL...NUMEROUS MODERATE TO
STRONG CONVECTION IS WITHIN 150 NM N AND 30 NM S OF THE CENTER.
STRENGTHENING IS FORECAST IN THE SHORT TERM AS ATMOSPHERIC
CONDITIONS APPEAR FAVORABLE AND OCEANIC CONDITIONS ARE MARGINAL.

...TROPICAL WAVES...

TROPICAL WAVE IS TILTED ALONG 52W/53W S OF 20N MOVING W 20 KT.
DESPITE THE HIGH AMPLIFICATION NOTED IN SATELLITE IMAGERY AND
SCATTEROMETER DATA...THERE IS MINIMAL ASSOCIATED CONVECTION.
SHALLOW SCATTERED SHOWERS ARE WITHIN 240 NM EITHER SIDE OF THE
AXIS.

THE LOW AMPLITUDE TROPICAL WAVE PREVIOUSLY ANALYZED NEAR 60W HAS
BEEN DROPPED FROM THE SFC ANALYSIS. THERE HAS BEEN LITTLE
EVIDENCE OF THIS FEATURE OVER THE PAST SEVERAL DAYS AND IT
APPEARS THAT MUCH OF ITS MOISTURE/ENERGY HAS BEEN DRAWN INTO THE
ITCZ...DUE TO THE ENHANCED NE FLOW ON THE W SIDE OF THE LARGE
WAVE TO ITS E.

TROPICAL WAVE IS OVER THE CENTRAL CARIBBEAN ALONG 70W/71W S OF
18N MOVING W 15-20 KT. ADDED A WEAK 1013 MB LOW ALONG THE AXIS
NEAR 15N BASED ON A SMALL SWIRL EVIDENT ON SHORTWAVE IR IMAGES.
THIS LOW MAY BE 1-2 MB LOWER IN PRES CURRENTLY BASED ON
SURROUNDING
BUOY DATA. ASSOCIATED SCATTERED SHOWERS AND TSTMS HAVE INCREASED
THIS MORNING...NE OF THE EXPOSED LOW-LEVEL SWIRL DUE TO S-SW
SHEAR...FROM 15N-17N BETWEEN 66W-70W.

TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN ALONG 81W/82W S OF
15N MOVING W 15 KT. THIS WAVE LIES IN AN UPPER DIFFLUENT ZONE ON
THE S SIDE OF AN UPPER HIGH...TRIGGERING SCATTERED SHOWERS AND
TSTMS FROM 12N-16N BETWEEN 80W-85W.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N16W 14N24W 9N31W 6N40W 6N55W.
SCATTERED MODERATE CONVECTION IS FROM 6N-11N BETWEEN 14W-17W...
WITHIN 120 NM S OF THE AXIS BETWEEN 37W-42W AND WITHIN 45 NM
EITHER SIDE OF THE AXIS BETWEEN 47W-49W. SCATTERED MODERATE TO
STRONG CONVECTION IS WITHIN 90 NM N AND 120 NM S OF THE AXIS
BETWEEN 28W-33W.

...DISCUSSION...

THE GULF OF MEXICO...
THE LARGE SCALE PATTERN CONSISTS OF AN ELONGATED UPPER TROUGH
EXTENDING SW ACROSS THE EAST AND CENTRAL WATERS...AN UPPER LOW
SPINNING OVER SOUTHEAST TEXAS AND BROAD RIDGING OVER CENTRAL
MEXICO. THIS PATTERN IS PRODUCING A FAIR AMOUNT OF MOISTURE
OVER THE REGION. HOWEVER...LIGHTNING DATA INDICATES THAT LITTLE
OF THIS IS LEADING TO SIGNIFICANT TSTM ACTIVITY OVER THE CENTRAL
AND EASTERN WATERS. HOWEVER...SCATTERED TO NUMEROUS SHOWERS AND
TSTMS ARE AFFECTING THE FAR W WATERS NEAR THE COAST OF MEXICO
AND SOUTH TEXAS S OF 27N W OF 95W...MAINLY ATTRIBUTED TO THE
DIFFLUENT PATTERN MENTIONED ABOVE. AT THE SFC...ATLC RIDGING
EXTENDS ACROSS THE AREA ALONG 28N ALLOWING SE TO S WINDS TO BE
LIGHT ACROSS THE N WATERS WHILE MODERATE TO FRESH ELY FLOW
EXISTS OVER THE S WATERS.

THE CARIBBEAN SEA...
A PAIR OF TROPICAL WAVES ARE PROPAGATING ACROSS THE SEA. THE
EASTERN ONE (ALONG 70W/71W) IS WELL DEFINED WITH A WEAK LOW
ANALYZED ALONG THE AXIS NEAR 15N. CONVECTION HAS INCREASED TO
THE NE OF THE LOW THIS MORNING. THE OTHER WAVE ALONG 81W/82W HAS
BEEN FAIRLY INACTIVE OVER THE PAST COUPLE OF DAYS BUT IT HAS
ALSO GAINED CONVECTION THIS MORNING AS IT TRACKED INTO AN UPPER
DIFFLUENT AREA. REFER TO THE TROPICAL WAVE SECTION ABOVE FOR
MORE DETAILS. ELSEWHERE...DEEP CONVECTION IS FAIRLY MINIMAL AT
THE MOMENT DESPITE A MOIST ENVIRONMENT ALOFT. HOWEVER...ITS
QUITE A DIFFERENT STORY OVER EL SALVADOR...S GUATEMALA AND
PORTIONS OF S MEXICO...WHERE NUMEROUS SHOWERS AND TSTMS ARE
OCCURRING IN ASSOCIATED WITH THE UPPER DIFFLUENT ZONE AND A
DISTURBANCE IN THE EAST PACIFIC NEAR 11N95W.

THE ATLANTIC OCEAN...
THE UPPER PATTERN REMAINS SOMEWHAT DIFFLUENT OVER THE W ATLC
BETWEEN ELONGATED TROUGHING OVER THE EASTERN SEABOARD OF THE
U.S. AND A NARROW RIDGE E OF THE BAHAMAS ALONG 70W. THIS PATTERN
IS PRODUCING CLOUDINESS BUT MUCH OF THE TSTM ACTIVITY NOTED
EARLIER HAS DIMINISHED. FARTHER E...A LARGE UPPER LOW IS
SPINNING NEAR 32N53W WITH TROUGHING EXTENDING S TOWARDS THE NE
CARIBBEAN. LARGE SCALE RIDGING HOLDS E OF THERE WITH AN UPPER
HIGH POSITIONED NEAR 19N45W. OVERALL...THIS PATTERN IS PRODUCING
LITTLE SENSIBLE WEATHER BESIDES FOR SCATTERED SHOWERS AND TSTMS
NEAR THE UPPER LOW N OF 29N BETWEEN 43W-59W AND A SMALL PATCH
FROM 26N-28N BETWEEN 48W-50W.

AT THE SFC...A PAIR OF QUASI-STATIONARY HIGHS ARE OVER THE
CENTRAL ATLC...ONE ANALYZED 1028 MB NEAR 35N43W...THE OTHER 1026
MB HIGH NEAR 33N60W. A SFC TROUGH IS WEAKENING THE RIDGE FROM
22N52W TO 33N46W. THIS TROUGH APPEARS TO BE PARTLY ASSOCIATED
WITH THE LARGE TROPICAL WAVE TO THE S AND THE UPPER LOW CENTERED
TO THE NW. SCATTERED LOW-LEVEL SHOWERS ARE WITHIN 180 NM OF THE
AXIS.

$$
CANGIALOSI


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