[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 130620
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT AUG 13 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 0000 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 0545 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM IRENE AT 13/0300 UTC WAS NEAR
29.2N 68.3W OR ABOUT 300 MILES/480 KM SOUTHWEST OF BERMUDA
AND ABOUT 590 MILES/950 KM SOUTHEAST OF CAPE HATTERAS NORTH
CAROLINA. IT WAS MOVING NORTHWEST 9 KT. THE ESTIMATED MINIMUM
CENTRAL PRESSURE 991 MB. THE MAXIMUM SUSTAINED WIND SPEEDS WERE
60 KT WITH GUSTS TO  75 KT. SEE THE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC OR
MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. NUMEROUS STRONG SHOWERS
AND THUNDERSTORMS FROM 29N TO 30N BETWEEN 68W AND 69W. THE
COLDEST CLOUD TOP TEMPERATURES WERE NEAR -80C FOR TOPS REACHING
ABOUT 53000 FEET RIGHT NEAR THE CENTER. SCATTERED MODERATE TO
STRONG SHOWERS AND THUNDERSTORMS ARE NORTH OF THE CENTER FROM
30.5N TO 31N BETWEEN 68W AND 69W. OTHER SHOWERS AND
THUNDERSTORMS ARE ELSEWHERE FROM 28.5N TO 30N BETWEEN 67W AND
70W.

A 1010 MB ATLANTIC OCEAN LOW PRESSURE CENTER WAS NEAR 12.5N43W
MOVING WEST-NORTHWEST 10 TO 15 KT. THIS CIRCULATION WAS MOVING
ALONG WITH A TROPICAL WAVE FOR AT LEAST A FEW DAYS AS IT BECAME
BETTER ORGANIZED. SCATTERED MODERATE TO ISOLATED STRONG SHOWERS
AND THUNDERSTORMS FROM 10N TO 15N BETWEEN 41W AND 46W. UPPER
LEVEL WINDS ARE FAVORABLE FOR DEVELOPMENT...ALTHOUGH A MIDDLE
TO UPPER LEVEL TROUGH WITH ITS BASE NEAR 18N49W IS APPROACHING
THE LOW CENTER SLOWLY.

...TROPICAL WAVES...

TROPICAL WAVE IS BETWEEN THE AFRICAN COAST AND THE CAPE VERDE
ISLANDS ALONG 22/23W SOUTH OF 21N MOVING WEST 5 TO 10 KT...WITH
A 1010 MB LOW ALONG THE WAVE NEAR 14.5N. A LARGE STRATOCUMULUS
SWIRL SURROUNDS THE LOW. NO DEEP SHOWERS AND THUNDERSTORMS ARE
NEAR THE LOW CENTER. ANY SIGNIFICANT PRECIPITATION IS IN THE
ITCZ.

AN EASTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 62W/63W SOUTH
OF 18N MOVING WEST 20 KT. ISOLATED MODERATE SHOWERS HAVE BEEN
DIMINISHING IN COVERAGE DURING THE LAST 4 TO 5 HOURS...AND NOW
ARE FOUND FROM 12N TO 17N BETWEEN 62W AND 68W. UPPER LEVEL
ANTICYCLONIC WIND FLOW FROM AN UPPER LEVEL RIDGE IS IN PLACE
EAST OF 70W.

A CARIBBEAN SEA TROPICAL WAVE IS ALONG 71W/72W SOUTH OF 19N
FROM CENTRAL HISPANIOLA TO LAKE MARACAIBO IN VENEZUELA...MOVING
WEST 15 KT. THE SHOWERS AND THUNDERSTORMS IN NORTHERN COASTAL
HAITI MAY BE DUE MORE TO THE SOUTHERLY WIND FLOW EAST OF THE
BAHAMAS-TO-JAMAICA MIDDLE TO UPPER LEVEL TROUGH AS OPPOSED TO
BEING ASSOCIATED WITH THE WAVE.

TROPICAL WAVE ALONG 96W/97W SOUTH OF THE MEXICO COAST IN THE
WESTERN GULF OF TEHUANTEPEC MAY BE AFFECTING THE SCATTERED
STRONG SHOWERS AND THUNDERSTORMS FROM 16N96W TO 17.5N95W TO
COASTAL MEXICO JUST SOUTHWEST OF THE YUCATAN PENINSULA NEAR
18N/19N ALONG 92W.

...THE ITCZ...

ITCZ 15N17W 15N21W...12N25W 13N40W...11N45W 10N49W 13N59W NEAR
BARBADOS. WIDELY SCATTERED MODERATE TO ISOLATED STRONG SHOWERS
AND THUNDERSTORMS FROM 7N TO 11N BETWEEN AFRICA AND 30W.
ISOLATED MODERATE SHOWERS AND THUNDERSTORMS FROM 7N TO 11N
BETWEEN 45W AND 55W.

...DISCUSSION...

THE GULF OF MEXICO...
PERSISTENT CUT-OFF LOW IS OVER THE SE UNITED STATES OVER
MISSISSIPPI...WITH A TROUGH SSW ACROSS LOUISIANA TO THE MEXICAN
COAST NEAR 23N98W. MOST OF THE CONVECTIVE PRECIPITATION ACTIVITY
FROM SIX HOURS IS NOT APPARENT NOW...BUT MAY RETURN GIVEN THE
ATMOSPHERIC INSTABILITY. THE 25N88W 21N94W SURFACE TROUGH FROM
THE 13/0000 UTC ANALYSIS HAS DISSIPATED...BEING REPLACE BY BROAD
ANTICYCLONIC WIND FLOW. NARROW MID/UPPER LEVEL RIDGE IS OVER THE
EASTERN GULF FROM THE YUCATAN PENINSULA TO THE FLORIDA BIG BEND.
UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE RIDGE HAS BEEN
ENHANCING DIURNAL CONVECTION OVER THE CENTRAL FLORIDA PENINSULA.
LITTLE SIGNIFICANT CHANGE IS LIKELY WITH THE BROAD LOW NEARLY
STATIONARY...ENHANCING DAILY TSTMS ALONG THE NRN GULF COAST.

THE CARIBBEAN SEA...
UPPER TROUGH EXTENDS FROM E CENTRAL CUBA THRU JAMAICA TO NEAR
13N79W...MOVING SLOWLY WESTWARD. ISOLATED TSTMS ARE OCCURRING
ALONG THE TROUGH AXIS AND FROM NORTHWESTERN HAITI TO JUST
NORTHWEST OF JAMAICA SOUTH OF CUBA. MIDDLE TO UPPER LEVEL RIDGE
IS ESTABLISHED IN THE EASTERN CARIBBEAN SEA...WITH AN
ANTICYCLONIC CIRCULATION NOTED OVER THE LEEWARD ISLANDS.
SOUITHERLY WIND FLOW BETWEEN THE RIDGE AND THE WESTERN CARIBBEAN
CYCLONIC CENTER IS PUSHING HIGH LEVEL MOISTURE NORTHWARD FROM
SOUTH AMERICA ACROSS THE CARIBBEAN SEA TO HISPANIOLA. UPPER
DIFFLUENCE ASSOCIATED WITH THE RIDGE AND ANTICYCLONE WAS
SUPPORTING SCATTERED TSTMS ASSOCIATED WITH TROPICAL WAVE OVER
THE ISLANDS YESTERDAY.

THE ATLANTIC OCEAN...
ONE WESTERN ATLANTIC OCEAN UPPER LEVEL CYCLONIC CIRCULATION
CENTERS IS IN THE NORTHERN BAHAMAS NEAR 25N77W...SOUTH OF
TROPICAL STORM IRENE. THIS CYCLONIC CENTER MARKS THE NORTHERN
EXTENT OF THE WESTERN CARIBBEAN SEA UPPER TROUGH. ANOTHER
CYCLONIC CENTER...SOUTHWEST OF T.S. IRENE...IS ROTATING
NORTHWARD OVER THE CIRCULATION OF IRENE NEAR 27N68W. SUBSIDENCE
WITH THE LOW NEAR 27N68W IS LIMITING SHOWER AND THUNDERSTORM
ACTIVITY AND OUTFLOW IN THE SOUTHERN QUADRANT OF IRENE...WITH
GENERAL SOUTHEASTERLY WIND FLOW ALOFT IN THE TROPICAL CYCLONE.
UPPER LEVEL RIDGE STRETCHES FROM ONE ANTICYCLONIC CIRCULATION
CENTER EAST OF BERMUDA TO THE LESSER ANTILLES ANTICYCLONE OVER
THE LESSER ANTILLES. A RATHER DEEP MID-OCEANIC TROUGH IS SETTING
UP IN THE CENTRAL ATLC FROM A LOW NEAR 32N43W SOUTH-SOUTHWESTWARD
TO 18N49W. THE TROUGH IS FORECAST TO REMAIN NEARLY STATIONARY
BUT DIG SOUTHWESTWARD TO 15N52W IN ABOUT 24 HOURS. THIS COULD
AFFECT THE FUTURE DEVELOPMENT OF THE SURFACE LOW NEAR 12.5N43W.
A 1018 MB SURFACE LOW PRESSURE CENTER IS NEAR 29N45W AND IT IS
DRIFTING SOUTHWESTWARD...SETTING OFF ISOLATED MODERATE SHOWERS
AND POSSIBLE THUNDERSTORMS FROM 27N TO 29N BETWEEN 39W AND 45W.
BROAD UPPER LEVEL CYCLONIC FLOW FROM A TROUGH COVERS THE FAR
NORTHERN PART OF THE EAST CENTRAL ATLANTIC OCEAN NORTH OF 28N
BETWEEN 25W AND 35W. MUCH OF THE EASTERN ATLANTIC OCEAN IS
DOMINATED BY HIGH PRESSURE ALOFT. ONE CENTER IS NEAR 19N33W AND
THE OTHER OVER W AFRICA NEAR 21N12W. BETWEEN THE TWO HIGHS...A
WEAK TROUGH/COL REGION EXTENDS FROM 24N23W TO 13N27W. THIS COL
REGION MARKS THE LEADING EDGE OF THE MOISTURE SURGE ASSOCIATED
WITH THE TROPICAL WAVE AND LOW PRES ALONG 22W/23W. A RIDGE WILL
BECOME ESTABLISHED EAST OF 30W AS THE HIGH NEAR 19N33W
WEAKENS...KEEPING EASTERLY FLOW AND LIGHT SHEAR ACROSS THE FAR
EASTERN ATLANTIC OCEAN. THE SHEAR WILL INCREASE GRADUALLY WEST
OF 30W IN ASSOCIATION WITH THE SOUTHERN PART OF THE MID-OCEANIC
TROUGH FROM 20N50W TO 15N52W.

$$
MT


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