[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 150513
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED JUL 15 2009

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0445 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 23W S OF 15N MOVING W NEAR 15 KT.
SATELLITE IMAGERY DEPICTS MID-LEVEL CYCLONIC CIRCULATION NEAR
THIS WAVE. SCATTERED MODERATE TO STRONG CONVECTION IS FROM
7N-12N BETWEEN 22W-29W.

A TROPICAL WAVE IS ALONG 40W S OF 18N MOVING W 15-20 KT. THIS
WAVE COINCIDES WITH A LOW AMPLITUDE MAXIMUM IN DEEP LAYER
MOISTURE BASED ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. SCATTERED MODERATE CONVECTION IS FROM 12N-15N BETWEEN
36W-40W.

A HIGHLY-AMPLIFIED TROPICAL WAVE IS OVER THE N TROPICAL ATLC AND
E CARIBBEAN...AND EXTENDS FROM 24N63W TO 13N63W TO 7N60W MOVING
W NEAR 20 KT. UPPER AIR DATA FROM BARBADOS AND GUADELOUPE AT
15/0000 UTC INDICATE THAT THE WAVE IS FOLLOWED BY A STRONG
EASTERLY 700-650 MB JET...WITH CORE WINDS OF 45 KT. RECENT
SATELLITE IMAGERY SHOW A WELL-DEFINED AND HIGHLY-AMPLIFIED
INVERTED-V PATTERN EVIDENT IN THE COVERAGE OF LOW-LEVEL CLOUDS
NEAR THE WAVE...COINCIDING WITH A MAXIMUM IN TOTAL PRECIPITABLE
WATER. THE WAVE IS LEADING AN AREA OF ABUNDANT DRY LOW/MID-LEVEL
SAHARAN AIR. THIS IS CONTRIBUTING TO A DENSITY DIFFERENCE
SUFFICIENT TO PROVIDE LOW LEVEL ATMOSPHERIC LIFT SUPPORTING
SCATTERED SCATTERED SHOWERS WITHIN 90 NM EITHER E OF THE WAVE
AXIS N OF 14N...WITH SCATTERED SHOWERS AND THUNDERSTORMS WITHIN
90 NM E OF THE WAVE AXIS S OF 14N WHERE A WEAK UPPER LEVEL
SHORTWAVE TROUGH IS PROVIDING ADDITIONAL SUPPORT FOR CONVECTION.
THIS DRY AIR IS LIMITING THE AREAL COVERAGE OF DEEP CONVECTION
NEAR THE WAVE. THE AFOREMENTIONED DRY AIR IS LIKELY CONTRIBUTING
TO STRONG DOWNDRAFTS AND GUSTY OUTFLOW WINDS WITH THE SHOWER AND
THUNDERSTORM ACTIVITY.

THE TROPICAL WAVE PREVIOUSLY ALONG 97W/98W S OF MEXICO AT
14/1800 UTC IS NOW IN THE E PACIFIC REGION AND IS FURTHER
DISCUSSED IN THE TROPICAL WEATHER DISCUSSION FOR THE E PACIFIC
FOUND UNDER AWIPS/WMO HEADERS MIATWDEP/AXPZ20 KNHC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 10N14W 9N29W 9N41W 9N53W 10N62W.
NUMEROUS MODERATE TO STRONG CONVECTION IS FROM 6N-15N E OF 21W.
SCATTERED MODERATE CONVECTION IS FROM 8N-10N BETWEEN 52W-55W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE EXTENDS SOUTHEASTWARD INTO THE GULF OF
MEXICO FROM THE SOUTHERN UNITED STATES AND IS ASSOCIATED WITH A
SURFACE RIDGE ACROSS THE N GULF AND A 1018 MB SURFACE HIGH NEAR
28N89W. GENERALLY FAIR WEATHER IS PRESENT ACROSS THE GULF. ONE
EXCEPTION IS OVER THE N CENTRAL GULF...WHERE SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS ARE PRESENT N OF 27N BETWEEN 86W-91W.
THIS ACTIVITY IS BEING SUPPORTED BY ATMOSPHERIC LIFT ASSOCIATED
WITH A WEAK UPPER LEVEL SHORTWAVE TROUGH TRANSLATING
SOUTHEASTWARD ON THE OUTER PERIPHERY OF THE AFOREMENTIONED UPPER
RIDGE. WINDS ARE LIGHT AND VARIABLE IN THE VICINITY OF THE
SURFACE RIDGE ACROSS THE N GULF...WITH ANTICYCLONIC FLOW AROUND
THE RIDGE SUPPORTING A BROAD SWATH OF E WINDS OF 10-15 KT ACROSS
THE S HALF OF THE GULF. NE WINDS UP TO 20 KT ARE OCCURRING NEAR
THE COAST OF THE YUCATAN PENINSULA...AND THESE WINDS WILL OCCUR
DURING THE LATE AFTERNOON AND EVENING HOURS DURING THE NEXT
SEVERAL DAYS NEAR THE COAST OF THE YUCATAN PENINSULA. LITTLE
CHANGE IS EXPECTED OVER THE NEXT DAY OR TWO AS BOTH THE UPPER
AND SFC RIDGE REMAIN IN PLACE.

CARIBBEAN SEA...
FRESH TO STRONG TRADE WINDS ARE OCCURRING BETWEEN THE
SUBTROPICAL RIDGE OVER THE CENTRAL ATLC AND A BROAD TROUGH OVER
NORTHERN SOUTH AMERICA...WITH THE STRONGEST FLOW NEAR THE COAST
OF COLOMBIA. THE QUIKSCAT PASS AROUND 14/2315 UTC INDICATED A
LARGE AREA OF NE TO E WINDS OF 20 TO 30 KT ACROSS THE CENTRAL
CARIBBEAN. THESE WINDS WILL REMAIN STRONG OVER THE NEXT SEVERAL
DAYS AS THE SUBTROPICAL RIDGE REMAINS IN PLACE AND A TROPICAL
WAVE MOVES ACROSS THE AREA. IN FACT...GALE CONDITIONS ARE
FORECAST TO BEGIN LATER TODAY THROUGH THE END OF THE WEEK...AS
THE LOW LEVEL FLOW STRENGTHENS ACROSS THE CARIBBEAN AND
INTERACTS THE LOCAL TOPOGRAPHICAL VARIATIONS NEAR THE COAST OF
COLOMBIA. ALOFT...INSTABILITY ASSOCIATED WITH AN UPPER LEVEL LOW
OVER THE N CENTRAL CARIBBEAN CENTERED NEAR 18N82W IS RESULTING
IN SCATTERED SHOWERS AND THUNDERSTORMS FROM 15N-20N BETWEEN
80W-85W. THE TROPICAL WAVE MOVING ACROSS THE E CARIBBEAN IS
ACCOMPANIED BY...AND FOLLOWED BY...STRONGER WINDS AND A STRONG
SURGE OF SAHARAN AIR.

ATLANTIC OCEAN...
DEEP LAYER MOISTURE IS COMBINING WITH UPPER LEVEL DIFFLUENCE IN
NORTHWESTERLY FLOW ALOFT TO RESULT IN SCATTERED SHOWERS AND
THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 29N W OF 74W.
ALSO...SCATTERED SHOWERS AND ISOLATED TSTMS ARE N OF 24N BETWEEN
65W-72W. THIS ACTIVITY IS BEING SUPPORTED BY LOW LEVEL
CONVERGENCE NEAR A SURFACE TROUGH EXTENDING FROM 28N68W TO
26N71W TO 22N73W. THIS ACTIVITY IS ALSO SUPPORTED BY ATMOSPHERIC
INSTABILITY ASSOCIATED WITH AN UPPER TROUGH OVER THE SW NORTH
ATLC. SUBSIDENCE AND GENERALLY FAIR WEATHER ARE PRESENT ACROSS
MUCH OF THE CENTRAL AND E ATLC AROUND A BROAD SURFACE RIDGE WITH
A 1031 MB HIGH NEAR 35N46W. ACROSS THE TROPICAL N ATLC...
NORTHEASTERLY UPPER LEVEL FLOW IS IN PLACE...WITH STRONG UPPER
LEVEL DIFFLUENCE SUPPORTING THE CONVECTION ASSOCIATED WITH THE
TROPICAL WAVE ALONG 40W S OF 18N.

$$
COHEN







This weather bulletin was brought to you by:
www.nashvilleweather.net