[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 192334
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN JUL 19 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2245 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 41W/42W S OF 19N MOVG W NEAR 20 KT.
THIS WAVE COINCIDES WITH A DEEP LAYER MOISTURE MAXIMUM OBSERVED
IN TOTAL PRECIPITABLE WATER IMAGERY. THIS WAVE IS JUST W OF A
DRY SAHARAN AIR LAYER. DUE TO THE PRESENCE OF THIS DRY AIR...NO
DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE WAVE.

A TROPICAL WAVE IS ALONG 52W S OF 18N MOVG W NEAR 15 KT. THIS
WAVE COINCIDES WITH A LOW TO MIDDLE LEVEL CYCLONIC CIRCULATION
NEAR THE WAVE AXIS AT 13N. SCATTERED MODERATE CONVECTION IS FROM
12N-15N BETWEEN 51W-54W.

A HIGH AMPLITUDE TROPICAL WAVE IS ALONG 71W S OF 26N MOVG W
20-25 KT. THIS WAVE COINCIDES WITH A HIGH AMPLITUDE MOISTURE
MAXIMUM OBSERVED ON TOTAL PRECIPITABLE WATER IMAGERY. AN
INVERTED-V PATTERN OF LOW CLOUDS IS ALSO EVIDENT ON VISIBLE
SATELLITE IMAGERY. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS FROM 16N-20N BETWEEN 69W-72W INCLUDING PORTIONS OF CUBA. THIS
WAVE MAY FRACTURE OVER THE NEXT DAY WITH THE N PORTION OF THE
WAVE FORMING A TROUGH THAT WILL CONTINUE TO THE NW...WHILE THE S
PORTION OF THE WAVE CONTINUES TO PROPAGATE WWD.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 12N15W 7N27W 10N40W 10N51W 9N62W.
SCATTERED MODERATE CONVECTION IS FROM 9N-13N BETWEEN 13W-17W. A
CLUSTER OF NUMEROUS MODERATE/SCATTERED STRONG CONVECTION IS FROM
5N-9N BETWEEN 26W-29W. SCATTERED MODERATE CONVECTION IS FROM
7N-14N BETWEEN 60W-64W.

...DISCUSSION...

THE GULF OF MEXICO...
A STATIONARY FRONT IS OVER THE NRN GULF OF MEXICO ALONG 31N81W
28N88W 29N96W. AN UPPER LEVEL TROUGH EXTENDING DOWN THE ERN
CONUS INTO THE GULF TO NEAR 26N90W SUPPORTS THE FRONT. SURFACE
CONVERGENCE AHEAD OF THE FRONT ALONG WITH UPPER LEVEL DIFFLUENCE
ARE SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 24N-29N E OF
96W. THE REMAINDER OF THE GULF IS UNDER A BROAD SURFACE RIDGE
ANCHORED BY A 1020 MB SURFACE HIGH NEAR 26N87W BRINGING
GENERALLY FAIR WEATHER S OF 24N. A MID-LEVEL DRY SAHARAN AIR
LAYER IS ACROSS THE SRN GULF OF MEXICO SUPPORTING THE NOTED FAIR
WEATHER. LIGHT ANTICYCLONIC FLOW IS AROUND THE SURFACE RIDGE
WITH E-SE WINDS UP TO 15 KT PRESENT ACROSS THE SRN GULF...EXCEPT
FOR A SMALL PORTION OF NE WINDS UP TO 20 KT NEAR THE YUCATAN
PENINSULA COAST. EXPECT THE FRONT TO STALL TONIGHT AND BECOME
DIFFUSE TOMORROW.

THE CARIBBEAN SEA...
FAIR WEATHER IS NOTED IN THE FAR NW PORTION OF THE CARIBBEAN AS
IT IS UNDER THE INFLUENCE OF A MID-LEVEL DRY SAHARAN AIR LAYER.
HOWEVER...ATMOSPHERIC INSTABILITY IS CAUSING A FEW ISOLATED
SHOWERS TO FLARE UP OVER CUBA AND THE YUCATAN PENINSULA. AN
UPPER LEVEL RIDGE DOMINATES THE MAJORITY OF THE CARIBBEAN
CENTERED NEAR 14N75W. UPPER LEVEL DIFFLUENCE AND THE PROXIMITY
OF THE E PACIFIC ITCZ ARE SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS OVER CENTRAL AMERICA S OF 14N W OF 80W
INCLUDING PORTIONS OF NICARAGUA...COSTA RICA...AND PANAMA.
SURFACE CONVERGENCE AROUND A 1008 MB SURFACE LOW OVER COLUMBIA
NEAR 8N76W IS SUPPORTING SCATTERED SHOWER/THUNDERSTORMS S OF 10N
BETWEEN 75W-78W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER LEVEL
RIDGE OVER THE CARIBBEAN AND AN UPPER LEVEL LOW IN THE ATLC NEAR
27N55W IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS OVER THE
ERN CARIBBEAN N OF 14N BETWEEN 63W-69W. THIS SHOWER ACTIVITY IS
PROBABLY BEING ENHANCED BY THE TROPICAL WAVE ALONG 71W.
SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO AFFECTING THE SRN
LESSER ANTILLES S OF 14N W OF 62W DUE TO UPPER LEVEL DIFFLUENCE
AND THE PROXIMITY OF THE ATLC ITCZ. EXPECT A SECOND TROPICAL
WAVE TO REACH THE ERN CARIBBEAN EARLY TUE.

THE ATLANTIC OCEAN...
SCATTERED SHOWERS/THUNDERSTORMS ARE ACROSS S FLORIDA ENTERING
THE ATLC AND APPROACHING THE BAHAMAS FROM 25N-29N W OF 79W. THIS
SHOWER ACTIVITY IS SUPPORTED BY A SMALL UPPER LEVEL LOW OVER THE
BAHAMAS NEAR 25N77W. UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER
LEVEL TROUGH OVER THE ERN CONUS AND AN UPPER LEVEL RIDGE
CENTERED AROUND 39N54W IS SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS ACROSS THE SW NORTH ATLC N OF 24N BETWEEN
68W-75W. THE REMAINDER OF THE ATLC IS DOMINATED BY A BROAD RIDGE
ANCHORED BY A 1029 MB SURFACE HIGH N OF THE DISCUSSION AREA NEAR
35N46W BRINGING GENERALLY FAIR WEATHER ACROSS THE MAJORITY OF
THE CENTRAL AND ERN ATLC. HOWEVER...A LINE OF SHOWERS ARE FROM
17N58W TO 24N50W DUE TO UPPER LEVEL DIFFLUENCE BETWEEN AN UPPER
LEVEL HIGH NEAR 15N50W AND AN UPPER LEVEL LOW NEAR 27N55W.

$$
WALTON






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