[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202333
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI JUL 20 2012

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2245 UTC.

...TROPICAL WAVES...

TROPICAL WAVE APPEARS TO HAVE LEFT THE COAST OF AFRICA AND WILL
LIKELY BE ADDED TO THE 0000 UTC SURFACE ANALYSIS.

TROPICAL WAVE IS ALONG 18N49W TO 8N53W MOVING W NEAR 20 KT. WAVE
COINCIDES WITH THE MAXIMUM MOISTURE VALUES SEEN IN A BROAD SURGE
OF MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. A LARGE
AREA OF DUST TO THE N OF THE WAVE IS DAMPENING ANY DEEP
CONVECTION NEAR THE AXIS EXCEPT FOR A SMALL AREA OF ISOLATED
MODERATE CONVECTION W OF THE AXIS FROM 9N-11N BETWEEN 53W-56W.

TROPICAL WAVE IS MOVING THROUGH THE N CENTRAL CARIBBEAN ALONG
23N80W TO 14N75W MOVING W NEAR 20-25 KT. THE WAVE LIES ON THE W
SIDE OF A TILTED SURGE OF DEEP LAYER MOISTURE PRESENT IN TOTAL
PRECIPITABLE WATER IMAGERY...WHICH EXPLAINS THE TILT OF THE
WAVE. THE WAVE IS ALSO INTERACTING WITH A BROAD UPPER LEVEL LOW
OVER THE NW CARIBBEAN CENTERED S OF CUBA NEAR 20N82W. THE
COMBINATION OF THE WAVE AND DIFFLUENCE ALOFT AROUND THE UPPER
LOW IS SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION
FROM 16N-19N BETWEEN 75W-80W. SIMILAR ACTIVITY COVERS HISPANIOLA
FROM 18N-20N BETWEEN 67W-73W. LARGE CLUSTERS OF STRONG
CONVECTION ARE ALSO OVER CUBA FROM 20N-21N BETWEEN 76W-79W...AND
FROM 22N-23N BETWEEN 80W-86W. IT IS HARD TO SAY WHETHER THE
ACTIVITY IS MORE ASSOCIATED WITH THE UPPER LOW OR THE WAVE.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM A 1007 MB LOW OVER AFRICA NEAR
24N14W TO 11N22W 6N32W. THE ITCZ BEGINS AT 6N32W AND CONTINUES
ALONG 5N42W 8N51W. SCATTERED MODERATE CONVECTION IS FROM 8N-11N
BETWEEN 13W-23W.

...DISCUSSION...

GULF OF MEXICO...
DESPITE SURFACE RIDGING AROUND A 1021 MB SURFACE HIGH NEAR
26N94W...THE NRN GULF OF MEXICO IS IMPACTED BY AN AREA OF STRONG
SHOWERS/THUNDERSTORMS. THE STORMS ARE SUPPORTED BY AN UPPER
LEVEL SHORTWAVE TROUGH THAT PARALLELS THE NRN GULF COASTLINE.
THE TROUGH SUPPORTS A SURFACE TROUGH ALONG 31N89W TO 27N92W. THE
COMBINATION OF THE UPPER AND LOWER TROUGHS IS SUPPORTING A LARGE
AREA OF STRONG SHOWERS/THUNDERSTORMS FROM 28N-31N BETWEEN
89W-93W...COVERING MUCH OF SRN LOUISIANA. ISOLATED
SHOWERS/THUNDERSTORMS CONTINUE N OF 26N BETWEEN 84W-94W. THE
REMAINDER OF THE BASIN IS FAIRLY DRY SUPPORTED BY DRY AIR ALOFT
WRAPPING AROUND AN UPPER LEVEL RIDGE COVERING THE MAJORITY OF
THE BASIN. HOWEVER...AN UPPER LEVEL LOW OVER SRN MEXICO NEAR
18N94W...AND A BROAD UPPER LOW OVER THE NW CARIBBEAN ARE
SUPPORTING STRONG SHOWERS/THUNDERSTORMS ACROSS THE YUCATAN
PENINSULA AND CUBA WITH ISOLATED SHOWERS/THUNDERSTORMS ACROSS
THE SE GULF AND EXTREME SW GULF. LIGHT ANTI-CYCLONIC SURFACE
WINDS AROUND THE SURFACE HIGH...EXCEPT NEAR THE THUNDERSTORMS IN
THE NRN GULF WHERE WIND SPEEDS WILL BE HIGHER. SURFACE RIDGING
WILL REMAIN ACROSS THE BASIN WITH A WEAK SURFACE TROUGH ALONG
THE NRN GULF. SHOWERS/THUNDERSTORMS WILL REMAIN ACROSS THE NRN
GULF...AND WILL LIKELY INCREASE OVER THE SRN GULF AS MOISTURE
ASSOCIATED WITH A TROPICAL WAVE IN THE CARIBBEAN APPROACHES THE
GULF.

CARIBBEAN SEA...
TWO UPPER LEVEL LOWS CENTERED OVER SRN MEXICO AND THE NW
CARIBBEAN NEAR 18N94W AND 20N82W RESPECTIVELY ARE HELPING
PRODUCE CLUSTERS OF STRONG SHOWERS/THUNDERSTORMS ACROSS THE
YUCATAN PENINSULA...CUBA...AND HISPANIOLA. SOME OF THE STORMS
ARE ALSO ENHANCED BY A TROPICAL WAVE EXTENDING FROM CENTRAL CUBA
INTO THE CENTRAL CARIBBEAN. SEE TROPICAL WAVE SECTION ABOVE FOR
MORE DETAILS. A FEW ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO
ACROSS THE YUCATAN CHANNEL AND JAMAICA. STRONG
SHOWERS/THUNDERSTORMS COVER PORTIONS OF COSTA RICA AND PANAMA
ASSOCIATED WITH THE E PACIFIC MONSOON TROUGH THAT EXTENDS
THROUGH BOTH COUNTRIES TO A 1008 MB LOW OVER NRN COLOMBIA. THE
REMAINDER OF THE BASIN IS EXPERIENCING MOSTLY FAIR WEATHER DUE
TO DRY AIR ALOFT ACROSS THE S CENTRAL CARIBBEAN AND AROUND AN
UPPER LEVEL RIDGE COVERING THE ERN CARIBBEAN. A FEW ISOLATED
SHOWERS/THUNDERSTORMS ARE NOTED OVER THE NRN LESSER ANTILLES DUE
TO SOME MOISTURE DRAGGED AHEAD OF THE NEXT TROPICAL WAVE STILL
IN THE ERN ATLC. SOME DUST IS STILL PRESENT ACROSS MUCH OF THE
BASIN EVIDENT IN SATELLITE IMAGERY AND SURFACE OBSERVATIONS.
EXPECT MOIST CONDITIONS TO REMAIN OVER THE NRN CARIBBEAN AS THE
TROPICAL WAVE MOVES WWD. DUSTY CONDITIONS WILL TRAIL BEHIND THE
WAVE.

ATLANTIC OCEAN...
FAIR CONDITIONS ARE ACROSS THE WRN AND CENTRAL ATLC DUE TO DRY
AIR ALOFT AROUND A PAIR OF UPPER LEVEL RIDGES CENTERED NEAR
36N67W AND 25N57W THAT SUPPORT A SURFACE RIDGE ANCHORED BY A
1027 MB HIGH NEAR 32N48W. A FEW SHOWERS/THUNDERSTORMS ACROSS
HISPANIOLA ARE MOVING TO THE N NEAR THE SE BAHAMAS. THE SAME
HIGH CENTER ALONG WITH A 1024 MB AZORES HIGH ARE PROVIDING THE
ERN ATLC WITH FAIR WEATHER AS WELL. THE AZORES HIGH IS SUPPORTED
BY ANOTHER UPPER LEVEL RIDGE CENTERED NEAR 41N31W. AN UPPER HIGH
ALSO COVERS THE ERN TRPCL ATLC CENTERED NEAR THE CAPE VERDE
ISLANDS. AN UPPER LEVEL TROUGH IS ALONG 42W SANDWICHED BETWEEN
THE RIDGE OVER THE CENTRAL ATLC AND THE CAPE VERDE RIDGE...BUT
IS NOT CAUSING ANY SIGNIFICANT WEATHER. SATELLITE IMAGERY
CONTINUES TO SHOW A LARGE AREA OF AFRICAN DUST EXTENDING ALL THE
WAY FROM THE COAST OF AFRICA TO N OF THE CENTRAL
CARIBBEAN...WHICH IS FURTHER SUPPORTING THE FAIR SURFACE
CONDITIONS.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
WALTON





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