[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 312336
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE JUL 31 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
2300 UTC.

...SPECIAL FEATURES...

A TROPICAL WAVE IS ALONG 16N40W TO A 1010 MB SURFACE LOW AT
10N41W. THE WAVE/LOW IS MOVING W AT ABOUT 10-15 KT. THE WAVE IS
FAIRLY LOW AMPLITUDE ALIGNING WITH AN EQUALLY LOW AMPLITUDE
SURGE IN TOTAL PRECIPITABLE WATER. HOWEVER...AN ANALYSIS OF THE
SAHARAN AIR LAYER CONTINUES TO SHOW A CLEARING IN THE WIDESPREAD
DUST NEAR THE WAVE AXIS INDICATING ITS PRESENCE. CONVECTION HAS
INCREASED AROUND THE LOW CENTER FROM 24 HOURS AGO. CURRENTLY
SCATTERED MODERATE/STRONG CONVECTION IS MAINLY W OF THE SYSTEM
FROM 7N-11N BETWEEN 41W-46W. ENVIRONMENTAL CONDITIONS ARE
CONDUCIVE FOR SLOW DEVELOPMENT OF THIS SYSTEM.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 17N21W TO A 1010 MB SURFACE LOW EMBEDDED
IN THE MONSOON TROUGH AT 12N23W. THE WAVE/LOW IS MOVING W AT
10-15 KT. A CLEARING IN THE WIDESPREAD DUST TO THE N OF THE WAVE
INDICATES THE PRESENCE OF THE WAVE. THERE IS ALSO A SMALL
NORTHWARD SURGE IN THE DEEP LAYER MOISTURE INDICATED BY TOTAL
PRECIPITABLE WATER IMAGERY. NO DEEP CONVECTION IS CURRENTLY
ASSOCIATED WITH THE WAVE.

TROPICAL WAVE NEAR 40/41 W IS DESCRIBED IN THE SPECIAL FEATURES
SECTION ABOVE.

ACTIVE TROPICAL WAVE IS PUSHING INTO THE CENTRAL CARIBBEAN FROM
23N70W TO 10N72W MOVING W NEAR 15 KT. TOTAL PRECIPITABLE WATER
IMAGERY INDICATES THAT THE WAVE LIES ON THE W SIDE OF A LARGE
SURGE OF DEEP LAYER MOISTURE THAT COVERS THE EASTERN CARIBBEAN.
THE WAVE LIES UNDERNEATH AN AREA OF DIFFLUENCE ALOFT THAT IS
HELPING ENHANCE CONVECTION. CURRENTLY SCATTERED MODERATE
CONVECTION IS FROM 15N-23N BETWEEN 62W-72W...EXCEPT FOR TWO
LARGE CLUSTERS OF STRONG CONVECTION FROM 15N-18N BETWEEN
66W-68W...AND FROM 16N-18N BETWEEN 69W-71W.

TROPICAL WAVE IS MOVING ACROSS GUATEMALA INTO THE E PACIFIC
BASIN FROM 17N89W TO 10N90W. THE WAVE IS HELPING PRODUCE
SCATTERED SHOWERS/THUNDERSTORMS ACROSS NORTHERN GUATEMALA AND
PORTIONS OF THE YUCATAN PENINSULA. SEE TWDEP FOR MORE DETAILS ON
THE WAVE IN THE E PACIFIC.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
MAURITANIA AT 19N16W OVER ATLC WATERS TO A 1010 MB LOW NEAR
12N23W TO 8N31W TO A SECOND 1010 MB SURFACE LOW AT 10N41W TO
8N52W. THE ITCZ BEGINS AT 8N48W TO 8N59W. THE TWO SURFACE LOWS
ARE CONNECTED TO TROPICAL WAVES. SEE TROPICAL WAVE SECTION
ABOVE. SCATTERED MODERATE CONVECTION IS FROM 5N-10N BETWEEN
27W-29W. SCATTERED MODERATE/STRONG CONVECTION IS FROM 8N-11N
BETWEEN 50W-59W.

...DISCUSSION...

GULF OF MEXICO...
SCATTERED SHOWERS/THUNDERSTORMS COVER MUCH OF THE NE GULF AND
THE FLORIDA PENINSULA ASSOCIATED WITH AN UPPER LEVEL TROUGH
EXTENDING JUST OFF THE EASTERN SEABOARD. THE UPPER TROUGH
SUPPORTS A SURFACE TROUGH ALONG 31N81W TO 27N84W. THE MOST
CONCENTRATED SHOWERS/THUNDERSTORMS ARE W OF THE TROUGH FROM
25N-28N BETWEEN 85W-90W. SIMILAR ACTIVITY IS FOUND OVER S OF THE
TROUGH OVER FLORIDA. ISOLATED SHOWERS ARE ACROSS THE REMAINDER
OF THE NE GULF. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO OVER
THE YUCATAN PENINSULA TIED TO A TROPICAL WAVE TO THE S ALONG
WITH TYPICAL DAYTIME HEATING. THE WESTERN AND SOUTHERN GULF ARE
MOSTLY DRY DUE TO DRY AIR ALOFT AROUND THE W SIDE OF AN UPPER
LEVEL LOW OVER CUBA...AND AN UPPER LEVEL RIDGE COVERING MUCH OF
THE NORTHERN GULF CENTERED OVER NORTHERN TEXAS. THE UPPER RIDGE
ALSO SUPPORTS A WEAK SURFACE RIDGE AROUND A 1019 MB HIGH NEAR
26N93W. LIGHT ANTI-CYCLONIC FLOW IS AROUND THE HIGH CENTER.
EXPECT LITTLE CHANGE OVER THE NEXT 24 HOURS.

CARIBBEAN SEA...
AN ACTIVE TROPICAL WAVE IS BRINGING THE NE CARIBBEAN
SHOWERS/THUNDERSTORMS COVERING MUCH OF HISPANIOLA AND PUERTO
RICO. THE REMAINDER OF THE BASIN IS FAIRLY DRY BESIDES A FEW
AFTERNOON STORMS OVER CUBA AND CENTRAL AMERICA. A LARGER CLUSTER
OF SHOWERS IS JUST OFFSHORE OF COSTA RICA DUE TO DIFFLUENCE FLOW
ALOFT BETWEEN EASTERLY FLOW ALOFT OVER THE E PACIFIC AND
NORTHERLY FLOW AROUND AN UPPER LEVEL RIDGE OVER THE CENTRAL
CARIBBEAN. A DRY UPPER LEVEL LOW IS COVERED OVER WESTERN CUBA
AND MAY BE CONTRIBUTING TO THE SHOWERS ACROSS THE ISLAND. EXPECT
THE WAVE TO CONTINUE TO MOVE WESTWARD DRAWING MOISTURE BEHIND IT.

ATLANTIC OCEAN...
A FEW SHOWERS/THUNDERSTORMS ARE OFFSHORE OF FLORIDA ASSOCIATED
WITH AN UPPER LEVEL TROUGH N OF THE DISCUSSION AREA...WHICH IS
SUPPORTING A SURFACE TROUGH ACROSS NORTHERN FLORIDA. A SMALL
AREA OF SHOWERS/THUNDERSTORMS IS ALSO FROM 28N-30N BETWEEN
73W-74W...SUPPORTED BY DIFFLUENCE ALOFT BETWEEN AN UPPER LEVEL
LOW CENTERED OVER CUBA AND AN UPPER LEVEL LOW CENTERED NEAR
31N66W. UPPER LEVEL RIDGING IS TO THE S...N OF THE EASTERN
CARIBBEAN. IT IS DRAWING MOISTURE INTO THE ATLC ALONG WITH
SHOWERS AND POSSIBLE THUNDERSTORMS ASSOCIATED WITH A TROPICAL
WAVE IN THE CENTRAL CARIBBEAN. THE UPPER RIDGE ALSO SUPPORTS A
WEAK SURFACE RIDGE AROUND A 1023 MB HIGH NEAR 32N61W. A THIRD
UPPER LEVEL LOW IS CENTERED NEAR 27N44W SUPPORTING A WEAK
SURFACE TROUGH ALONG 35N46W TO 27N52W. POSSIBLE ISOLATED SHOWERS
ARE NEAR THE TROUGH AXIS. THE REMAINDER OF THE EASTERN ATLC IS
COVERED BY SURFACE RIDGING AROUND A 1024 MB HIGH NEAR 34N37W.
THE RIDGE IS SUPPORTED BY AN UPPER LEVEL RIDGE TO THE N...AS
WELL AS AN UPPER LEVEL RIDGE COVERING THE TROPICAL ATLC.
SATELLITE IMAGERY CONTINUES TO SHOW A LARGE AREA OF SAHARAN DUST
THAT EXTENDS FROM THE COAST OF AFRICA TO NEAR 60W...WHICH
FURTHER SUPPORTS FAIR WEATHER.

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

$$
WALTON




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