[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 182345
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON JUN 18 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
2315 UTC.

...SPECIAL FEATURES...

AN UPPER LEVEL TROUGH OVER THE W ATLC ALONG 65W SUPPORTS A 1004
MB OCCLUDED SURFACE LOW CENTERED NEAR 38N61W. THE LOW IS
GENERATING GALE FORCE WINDS...BUT LACKS MUCH CONVECTION NEAR THE
LOW CENTER. IT WOULD ONLY TAKE A SLIGHT INCREASE IN CONVECTION
NEAR THE CENTER FOR A TROPICAL CYCLONE OR SUBTROPICAL CYCLONE TO
FORM. THERE IS A HIGH CHANCE OF FORMATION IN TO A TROPICAL OR
SUBTROPICAL CYCLONE DURING THE NEXT 48 HOURS.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 13N40W TO 5N42W MOVING W AT 15-20 KT. THE
WAVE IS LOW-AMPLITUDE AND ALIGNS WITH A EQUALLY LOW-AMPLITUDE
SURGE IN DEEP LAYER MOISTURE. THERE IS ALSO A CLEARING IN AN
AREA OF AFRICAN DUST TO THE N AND E OF THE WAVE INDICATING ITS
PRESENCE. DUE TO THE ABUNDANCE OF DRY AIR SURROUNDING THE WAVE
TO THE N AND E...ONLY AN AREA OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS W OF THE AXIS FROM 7N-11N BETWEEN 43W-50W.

TROPICAL WAVE IS ALONG 13N55W TO 4N57W MOVING W NEAR 15-20 KT.
THE WAVE LIES ON THE WRN LEADING EDGE OF A SURGE IN DEEP LAYER
MOISTURE PRESENT IN TOTAL PRECIPITABLE WATER IMAGERY. THE WAVE
ALSO LIES UNDERNEATH A DRY UPPER LEVEL TROUGH. THE UPPER TROUGH
IS LIKELY DRAWING ENERGY TO THE N...WHICH IS WHY THERE IS AN
ELONGATION IN THE DEEP LAYER MOISTURE FIELD. CURRENTLY ONLY A
SMALL AREA OF MODERATE CONVECTION IS FROM 7N-8N BETWEEN
53W-56W...AND FROM 5N-6N BETWEEN 55W-58W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS W AFRICA TO THE COAST OF
SENEGAL AT 15N17W TO 8N26W. THE ITCZ CONTINUES AT 8N26W ALONG
7N41W 4N55W. CONVECTION ALONG THE AXIS IS LIMITED DUE TO A LARGE
AREA OF SAHARAN DUST EXTENDING FROM THE COAST OF AFRICA TO THE
ERN MOST TROPICAL WAVE. ONLY A SMALL AREA OF MODERATE CONVECTION
IS NOTED FROM 6N-7N BETWEEN 21W-24W.

...DISCUSSION...

GULF OF MEXICO...
SURFACE RIDGING IS ACROSS THE GULF OF MEXICO TODAY AROUND A 1020
MB HIGH OVER GEORGIA. SE-S WINDS OF 10-15 KTS ARE PRESENT AROUND
THE RIDGE. HOWEVER...AN UPPER LEVEL LOW OVER OVER SRN TEXAS NEAR
27N98W IS CAUSING SHOWER/THUNDERSTORM ACTIVITY ACROSS THE NW
GULF. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 26N W OF
90W. AN UPPER TROUGH AXIS EXTENDS FROM THE UPPER LOW CENTER TO
THE NRN TIP OF THE YUCATAN PENINSULA. THE TROUGH IS HELPING
SUPPORT SCATTERED SHOWERS FROM 23N-26N BETWEEN 87W-91W...AS WELL
AS SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE NRN YUCATAN
PENINSULA. SURFACE RIDGING WILL REMAIN ACROSS MOST OF THE BASIN
FOR THE NEXT 24 HOURS...BUT A LARGE AREA OF BROAD LOW PRESSURE
IN THE NW CARIBBEAN IS EXPECTED TO DRIFT INTO THE SE GULF
BEGINNING LATE TOMORROW. THIS WILL MEAN MOIST CONDITIONS ACROSS
MUCH OF THE SE GULF.

CARIBBEAN SEA...
BROAD CYCLONIC SURFACE FLOW ALONG WITH A LARGE AREA OF
SHOWERS/THUNDERSTORMS COVER PORTIONS OF THE CENTRAL AND WRN
CARIBBEAN. CURRENTLY A LARGE CLUSTER OF STRONG
SHOWERS/THUNDERSTORMS IS S OF HISPANIOLA FROM 16N-19N BETWEEN
72W-76W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ALSO COVER THE
AREA N OF 15N BETWEEN 70W-87W. SHOWERS/THUNDERSTORMS ARE ALSO
OVER ERN HISPANIOLA. A SURFACE TROUGH EXTENDS FROM CUBA NEAR
21N77W TO A 1009 MB LOW NEAR 16N83W WHICH DEPICTS THE AXIS OF
THE CYCLONIC FLOW. A PORTION OF THE MONSOON TROUGH ALSO EXTENDS
FROM THE LOW CENTER WWD ACROSS NRN CENTRAL AMERICA INTO SRN
MEXICO. THIS IS HELPING SUPPORT SCATTERED SHOWERS/THUNDERSTORMS
ACROSS THESE AREAS. ALOFT...MOIST SWLY FLOW COVERS THE WRN AND
CENTRAL CARIBBEAN BETWEEN AN UPPER LEVEL TROUGH OVER THE WRN
GULF OF MEXICO AND AN UPPER LEVEL RIDGE OVER THE ERN CARIBBEAN
EXTENDING INTO THE CENTRAL ATLC. DRY AIR ALOFT IS WRAPPING
AROUND THE E SIDE OF THE UPPER RIDGE PROVIDING FAIR CONDITIONS
ACROSS THE ERN CARIBBEAN. THE BROAD AREA OF LOW PRESSURE ACROSS
THE WRN CARIBBEAN IS EXPECTED TO GRADUALLY DRIFT NW OVER THE
NEXT SEVERAL DAYS. THIS WILL CONTINUE TO BRING THE NW CARIBBEAN
RAIN AND THUNDERSTORMS. FLOODING AND MUDSLIDES ARE POSSIBLE IN
PORTIONS OF THE NRN CENTRAL AMERICA...CUBA...AND HISPANIOLA IN
AREAS THAT HAVE ALREADY RECEIVED HEAVY RAINFALL.

ATLANTIC OCEAN...
A WEAK UPPER LEVEL RIDGE IS OVER THE FLORIDA PENINSULA AND FAR
WRN ATLC SUPPORTING A SURFACE RIDGE AROUND A 1020 MB HIGH OVER
GEORGIA PROVIDING FAIR CONDITIONS ACROSS THE FAR W ATLC. AN
UPPER LEVEL TROUGH IS TO THE E ALONG 65W. THE UPPER TROUGH
SUPPORTS A 1004 MB LOW TO THE N OF THE AREA NEAR 38N61W. SEE
SPECIAL FEATURES ABOVE FOR MORE DETAILS. A SURFACE TROUGH IS
ALSO SUPPORTED BY THE UPPER TROUGH EXTENDING FROM 31N62W TO THE
SE BAHAMAS AT 21N73W. A LARGE CLUSTER OF SHOWERS/THUNDERSTORMS
IS E OF THE AXIS FROM 22N-24N BETWEEN 68W-72W. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS EXTEND UP TO 500 NM E OF THE
TROUGH AXIS ELSEWHERE IN THE AREA OF LARGEST DIFFLUENCE ALOFT.
AN UPPER LEVEL RIDGE EXTENDS FROM THE NE CARIBBEAN TO THE
CENTRAL ATLC ALONG 52W SUPPORTING A 1027 MB HIGH NEAR 29N44W
WHICH IS PROVIDING FAIR CONDITIONS ACROSS THE REMAINDER OF THE
BASIN. A SECOND UPPER RIDGE ALSO COVER THE TROPICAL ATLC
CENTERED OVER W AFRICA NEAR 18N11W. THE LAST VISIBLE SATELLITE
IMAGES OF THE DAY ALONG WITH GOES-R IMAGERY ENHANCEMENTS
INDICATE THAT A LARGE AREA OF SAHARAN DUST EXTENDS FROM THE
COAST OF AFRICA TO NEAR 50W WITH CLEARING AROUND THE TROPICAL
WAVE.

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

$$
WALTON





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