Tropical Weather Discussion
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000
AXNT20 KNHC 270001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI JUN 26 2015

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
2345 UTC.

...SPECIAL FEATURES...

...GALE WARNING IN THE CARIBBEAN SEA...
A GALE WARNING FOR MINIMAL GALE FORCE WINDS REMAINS IN EFFECT
FOR THE SW CARIBBEAN FROM 11N-15N BETWEEN 71W-77W THROUGH THIS
EVENING THEN REDUCING TO AN AREA ALONG THE COAST OF COLOMBIA
THROUGH SAT AFTERNOON AT WHICH TIME THEY ARE FORECAST TO
DIMINISH TO JUST BELOW GALE FORCE. THESE WINDS ARE BEING
GENERATED DUE TO A TIGHT PRESSURE GRADIENT CREATED BETWEEN
PERSISTENT STRONG HIGH PRESSURE OVER THE WESTERN ATLC AND THE
LOWER PRESSURES OVER SOUTH AMERICA AND THE SW CARIBBEAN SEA. THE
WINDS ARE FORECAST TO BRIEFLY INCREASE BACK UP TO GALE FORCE SAT
NIGHT BEFORE DIMINISHING TO JUST UNDER GALE FORCE AGAIN ON SUN.
SEE LATEST NWS HIGH SEAS FORECAST UNDER AWIPS/WMO HEADERS
MIAHSFAT2/FZNT02 KNHC AND THE OFFSHORE FORECAST...MIAOFFNT3/
FZNT23 FOR MORE DETAILS.

...TROPICAL WAVES...

A TROPICAL WAVE AXIS IS OVER THE FAR EASTERN TROPICAL ATLC ALONG
26W FROM 6N-14N MOVING W 5 KT. THE SSMI TOTAL PRECIPITABLE WATER
(TPW)IMAGERY SHOWS THE WAVE EMBEDDED IN LOW LEVEL MOISTURE FROM
05N-10N...HOWEVER ONLY ISOLATED SHOWERS ARE POSSIBLE WITHIN 60
NM OF THE WAVE AS THE SURROUNDING ENVIRONMENT IS SUBSTANTIALLY
STABLE AS EXTENSIVE AFRICAN SAHARAN DUST SWEEPS WESTWARD ACROSS
THE EASTERN ATLANTIC.

A TROPICAL WAVE AXIS IS OVER THE CENTRAL TROPICAL ATLC ALONG 46W
FROM 05N-14N MOVING W AT 20-25 KT UNDER THE SOUTHERN PERIPHERY
OF STRONG CENTRAL ATLC HIGH PRESSURE. THE SSMI TOTAL
PRECIPITABLE WATER (TPW)IMAGERY ALSO SHOWS THE WAVE EMBEDDED IN
DEEP LOW LEVEL MOISTURE. THE DUST SURGE IS TO THE N OF 12N IN
THE VICINITY OF THIS ALLOWING FOR THE MOISTURE TO HELP PRODUCE
WIDELY SCATTERED MODERATE CONVECTION WITHIN 180 NM E OF THE WAVE
JUST TO THE N OF THE ITCZ RELATED CONVECTIVE ACTIVITY. SIMILAR
ACTIVITY IS 60 NM W OF THE WAVE. THIS WAVE IS LIKELY TO AMPLIFY
SOME IN LONGITUDINAL SIZE AS IT MOVES FARTHER W DURING THE NEXT
24-48 HOURS.

A TROPICAL WAVE AXIS IS ALONG 60W FROM 08N-20N MOVING W NEAR
18 KT. LATEST SATELLITE IMAGERY SHOWS THAT THIS WAVE CONTINUES
TO EXHIBIT AN INVERTED-V SHAPE LOW-LEVEL CLOUD PATTERN...
...ALTHOUGH A BIT LESS DEFINED...AS SEEN EARLIER TODAY. THE WAVE
SHOWS VERY WELL IN THE LOW-LEVEL TPW MOISTURE AS WELL AS IN THE
GFS MODEL RELATIVE HUMIDITY FIELD. THE NE TO SE WIND SHIFT
ASSOCIATED WITH THIS WAVE IS ALSO NOTED NICELY IN THE GFS 700 MB
MODEL FIELD. SCATTERED TO BROKEN LOW CLOUDS WITH ISOLATED
SHOWERS AND WEAK ISOLATED TSTMS ARE ALONG AND WITHIN 60-75 NM W
OF THE WAVE. THIS WAVE WILL INCREASE MOISTURE ACROSS THE EASTERN
CARIBBEAN THROUGH LATE SAT...AND WILL FOLLOWED BY MUCH DRIER
ATMOSPHERIC CONDITIONS AS A RATHER EXTENSIVE AREA OF SUSPENDED
SAHARAN DUST FOLLOWS IN BEHIND IT.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM WELL INLAND AFRICA SW TO THE
COAST OF GUINEA-BISSAU NEAR 12N16W...AND CONTINUES TO 10N17W TO
JUST E OF THE TROPICAL WAVE ALONG 26W. THE ITCZ BEGINS W OF THIS
SAME WAVE...AND CONTINUES TO 09N36W TO JUST E OF THE WAVE ALONG
46W...THEN RESUMES JUST OF THE WAVE AT 06N47W TO INLAND S
AMERICA NEAR 05N52W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 90 NM S OF THE ITCZ BETWEEN 32W-34W..AND
WITHIN 30 NM OF 09N40W.

...DISCUSSION...

GULF OF MEXICO...
A SMALL UPPER ANTICYCLONE IS OBSERVED OVER W CENTRAL FLORIDA
WITH A RIDGE SW TO YUCATAN CHANNEL. THE REMAINDER OF THE GULF IS
UNDER THE INFLUENCE OF A LARGE UPPER LOW THAT IS CENTERED OVER
THE FAR WESTERN GULF NEAR 25N96W. A DIFFLUENT FLOW PATTERN TO SE
THE LOW IS HELPING TO SUSTAIN SCATTERED MODERATE/ISOLATED STRONG
CONVECTIVE CLUSTERS THAT ARE QUICKLY MOVING NORTHWARD FROM THE
NORTHERN YUCATAN PENINSULA N TO NEAR 24N BETWEEN 87.5W-91W.
SCATTERED SHOWERS AND ISOLATED TSTMS ARE EVIDENT OVER THE
EASTERN PORTION OF THE SW GULF S OF 25N BETWEEN 91W-94W. THIS
ACTIVITY IS FURTHER SUPPORTED BY A SURFACE TROUGH ALONG 94W S
OF 22N. THE REMAINDER OF THE GULF REMAINS UNDER GENERALLY FAIR
CONDITIONS WITH WEAK HIGH PRESSURE REMAINS IN PLACE AS A 1018 MB
HIGH IS ANALYZED NEAR 26N89W. THE WEAK HIGH PRESSURE IS FORECAST
TO CHANGE LITTLE THROUGH SAT...THEN BE REPLACED BY DEEP LAYER
TROUGHING WITH A SURFACE FRONT OVER THE N CENTRAL AND NW GULF
PORTIONS LATE SAT INTO SUN. THIS SET-UP SHOULD BRING INCREASES
CHANCES FOR SHOWERS AND TSTMS TO THOSE AREAS OF THE GULF WHILE
WEAK HIGH PRESSURE REMAINS PRESENT ELSEWHERE. THE SURFACE TROUGH
ALONG 94W WILL WNW ACROSS THE SW GULF TONIGHT INTO EARLY SAT.

CARIBBEAN SEA...
A WEAK NARROW UPPER RIDGE EXTENDS FROM JUST N OF NE HONDURAS
NORTHWARD THROUGH THE YUCATAN CHANNEL. TO THE W OF THE RIDGE...
DEEP ATMOSPHERIC MOISTURE IS PRODUCING SCATTERED MODERATE/
ISOLATED STRONG CONVECTION THAT IS MOVING QUICKLY NORTHWARD OVER
THE NORTHERN YUCATAN PENINSULA. SIMILAR CONVECTION IS MOVING SW
OVER MUCH OF THE INTERIOR OF CUBA. THIS IS IN RESPONSE TO NE
UPPER FLOW NOTED TO THE W OF BROAD CYCLONIC UPPER FLOW THAT IS
PRESENT OVER MUCH OF THE CENTRAL AND WESTERN CARIBBEAN IN
ASSOCIATION WITH THE UPPER LOW NEAR THE SE BAHAMAS. MODERATE
SUBSIDENCE TO THE SE OF THE AFOREMENTIONED UPPER LOW IS PRESENT
OVER THE CENTRAL CARIBBEAN KEEPING GENERALLY FAIR WEATHER THERE.
A SHORTWAVE TROUGH EMBEDDED IN THE SW FLOW SE OF THE UPPER LOW
IS RESULTING IN A BATCH OF MOISTURE WITH SCATTERED SHOWERS AND
ISOLATED TSTMS CONFINED TO THE EASTERN CARIBBEAN SEA S OF ABOUT
16N E OF 68W. THE TROPICAL WAVE CURRENTLY JUST E OF THE LESSER
ANTILLES IS FORECAST TO ENTER THE EASTERN CARIBBEAN TONIGHT
...AND MOVE ACROSS THE CENTRAL CARIBBEAN SAT...AND THE SW
CARIBBEAN SUN. THE WAVE WILL BE ATTENDANT BY INCREASING LOW-
LEVEL MOISTURE ALONG WITH SCATTERED SHOWERS AND ISOLATED TSTMS
WITH GUSTY WINDS. SUSPENDED AFRICAN SAHARAN DUST WILL FOLLOW IN
BEHIND THIS WAVE.

...HISPANIOLA...
SCATTERED TO LOCALLY BROKEN LOW CLOUDS WITH POSSIBLE ISOLATED
SHOWERS ARE OVER MUCH OF THE INTERIOR PORTIONS OF THE ISLAND.
A SMALL UPPER LOW IS JUST TO THE NW OF THE ISLAND NEAR THE SE
BAHAMAS. DRY AIR TO ITS SE IS NOT ALLOWING DEEP CONVECTION TO
FORM NEAR THE ISLAND. A RECENTLY DEVELOPED ISOLATED TSTM IS SEEN
JUST OFFSHORE THE NE COAST. THIS TSTM IS UNDER DIFFLUENT FLOW
ALOFT NOTED TO THE E OF THE UPPER LOW. THE NORTHERN PORTION OF
A TROPICAL WAVE CURRENTLY JUST E OF THE LESSER ANTILLES SHOULD
PASS ACROSS THE ISLAND SAT ACCOMPANIED BY AN INCREASE IN
MOISTURE AND INSTABILITY THAT SHOULD LEAD TO THE DEVELOPMENT OF
SCATTERED SHOWERS AND TSTMS...SOME WHICH COULD PRODUCE GUSTY
WINDS AS DRY AIR ALOFT MIXES DOWNWARD TO THE BOUNDARY LAYER.

ATLANTIC OCEAN...
BROAD BUT WEAK UPPER TROUGH COVERS THE W ATLC WITH A PAIR OF
UPPER LOWS...ONE NEAR THE SE BAHAMAS AT 21N75W...AND THE OTHER
ONE NE OF THE BAHAMAS NEAR 25N76W. THESE LOWS ARE EMBEDDED
WITHIN A BROAD CYCLONIC SHEAR AXIS THAT STRETCHES FROM NEAR
32N63W SW THROUGH THE LOWS...AND CONTINUES SW TO THE CENTRAL
CARIBBEAN SEA NEAR 15N78W. A DIFFLUENT FLOW PATTERN TO THE E OF
THE LOW NEAR THE SE BAHAMAS IS SUPPORTING ISOLATED SHOWERS AND
TSTMS FROM 21N-24N BETWEEN 63W-67W. AT THE SURFACE...BROAD
RIDGING COVERS THE AREA DUE TO A 1029 MB HIGH LOCATED AT 28N49W.
THE RIDGE AXIS ASSOCIATED WITH THIS HIGH EXTENDS ROUGHLY ALONG
27N/28N E OF THE BAHAMAS. SCATTERED SHOWERS AND A FEW TSTMS ARE
SEEN MAINLY N OF THE RIDGE BETWEEN 73W-76W...AND TO THE SW OF
THE RIDGE FROM THE CENTRAL BAHAMAS TO PORTIONS OF THE STRAITS OF
FLORIDA. NOAA/NESDIS AEROSOL PRODUCT AND LATEST VISIBLE
SATELLITE IMAGERY INDICATES THAT A LARGE DENSE PLUMB OF AEROSOLS
OR SAHARAN DUST COVERS THE TROPICS S OF 27N E OF 61W AND IS
HELPING TO SUPPRESS DEEP CONVECTIVE ACTIVITY FROM DEVELOPING
OUTSIDE THAT DISCUSSED WITH THE TROPICAL WAVES AND ITCZ. THE
SURFACE RIDGE IS FORECAST TO SHIFT SOUTHWARD TO NEAR 26N SUN AND
MON AS MID/UPPER LEVEL TROUGHING AND ASSOCIATED ATMOSPHERIC
INSTABILITY BEGINS TO ENCROACH ONTO THE FAR WESTERN PORTION OF
THE BASIN.

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

$$
AGUIRRE


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