[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181750
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT JUL 18 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...TROPICAL WAVES...
TROPICAL WAVE EXTENDS FROM 05N30W TO 17N27W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH A BROAD 700 MB TROUGH BETWEEN 20W-
33W. 850 MB RELATIVE VORTICITY FIELDS ALSO SHOW MAXIMUM VALUES
ACROSS THE NORTHERN HALF OF THE WAVE AXIS. DURING THE PAST 24
HOURS...THIS AREA IS LIKELY THE NORTHERN VORTEX ENERGY THAT WAS
ABSORBED INTO THE OVERALL WAVE ENERGY. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION IS FROM 03N-11N BETWEEN 24W-34W.

TROPICAL WAVE EXTENDS FROM 08N44W TO 18N44W MOVING W AT 20 KT.
THIS WAVE WAS ADDED TO THE 18/1200 UTC SURFACE ANALYSIS BASED ON
FURTHER RE-ANALYSIS OF THE PAST FEW DAYS. EXAMINING THE DAKAR
SENEGAL UPPER AIR TIME-SECTION ANALYSES...THIS WAVE EMERGED OFF
THE WEST AFRICAN COAST EARLY ON THE 12TH OF JULY...WHILE THE
WAVE TO THE WEST EMERGED OFF THE COAST A FEW DAYS EARLIER ON THE
10TH OF JULY. BOTH AREAS OF TROPICAL ENERGY HAVE BEEN TRACKABLE
DURING THE PAST FEW DAYS AS SEPARATE AREAS USING LONG-TERM IR
SATELLITE IMAGERY LOOPS AND PAST GLOBAL MODEL ANALYSES...
ALTHOUGH VERY DIFFICULT TO DISCERN AS TWO AREAS UNTIL SOME
CONTINUITY AND A HIGHER CONFIDENCE WAS OBTAINED. GOES TO SHOW
THESE WAVES CAN BE DIFFICULT TO TRACK...EVEN WITH MANY TOOLS AT
HAND. ISOLATED MODERATE CONVECTION IS FROM 10N-13N BETWEEN 43W-
49W.

TROPICAL WAVE EXTENDS FROM 11N55W TO 19N51W MOVING W AT 20 KT.
THE WAVE COINCIDES WITH A GLOBAL MODEL INDICATED 700 MB
TROUGHING BETWEEN 49W-58W. AS MENTIONED ABOVE...THIS WAVE
EMERGED OFF THE WEST AFRICAN COAST ON JULY 10TH. EXAMINING THE
SAHARAN AIR LAYER TRACKING PRODUCT FROM UW-CIMSS...THE WAVE
REMAINS EMBEDDED WITHIN A SIGNIFICANT AREA OF DUST AND A STABLE
ENVIRONMENT AS A RESULT. NO SIGNIFICANT CONVECTION IS OCCURRING
WITH THE WAVE AT THIS TIME.

TROPICAL WAVE EXTENDS FROM 10N84W TO 18N86W MOVING W AT 15-20
KT. THE WAVE COINCIDES WITH BROAD GLOBAL MODEL INDICATED 700 MB
TROUGHING ACROSS THE FAR WESTERN CARIBBEAN SEA AND CENTRAL
AMERICA. ISOLATED MODERATE CONVECTION IS CONFINED S OF 13N
BETWEEN 81W-89W...AND LIKELY MORE ASSOCIATED WITH THE CLOSE
PROXIMITY TO THE MONSOON TROUGH AXIS ALONG 09N/10N.

...ITCZ/MONSOON TROUGH...
THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 05N34W TO
05N52W. ASIDE FROM CONVECTION ASSOCIATED WITH THE TROPICAL WAVE
ALONG 29W...WIDELY SCATTERED MODERATE CONVECTION IS FROM 02N-
07N BETWEEN 34W-44W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL NORTHEASTERLY FLOW IS OCCURRING OVER MUCH OF THE
GULF ON THE SOUTHEASTERN PERIPHERY OF A MIDDLE TO UPPER LEVEL
RIDGE ANCHORED OVER EAST TEXAS. A MID-LEVEL WEAKNESS NOTED ON
WATER VAPOR IMAGERY OVER THE NE GULF NEAR 29N86W SUPPORTS A
SMALL AREA OF LOWER PRESSURE FOCUSED IN THE VICINITY OF A 1015
MB LOW CENTERED IN THE FLORIDA BIG BEND REGION NEAR 29N84W. A
SURFACE TROUGH IS ANALYZED FROM THE LOW WEST TO 29N90W. LOW-
LEVEL MOISTURE CONVERGENCE ALONG AND TO THE SOUTH OF THE
BOUNDARY ALONG WITH FAVORABLE MIDDLE TO UPPER LEVEL DIFFLUENCE
IS GENERATING SCATTERED SHOWERS AND TSTMS FROM 24N-29N BETWEEN
82W-90W. OTHERWISE...THE REMAINDER OF THE BASIN IS UNDER THE
INFLUENCE OF SURFACE RIDGING ANCHORED BY A 1017 MB HIGH CENTERED
NEAR 25N89W. A RIDGE AXIS EXTENDS NW FROM THE HIGH TO THE
LOUISIANA COAST AND EAST ALONG 25N INTO THE SW NORTH ATLC.
GENERALLY GENTLE TO MODERATE ANTICYCLONIC WINDS PREVAIL. THE
RIDGE IS FORECAST TO REMAIN NEARLY STATIONARY AND ANCHORED
ACROSS THE CENTRAL GULF WATERS THROUGH MONDAY.

CARIBBEAN SEA...
GENERALLY NORTHEASTERLY FLOW ALOFT IS NOTED ON WATER VAPOR
WITHIN THE WESTERN PERIPHERY OF UPPER LEVEL TROUGHING STEMMING
FROM AN UPPER LEVEL LOW CENTERED NE OF PUERTO RICO NEAR 26N58W.
THE TROUGH AXIS EXTENDS FROM THE UPPER LEVEL LOW SW TO OVER
HISPANIOLA NEAR 20N70W TO A BROAD BASE OVER THE SW CARIBBEAN.
MOST OF THE WESTERN CARIBBEAN REMAINS RELATIVELY STABLE...
HOWEVER MID-LEVEL ENERGY IS FOUND SOUTH OF CUBA GENERATING A FEW
ISOLATED SHOWERS AND TSTMS FROM 16N-21N BETWEEN 75W-83W.
OTHERWISE...SCATTERED SHOWERS AND TSTMS CONTINUE S OF 13N
BETWEEN 76W-85W DUE TO A TROPICAL WAVE MOVING ACROSS CENTRAL
NICARAGUA AND HONDURAS AND THE MONSOON TROUGH ANALYZED ALONG
09N/10N IMPACTING MUCH OF PANAMA THIS AFTERNOON. TO THE EAST OF
THE UPPER LEVEL TROUGH AXIS...SOUTHWESTERLY FLOW ALOFT PREVAILS
WITH ONLY SCATTERED MIDDLE TO UPPER LEVEL CLOUDINESS NOTED ON
SATELLITE IMAGERY AT THIS TIME. FINALLY...FRESH TO STRONG TRADES
CONTINUE ACROSS CENTRAL PORTIONS DUE TO A STRENGTHENED PRESSURE
GRADIENT. THESE WINDS ARE EXPECTED TO PERSIST THROUGH THE
UPCOMING WEEKEND GENERALLY BETWEEN 70W-80W AND GRADUALLY
DIMINISH LATE SUNDAY NIGHT INTO MONDAY MORNING.

...HISPANIOLA...
CURRENTLY...MOSTLY CLEAR SKIES PREVAIL ACROSS THE ISLAND AND THE
ADJACENT COASTAL WATERS. EXAMINING THE MORNING 18/1200 UTC SAN
JUAN PUERTO RICO SOUNDING...DRY CONDITIONS EXIST ALOFT ABOVE 850
MB DUE LARGELY IN PART TO SAHARAN DUST AND THE SAHARAN AIR LAYER
PROVIDING FOR A STABLE ENVIRONMENT FOR PUERTO RICO AND ALSO FOR
HISPANIOLA. ISOLATED LATE AFTERNOON AND EARLY EVENING SHOWERS
AND TSTMS ARE POSSIBLE DUE TO PEAK DAYTIME HEATING AND
INSTABILITY...HOWEVER THE PROBABILITY REMAINS LOW THROUGH MONDAY.

ATLANTIC OCEAN...
UPPER LEVEL NORTHERLY FLOW INFLUENCES MUCH OF THE SW NORTH ATLC
W OF 68W ON THE EASTERN PERIPHERY OF UPPER LEVEL RIDGING
ANCHORED OVER THE LOWER MISSISSIPPI RIVER VALLEY THIS AFTERNOON.
THIS IS PROVIDING FOR A RELATIVELY DIFFLUENT ENVIRONMENT ALOFT
AND COUPLED WITH LOW-LEVEL MOISTURE CONVERGENCE FOCUSED ALONG
AND SOUTH OF A DISSIPATING STATIONARY FRONT ANALYZED FROM 35N67W
TO JACKSONVILLE FLORIDA NEAR 31N81W...GENERATING SCATTERED
SHOWERS AND TSTMS N OF 26N BETWEEN 66W-80W. TO THE SOUTHEAST OF
THE FRONT...AN UPPER LEVEL LOW IS CENTERED NEAR 26N58W AND IS
GENERATING AN AREA OF ISOLATED SHOWERS AND TSTMS FROM 23N-29N
BETWEEN 61W-66W ON THE SOUTHERN PERIPHERY OF A SURFACE RIDGE
ANCHORED BY A 1024 MB HIGH CENTERED NEAR 30N63W. FARTHER
EAST...THE REMAINDER OF THE EASTERN ATLC IS UNDER THE INFLUENCE
OF ANOTHER SURFACE RIDGE ANCHORED BY A 1025 MB HIGH CENTERED
NEAR 33N25W.

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

$$
HUFFMAN
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