[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202322
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON JUL 20 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
2315 UTC.

...TROPICAL WAVES...
TROPICAL WAVE HAS MOVED OFF THE COAST OF AFRICA AND EXTENDS FROM
05N18W TO 16N17W MOVING W AT 15-20 KT. THE WAVE COINCIDES WITH
BROAD 700 MB TROUGHING ALOFT BETWEEN 15W-20W. 850 MB VORTICITY
MAXIMUM ARE LOCATED NEAR THE WAVE AXIS FROM 08N-14N. SCATTERED
MODERATE AND ISOLATED STRONG CONVECTION IS FROM 05N-09N BETWEEN
18W-28W.

TROPICAL WAVE EXTENDS FROM 06N50W TO 17N49W MOVING W AT 20 KT.
THE WAVE COINCIDES WITH BROAD 700 MB TROUGHING ALOFT BETWEEN 47W-
53W ON THE SOUTHERN PERIPHERY OF A MID-LEVEL RIDGE CENTERED NEAR
23N45W. 850 MB VORTICITY MAXIMUM IS LOCATED NEAR THE NORTHERN
HALF OF THE WAVE FROM 12N-15N. ISOLATED MODERATE CONVECTION IS
FROM 08N-10N BETWEEN 50W-60W.

TROPICAL WAVE EXTENDS FROM 08N61W TO 18N61W MOVING W AT 15-20
KT. THE WAVE REMAINS EMBEDDED WITHIN A MAXIMUM OF TOTAL
PRECIPITABLE WATER BETWEEN 59W-64W THAT STRETCHES AS FAR NORTH
AS 23N THEN NORTHEASTWARD INTO THE INFLUENCE OF AN UPPER LEVEL
TROUGH AXIS EXTENDING OVER THE CENTRAL ATLC. ISOLATED TO WIDELY
SCATTERED MODERATE TO STRONG CONVECTION IS FROM 11N-18N BETWEEN
59W-64W. SURFACE OBSERVATIONS ACROSS THE LESSER ANTILLES
RECENTLY INDICATED A WIND SHIFT WITH THE PASSAGE OF THE WAVE
AXIS.

TROPICAL WAVE EXTENDS FROM 06N69W TO 16N68W MOVING W AT 15-20
KT. THE WAVE NEARLY COINCIDES WITH 700 MB TROUGHING BETWEEN 66W-
72W AND IS LARGELY INFLUENCED ALOFT BY SOUTHWESTERLY WIND SHEAR
OVER THE CENTRAL AND EASTERN CARIBBEAN. AS A RESULT...NO
SIGNIFICANT DEEP CONVECTION IS OCCURRING WITH THE WAVE AT THIS
TIME.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH AXIS EXTENDS FROM NEAR 08N18W TO 07N30W. THE
INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 07N30W TO
09N48W.

...DISCUSSION...

GULF OF MEXICO...
NORTHEASTERLY FLOW ALOFT PREVAILS OVER MUCH OF THE GULF THIS
EVENING BETWEEN AN UPPER LEVEL ANTICYCLONE CENTERED OVER EAST
CENTRAL TEXAS NEAR 31N96W AND AN UPPER LEVEL LOW CENTERED OVER
THE NW CARIBBEAN SEA NEAR 20N86W. WHILE A MAJORITY OF THE BASIN
IS UNDER THIS RELATIVELY STABLE FLOW...AT THE SURFACE...WEAK
TROUGHING AND LOW-LEVEL MOISTURE CONVERGENCE IS PRESENT ACROSS
THE NE TO N CENTRAL GULF EXTENDING FROM 30N84W TO 30N90W. THE
SURFACE TROUGH BOUNDARY IS PROVIDING FOCUS FOR SCATTERED SHOWERS
AND TSTMS OCCURRING FROM 26N-30N BETWEEN 83W-96W. OTHERWISE...A
SURFACE RIDGE AXIS EXTENDS FROM THE SW NORTH ATLC INTO THE SE
GULF NEAR 24N84W TO THE NW GULF ALONG THE TEXAS COAST NEAR
28N96W. MAINLY LIGHT TO MODERATE ANTICYCLONIC FLOW IS FORECAST
ACROSS THE BASIN THROUGH WEDNESDAY EVENING. AN EXCEPTION WILL BE
NW OF THE YUCATAN PENINSULA WHERE WINDS WILL INCREASE TO 15-20
KT EACH NIGHT AS DIURNAL TROUGHING DEVELOPS OVER THE PENINSULA
AND PUSHES OFFSHORE INTO THE SW GULF.

CARIBBEAN SEA...
AN UPPER LEVEL LOW IS NOTED ON WATER VAPOR IMAGERY OVER THE NW
CARIBBEAN CENTERED NEAR 20N86W. CONDITIONS AT THE SURFACE REMAIN
FAIRLY TRANQUIL ACROSS THE NW CARIBBEAN. OTHERWISE...THE
REMAINDER OF THE CARIBBEAN BASIN IS UNDER THE INFLUENCE OF
SOUTHWESTERLY FLOW ALOFT ON THE NORTHERN PERIPHERY OF AN UPPER
LEVEL RIDGE AXIS EXTENDING ALONG 12N-14N. THE DIFFLUENCE
ASSOCIATED WITH THE RIDGING IS GENERATING SCATTERED SHOWERS AND
TSTMS ACROSS PORTIONS OF THE SW CARIBBEAN AND INLAND AREAS OF
PANAMA AND COSTA RICA S OF 10N BETWEEN 74W-82W. FINALLY...A PAIR
OF TROPICAL WAVES ARE MOVING ACROSS THE EASTERN CARIBBEAN.
INFLUENCE OF THE WESTERN-MOST WAVE ALONG 68W-69W IS LARGELY
CONFINED S OF 13N WITH ISOLATED SHOWERS OCCURRING BETWEEN 66W-
71W...WITH STRONGER CONVECTION OCCURRING ACROSS PORTIONS OF
NORTHERN VENEZUELA AND NORTHERN COLOMBIA. THE EASTERN WAVE
ALONG 61W DID RESULT IN A WIND SHIFT ACROSS THE LESSER ANTILLES
WITH CONVECTION OCCURRING AS IS DESCRIBED ABOVE RESULTING IN AN
INCREASED PROBABILITY OF PRECIPITATION DURING THE NEXT 12-24
HOURS. MAINLY GENTLE TO MODERATE TRADES WILL PREVAIL ACROSS THE
BASIN THROUGH THE NEXT 24-48 HOURS...EXCEPT IN THE S CENTRAL
CARIBBEAN WHERE FRESH TO STRONG TRADES WILL OCCUR DUE TO A TIGHT
PRESSURE GRADIENT BETWEEN CENTRAL ATLC HIGH PRES N-NE OF THE
AREA AND LOW PRESSURE LOCATED ALONG THE NW COAST OF COLOMBIA.
WINDS WILL ALSO PULSE TO 20 KT IN THE GULF OF HONDURAS DURING
THE OVERNIGHT HOURS DUE TO A DIURNALLY RELATED PRESSURE GRADIENT
INCREASE.

...HISPANIOLA...
CURRENTLY...MOSTLY CLEAR SKIES PREVAIL...HOWEVER WITH THE
APPROACH OF MULTIPLE TROPICAL WAVES PROGRESSING WESTWARD TO
THE SOUTH OF THE ISLAND DURING THE NEXT COUPLE OF DAYS...HIGHER
PROBABILITY OF SCATTERED SHOWERS AND TSTMS IS LIKELY THROUGH
LATE THURSDAY INTO FRIDAY.

ATLANTIC OCEAN...
NORTH-NORTHEASTERLY FLOW ALOFT PREVAILS OVER MUCH OF THE SW
NORTH ATLC ON THE WESTERN PERIPHERY OF AN UPPER LEVEL TROUGH
AXIS EXTENDING FROM 32N45W TO 23N66W TO THE MONA PASSAGE. WHILE
OVERALL CONDITIONS REMAIN STABLE ACROSS THE SW NORTH ATLC WITHIN
A SURFACE RIDGE WITH AXIS ALONG 26N-27N...LOW-LEVEL MOISTURE
CONVERGENCE IS MAXIMIZED ALONG 30N BETWEEN 66W-76W GENERATING
SCATTERED SHOWERS AND ISOLATED SHOWERS AND TSTMS. FARTHER
EAST...WITHIN THE INFLUENCE OF THE SOUTHWESTERLY FLOW ALOFT OF
THE UPPER LEVEL TROUGHING...AMPLE MIDDLE TO UPPER LEVEL DYNAMICS
AND LIFT ARE GENERATING AN AREA OF SCATTERED SHOWERS AND TSTMS
FROM 24N-28N BETWEEN 45W-55W. THIS AREA IS OCCURRING WITHIN A
NEARLY STATIONARY RIDGE ANCHORED BY A 1023 MB HIGH CENTERED NEAR
29N45W. THE RIDGE AXIS EXTENDS FROM THE HIGH TO THE CENTRAL
BAHAMAS THEN WESTWARD ALL THE WAY INTO THE SE GULF OF MEXICO.
PRIMARILY MODERATE ANTICYCLONIC WINDS WILL PREVAIL THROUGH THE
NEXT 48 HOURS...LOCALLY UP TO 20 KT AROUND THE SOUTHERN AND
WESTERN PERIPHERY OF THE SURFACE RIDGING.

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

$$
LEWITSKY
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