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AXPZ20 KNHC 292130
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC WED JUL 29 2015

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2145 UTC.


...SPECIAL FEATURES...

THE CENTER OF TROPICAL DEPRESSION EIGHT-E AT 29/2100 UTC IS NEAR 16.6N 135.6W. THE MINIMUM CENTRAL PRESSURE IS 1007 MB. THE DEPRESSION IS MOVING WESTWARD...OR 265 DEG...14 KNOTS. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 30 KNOTS WITH GUSTS TO 40 KNOTS. CURRENTLY SCATTERED MODERATE ISOLATED STRONG CONVECTION IS WITHIN 180 NM NE SEMICIRCLE. THIS CONVECTION IS WEAKENING WITH TIME AND THE DEPRESSION IS EXPECTED TO DISSIPATE WITHIN THE NEXT 36 TO 48 HOURS AS IT CROSSES 140W. PLEASE READ THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMEP3/WTPZ23 KNHC FOR MORE DETAILS.

A 1006 MB LOW PRESSURE CENTER IS NEAR 08N123W. THIS LOW CENTER IS BECOMING BETTER ORGANIZED WITH INCREASED BANDING NOTED IN THE CONVECTIVE CLOUDS. CURRENTLY SCATTERED MODERATE TO STRONG CONVECTION IS NOTED WITHIN 150 NM IN THE W SEMICIRCLE. A LARGER AREA OF SCATTERED MODERATE ISOLATED STRONG CONVECTION WAS ELSEWHERE WITHIN 360 NM NE AND 210 NM SW SEMICIRCLES. HIGH CONFIDENCE IN THE MODEL FORECASTS NECESSITATED THE ISSUANCE OF STORM WARNINGS FOR THE HIGH SEAS IN ASSOCIATION WITH THIS LOW. TROPICAL CYCLONE MARINE WARNINGS WILL LIKELY BE ISSUED LATER TONIGHT IN ASSOCIATION WITH THIS SYSTEM. THIS FEATURE HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.


...TROPICAL WAVES...

A TROPICAL WAVE IS 83W FROM 20N SOUTHWARD. THE WAVE IS MOVING THROUGH THE WESTERNMOST SECTIONS OF THE CARIBBEAN SEA... APPROACHING CENTRAL AMERICA. CONVECTIVE PRECIPITATION...PLEASE REFER TO THE MONSOON TROUGH/ITCZ SECTION FOR INFORMATION ABOUT THE CONVECTIVE PRECIPITATION.

A TROPICAL WAVE IS ALONG 96W FROM 17N IN THE ISTHMUS OF TEHUANTEPEC OF SOUTHERN MEXICO SOUTHWARD. THE WAVE IS MOVING WESTWARD 15 KNOTS. THE WAVE IS INTERACTING WITH AN UPPER LEVEL CYCLONIC CIRCULATION CENTER THAT IS ALONG THE SOUTHEASTERN COAST OF CENTRAL MEXICO. THIS INTERACTION WAS PRODUCING SCATTERED MODERATE TO STRONG CONVECTION WITHIN 180 NM W OF THE WAVE AXIS FROM 09N TO 14N.

A TROPICAL WAVE EARLIER ALONG 118W/119W HAS BECOME ABSORBED INTO THE EASTERN PERIPHERY OF THE 1007 MB LOW PRESSURE NOTED IN THE SPECIAL FEATURES SECTION ABOVE.


...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...

MONSOON TROUGH AXIS FROM 10N85W TO 07N100W TO 09N115W. SCATTERED MODERATE ISOLATED STRONG WITHIN 240 NM EITHER SIDE OF THE AXIS BETWEEN 82W AND 105W.


...DISCUSSION...

A SURFACE RIDGE PASSES THROUGH 32N139W TO 26N126W TO 20N111W. THE SLACKENED PRESSURE GRADIENT BETWEEN THE RIDGE AND THE TYPICAL TROUGH THAT IS SEEN ALONG BAJA CALIFORNIA HAS ALLOWED NW WINDS TO SUBSIDE TO DAY TO THE 10-15 KT RANGE WITHIN ABOUT 180 NM W OF THE BAJA CALIFORNIA PENINSULA WITH RESULTANT SEAS OF 5 TO 6 FT.

THE SURFACE PRESSURE GRADIENT THAT EXISTS BETWEEN THE SUBTROPICAL RIDGE AND LOWER SURFACE PRESSURES THAT ARE ACROSS THE DEEP TROPICS IS ALLOWING FOR MODERATE BUT WEAKENING TRADE WINDS TO PREVAIL IN THE WESTERN PART OF THE AREA FROM 14N TO 28N AND TO THE WEST OF 130W. THESE WINDS WILL BE REPLACED BY STRONGER WINDS ON THE PERIPHERY OF WEAKENING TROPICAL DEPRESSION EIGHT AS IT MOVES WEST-NORTHWESTWARD. THE PRESENT SEAS OF 6 TO 8 FEET ARE EXPECTED TO BUILD TO 6 TO 9 FEET WITH THE APPROACH OF THE TROPICAL DEPRESSION...AND THEN FRESHEN MORE ON THURSDAY AND FRIDAY. THE 1006 MB LOW PRESSURE CENTER ALSO IS FORECAST TO MOVE WESTWARD THROUGH THE TROPICS AND INCREASE THE SURFACE PRESSURE GRADIENT TO THE NORTH.

GAP WINDS... THE GULF OF PAPAGAYO...STRONG TO NEAR GALE FORCE TRADE WINDS FROM THE SOUTHERN CARIBBEAN CONTINUE TO FUNNEL ACROSS THE HIGHER TERRAIN OF CENTRAL AMERICA AND SPILL ACROSS THE PACIFIC COASTAL WATERS THAT ARE TO THE EAST OF 90W. THE WINDS IN THIS AREA WILL HAVE DIMINISHED TO 15 TO 20 KNOTS THIS AFTERNOON...AND THEN INCREASE AGAIN TONIGHT AND LIKELY ON FRIDAY NIGHT...AS NOCTURNAL DRAINAGE FLOW ALLOWS THE WIND SPEEDS TO REACH THE 20 TO 25 KNOT RANGE AGAIN.

A NARROW PLUME OF NORTHERLY WINDS IN THE RANGE OF 20 TO 25 KNOTS IS FORECAST TO MOVE THROUGH THE GULF OF TEHUANTEPEC LATER TONIGHT. THESE WINDS ALSO WILL PULSE AGAIN TO 20 TO 25 KNOTS OVERNIGHT THU INTO THE MORNING HOURS ON FRI.

$$ COBB

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