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AXPZ20 KNHC 291603
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 1500 UTC.


...SPECIAL FEATURE...

THE CENTER OF TROPICAL DEPRESSION EIGHT-E AT 29/1500 UTC IS NEAR 17.0N 133.6W. THE MINIMUM CENTRAL PRESSURE IS 1007 MB. THE DEPRESSION IS MOVING WESTWARD...OR 270 DEG...11 KNOTS. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 30 KNOTS WITH GUSTS TO 40 KNOTS. CONVECTIVE PRECIPITATION...NUMEROUS STRONG FROM 14N TO 17N BETWEEN 132W AND 134W. SCATTERED MODERATE TO ISOLATED STRONG FROM 17N TO 18N BETWEEN 132W AND 134W. 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 07N121W. THIS LOW CENTER IS EMBEDDED IN THE MONSOON TROUGH...AND IT CONTINUES TO MOVE WESTWARD 15 KNOTS. CONVECTIVE PRECIPITATION...SCATTERED MODERATE TO ISOLATED STRONG IN BROKEN BANDS...FROM 02N TO 13N BETWEEN 120W AND 130W. ISOLATED MODERATE TO LOCALLY STRONG FROM 06N TO 13N BETWEEN 110W AND 120W. THE LOW WILL CONTINUE TO MOVE WEST- NORTHWESTWARD DURING THE NEXT SEVERAL DAYS. IT IS EXPECTED TO IMPROVE GRADUALLY IN ITS ORGANIZATION. THIS FEATURE HAS A MEDIUM 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 94W/95W 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.

A TROPICAL WAVE IS ALONG 118W/119W FROM 17N SOUTHWARD...MOVING WESTWARD 15 KNOTS. CONVECTIVE PRECIPITATION...THE PRECIPITATION IS BECOMING ABSORBED INTO THE EASTERN PERIPHERY OF A 1008 MB LOW PRESSURE CENTER THAT IS NEAR 07N121W. IT IS LIKELY THAT THIS WAVE WILL INTERACT WITH AND/OR BECOME ABSORBED INTO THE 1008 MB LOW CENTER DURING THE NEXT 12 TO 24 HOURS.


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

THE MONSOON TROUGH IS ALONG 09N94W 07N88W 07N92W 07N105W 09N115W. CONVECTIVE PRECIPITATION...WIDELY SCATTERED TO SCATTERED MODERATE TO ISOLATED STRONG FROM 02N TO 12N FROM 110W EASTWARD.


...DISCUSSION...

A SURFACE RIDGE PASSES THROUGH 32N139W TO 26N126W TO 20N111W. THE SURFACE PRESSURE GRADIENT BETWEEN THE RIDGE AND THE TYPICAL TROUGH THAT IS SEEN ALONG BAJA CALIFORNIA IS HELPING TO INDUCE NW WINDS AROUND 15 KT WITHIN ABOUT 180 NM W OF THE BAJA CALIFORNIA PENINSULA WITH RESULTANT SEAS OF 6-7 FT. THE GRADIENT IS FORECAST TO RELAX ENOUGH THIS AFTERNOON TO ALLOW THESE WINDS TO DIMINISH TO 10-15 KT WITH SEAS LOWERING TO AROUND 5-6 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 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 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 MOST RECENT SCATTEROMETER DATA SHOWED NORTHEAST-TO-EAST WINDS 20-25 KNOTS OFF OF THE NICARAGUAN COAST DOWNSTREAM OF LAKES NICARAGUA AND MANAGUA...EXTENDING WESTWARD TO NEAR 89W...WHERE MAX SEAS WERE 8 FEET. THE WINDS IN THIS AREA WILL DIMINISH TO 15 TO 20 KNOTS BY THE 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 WAS MOVING THROUGH THE GULF OF TEHUANTEPEC EARLIER THIS MORNING...AHEAD OF THE TROPICAL WAVE THAT IS MOVING THROUGH THE WESTERN PARTS OF THE CARIBBEAN SEA. THESE WINDS ALSO WILL PULSE TO A PEAK OF 20 TO 25 KNOTS OVERNIGHT DURING THE MORNING HOURS FOR THE NEXT 2 DAYS...BEFORE DIMINISHING TO 15 TO 20 KNOTS EACH AFTERNOON.

$$ MT

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