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AXPZ20 KNHC 040242
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT JUL 04 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0200 UTC.


...SPECIAL FEATURES...

BANDS OF CONVECTION AROUND A 1007 MB LOW PRES CENTERED NEAR 06N120W HAVE BECOME BETTER ORGANIZED ALTHOUGH CLOUD TOPS HAVE WARMED SLIGHTLY IN THE PAST SEVERAL HOURS. THE LOW FORMED ALONG A WELL DEFINED TROPICAL WAVE IN A LARGE AREA OF CONVECTION THAT HAS BEEN FAIRLY PERSISTENT FOR THE PAST COUPLE OF DAYS ALONG THE ITCZ BETWEEN 115W AND 135W. AN UPPER ANTICYCLONE HAS FORMED NE OF THE LOW LEVEL CENTER IN THE CONTINUOUS OUTFLOW OF THESE THUNDERSTORMS. THE LOW LEVEL CENTER IS SOMEWHAT EXPOSED CURRENTLY WITH WEAK EASTERLY SHEAR...BUT CONVECTION IS EXPECTED TO PERSIST AND TROPICAL CYCLONE DEVELOPMENT IS POSSIBLE OVER THE NEXT COUPLE OF DAYS AS THE LOW MOVES SLOWLY W-NW.

A 1007 MB LOW IS CENTERED NEAR 12N138W IS CURRENTLY STATIONARY BUT WILL DRIFT SLOWLY NW THROUGH SAT. AN 18 UTC ASCAT PASS INDICATED FRESH WINDS N THE E AND NW QUADRANTS OF THE LOW PRES. CONVECTION HAS WEAKENED CONSIDERABLY OVER THE PAST SEVERAL HOURS. ENVIRONMENTAL SHEAR AND CONDITIONS ARE MARGINAL FOR POSSIBLE TROPICAL CYCLONE DEVELOPMENT OVER THE NEXT COUPLE OF DAYS AS THE LOW CONTINUES TO DRIFT SLOWLY NW.


...TROPICAL WAVES... TROPICAL WAVE ALONG 93W/94W N OF 10N MOVING W AT 10 TO 15 KT. NO SIGNIFICANT CONVECTION NOTED DIRECTLY RELATED TO THE WAVE OVER THE WATER.

TROPICAL WAVE ALONG 109W/110W FROM 08N TO 14N MOVING W AT 10 TO 15 KT. THE WAVE SHOWS UP WEAKLY IN REMOTE SENSED DATA BUT IS WELL INITIALIZED IN THE LOWER TO MID LEVELS OF THE ATMOSPHERE IN GLOBAL MODELS. SCATTERED MODERATE CONVECTION IS NOTED NEAR THE WAVE WITHIN 120 NM EITHER SIDE OF THE ITCZ AXIS 107W AND 113W.


...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH EXTENDS FROM 07N77W TO 06N80W TO 08N85W TO 10N93W. THE ITCZ EXTENDS FROM 10N93W TO 09N110W TO 13N117W...AND FROM LOW PRES NEAR 06N120W 1007 MB TO 09N130W. SCATTERED MODERATE CONVECTION NOTED WITHIN 180 NM S OF MONSOON TROUGH E OF 80W. SCATTERED MODERATE CONVECTION NOTED WITHIN 240 NM EITHER SIDE OF ITCZ BETWEEN 95W AND 115W. SCATTERED MODERATE ISOLATED STRONG CONVECTION NOTED FROM 06N TO 11N BETWEEN 115W AND 125W.


...DISCUSSION... N OF 15N E OF 120W...A RELATIVELY TIGHT PRES GRADIENT IS IN PLACE BETWEEN 1005 MB LOW PRES IN THE LOWER COLORADO RIVER VALLEY AND WEAK 1017 MB HIGH PRES W OF THE AREA IS ENOUGH TO ALLOW FRESH TO STRONG NW WINDS ALONG THE COAST OF BAJA CALIFORNIA FROM CABO SAN LAZARO TO PUNTA EUGENIA. THIS IS EXPECTED TO DIMINISH LATE THIS EVENING AS THE GRADIENT WEAKENS...AND SEAS WILL REMAIN LESS THAN 8 FT. FARTHER SOUTH...A SMALL UPPER LOW CENTERED NEAR 12N97W IS SUPPORTING A FEW SHOWERS AND THUNDERSTORMS TO ITS SOUTH CLOSER TO THE ITCZ. RECENT SCATTEROMETER AND ALTIMETER PASSES INDICATE LIGHT TO MODERATE WINDS AND SEAS OF 3 TO 5 FT OVER OPEN WATERS ELSEWHERE N OF 15N E OF 120W.

S OF 15N E OF 110W...A 2230 UTC RAPIDSCAT PASS INDICATES 20 TO 25 KT IN THE GULF OF PAPAGAYO...INDICATIVE OF STRONG TRADE WIND FLOW OVER THE SW CARIBBEAN THAT CONTINUES TO PRODUCE STRONG GAP WINDS INTO THE GULF OF PAPAGAYO AND OTHER AREAS ALONG THE NICARAGUAN COAST. THE MAIN PULSES ARE OCCURRING OVERNIGHT...WITH A PLUME OF FRESH SWELL TO 8 FT PROPAGATING AS FAR WEST AS 92W DOWNSTREAM DURING THE DAY. THESE CONDITIONS WILL START TO ABATE BY 48 HOURS. FRESH GAP WINDS WILL CONTINUE THROUGH THE GULF OF PANAMA AS WELL OVER THE NEXT 24 TO 48 HOURS. SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE ALONG THE ITCZ BETWEEN 90W AND 100W...ENHANCED BY GAP WIND CONVERGENCE TO SOME EXTENT. LITTLE CHANGE IS EXPECTED OVER THE NEXT 48 HOURS.

ELSEWHERE...A KELVIN WAVE MOVING THROUGH THE AREA HAS HELPED INCREASE LOW LEVEL CONVERGENCE MAKING MUCH OF THE ITCZ REGION ACTIVE BETWEEN 90W AND 125W AS NOTED IN THE ITCZ SECTION ABOVE. THIS IS RESULTING IN A BREAKDOWN OF THE ITCZ AS EVIDENCED BY THE DEVELOPING LOW PRES AREAS NEAR 06N120W AND 13N138W. THE ONLY OTHER MAIN WEATHER INFLUENCE AT THE SURFACE IS A WEAK SUBTROPICAL RIDGE N OF 20N...SUPPORTING WEAK MODEST TRADE WINDS OUTSIDE OF AREAS NEAR THE DEVELOPING LOW PRES AREAS.

$$ CHRISTENSEN

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