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Eastern Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 210922
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 UTC FRI NOV 21 2014

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC.                       

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...            
MONSOON TROUGH EXTENDS FROM 10N85W TO 08N105W TO A 1010 MB LOW 
PRES NEAR 11N116W TO 09N123W. ITCZ CONTINUES FROM 09N123W TO 
BEYOND 08N140W. SCATTERED MODERATE ISOLATED STRONG CONVECTION IS 
NOTED N OF 07N BETWEEN 81W AND 85W. SIMILAR CONVECTION IS FROM 
06N TO 10N BETWEEN 87W AND 91W. CLUSTERS OF MODERATE TO ISOLATED 
STRONG CONVECTION CAN BE FOUND FROM 06N TO 10N BETWEEN 93W AND 
101W. SCATTERED MODERATE CONVECTION IS FROM 07N TO 10N BETWEEN 
130W AND 137W.

...DISCUSSION...                                                 

ALOFT...AN UPPER-LEVEL TROUGH SHIFTING EASTWARD EXTENDS SE FROM 
CENTRAL BAJA CALIFORNIA TO NEAR 25N122W THEN CONTINUES MAINLY 
WESTWARD TO BEYOND 25N140W. A BELT OF NEARLY ZONAL FLOW IS S OF 
THE TROUGH TO ABOUT 19N. AMPLE SUBSIDENCE AND IMPLIED DRY AIR 
MASS IS NOTED ON WATER VAPOR IMAGERY BETWEEN 19N AND 27N. S OF 
19N...THE ATMOSPHERE REMAINS VERY MOIST AS NOTED BY THE ACTIVE 
CONVECTION ALONG AND NEAR THE ITCZ AND MONSOON TROUGH AS 
DESCRIBED ABOVE. UPPER DIFFLUENCE IS HELPING TO INDUCE THIS 
CONVECTIVE ACTIVITY.

AT THE SURFACE...THE AFOREMENTIONED UPPER-LEVEL TROUGH SUPPORTS 
A COLD FRONT THAT NOW IS REACHING THE COAST OF CALIFORNIA AND 
EXTENDS SW TO NEAR 30N127W. THIS FRONT IS FORECAST TO STAY JUST 
N OF THE AREA AS IT QUICKLY MOVES EASTWARD OVER THE NEXT 24 HRS. 
A RIDGE EXTENDS FROM A 1027 MB HIGH LOCATED AT 29N143W TO NEAR 
22N115W. THE PRES GRADIENT BETWEEN THE RIDGE AND LOWER PRES IN 
THE VICINITY OF THE ITCZ IS INDUCING AN AREA OF FRESH TO STRONG 
TRADE WINDS...PARTICULARLY FROM 09N TO 21N W OF 130W BASED ON 
RECENT SCATTEROMETER PASSES. THESE WINDS WILL EXPAND NORTHWARD 
TO NEAR 23N AND EASTWARD TO NEAR 127W BY 48 HRS WITH RESULTANT 
SEAS OF 8-10 FT AS THE HIGH PRES BUILDS SOME TO THE SE. 

SURFACE TROUGH FROM 16N113W TO A 1010 MB LOW PRES NEAR 11N116W. 
THE LOW IS FORECAST TO GRADUALLY WEAKEN TO A TROUGH IN ABOUT 24 
HRS. THE NIGHT CHANNEL VISIBLE IMAGES STILL SHOW A SWIRL OF LOW 
CLOUDS IN ASSOCIATION WITH THE LOW CENTER. SCATTERED MODERATE TO 
ISOLATED STRONG CONVECTION IS NOTED ON EITHER SIDE OF THE TROUGH 
AXIS...MAINLY FROM 10N TO 16N BETWEEN 110W AND 116W. SIMILAR 
CONVECTION IS ALSO SEEN E OF THE AXIS FROM 12N TO 15N BETWEEN 
104W AND 110W. THE 0536 ASCAT PASS PROVIDED OBSERVATIONS OF NE 
WINDS IN THE 20-25 KT RANGE FROM 12N TO 15N W OF THE TROUGH AXIS 
TO 119W. THIS TROUGH WILL MOVE WESTWARD WITH AN AREA OF FRESH TO 
LOCALLY STRONG NE WINDS AHEAD OF IT...THAT IS FORECAST TO MERGE 
WITH THE AREA OF THE TRADE WINDS IN ABOUT 48 HOURS.

LONG PERIOD NW SWELL DOMINATES MUCH OF THE FORECAST WATERS W OF 
115W. THIS SWELL EVENT IS MIXING WITH SHORT PERIOD WIND WAVES 
GENERATED BY THE TRADE WIND FLOW. WAVEWATCH GUIDANCE SUGGESTS 
THAT A NEW SET OF NW SWELLS WILL REACH THE FAR NW CORNER OF THE 
FORECAST REGION BY SAT MORNING THEN WILL PROPAGATE SEW ACROSS 
THE NW AND N CENTRAL WATERS BY 48 HOURS WITH SEAS TO 9 FT 
COVERING THE AREA N OF ABOUT 18N AND W OF 118W.

GAP WINDS...AN ASCAT PASS AND A WINDSAT PASS SHOWED NORTHERLY 
WINDS OF 20-25 KT ACROSS THE GULF OF TEHUANTEPEC...MAINLY N OF 
14N BETWEEN 94W AND 96W. WINDS ARE EXPECTED TO DIMINISH BELOW 20 
KT LATE THIS MORNING WITH SEAS LESS THAN 8 FT. IN ADDITION... 
EXPECT GAP WINDS OF 20 KT ACROSS THE GULF OF PAPAGAYO DURING THE 
EARLY MORNING HOURS WITH THE ASSISTANCE OF THE NOCTURNAL 
DRAINAGE FLOW WITH SEAS OF 6-7 FT.

LOOKING FURTHER AHEAD...THE NEXT GULF OF TEHUANTEPEC IS FORECAST 
TO BE A STRONGER ONE. CURRENTLY...THE GFS AND THE UKMET GLOBAL 
MODELS SUGGEST WINDS OF 40-50 KT BY WED MORNING WHILE THE 
EUROPEAN GLOBAL MODEL INDICATES THAT WINDS COULD REACH 40 KT. 
THE GEFS PROBABILITIES OF GALE FORCE WINDS IS 80 PERCENT WITH 
THE 21/0000 UTC RUN. WAVEWATCH GUIDANCE SUGGESTS BUILDING SEAS 
UP TO 20-23 FT WITH THIS EVENT. 

$$
GR



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Page last modified: Friday, 21-Nov-2014 09:22:32 UTC