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Eastern Pacific Tropical Weather Discussion (Text)



000
AXPZ20 KNHC 170232
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC THU APR 17 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0215 UTC. 

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

THE EPAC MONSOON TROUGH EXTENDS SW FROM THE COAST OF COSTA RICA 
AT 09N83W TO 07N92W WHERE SCATTEROMETER WINDS INDICATE A 
TRANSITION TO AN ITCZ AXIS...WHICH CONTINUES SW TO 04N111W THEN 
WIGGLES WESTWARD ALONG 04N TO BEYOND 140W. 

SCATTERED MODERATE CONVECTION IS OBSERVED OVER AND TO THE S OF 
THE MONSOON TROUGH WITHIN 90 NM EITHER SIDE OF A LINE FROM 
10N85W TO 05N91W TO 05N98W. SIMILAR CONVECTION IS NOTED JUST S 
OF THE ITCZ AXIS WITHIN 60 NM EITHER SIDE OF LINES FROM 03N106W 
TO 04N114W. SCATTERED MODERATE ISOLATED STRONG IS NOTED OVER AND 
TO THE N OF THE ITCZ WITHIN 150 NM EITHER SIDE OF A LINE 
FROM 08N128W TO 06N140W. 

...DISCUSSION...                                                

AN UPPER CYCLONE IS OVER THE FAR NW PORTION OF THE DISCUSSION 
AREA NEAR 34N133W WITH AN UPPER TROUGH EXTENDING SW ACROSS THE 
HAWAIIAN ISLANDS. A SHORTWAVE TROUGH IS SWINGING E ACROSS THE 
WESTERN CONUS WITH THE TROUGH AXIS EXTENDING SW ACROSS SOUTHERN 
ARIZONA TO A BASE OVER THE BAJA CALIFORNIA PENINSULA AT 28N114W. 
BOTH OF THESE TROUGHS ARE ACCOMPANIED BY VERY DRY UPPER AIR.

AN UPPER LEVEL ANTICYCLONE IS QUASI-STATIONARY NEAR 10N123W WITH 
AN UPPER RIDGE EXTENDING N TO 33N125W...BUT CURRENTLY BEING 
ERODED BY THE PREVIOUSLY MENTIONED UPPER TROUGHS E AND W OF THE 
RIDGE CREST. THE ENVELOPE OF ANTICYCLONIC FLOW DOMINATES THE 
DISCUSSION AREA N OF THE ITCZ TO THE W OF 114W. DENSE UPPER 
MOISTURE IS ADVECTED NE ALONG THE PERIPHERY OF THIS RIDGE... 
WITHIN 360 NM EITHER SIDE OF A LINE FROM 16N140W TO 26N123W TO 
25N98W OVER MEXICO...WITH THE PLUME NOW MOVING OVER THE NW GULF 
OF MEXICO. UPPER DIFFLUENCE ALONG THE SW PERIPHERY OF THE LARGE 
UPPER ANTICYCLONE IS ENHANCING THE CONVECTION ALONG THE WESTERN 
PORTION OF THE ITCZ AS PREVIOUSLY MENTIONED. 

AN UPPER TROUGH IS ADVANCING E ACROSS THE SE CONUS AND CONTINUES 
SW ACROSS THE CENTRAL GULF OF MEXICO AND SOUTHERN MEXICO INTO AN 
UPPER CYCLONE DISSIPATING OVER THE TROPICAL PACIFIC NEAR 11N103W 
WITH A TROUGH STILL CONTINUING SW TO A BASE AT 02N117W. THIS 
TROUGH SEPARATES THE BROAD ANTICYCLONIC FLOW ALREADY MENTIONED 
OVER THE NW PORTION FROM ANTICYCLONIC FLOW OVER THE DISCUSSION 
AREA TO THE S OF 14N E OF 97W. THE ASSOCIATED UPPER DIFFLUENCE E 
OF THE FAR SOUTHERN PORTION OF THE UPPER TROUGH SUPPORTED THE 
CONVECTION DECAYING ALONG THE ITCZ AXIS BETWEEN 106-113W AS 
PREVIOUSLY DESCRIBED.

A SURFACE HIGH PRES RIDGE EXTENDS FROM 32N136W TO NEAR 20N114W. 
NE TRADES ARE ENHANCED TO 15-20 KT S OF THE RIDGE ACROSS THE 
PACIFIC WATERS FROM 06-19N BETWEEN 124-140W WITH SEAS OF 6-8 FT 
IN MIXED LONG PERIOD NW AND CROSS-EQUATORIAL SE SWELL. THIS 
AFFECTED AREA S OF THE RIDGE WILL SHRINK WESTWARD OVER THE NEXT 
FEW DAYS AS NE WINDS OF 15-20 KT FORM NE OF THE RIDGE AND SPREAD 
S INTO THE AREA N OF 28N BETWEEN 119-126W ON FRI. 

N-NE SWELL FROM TODAYS STORM/GALE EVENT IN THE GULF OF 
TEHUANTEPEC WILL CONTINUE TO PROPAGATE SW MIXING WITH LONG-
PERIOD CROSS EQUATORIAL S SWELL. SEAS WILL FINALLY SUBSIDE BELOW 
8 FT NEAR 06N105W LATE THU NIGHT. SOUTHERLY WINDS AT 5-15 KT ARE 
THEN EXPECTED EACH DAY...AND LATE NIGHT DRAINAGE FLOW OF 10-15 
KT IS EXPECTED EACH NIGHT THROUGH THU NIGHT. THE LATEST GUIDANCE 
IS SUGGESTING A SURFACE LOW WILL FORM ALONG A NORTHWARD DRIFTING 
WARM FRONT OVER THE NE GULF OF MEXICO. AS THE LOWS OUT TO THE NE 
IT WILL MOVE THE SOUTHERN END OF THE FRONT E AGAIN AS A COLD 
FRONT WITH NORTHERLY FLOW INCREASING ACROSS THE WESTERN GULF OF 
MEXICO. NORTHERLY FLOW WILL INCREASE TO 20-25 KT IN THE GULF OF 
MEXICO ON FRI EVENING WITH A MINIMAL GALE AROUND SUNRISE 
SAT...THEN QUICKLY DIMINISHING THROUGHOUT THE DAY ON SAT. 

$$ 
NELSON


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Page last modified: Thursday, 17-Apr-2014 02:32:46 UTC