000
AXPZ20 KNHC 172125
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
2205 UTC TUE MAR 17 2009

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. 

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
2115 UTC.

...ITCZ...
THE ITCZ AXIS WAS ALONG A LINE FROM 04N76W TO 04N97W TO 03N116W 
TO 06N140W. NO SIGNIFICANT CONVECTION ALONG THE ITCZ.

...DISCUSSION...

THE UPPER LEVEL PATTERN FEATURES A FAIRLY ELONGATED POLAR JET 
STREAM THAT EXTENDS FROM THE E PACIFIC REGION INTO THE NORTHERN 
ROCKIES OF THE CONUS. THE CORRESPONDING VERTICAL SHEAR IS 
ASSOCIATED WITH A STATIONARY FRONT THAT REMAINS WELL N OF THE 
DISCUSSION AREA. HOWEVER...THE UPPER LEVEL FLOW N OF THE REGION 
IS FORECAST TO AMPLIFY LATER THIS WEEK...AS A SHORTWAVE TROUGH 
CURRENTLY OVER THE GULF OF ALASKA DIVES SOUTHEASTWARD. IN 
RESPONSE...THE STATIONARY FRONT WILL BE FORCED SOUTHWARD BY 
FRIDAY...WITH A WEAKENING COLD FRONT ENTERING THE NORTHWESTERN 
PORTION OF THE DISCUSSION AREA BY FRIDAY. WHILE THE WIND IMPACT 
WILL BE RELATIVELY MINIMAL...NORTHWESTERLY SWELL CONTAINING SEA 
HEIGHTS UP OVER 10 FT WILL APPROACH THE NORTHWESTERN WATERS BY 
SATURDAY. IN THE MEANTIME...NORTHWESTERLY SWELL WITH SEA HEIGHTS 
OF UP TO 11 FT CONTINUE TO DRIFT SOUTHEASTWARD ACROSS THE 
NORTHEASTERN HALF OF THE DISCUSSION AREA. THESE SEAS CONTINUE 
SUBSIDING AS THEY DEPART THEIR SOURCE REGION N OF THE AREA.

A 1029 MB SURFACE HIGH IS CENTERED N OF THE AREA NEAR 
33N130W...WITH THE ENHANCED SURFACE PRESSURE GRADIENT AT THE 
SOUTHERN PERIPHERY OF THIS FEATURE ENHANCING NE TO E TRADES 
ACROSS THE REGION. THE QUIKSCAT PASS AROUND 17/1400 UTC SHOWED 
NE TO E WINDS OF 20 TO 25 KT FROM 07N TO 25N W OF 120W...WITH 
WAVES TO 11 FT IN THIS AREA IN MIXED NW AND NE SWELL. AS THE 
UPPER FLOW N OF THE AREA AMPLIFIES...THE SURFACE HIGH IS 
EXPECTED TO WEAKEN DURING THE NEXT FEW DAYS AND MOVE NW OF THE 
AREA. IN RESPONSE...TRADE WINDS WILL SLACKEN...WITH SEAS 
GRADUALLY SUBSIDING.

AS FOR CONVECTIVE ACTIVITY...UPPER LEVEL DIFFLUENCE N OF THE 
ITCZ AXIS CONTINUES IS SUPPORTING SCATTERED MODERATE CONVECTION 
WITHIN 90 NM EITHER SIDE OF LINE FROM 12N122W TO 10N132W. THE 
DIFFLUENCE IS EMBEDDED WITHIN AN UPPER TROUGH LOCATED S OF 17N W 
OF 110W. FARTHER TO THE E...DEEP LAYER DRY AIR AND STABLE 
ATMOSPHERIC CONDITIONS EMBEDDED WITHIN AN UPPER RIDGE ARE 
RESULTING IN FAIR WEATHER CONDITIONS. ALSO...THE REMNANT UPPER 
LOW NE OF HAWAII APPEARS TO BE MOSTLY DISCONNECTED WITH THE 
NORTHERN STREAM AND CONTINUES TO WEAKEN...WHILE THE 
CORRESPONDING 1017 MB SURFACE LOW NEAR 30N148W SPINNING DOWN AS 
WELL. UPPER LEVEL DIFFLUENCE E OF THE UPPER LEVEL TROUGH IS 
SUPPORTING SCATTERED MODERATE CONVECTION THAT HAS NOW MOVED N OF 
THE DISCUSSION AREA.

GAP WINDS...
SURFACE HIGH PRESSURE BUILDING SOUTHWARD OVER EASTERN MEXICO IN 
THE WAKE OF A FRONT OVER THE GULF IS SUPPORTING A RELATIVELY 
STRONG SURFACE PRESSURE GRADIENT ACROSS THE ISTHMUS OF 
TEHUANTEPEC...WITH STRONG N TO NE WINDS FUNNELING INTO THE GULF 
OF TEHUANTEPEC. THE 1218 UTC HIGH RESOLUTION QUIKSCAT PASS 
INDICATED N TO NE WINDS OF 30 TO 35 KT IN THIS AREA...WHERE A 
GALE WARNING CONTINUES. THE FRONT OVER THE GULF CONTINUES TO 
WEAKEN WITH SURFACE HIGH PRESSURE N OF THE FRONT WEAKENING AS 
WELL. IN RESPONSE...WINDS IN THE GULF OF TEHUANTEPEC WILL 
GRADUALLY DIMINISH DURING THE NEXT FEW DAYS. THE STRONGEST WINDS 
ARE EXPECTED LATE AT NIGHT...WHEN DRAINAGE FLOW OFF HIGHER 
TERRAIN IS MAXIMIZED IN THE PRESENCE OF DEEP LAYER DRY AIR.
 
TRADE WINDS ACROSS THE CARIBBEAN CONTINUE WITH A PERSISTENT 
SURFACE LOW OVER NW COLOMBIA. THESE WINDS CONTINUE TO BLEED INTO 
THE E PACIFIC REGION INTO THE GULF OF PANAMA AND THE GULF OF 
PAPAGAYO. WINDS SPEEDS IN THESE AREAS OF AROUND 20 KT ARE 
FORECAST TO CONTINUE PERIODICALLY DURING THE NEXT FEW 
DAYS...WITH THE STRONGEST WINDS EXPECTED LATE AT NIGHT AS WELL.

$$

COHEN