000
AXPZ20 KNHC 051603
TWDEP 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC SUN MAY 05 2013

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.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
MONSOON TROUGH EXTENDS FROM NEAR 09N74W TO 04N79W TO 10.5N92W TO 
08N101W TO 10N110W WHERE IT TERMINATES. ITCZ AXIS EXTENDS FROM 
TO 10N115W TO 08.5N125W TO BEYOND 05N140W. SCATTERED TO NUMEROUS 
MODERATE TO STRONG CONVECTION NOTED WITHIN 180 NM N AND 150 NM S 
OF MONSOON TROUGH BETWEEN 78W AND 87W. SCATTERED MODERATE TO 
STRONG CONVECTION NOTED WITHIN 120 NM EITHER SIDE OF TROUGH 
BETWEEN 93W AND 100W. SCATTERED MODERATE TO STRONG CONVECTION 
NOTED WITHIN 60 NM S AND 90 NM N OF ITCZ W OF 117W. 

...DISCUSSION... 
BLOCKING MID LATITUDE UPPER PATTERN ACROSS N AMERICA CONTINUES 
THIS MORNING AND IS PROMOTING STRONG SOUTHERN UPPER FLOW ACROSS 
THE SUB TROPICS FROM THE EPAC EASTWARD INTO THE CENTRAL ATLC. A 
HIGH AMPLITUDE LONGWAVE TROUGH PREVAILS FROM E OF THE HAWAIIAN 
ISLANDS ALONG 150W N-NW INTO THE CENTRAL N PACIFIC...WHILE 
DOWNSTREAM...A CUTOFF LOW A FEW DAYS AGO ACROSS N PORTIONS OF 
THE DISCUSSION AREA HAS BECOME ELONGATED AND IS ACCELERATING E-
NE ALONG 127W...NOW ROTATING THROUGH THE BASE OF SLOWLY 
RETROGRADING CUTOFF LOW OFF THE COAST OF NORTHERN CALIFORNIA. 
SOUTHEAST OF THESE FEATURES LIES A BROAD FLAT UPPER 
RIDGE...CENTERED ON AN UPPER ANTICYCLONE NEAR 11N11W...WITH 
RIDGE AXIS ALONG ABOUT 110W EXTENDING N THEN NNE INTO THE DESERT 
SW OF THE U.S. AND IS SHIFTING VERY SLOWLY E. A SECOND MINOR 
EQUATORIAL RIDGE IS ALONG ABOUT 135W AND S OF 14N. A BROAD ZONE 
OF SW TO W FLOW ALOFT PREVAILS BETWEEN THE TROUGHING DESCRIBED 
ABOVE AND THE RIDGES AND SPILLS OVER THE RIDGE ALONG 110W AND 
CONTINUES ACROSS THE GULF OF MEXICO. CORE JET SPEEDS OF 65-90 KT 
ENTER THE AREA NEAR 11N150W PER RECENT CIMSS/NESDIS 
ANALYSIS...MOVING ACROSS THE RIDGE CREST AT 110W NEAR 25N. 
BROAD TROUGHING PREVAILS E OF THIS RIDGE...FROM NEAR 10N101W 
NORTHEASTWARD ACROSS SE MEXICO AND INTO THE CENTRAL GULF OF 
MEXICO...AND IS BEING TILTED NE IN TIME AS THE RIDGE NUDGES EWD. 
THE LONGWAVE TROUGH N THROUGH NE OF HAWAII IS FORECAST TO BEGIN 
TO SHIFT E DURING THE NEXT FEW DAYS ALLOWING UPPER LEVEL 
WESTERLIES TO DOMINATE THE AREA GENERALLY N OF 12N BY TUE... 
UPPER RIDGING TO REDEVELOP AND BUILD ALONG 125W.

...AT THE LOWER LEVELS...
WEAK SURFACE HIGH PRES IS CENTER ACROSS NW PORTIONS OF THE AREA 
THIS MORNING...SOUTH OF A WEAK REINFORCING COLD FRONT SINKING S 
ACROSS 30N THIS MORNING. A VERY MODEST PRESSURE GRADIENT BETWEEN 
THIS 1016 MB HIGH AND LOWER PRESSURE ALONG THE ITCZ IS PROMOTING 
MODERATE NE TRADE WINDS OF 10-15 KT W OF 128W. THE FRONT ALONG 
30N WILL SINK SLOWLY S TO ABOUT 28N DURING THE NEXT 36-48 
HOURS... BRINGING WESTERLY WINDS 20-25 KT N OF THE FRONT...WITH 
SEAS BUILDING 8 TO 10 FT IN NW SWELL. THE WEAK HIGH PRES S OF 
THE FRONT WILL PERSIST ACROSS NW PORTIONS FOR THE NEXT FEW 
DAYS...BUT WITH A PRESSURE OF ONLY ABOUT 1018 MB...IS NOT 
EXPECTED TO STRENGTHEN THE TRADEWINDS. THIS GENERAL PATTERN IS 
EXPECTED TO CONTINUE ACROSS THE AREA THROUGH WED BEFORE THE HIGH 
BEGINS TO STRENGTHEN ACROSS N PORTIONS BY WEEKS END.

E OF 120W...LIGHT WINDS AND MODERATE SEAS PREVAIL IN MAINLY SW 
SOUTHERN HEMI SWELL. THE EPAC MONSOON TROUGH IS SLOWLY BECOMING 
THE DOMINANT FEATURE ACROSS THIS AREA...WITH S TO SW WINDS TO 
THE SOUTH OF THE TROUGH NOW EXTENDING W FROM S AMERICA TO NEAR 
115W.

$$
STRIPLING