000
AXPZ20 KNHC 070320
TWDEP 

TROPICAL WEATHER DISCUSSION    
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT APR 07 2007

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 
0315 UTC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 10N86W 6N100W 3N120W 2N140W. 
SCATTERED MODERATE TO STRONG WITHIN 90-120 NM OF THE AXIS 
BETWEEN 86W AND 91W. SCATTERED MODERATE ISOLATED STRONG WITHIN 
120-150 NM OF THE AXIS BETWEEN 105W AND 112W...AND BETWEEN 116W 
AND 122W.

...DISCUSSION...

SOMEWHAT PROGRESSIVE PATTERN DOMINATES THE SUBTROPICS WITH A 
SERIES OF TROUGHS AND RIDGES SWEEPING ACROSS THE DISCUSSION AREA 
N OF 20N. THIS IS IN STRONG CONTRAST TO THE MID-LATITUDE PATTERN 
OVER THE CONUS AND CANADA WHERE LATE SEASON BLOCKING DOMINATES 
IN A STRONG POSITIVE PNA PATTERN.   

NEGATIVELY TILTED TROUGH WELL N OF THE AREA EXTENDING SEWD TO 
33N127W IS ROTATING NWD AROUND THE PERIPHERY OF A BLOCKING HIGH 
OVER THE PAC NW REGION OF THE U.S. A WEAK SHORTWAVE RIDGE WAS 
NOTED SE OF THE TROUGH FROM 32N122W SWWD TO 22N140W. A CUT-OFF 
MID/UPPER LOW OVER SW ARIZONA WAS BEGINNING TO EMERGE FROM UNDER 
THE BLOCKING HIGH NOTED ABOVE AND GENERALLY DRIFTING ESEWD. A 
MID/UPPER LEVEL SHEARED TROUGH TRAILS SWWD FROM THE CUT-OFF LOW 
THROUGH NORTHERN BAJA THEN SWWD TO 24N125W 19N135W. CONFLUENT 
FLOW WITHIN THE BASE OF THE TROUGH MANIFESTED ITSELF IN AN AREA
OF STRONG UPPER LEVEL SUBSIDENCE WITHIN 120-180 NM EITHER SIDE 
OF THE SHEARED TROUGH AXIS S OF 25N. THIS AREA OF SUBSIDENCE WAS 
ALSO OVER THE POLEWARD SIDE OF A SUBTROPICAL JET STREAM WHICH 
ENTERS THE WRN PART OF THE DISCUSSION AREA THROUGH 16N140W...AND 
EXTENDS NEWD THROUGH 21N125W TO ACROSS CENTRAL BAJA CALIFORNIA 
AND TO NORTHERN MEXICO. SOME DEEP TROPICAL MOISTURE IN THE FORM 
OF SCATTERED/BROKEN CIRRUS CLOUDS WITHIN 360 NM SOUTHEAST OF THE 
JET STREAM ARE SUGGESTING TRANSVERSE BANDING BETWEEN 114W-123W. 
RIPPLES OF ENERGY ALONG THE JET STREAM ARE PROPAGATING QUICKLY 
TO THE NORTHEAST MAINLY EAST OF 132W WHERE SATELLITE DERIVED 
UPPER AIR DATA INDICATED MAXIMUM JET CORE WINDS IN THE RANGE OF 
80-100 KT. A FLATTENING MID/UPPER LEVEL RIDGE HAS SHIFTED EWD 
OVER CENTRAL MEXICO ALONG 100W. 

THE MID/UPPER LEVEL FLOW JUST WEST OF THE AREA BECOMES SHARPLY 
NORTHWEST TO NORTH DUE TO LARGE MID/UPPER ANTICYCLONIC HIGH WEST 
SITUATED WELL TO THE WEST OF 140W.

A WEAKENING COLD FRONT HAS MOVED INTO THE FAR NW CORNER OF THE 
REGION AND IS ASSOCIATED WITH THE LIFTING TROUGH N OF THE AREA. 
SOUTHWEST WINDS OVER THE NW PART OF THE AREA HAVE DECREASED TO 
20 KT WITH LARGE NW SWELL SPREADING INTO THE AREA. THESE WINDS 
SHOULD DIMINISH WITHIN 12 HRS...HOWEVER THE SWELLS REMAIN. 

IN THE DEEP TROPICS...A MID/UPPER LEVEL TROUGH AXIS EXTENDING 
FROM ROUGHLY 11N106W SOUTHWEST TO BEYOND THE EQUATOR AT 110W. 
THIS TROUGH IS ENHANCING ITCZ CONVECTION GENERALLY BETWEEN 105W 
AND 112W. MID/UPPER LEVEL RIDGING EXTENDS ALONG 6N TO THE EAST 
OF THE TROUGH SUPPORTING CONVECTION ELSEWHERE ALONG THE ITCZ 
BETWEEN 86W AND 91W. THE TROUGH IS FORECAST TO MOVE EAST THROUGH 
SAT THEN DISSIPATE LATE SAT INTO SUN. BROAD MID/UPPER LEVEL 
ANTICYCLONIC FLOW COVERS THE AREA SOUTH OF 10N WEST OF THE 
TROUGH. CONVECTION IS ALSO ACTIVE ALONG THE ITCZ FROM 4N-6N 
BETWEEN 116W-122W.

GAP WINDS...A 0002 UTC QUIKSCAT PASS INDICATED THAT THE WINDS IN 
THE GULF OF TEHUANTEPEC HAVE DECREASED MARKEDLY TO 20-25 KT. 
THESE WINDS ARE EXPECTED TO DIMINISH TO LESS THAN 20 KT WITHIN
24 HOURS. PAPAGAYO WINDS MAY BRIEFLY INCREASE TO 20 KT SAT 
MORNING AND AGAIN SUN MORNING DUE TO THE WIND REGIME ACROSS 
COSTA RICA ENHANCED BY SLIGHT TIGHTENING OF THE GRADIENT AND 
INTERACTING UPON THE LOCAL TOPOGRAPHY.

$$
COBB