000 AXPZ20 KNHC 190915 TWDEP TROPICAL WEATHER DISCUSSION NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 1005 UTC MON OCT 19 2009 TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM THE EQUATOR TO 32N...EAST OF 140W. BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0900 UTC. ...SPECIAL FEATURE... HURRICANE RICK CENTERED NEAR 17.5N 111.1W AT 19/0900 UTC...OR ABOUT 330 NM S-SW OF THE SOUTHERN TIP OF BAJA CALIFORNIA ...MOVING NW AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 950 MB. MAXIMUM SUSTAINED WIND SPEED IS 110 KT WITH GUSTS TO 135 KT. THE EYE HAS BECOME INDISTINCT IN THE LAST SEVERAL HOURS. LATEST SATELLITE IMAGERY SHOWS THAT RICK HAS WEAKENED OVER THE PAST SEVERAL HOURS AS INDICATED BY WARMING CLOUD TOPS SURROUNDING THE EYE...AND IS MOST EVIDENT OVER THE W QUADRANT. THIS WAS DUE TO THE INTRUSION OF DRY AIR INTO THE W SIDE OF THE CYCLONE. VERTICAL WIND SHEAR IS FORECAST TO INCREASE ALONG WITH FURTHER INTRUSION OF DRY AIR OVER THE NEXT 48 HOURS...BUT RICK IS STILL EXPECTED TO APPROACH THE SOUTHERN BAJA CALIFORNIA PENINSULA AS A HURRICANE. RICK IS CURRENTLY BEING STEERED BY A MIDDLE/UPPER LEVEL RIDGE LOCATED OVER MEXICO. NUMEROUS STRONG CONVECTION IS WITHIN 100 NM OVER THE NE SEMICIRCLE AND 60 NM OVER THE SW SEMICIRCLE. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION IS ELSEWHERE WITHIN 200 NM OVER THE NE SEMICIRCLE AND 100 NM OVER THE SW SEMICIRCLE. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMEP5/WTPZ25 KNHC FOR MORE DETAILS. ...TROPICAL WAVES... A TROPICAL WAVE IS ALONG 84W N OF 05N TO ACROSS WESTERN COSTA RICA AND EASTERN NICARAGUA. THE WAVE IS MOVING W ABOUT 12 KT. CONVECTION EARLIER NOTED HAS DISSIPATED. A TROPICAL WAVE IS ALONG 125W FROM 06N TO 16N MOVING W 10 KT. THE WAVE IS WEAK AND ASSOCIATED CONVECTION IS WITHIN THE ITCZ AND IS DESCRIBED BELOW. ...ITCZ... THE AXIS OF THE INTERTROPICAL CONVERGENCE ZONE IS CENTERED ALONG 05N77W TO 07N95W TO 12N110W TO 08N115W TO 08N120W TO 13N140W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION IS WITHIN 60 NM EITHER SIDE OF ITCZ FROM 109W TO 127W. OTHER CONVECTION... SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION IS WITHIN 60 NM OF THE POINT 12N89W. ...DISCUSSION... A MOSTLY UPPER TROUGH IS OVER THE NORTH AND NORTHWEST PART OF THE AREA NORTHWEST OF A LINE FROM 32N116W TO 26N125W TO 21N140W. SOUTH OF 31N WITHIN THIS AREA THE ATMOSPHERE IS DRY AND CLOUD FREE IN THE MIDDLE AND UPPER LEVELS. S OF 29N WITHIN THIS AREA OVERCAST STRATOCUMULUS IS IN THE LOWER LEVELS. NORTH OF 29N SCATTERED TO BROKEN STRATOCUMULUS PREVAIL. IN THE DEEP LAYER THERE IS MOISTURE NORTH OF 31N BUT NO CLOUDS. THE SOUTHWESTERLY FLOW AHEAD OF THE TROUGH IS ADVECTION MOIST AIR OVER FAR NORTHWEST MEXICO BUT LITTLE IN THE WY OF CLOUDS. MOIST FLOW OVER THE SIERRA MADRE OCCIDENTAL IS CAUSED AFTERNOON CONVECTION OVER THE MOUNTAIN PEAKS BUT THIS ACTIVITY HAS DIMINISHED TO ISOLATED TONIGHT. ANOTHER MOSTLY UPPER TROUGH IS SOUTH OF EASTERN MEXICO AND NORTHERN CENTRAL AMERICA FROM 88W TO 100W. SUBSIDENCE PREVAILS HERE WITH ONLY ISOLATED CONVECTION EMBEDDED WITHIN THE MOSTLY DRY AIR. LARGE ANTICYCLONIC OUTFLOW IS OVER RICK. THE OUTFLOW IS GOOD EXCEPT FOR SOME RESTRICTED OUTFLOW ON THE WEST SIDE OF THE SYSTEM. ELSEWHERE IN THE MIDDLE AND UPPER LEVELS BROAD ANTICYCLONIC FLOW IS OBSERVED. EXCEPT FOR NEAR THE ITCZ THE AREA WEST OF 110W NORTH OF 23N AND WEST OF 115W SOUTH OF 23N IS DRY AND CLOUD FREE IN THE MIDDLE AND UPPER LEVELS. IN THE LOWER LEVEL OVERCAST STRATOCUMULUS IS FROM 18N TO 29N WEST OF 117W. MODERATE SURFACE RIDGE IS NORTH OF 18N WEST OF 118W. BESIDES THE TROPICAL CYCLONE BROAD TROUGH IS ANALYZED ELSEWHERE AT THE SURFACE. GAP WINDS... A GALE WARNING IS CURRENTLY IN EFFECT FOR THE GULF OF TEHUANTEPEC...BUT IS EXPECTED TO DIMINISH TO LESS THAN GALE IN 24 HOURS. AN OVERNIGHT ASCAT PASS INDICATED WINDS OF UP TO 40 KNOTS. $$ LL