000 WTPZ42 KNHC 200852 TCDEP2 TROPICAL STORM BEATRIZ DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL EP022011 200 AM PDT MON JUN 20 2011 A SIGNIFICANT BURST OF VERY COLD TOPPED CONVECTION HAS DEVELOPED OVER THE LOW-LEVEL CIRCULATION CENTER AND THE CONVECTIVE PATTERN HAS TAKEN ON A CDO-LIKE APPEARANCE. HOWEVER...THE LOW-LEVEL CENTER OF BEATRIZ IS NOT LOCATED DIRECTLY IN THE CENTER OF THE CLOUD MASS...BUT INSTEAD IS LOCATED IN THE EASTERN PORTION OF THE CDO NEAR SOME VERY COLD OVERSHOOTING CLOUD TOPS OF -85 TO -88C. THIS MORE EASTWARD ADVISORY POSITION IS SUPPORTED BY EARLIER MICROWAVE SATELLITE DATA. THE INITIAL INTENSITY OF 50 KT IS BASED ON A BLEND OF SATELLITE ESTIMATES OF T3.5/55 KT FROM TAFB...T3.1/47 KT FROM UW-CIMSS ADT...AND AN INCREASED ORGANIZATION OF THE INNER CORE CONVECTION. THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 315/9. ALL OF THE MODELS MOVE A SHORTWAVE TROUGH ACROSS THE SOUTHERN U.S. PLAINS STATES AND NORTHERN MEXICO DURING THE NEXT 24-36 HOURS..WHICH BRIEFLY WEAKENS THE RIDGE TO THE NORTH OF BEATRIZ AND ALLOWS THE CYCLONE TO SLOW DOWN AND MOVE CLOSER TO THE COAST OF MEXICO. THERE IS...HOWEVER... A SLIGHT BIFURCATION IN THE MODEL GUIDANCE. THE NOGAPS AND UKMET MODELS KEEP THE CYCLONE MOVING NORTHWESTWARD JUST OFFSHORE OF THE COAST OF MEXICO...AND THEN TURN IT WESTWARD BY 72 HOURS AS THE MID-LEVEL RIDGE BUILDS BACK IN TO THE NORTH OF THE CYCLONE. THE ECMWF...GFS...GFDL...AND HWRF MODELS...HOWEVER...TAKE BEATRIZ JUST INLAND ALONG THE SOUTHWESTERN COAST OF MEXICO IN ABOUT 36 HOURS. ALTHOUGH THE LATTER MODELS MOVE THE CENTER JUST INLAND ALONG THE COAST AND RAPIDLY WEAKEN THE CYCLONE...ALL OF THE MODELS TAKE THE MID-LEVEL CIRCULATION WESTWARD AFTER 48 HOURS. THE OFFICIAL FORECAST IS SIMILAR TO THE PREVIOUS TRACK AND KEEPS BEATRIZ JUST OFFSHORE THROUGH 48 HOURS AND THEN TURNS THE CYCLONE WESTWARD AFTER THAT AS THE MID-LEVEL RIDGE IS EXPECTED TO BUILD BACK IN TO THE NORTH OF THE CYCLONE BY 48 HOURS. THIS IS BASED ON THE ASSUMPTION THAT BEATRIZ WILL MAINTAIN ITS VERTICAL CONTINUITY AND NOT DECOUPLE DUE TO LAND INTERACTION. HOWEVER...ONLY A SLIGHT DEVIATION TO THE RIGHT OF THE FORECAST TRACK IS NEEDED TO BRING THE CYCLONE NEAR OR INLAND ALONG THE SOUTHWESTERN COAST OF MEXICO. FOR THIS REASON... WATCHES AND WARNINGS HAVE BEEN EXTENDED NORTHWARD ALONG THE COAST. THE INNER CORE CONVECTION AND UPPER-LEVEL OUTFLOW PATTERNS HAVE IMPROVED CONSIDERABLY DURING THE PAST 6 HOURS. WITH AN ALREADY EXPANSIVE EQUATORWARD OUTFLOW PATTERN PRESENT...AND THE POLEWARD OUTFLOW EXPECTED TO IMPROVE BY 24 HOURS...THERE APPEARS TO BE NO PHYSICAL REASONS WHY BEATRIZ SHOULD NOT CONTINUE TO INTENSIFY FOR THE NEXT 48 HOURS OR SO...AND POSSIBLY EVEN RAPIDLY INTENSIFY DURING THAT TIME. THE OFFICIAL INTENSITY FORECAST IS HIGHER THAN THE AVAILABLE MODEL GUIDANCE AND INDICATES A SLIGHTLY FASTER THAN NORMAL RATE OF INTENSIFICATION FOR THE NEXT 24 HOURS SINCE THE VERTICAL SHEAR IS EXPECTED TO DECREASE TO NEAR 10 KT WHILE THE CYCLONE REMAINS OVER SSTS ABOVE 29C. BEYOND 48 HOURS...BEATRIZ IS EXPECTED TO ENCOUNTER SEA SURFACE TEMPERATURES OF 22-24C AND ALSO MOVE INTO A MORE STABLE AIR MASS...WHICH SHOULD RESULT IN THE CYCLONE WEAKENING INTO A REMNANT LOW BY DAY 5...IF NOT SOONER. FORECAST POSITIONS AND MAX WINDS INIT 20/0900Z 15.7N 102.6W 50 KT 60 MPH 12H 20/1800Z 16.6N 103.2W 60 KT 70 MPH 24H 21/0600Z 17.6N 104.0W 75 KT 85 MPH 36H 21/1800Z 18.7N 104.7W 80 KT 90 MPH 48H 22/0600Z 19.4N 105.8W 80 KT 90 MPH 72H 23/0600Z 20.2N 109.1W 60 KT 70 MPH 96H 24/0600Z 20.2N 112.5W 35 KT 40 MPH 120H 25/0600Z 20.2N 116.5W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ FORECASTER STEWART