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