WTPZ43 KNHC 212037 RRA

TCDEP3



TROPICAL DEPRESSION EIGHT-E DISCUSSION NUMBER   1

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP082016

300 PM MDT THU JUL 21 2016



AN ASCAT-B PASS AT 1742Z SHOWED THAT THE AREA OF LOW PRESSURE

LOCATED WELL SOUTHWEST OF MEXICO NOW HAS A WELL-DEFINED CENTER, AND

THE GEOSTATIONARY IMAGERY SHOWS A CURVED CONVECTIVE BAND WRAPPING

NEARLY HALFWAY AROUND THE SYSTEM.  GIVEN THIS, THE LOW IS NOW

CLASSIFIED AS A TROPICAL CYCLONE.  THE INITIAL INTENSITY IS SET TO

30 KT BASED ON THE ASCAT DATA, WHICH IS ALSO IN AGREEMENT WITH THE

LATEST DVORAK ESTIMATE FROM SAB.  THE DEPRESSION WILL BE MOVING OVER

SSTS OF 28C OR HIGHER FOR THE NEXT COUPLE OF DAYS, BUT WILL ALSO BE

IN A MODERATE EASTERLY TO NORTHEASTERLY SHEAR ENVIRONMENT DURING

THAT TIME.  GIVEN THESE CONDITIONS, GRADUAL INTENSIFICATION IS

FORECAST IN THE SHORT TERM.  THE CYCLONE IS FORECAST TO PEAK IN

ABOUT 72 HOURS BEFORE IT MOVES OVER COOLER WATERS AND INTO A MORE

STABLE ENVIRONMENT, WHICH SHOULD RESULT IN SLOW WEAKENING.  THE NHC

INTENSITY PREDICTION IS CLOSE TO THE INTENSITY CONSENSUS THROUGH THE

FORECAST PERIOD.



THE INITIAL MOTION ESTIMATE IS A SOMEWHAT UNCERTAIN 290/10 GIVEN THE

RECENT FORMATION OF THE SYSTEM.  THE DOMINANT STEERING MECHANISM FOR

THE FIRST 2-3 DAYS OF THE FORECAST PERIOD WILL BE A LARGE

SUBTROPICAL RIDGE THAT WILL MIGRATE WESTWARD FROM CENTRAL NORTH

AMERICA OVER THE EASTERN PACIFIC.  THIS SHOULD KEEP THE CYCLONE

MOVING GENERALLY WEST-NORTHWESTWARD FOR THE FIRST 48 HOURS OR SO.

AFTER THAT TIME, THERE IS AN INCREASE IN THE SPREAD OF THE GUIDANCE.

THE ECMWF AND HWRF SHOW THE CYCLONE TURNING MORE POLEWARD INTO A

WEAKNESS IN THE RIDGE CAUSED BY AN UPPER-LEVEL LOW, WITH THE ECMWF=