WTPZ45 KNHC 121432 RRA

TCDEP5



TROPICAL STORM DARBY DISCUSSION NUMBER   4

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052016

900 AM MDT TUE JUL 12 2016



RECENT MICROWAVE DATA INDICATE THAT THE DEPRESSION HAS A WELL-

DEFINED CIRCULATION WITH THE CENTER LOCATED TO THE NORTHEAST OF THE

STRONGEST CONVECTION.  SUBJECTIVE DVORAK INTENSITY ESTIMATES ARE

T2.0 FROM TAFB AND T3.0 FROM SAB, AND THE LATEST ADT ESTIMATE IS

RIGHT AT THE TROPICAL STORM THRESHOLD.  A CONSENSUS OF THESE VALUES

SUPPORTS UPGRADING THE DEPRESSION TO A TROPICAL STORM, WITH THE

INITIAL INTENSITY SET AT 35 KT.  AFTER STARTING OFF MAY AND JUNE

VERY QUIETLY, THE EASTERN NORTH PACIFIC SEASON HAS ALREADY CAUGHT

UP TO WHERE IT SHOULD BE CLIMATOLOGICALLY IN TERMS OF NAMED STORMS.



DARBY APPEARS TO HAVE TURNED WESTWARD WITH AN INITIAL MOTION OF

270/9 KT.  A SUBTROPICAL RIDGE EXTENDING WESTWARD FROM NORTHERN

MEXICO IS EXPECTED TO STRENGTHEN DURING THE NEXT THREE DAYS, WHICH

WILL STEER DARBY WESTWARD, OR EVEN A LITTLE SOUTH OF DUE WEST,

DURING THAT TIME.  THE MODEL FIELDS CONTINUE TO SHOW DIFFERENCES IN

THE STRENGTH OF THE RIDGE AT THE END OF THE FORECAST PERIOD.  THE

ECMWF MAINTAINS A STRONGER RIDGE, WITH DARBY POSSIBLY CONTINUING A

WESTWARD MOTION, WHILE THE GFS ERODES THE RIDGE AND ALLOWS DARBY TO

GAIN SOME LATITUDE.  THE TRACK MODEL ENVELOPE HAS AGAIN SHIFTED

SOUTHWARD ON THIS CYCLE, AND THE UPDATED NHC TRACK FORECAST HAS

BEEN NUDGED IN THAT DIRECTION CLOSE TO A CONSENSUS OF THE GFS AND

ECMWF.



DARBY WILL BE MOVING OVER A WARM POOL OF SSTS AROUND 29.5 DEGREES

CELSIUS DURING THE NEXT 24 HOURS, AND THE NORTHEASTERLY VERTICAL

SHEAR AFFECTING THE CYCLONE SHOULD ABATE A BIT.  DEPENDING ON=