WTPZ45 KNHC 052033 RRA

TCDEP5



TROPICAL STORM IVETTE DISCUSSION NUMBER  13

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102016

200 PM PDT FRI AUG 05 2016



VISIBLE AND MICROWAVE SATELLITE IMAGERY INDICATE THAT DEEP-LAYER

WESTERLY SHEAR CONTINUES TO AFFECT IVETTE.  HOWEVER, WATER VAPOR

IMAGERY DOES SHOW CIRRUS EXPANDING WESTWARD, SO THE SHEAR IS MOST

LIKELY CONFINED TO THE LAYER BELOW THE OUTFLOW LEVEL.  NONETHELESS,

DVORAK INTENSITY ESTIMATES FROM TAFB AND SAB ARE T3.0/45 KT AND

T3.5/55 KT, RESPECTIVELY, AND THE UW-CIMSS ADT IS UP TO T5.3/53 KT.

BASED ON THESE DATA, THE INITIAL INTENSITY IS RAISED TO 50 KT.



THE INITIAL MOTION IS 280/11 KT.  IVETTE IS LOCATED DUE SOUTH OF A

MID-LEVEL ANTICYCLONE, WHICH IS CAUSING THE CYCLONE'S WESTWARD

MOTION.  IVETTE WILL SOON BE REACHING THE WESTERN EDGE OF THE

ANTICYCLONE, CAUSING IT TO TURN WEST-NORTHWESTWARD AND SLOW DOWN

SOON WHILE IT APPROACHES A MID- TO UPPER-LEVEL TROUGH NORTHEAST OF

HAWAII.  AFTER DAY 3, THE REMNANT LOW ASSOCIATED WITH IVETTE SHOULD

TURN WESTWARD, STEERED BY THE LOW-LEVEL TRADES.  ALTHOUGH THE ECMWF

IS SOMEWHAT FASTER AND FARTHER SOUTH THAN THE OTHER MODELS, THERE

IS STILL VERY LITTLE SPREAD AMONG THE GUIDANCE.  THE NHC TRACK

FORECAST IS JUST A LITTLE SOUTH OF THE MULTI-MODEL CONSENSUS AND

NOT TOO DIFFERENT FROM THE PREVIOUS FORECAST.



VERTICAL SHEAR IS PROBABLY NOT GOING TO DECREASE, AND, IN FACT, IT

SHOULD INCREASE TO OVER 20 KT IN ABOUT 36 HOURS, LASTING THROUGH THE

REST OF THE 5-DAY PERIOD.  IVETTE DOES APPEAR THAT IT WILL REACH

WARMER WATERS (AROUND 29C) IN ABOUT 24 HOURS, WHICH COULD FOSTER

JUST A LITTLE MORE STRENGTHENING.  AFTER THAT TIME, HOWEVER, THE=