WTPZ45 KNHC 040251 RRA

TCDEP5



TROPICAL STORM IVETTE DISCUSSION NUMBER   6

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP102016

800 PM PDT WED AUG 03 2016



MODERATE NORTHEASTERLY VERTICAL SHEAR CONTINUES TO AFFLICT

IVETTE, AS THE DEEP CONVECTION IS ASYMMETRIC WITH MOST OF THE COLD

CLOUD TOPS SOUTHWEST OF THE CENTER.  A BLEND OF THE TAFB AND SAB

SUBJECTIVE DVORAK, THE CIMSS ADVANCED DVORAK, AND AMSU ESTIMATES

GIVES AN INTENSITY OF 40 KT, UNCHANGED FROM THE PREVIOUS ADVISORY.

A PAIR OF ASCAT SCATTEROMETER PASSES AROUND 18Z INDICATES THAT

IVETTE REMAINS SMALL SIZED, BUT SLIGHTLY LARGER IN

TROPICAL-STORM-FORCE WIND RADII THAN PREVIOUSLY ESTIMATED.



THE SCATTEROMETER PASSES AND AN AMSR2 IMAGE AT 2023Z SUGGESTED THAT

IVETTE'S CENTER WAS FARTHER SOUTH THAN PREVIOUSLY ANALYZED.  THIS

WAS CONFIRMED BY THE BRIEF APPEARANCE OF THE LOW-LEVEL CENTER IN

GEOSTATIONARY VISIBLE IMAGERY, AS IT PEEKED OUT FROM THE EDGE OF THE

DEEP CONVECTION.  IVETTE IS MOVING TOWARD THE WEST AT 14 KT, ALONG

THE SOUTHERN EDGE OF A DEEP-LAYER SUBTROPICAL RIDGE EXTENDING

WESTWARD FROM MEXICO.  THE TROPICAL CYCLONE SHOULD CONTINUE MOVING

TOWARD THE WEST OR WEST-NORTHWEST AT A SLIGHTLY SLOWER RATE OF

FORWARD SPEED FOR THE NEXT FEW DAYS.  THE NHC TRACK FORECAST IS

BASED UPON THE TIGHTLY CLUSTERED GLOBAL AND REGIONAL HURRICANE

MODELS, AND IS SLIGHTLY SOUTH OF THE PREVIOUS ADVISORY BECAUSE OF

THE SOUTHWARD REVISION TO THE INITIAL POSITION.



THE CONTINUING STEADY STATE OF IVETTE WOULD ARGUE FOR LITTLE

CHANGE IN THE SHORT TERM, BUT THE GLOBAL MODELS INSIST THAT THE

VERTICAL SHEAR SHOULD BE DIMINISHING NOW.  THE NHC INTENSITY

FORECAST ASSUMES THAT THE SHEAR WILL LOWER DURING THE NEXT TWO TO=