WTPZ43 KNHC 190252 RRA

TCDEP3



TROPICAL DEPRESSION EIGHT-E DISCUSSION NUMBER   3

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP082017

800 PM PDT TUE JUL 18 2017



THE DEPRESSION CONTINUES TO PRODUCE SMALL BURSTS OF DEEP CONVECTION,

BUT MICROWAVE DATA AND THE LAST FEW VISIBLE IMAGES OF THE DAY

INDICATE THAT THE LOW-LEVEL CENTER IS EXPOSED TO THE NORTHEAST OF

THE THUNDERSTORM ACTIVITY.  VISIBLE IMAGERY ALSO SHOWS A BAND OF

CIRRUS FLOWING RIGHT OVER THE DEPRESSION'S CIRCULATION, INDICATIVE

OF ABOUT 25 KT OF WEST-NORTHWESTERLY SHEAR.  SINCE DVORAK INTENSITY

ESTIMATES HAVE NOT CHANGED FROM SIX HOURS AGO, THE INITIAL INTENSITY

IS HELD AT 30 KT FOR THIS ADVISORY.



THE BIG QUESTION MARK FOR BOTH THE DEPRESSION'S FUTURE TRACK AND

INTENSITY IS HOW IT WILL INTERACT WITH TROPICAL STORM GREG TO ITS

EAST.  ALL THE GLOBAL MODELS SHOW THE DEPRESSION SWINGING TO THE

SOUTHWEST AND SOUTH OF GREG DURING THE NEXT SEVERAL DAYS AS THE TWO

CIRCULATIONS INTERACT.  THE GFS MODEL SHOWS GREG BECOMING THE

DOMINANT CYCLONE, WITH THE DEPRESSION EVENTUALLY DISSIPATING.

HOWEVER, THE ECMWF AND CANADIAN MODELS SEEM TO PREFER THE DEPRESSION

BECOMING THE DOMINANT SYSTEM AND ABSORBING GREG.  THE UKMET IS

SOMEWHERE IN BETWEEN, WITH THE TWO CIRCULATIONS MERGING. SINCE GREG

IS THE STRONGER OF THE TWO SYSTEMS AT THIS POINT, WE ARE FAVORING

THAT BEING THE DOMINANT ONE, AND THE NEW NHC FORECAST SHOWS THE

DEPRESSION WEAKENING OVER TIME AND DISSIPATING BY 96 HOURS.

HOWEVER, THERE IS A LOT OF UNCERTAINTY IN THIS FORECAST, AND

ADJUSTMENTS WOULD BE NEEDED IF IT BECOMES APPARENT THAT THE

DEPRESSION WILL END UP BEING THE DOMINANT CYCLONE.



THE DEPRESSION IS MOVING SLOWLY WESTWARD WITH AN INITIAL MOTION OF