WTPZ42 KNHC 180840 RRA

TCDEP2



TROPICAL STORM GREG DISCUSSION NUMBER   4

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072017

300 AM MDT TUE JUL 18 2017



DEEP CONVECTION HAS INCREASED IN BOTH INTENSITY AND COVERAGE DURING

THE LAST SEVERAL HOURS OVER AND TO THE SOUTHEAST OF THE CENTER OF

THE CYCLONE.  THE DVORAK CLASSIFICATIONS FROM TAFB AND SAB AT 0600

UTC WERE 2.0/30 KT, BUT ADT VALUES AND SATELLITE CONSENSUS ESTIMATES

FROM CIMSS AT THE UNIVERSITY OF WISCONSIN SUGGEST A SLIGHTLY HIGHER

INTENSITY.  BASED ON THE IMPROVEMENT IN CONVECTIVE ORGANIZATION

DURING THE PAST FEW HOURS, THE INITIAL INTENSITY IS INCREASED TO 35

KT, MAKING THE SYSTEM TROPICAL STORM GREG.



THE NORTHWESTERLY SHEAR CURRENTLY AFFECTING GREG IS EXPECTED TO

GRADUALLY LESSEN, AND THE UPPER-LEVEL WIND PATTERN WILL LIKELY

BECOME FAVORABLE IN THE 24- TO 60-H TIME FRAME.  THEREFORE, THE NHC

INTENSITY FORECAST CONTINUES TO SHOW MODEST STRENGTHENING DURING THE

NEXT COUPLE OF DAYS.  AFTER THAT TIME, HOWEVER, THE SHEAR IS

EXPECTED TO INCREASE OUT OF THE SOUTH OR SOUTHWEST AS THE CYCLONE

APPROACHES AN UPPER-LEVEL LOW. THIS INCREASE IN SHEAR COMBINED WITH

DRIER AIR AND COOLER WATERS SHOULD END THE STRENGTHENING TREND AND

CAUSE WEAKENING.  THE DEPRESSION WILL LIKELY DEGENERATE TO A REMNANT

LOW IN 4 TO 5 DAYS WHEN IT MOVES OVER SSTS BELOW 26 DEG C.  THE NHC

INTENSITY FORECAST IS THE SAME AS THE PREVIOUS ONE, AND IS IN LINE

WITH THE BULK OF THE GUIDANCE.



GREG IS MOVING WEST-NORTHWESTWARD AT 8 KT TO THE SOUTH OF A LOW- TO

MID-LEVEL RIDGE.  A WESTWARD TO WEST-NORTHWESTWARD MOTION WITH SOME

INCREASE IN FORWARD SPEED IS EXPECTED DURING THE NEXT FEW DAYS AS