WTPZ42 KNHC 212050 RRA

TCDEP2



TROPICAL STORM GREG DISCUSSION NUMBER  18

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072017

200 PM PDT FRI JUL 21 2017



GREG HAS THROWN ME A CURVEBALL TODAY WITH THE CENTER UNEXPECTEDLY

BECOMING EXPOSED SOUTHWEST OF THE MAIN BALL OF CONVECTION.  WHILE

THERE IS CLEARLY AN IMPRESSIVE LOW-LEVEL CIRCULATION, AS SEEN BY

BOTH CONVENTIONAL AND MICROWAVE IMAGES, GREG HAS BECOME LESS

ORGANIZED OVERALL.  SATELLITE INTENSITY ESTIMATES, CONSEQUENTLY,

HAVE DROPPED, AND THE INITIAL WIND SPEED IS REDUCED TO 45 KT.



WHILE GREG IS FORECAST TO REMAIN OVER WARM WATERS FOR THE NEXT

COUPLE OF DAYS, DRY AIR IN THE MID-LEVELS AND SOME WESTERLY SHEAR

IS LIKELY TO IMPEDE THE STRENGTHENING PROCESS, DESPITE AN INTACT

LOW-LEVEL CORE PRESENT ON MICROWAVE DATA.  THUS THE INTENSITY

FORECAST IS HELD STEADY FOR ABOUT A DAY.  THEREAFTER, THE REGIONAL

HURRICANE MODELS SUGGEST GREG WILL HAVE A CHANCE TO REINTENSIFY,

ALTHOUGH THIS IS FAR FROM A SLAM DUNK WITH AN UNCERTAIN

ENVIRONMENT.  I HAVE ELECTED TO SHOW SOME INTENSIFICATION ON DAY 2

OF THE FORECAST, BUT REDUCED BY ONLY ABOUT 10 KT FROM THE PREVIOUS

PREDICTION DUE TO CONTINUITY CONSTRAINTS.  THE GUIDANCE CONTINUES TO

INDICATE A WEAKER STORM, SO IT WOULD NOT BE SURPRISING IF LATER

SHIFTS HAD TO LOWER THE FORECAST WINDS MORE.



THE INITIAL MOTION HAS SHIFTED TO 275/11.  THE SUBTROPICAL RIDGE

SHOULD HOLD TO THE NORTH OF GREG FOR THE NEXT FEW DAYS, STEERING

THE STORM GENERALLY WESTWARD.  THEREAFTER, GREG SHOULD TURN TO THE

WEST-NORTHWEST DUE TO A SMALL LOW- TO MID-LEVEL TROUGH DROPPING OUT

OF THE MID-LATITUDES, WEAKENING THE PERIPHERY OF THE AFOREMENTIONED