WTPZ42 KNHC 182034 RRA

TCDEP2



TROPICAL STORM GREG DISCUSSION NUMBER   6

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072017

300 PM MDT TUE JUL 18 2017



SATELLITE IMAGERY SUGGESTS THAT THE CIRCULATION OF GREG HAS BECOME

BETTER DEFINED TODAY.  HOWEVER, THE EARLIER DENSE CONVECTIVE

OVERCAST HAS DISSIPATED, LEAVING A SMALL AREA OF CONVECTION NEAR

THE CENTER AND SOME THIN OUTER BANDING.  SUBJECTIVE SATELLITE

INTENSITY ESTIMATES FROM TAFB AND SAB ARE 35 KT, WHILE ESTIMATES

BASED ON MICROWAVE SOUNDER DATA ARE 40-45 KT.  BASED ON THE CURRENT

CONVECTIVE TRENDS, THE INITIAL INTENSITY REMAINS 35 KT, AND IT IS

POSSIBLE THIS IS CONSERVATIVE.  WATER VAPOR IMAGERY INDICATES THAT

UPPER-LEVEL WESTERLIES PRODUCED BY THE OUTFLOW OF HURRICANE

FERNANDA AND TROPICAL DEPRESSION EIGHT-E ARE IMPINGING ON THE

WESTERN SIDE OF GREG, ALTHOUGH THE ANALYZED VERTICAL SHEAR IS

CURRENTLY LOW.



THE INITIAL MOTION IS 275/8.  FOR THE FIRST 48 H, GREG SHOULD MOVE

GENERALLY WESTWARD TO THE SOUTH OF A MID-LEVEL RIDGE.  AFTER THAT,

THE FORECAST BECOMES LOW CONFIDENCE DUE TO INTERACTION, AND

POSSIBLE MERGER, WITH TROPICAL DEPRESSION EIGHT-E.  THE

LARGE-SCALE MODELS ARE SHOWING RUN-TO-RUN INCONSISTENCY ON WHICH OF

THE CYCLONES WILL BE DOMINANT DURING THIS PROCESS AND WHICH MIGHT

GET DESTROYED.  THE CURRENT FORECAST SCENARIO IS THAT BOTH SYSTEMS

WILL SURVIVE, WITH GREG MOVING QUICKLY AROUND THE NORTH SEMICIRCLE

OF THE CIRCULATION OF EIGHT-E.  THE NEW FORECAST TRACK IS NEAR THE

MODEL CONSENSUS THROUGH 72 H AND NORTH OF THE MODEL CONSENSUS AFTER

THAT TIME.



A COMBINATION OF LIGHT/MODERATE VERTICAL WIND SHEAR AND WARM SEA

SURFACE TEMPERATURES SHOULD ALLOW GREG TO SLOWLY STRENGTHEN DURING