WTPZ42 KNHC 190858 RRA

TCDEP2



TROPICAL STORM GREG DISCUSSION NUMBER   8

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP072017

300 AM MDT WED JUL 19 2017



THE INCREASED CONVECTIVE ORGANIZATION OF GREG PROVED TO BE

SHORT-LIVED.  ALTHOUGH THE SHIPS-ANALYZED SHEAR REMAINS LOW, THE

CLOUD PATTERN NOW RESEMBLES THAT OF A SHEARED TROPICAL CYCLONE.  A

0458 UTC ASCAT-B OVERPASS CAUGHT THE EASTERN HALF OF THE

CIRCULATION, SHOWING NO WINDS ABOVE 30 KT, WHILE  DVORAK-BASED

ESTIMATES OF THE CURRENT INTENSITY RANGE FROM 45 TO 57 KT.  THE

INITIAL INTENSITY HAS ONLY BEEN LOWERED TO 40 KT SINCE THE ASCAT

PASS MISSED THE WESTERN HALF OF THE CIRCULATION, BUT THIS COULD BE

GENEROUS.



BASED ON THE AFOREMENTIONED ASCAT PASS, THE ANALYZED CENTER OF THE

TROPICAL STORM HAS BEEN SHIFTED FARTHER SOUTH, AND THE OVERALL

TRACK FORECAST NUDGED SOUTHWARD ACCORDINGLY.  WHILE THE REASONING

BEHIND THE FORECAST IS UNCHANGED, THE MODEL SPREAD IS STILL FAIRLY

HIGH, AND RUN-TO-RUN CONSISTENCY IS LOW.  FOR INSTANCE, THE 120-H

FORECAST POINTS FROM THE 18Z AND 00Z GFS MODEL DIFFER BY NEARLY 300

NMI. THE CMC, ECMWF, GFS, AND UKMET GLOBAL MODELS STILL SHOW GREG

AND TD EIGHT-E INTERACTING TO VARIOUS DEGREES, WITH EACH CYCLONE

BEGINNING TO AFFECT THE OTHERS TRACK IN ABOUT 36 HOURS.  THIS

INTERACTION SHOULD ULTIMATELY CAUSE GREG TO ACCELERATE TOWARD THE

WEST-NORTHWEST.  AFTER ABOUT 72 HOURS IT IS STILL ASSUMED THAT GREG

WILL BE THE DOMINANT CYCLONE, SO ONLY A SLIGHT TURN BACK TOWARD THE

WEST-SOUTHWEST IS FORECAST. IF TD EIGHT-E INSTEAD BECOMES DOMINANT,

THEN A MORE PRONOUNCED SOUTHERN TURN WOULD BE EXPECTED.



ALTHOUGH THE INITIAL INTENSITY IS A LITTLE LOWER THAN THE PREVIOUS