WTPZ41 KNHC 150252 RRA

TCDEP1



TROPICAL STORM ORLENE DISCUSSION NUMBER  17

NWS NATIONAL HURRICANE CENTER MIAMI FL       EP162016

800 PM PDT WED SEP 14 2016



ORLENE'S CONVECTIVE SIGNATURE REMAINS A SMALL, SYMMETRIC CENTRAL

DENSE OVERCAST WITH SOME BANDING IN THE NORTHERN SEMICIRCLE.

HOWEVER, THE CLOUD TOP TEMPERATURES HAVE WARMED SOME AND THE EXTENT

OF THE COLD CLOUDINESS HAS DIMINISHED SLIGHTLY DURING THE LAST

SEVERAL HOURS.  A BLEND OF THE TAFB/SAB SUBJECTIVE DVORAK, CIMSS

ADVANCED DVORAK, AND CIMSS/CIRA AMSU SUGGEST THAT ORLENE HAS

WEAKENED TO A TROPICAL STORM WITH 60 KT AS THE INITIAL INTENSITY.



ORLENE IS SITUATED DIRECTLY UNDER THE UPPER-LEVEL SUBTROPICAL RIDGE

AND THUS IS EXPERIENCING VERY LOW VERTICAL SHEAR.  HOWEVER, THE

TROPICAL STORM IS EXPECTED TO RIDE ALONG THE 26C SST CONTOUR WHILE

THE NOT-VERY-MOIST ENVIRONMENT BECOMES QUITE DRY DURING THE NEXT

THREE DAYS.  IN ADDITION, BY DAYS FOUR AND FIVE, THE SHEAR SHOULD

GO UP SUBSTANTIALLY AS ORLENE APPROACHES A MID- TO UPPER-LEVEL LOW.

THE BOTTOM LINE IS THAT THE TROPICAL STORM SHOULD GRADUALLY WEAKEN.

THE NHC INTENSITY FORECAST IS BASED UPON A BLEND OF THE LGEM/SHIPS

STATISTICAL MODELS AND THE COAMPS DYNAMICAL MODEL, AND IS QUITE

SIMILAR TO THAT FROM THE PREVIOUS ADVISORY.  PERHAPS THE BIGGEST

UNCERTAINTY IS WHEN THE DEEP CONVECTION WILL CEASE.  THE FORECAST

IS FOR THAT TO OCCUR AROUND DAY FIVE, BUT IT WOULD NOT BE SURPRISING

IF THIS OCCURRED SIGNIFICANTLY EARLIER.



ORLENE IS MOVING TOWARD THE WEST-NORTHWEST AT ABOUT 5 KT.  THE

SYSTEM IS EXPECTED TO TURN TOWARD THE WEST OR WEST-SOUTHWEST AND

MOVE FASTER FOR THE NEXT THREE TO FOUR DAYS AS MID-LEVEL RIDGING=