“OVERALL SYSTEM ORGANIZATION HAS IMPROVED A BIT SINCE LAST NIGHT… WITH THE LOW LEVEL CIRCULATION CENTER… LLCC… LOCATED ON THE EASTERN EDGE OF DEEP CONVECTION. ADDITIONAL RAINBANDS ARE FORMING ACROSS THE NORTHEAST QUADRANT…AND ANIMATION OF THESE IN THE FEW VISIBLE IMAGES AVAILABLE INCREASES FIX CONFIDENCE. SUBJECTIVE DVORAK SATELLITE INTENSITY ESTIMATES RANGE FROM 2.0… 30 KT… FROM PHFO AND SAB TO 2.5… 35 KT… FROM JTWC. UW-CIMSS ADT WAS HIGHEST AT 2.7… 39 KT. THE BEST CHOICE FOR INITIAL INTENSITY IS A BLEND OF THESE, AND WE WILL KEEP OHO AS A 35 KT TROPICAL STORM FOR THIS ADVISORY.

OHO CONTINUES TO MEANDER TO THE SOUTH OF THE HAWAIIAN ISLANDS THIS MORNING, AND THE INITIAL MOTION OF 360/02 KT MAY BE JUST A SNAPSHOT OF THIS MEANDERING. UW-CIMSS AND SHIPS ANALYSIS SHOW EASTERLY SHEAR ACROSS OHO RANGES FROM 10 TO 15 KT, SO IT MAKES SENSE THAT ASSOCIATED DEEP CONVECTION LIES WEST OF THE LLCC AND THAT THE CORE IS TILTED TOWARD THE WEST WITH HEIGHT. THIS TILTING ADDS UNCERTAINTY TO MOTION IN SPITE OF VISIBLE IMAGE ANIMATION. STEERING INFLUENCES ARE WEAK AND INCLUDE A MID-LEVEL RIDGE WHICH EXTENDS WESTWARD FROM THE EASTERN PACIFIC AND THE FIRST GENTLE NUDGES FROM A DEEP TROUGH DEVELOPING NORTHWEST OF THE HAWAIIAN ISLANDS. WHILE FORECAST TRACK GUIDANCE REMAINS CLUSTERED AROUND NORTHERLY MOTION TODAY BECOMING NORTHEASTERLY MOTION MONDAY AND AFTERWARDS, FORWARD SPEED BETWEEN MODELS VARIES WIDELY, WITH ECMWF DEPICTING LONG RANGE FORWARD SPEED ABOUT DOUBLE WHAT GFS DEPICTS. THIS IS LIKELY DUE TO DIFFERENCES IN HOW EACH MODEL SEES THE INTERACTION BETWEEN OHO AND THE EXPECTED DEEP TROUGHING NORTH OF HAWAII BEYOND 48 HOURS, AND WITH THE INTERACTION WITH ANOTHER LOW FARTHER TO THE EAST. THE CURRENT FORECAST TRACK CLOSELY ALIGNS WITH THE PREVIOUS ONE THROUGH 72 HOURS, THEN IS ADJUSTED TO THE LEFT AT 96 AND 120 HOURS TO REMAIN WITHIN THE CONSENSUS ENVELOPE.

INTENSITY GUIDANCE CONTINUES TO INDICATE THAT OHO WILL REMAIN A TROPICAL STORM THROUGH THE FORECAST PERIOD, IN SPITE OF MOVING ACROSS 28C TO 29C WATER THROUGH 48 HOURS. SHEAR IS EXPECTED TO INCREASE DRAMATICALLY ACROSS OHO BEYOND 48 HOURS AS THE DEEP TROUGH NORTH OF HAWAII DIGS SOUTHEASTWARD AND BEGINS TO SCOOP THIS SYSTEM OUT OF THE DEEP TROPICS. HOWEVER, SOME STRENGTHENING IS EXPECTED UNTIL THEN AS SHEAR REMAINS MODERATE TODAY, THEN ACTUALLY DECREASES TEMPORARILY MONDAY. THE INTENSITY TREND FOR THIS ADVISORY CLOSELY FOLLOWS THE PREVIOUS ONE, BUT CAPS INTENSITY AT 55 KT.THIS IS SLIGHTLY HIGHER THAN SHIPS BUT BELOW HWRF AND GFDL.

THE 53RD WEATHER RECONNAISSANCE SQUADRON HAS BEEN TASKED TO FLY THIS SYSTEM IN SUPPORT OF CPHC OPERATIONS. INITIAL FLIGHTS INTO THE SYSTEM ARE PLANNED FOR THIS EVENING AND MONDAY MORNING. ADDITIONALLY, THE G-IV AIRCRAFT WILL FLY SYNOPTIC MISSIONS WITH A HIGH-ALTITUDE FLIGHT PLANNED MONDAY MORNING, IN ORDER FOR THE DATA TO BE UTILIZED BY AFTERNOON MODEL RUNS.

FORECAST POSITIONS AND MAX WINDS

INIT 04/2100Z 13.6N 154.9W 35 KT 40 MPH
12H 05/0600Z 14.0N 155.0W 40 KT 45 MPH
24H 05/1800Z 14.6N 154.6W 45 KT 50 MPH
36H 06/0600Z 15.5N 153.8W 50 KT 60 MPH
48H 06/1800Z 16.3N 152.7W 55 KT 65 MPH
72H 07/1800Z 18.3N 150.5W 55 KT 65 MPH
96H 08/1800Z 22.0N 148.3W 55 KT 65 MPH
120H 09/1800Z 26.2N 146.2W 50 KT 60 MPH”National Weather Service on Oct. 4, 2015