000
WTPA45 PHFO 130851 RRA
TCDCP5

TROPICAL STORM EMA DISCUSSION NUMBER   4
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP012019
1100 PM HST SAT OCT 12 2019

CONVENTIONAL INFRARED SATELLITE IMAGERY CLEARLY SHOWS THE EXPOSED
LOW-LEVEL CIRCULATION CENTER (LLCC) OF EMA THIS EVENING. THERE HAS
RECENTLY BEEN SPORADIC DEEP CONVECTION DEVELOPING IN THE NORTHWEST
QUADRANT OF THE SYSTEM. HOWEVER, EVEN THOUGH TOPS OF THESE
THUNDERSTORMS ARE ESTIMATED TO BE UP TO 50 THOUSAND FEET, THEY HAVE
BEEN DISSIPATING SOON AFTER DEVELOPING. THE LATEST ESTIMATES OF
VERTICAL WIND SHEAR IN THE VICINITY OF EMA ARE FROM THE SOUTHWEST
AT ABOUT 25 KT. AS A RESULT OF THE CONTINUED STEADY WEAKENING OF
THE TROPICAL CYCLONE, THE INITIAL INTENSITY ESTIMATE FOR THIS
ADVISORY HAS BEEN LOWERED TO 35 KT.

WITH THE CYCLONE BECOMING INCREASINGLY SHALLOW, THE PRIMARY
STEERING MECHANISM IS A SURFACE HIGH CENTERED FAR TO THE NORTHEAST
OF THE MAIN HAWAIIAN ISLANDS. THE INITIAL MOTION ESTIMATE FOR THIS
ADVISORY IS 305/9 KT. MOST OF THE RELIABLE GUIDANCE REMAINS IN CLOSE
AGREEMENT ON THE NEAR-TERM TRACK FORECAST. THEREFORE, THIS GENERAL
MOTION IS EXPECTED TO PERSIST UNTIL DISSIPATION OCCURS. NOW THAT EMA
HAS MOVED NORTH OF A MID- TO UPPER-LEVEL RIDGE AXIS, THE FORECAST
GUIDANCE SHOWS THAT EVEN STRONGER SOUTHWESTERLY VERTICAL WIND SHEAR
WILL LIKELY PRECLUDE ANY SIGNIFICANT DEEP CONVECTION FROM PERSISTING
OVER THE CENTER. AS A RESULT, THE LATEST FORECAST CONTINUES TO SHOW
A STEADY SPIN-DOWN OF THE TROPICAL CYCLONE DURING THE NEXT 12 TO 24
HOURS. THE LATEST FORECAST FOR TRACK AND INTENSITY CLOSELY FOLLOWS
THE PREVIOUS ADVISORY. THEREFORE, EMA IS EXPECTED TO BECOME A