TROPICAL STORM ANA DISCUSSION NUMBER 4
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI CP022014
500 AM HST TUE OCT 14 2014
OVERNIGHT INFRARED IMAGERY SHOWS THE LLCC IS EMBEDDED FIRMLY WITHIN
A WELL-PROPORTIONED AND SYMMETRICAL 220 TO 250 MILE WIDE CDO. DEEP
CONVECTION NO LONGER APPEARS TO BE MERELY PULSING AROUND THE CENTER.
THE COMBINATION OF FAINT BANDING IN ENHANCED IR AND THE AVAILABILITY
OF RECENT GMI DATA INCREASES INITIAL POSITION CONFIDENCE. ALL THREE
SATELLITE AGENCIES...PHFO...SAB AND JTWC...DERIVED A DVORAK
INTENSITY OF 3.0/45 KT THIS MORNING. THIS CONSENSUS...ALONG WITH A
CONTINUOUSLY IMPROVING SATELLITE PRESENTATION...PROMPTS US TO
INCREASE THE INITIAL INTENSITY THIS FORECAST CYCLE TO 45 KT.
ANA HAS SLOWED SLIGHTLY OVER THE PAST 6 HOURS...WITH A MOTION OF
305/04 KT...AS THE STORM IS STEERED BY A RIDGE TO ITS NORTH AND
NORTHEAST. SLOW MOVEMENT GENERALLY TO THE NORTHWEST WILL CONTINUE AS
A WESTWARD-MOVING UPPER LOW AFFECTING THE MAIN HAWAIIAN ISLANDS
SLIDES WESTWARD AND THE RIDGE REMAINS DISPLACED NORTHWARD.
HOWEVER...ANA IS EXPECTED TO TAKE ON A WEST NORTHWEST MOTION IN THE
MID-TERM...FROM 24 THROUGH 48 HOURS...AS RIDGING TEMPORARILY
STRENGTHENS TO ITS NORTH. THIS RIDGING IS FORECAST TO WEAKEN AGAIN
AFTER 48 HOURS AS DEEP TROUGHING FAR NORTH OF THE MAIN HAWAIIAN
ISLANDS DIGS SOUTHEASTWARD...ALLOWING ANA TO ASSUME A MORE
NORTHWESTERLY MOTION BEYOND 48 HOURS. INTERESTINGLY...TVCN CONSENSUS
HAS SHIFTED SLIGHTLY TO THE RIGHT BEYOND 48 HOURS...NOW CLOSELY
MATCHING THE PREVIOUS FORECAST TRACK. GIVEN THIS...AND THE SEEMINGLY
WELL-BEHAVED INITIAL MOTION...WE WILL KEEP THE FORECAST TRACK
UNCHANGED FOR THIS CYCLE.
INTENSITY GUIDANCE SHOWS MORE RAPID STRENGTHENING THROUGH 36
HOURS...WITH SHIPS SHOWING ANA REACHING HURRICANE STRENGTH AT 24
HOURS...AS EASTERLY SHEAR CURRENTLY OVER THE SYSTEM GRADUALLY
DIMINISHES AND THEN REMAINS LIGHT. SO...IN ADDITION TO THE INCREASE
IN INITIAL INTENSITY...OUR FORECAST NOW HAS ANA BECOMING A HURRICANE
AT 36 HOURS...OR WEDNESDAY AFTERNOON. FOR THE PAST FEW FORECAST
CYCLES...SHIPS EITHER CAPPED OR SLIGHTLY WEAKENED ANA AT 96 AND 120
HOURS. WITH THIS RUN...SHIPS PEAKS ANA INTENSITY BETWEEN 48 AND 72
HOURS...THEN WEAKENS THIS SYSTEM BACK TO TROPICAL STORM STRENGTH BY
120 HOURS. WE WILL NOW FOLLOW THIS TREND...CAPPING ANA AT 75
KT...THEN SLIGHTLY WEAKENING IT AT 96 AND 120 HOURS. NOTE THAT ANA
IS STILL FORECAST TO REMAIN A HURRICANE AT 120 HOURS.
INTERESTS IN THE MAIN HAWAIIAN ISLANDS SHOULD MONITOR THE PROGRESS
OF THIS SYSTEM THROUGH THE WEEK.
FORECAST POSITIONS AND MAX WINDS
INIT 14/1500Z 13.4N 143.3W 45 KT 50 MPH
12H 15/0000Z 13.8N 144.0W 50 KT 60 MPH
24H 15/1200Z 14.2N 145.1W 60 KT 70 MPH
36H 16/0000Z 14.6N 146.2W 65 KT 75 MPH
48H 16/1200Z 14.9N 147.3W 75 KT 85 MPH
72H 17/1200Z 15.7N 149.5W 75 KT 85 MPH
96H 18/1200Z 17.0N 151.6W 70 KT 80 MPH
120H 19/1200Z 18.4N 153.8W 70 KT 80 MPH
$$
FORECASTER POWELL
