Tropical Cyclone Iselle Number 30A Public Advisory

WTPA33 PHFO 071754
TCPCP3

BULLETIN
HURRICANE ISELLE INTERMEDIATE ADVISORY NUMBER 30A
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP092014
800 AM HST THU AUG 07 2014

…DANGEROUS ISELLE MAKING A BEELINE FOR THE BIG ISLAND…

SUMMARY OF 800 AM HST…1800 UTC…INFORMATION
———————————————-
LOCATION…18.6N 151.4W
ABOUT 255 MI…410 KM ESE OF HILO HAWAII
ABOUT 460 MI…740 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS…80 MPH…130 KM/H
PRESENT MOVEMENT…WNW OR 285 DEGREES AT 17 MPH…28 KM/H
MINIMUM CENTRAL PRESSURE…986 MB…29.12 INCHES

WATCHES AND WARNINGS
——————–
CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY…

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT…

A HURRICANE WARNING IS IN EFFECT FOR…
* HAWAII COUNTY

A TROPICAL STORM WARNING IS IN EFFECT FOR…
* MAUI COUNTY…INCLUDING THE ISLANDS OF MAUI…MOLOKAI…LANAI…
AND KAHOOLAWE.
* OAHU
* KAUAI COUNTY INCLUDING THE ISLANDS OF KAUAI AND NIIHAU.

A HURRICANE WARNING MEANS THAT HURRICANE CONDITIONS ARE EXPECTED
SOMEWHERE WITHIN THE WARNING AREA. PREPARATIONS TO PROTECT LIFE AND
PROPERTY SHOULD BE RUSHED TO COMPLETION.

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

INTERESTS IN THE NORTHWEST HAWAIIAN ISLANDS SHOULD MONITOR THE
PROGRESS OF ISELLE.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA…PLEASE MONITOR
PRODUCTS ISSUED BY THE NATIONAL WEATHER SERVICE OFFICE IN
HONOLULU HAWAII.

DISCUSSION AND 48-HOUR OUTLOOK
——————————
AT 800 AM HST…1800 UTC…THE CENTER OF HURRICANE ISELLE WAS
LOCATED NEAR LATITUDE 18.6 NORTH…LONGITUDE 151.4 WEST. THE MOTION
OF ISELLE HAS NOT CHANGED…AND THE HURRICANE IS STILL MOVING TOWARD
THE WEST-NORTHWEST NEAR 17 MPH…28 KM/H. THIS MOTION IS EXPECTED TO
CONTINUE THROUGH FRIDAY…WITH SOME SLOWING IN FORWARD SPEED ON
FRIDAY NIGHT. ON THE FORECAST TRACK…THE CENTER OF ISELLE IS
EXPECTED TO PASS OVER THE BIG ISLAND TONIGHT…AND PASS JUST SOUTH
OF THE SMALLER ISLANDS FRIDAY.

MAXIMUM SUSTAINED WINDS ARE NEAR 80 MPH…130 KM/H…WITH HIGHER
GUSTS. SOME WEAKENING IS FORECAST DURING THE NEXT 48 HOURS…BUT
ISELLE IS EXPECTED TO STILL BE NEAR HURRICANE STRENGTH AS IT MAKES
LANDFALL ON THE BIG ISLAND TONIGHT.

REMEMBER THAT THE EFFECTS OF HURRICANES ARE FAR REACHING. DO NOT
FOCUS ON THE CENTER POSITION ALONE. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO 35 MILES…55 KM…FROM THE CENTER…AND TROPICAL
STORM FORCE WINDS EXTEND OUTWARD UP TO 140 MILES…220 KM.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 986 MB…29.12 INCHES.

HAZARDS AFFECTING LAND
———————-
WIND…CONDITIONS WILL STEADILY DETERIORATE OVER THE BIG ISLAND
THIS AFTERNOON…WITH TROPICAL STORM CONDITIONS EXPECTED TO ARRIVE
WELL BEFORE DARK. HURRICANE CONDITIONS ARE EXPECTED FOR PORTIONS OF
THE BIG ISLAND TONIGHT. TROPICAL STORM CONDITIONS ARE EXPECTED OVER
MAUI COUNTY TONIGHT…AND FOR OAHU LATE TONIGHT AND FRIDAY. TROPICAL
STORM CONDITIONS ARE EXPECTED FOR KAUAI COUNTY LATER FRIDAY.

RAINFALL…RAINFALL TOTALS OF 5 TO 8 INCHES…WITH ISOLATED MAXIMUM
AMOUNTS TO 12 INCHES…ARE EXPECTED ALONG THE TRACK OF ISELLE.
THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AS WELL AS
ROCK AND MUD SLIDES.

SURF…SWELLS GENERATED BY ISELLE WILL CONTINUE TO RISE ALONG EAST
FACING SHORES. VERY LARGE…DAMAGING SURF IS EXPECTED ALONG SOME
EAST AND SOUTH SHORES STARTING TODAY.

STORM SURGE…THE COMBINATION OF A DANGEROUS STORM SURGE AND THE
TIDE WILL CAUSE NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY
RISING WATERS. THE WATER COULD REACH THE FOLLOWING HEIGHTS ABOVE
GROUND IF THE PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE…

BIG ISLAND WINDWARD AND KAU…1 TO 3 FT

THE HIGHEST WATER WILL OCCUR ALONG THE IMMEDIATE COAST IN AREAS OF
ONSHORE FLOW. THE SURGE WILL BE ACCOMPANIED BY LARGE AND DAMAGING
WAVES. SURGE RELATED FLOODING DEPENDS ON THE RELATIVE TIMING OF THE
SURGE AND THE TIDAL CYCLE…AND CAN VARY GREATLY OVER SHORT
DISTANCES.

NEXT ADVISORY
————-
NEXT COMPLETE ADVISORY…1100 AM HST.

$$
FORECASTER R BALLARD

 


000
WTPA43 PHFO 071501
TCDCP3

HURRICANE ISELLE DISCUSSION NUMBER 30
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP092014
500 AM HST THU AUG 07 2014

ALTHOUGH THE SATELLITE PRESENTATION OF ISELLE HAS DEGRADED SLIGHTLY
OVER THE PAST COUPLE OF HOURS…A PERSISTENT EYE FEATURE CONTINUES
TO BE OBSERVED…AND ISELLE REMAINS A HURRICANE. DATA FROM AN AIR
FORCE RECONNAISSANCE AIRCRAFT CORROBORATE THE SLIGHT WEAKENING
TREND OBSERVED BY SATELLITE…AS MAXIMUM FLIGHT LEVEL WINDS IN THE
NORTHEAST QUADRANT DIMINISHED FROM 100 KT TO 85 KT OVERNIGHT…AND
MAXIMUM SFMR WINDS HAVE LOWERED TO NEAR 60 KT. BASED ON A BLEND OF
THE AIRCRAFT DATA AND SATELLITE INTENSITY ESTIMATES BETWEEN 4.0/65
KT AND 4.5/77 KT…THE INITIAL INTENSITY OF ISELLE IS BEING LOWERED
TO 70 KT FOR THIS ADVISORY.

INITIAL MOTION ESTIMATE IS 285/15 KT…WHICH HAS BEEN FAIRLY
CONSISTENT OVER THE PAST 12 HOURS…WITH ISELLE BEING STEERED BY A
MID LEVEL RIDGE TO THE NORTH. THE UPDATED FORECAST TRACK REMAINS
CONSISTENT WITH THE LAST SEVERAL FORECASTS IN THE SHORT TERM…AND
REMAINS IN GOOD AGREEMENT WITH THE MULTI-MODEL CONSENSUS…WHICH HAS
BEEN CONSISTENT IN DEPICTING LANDFALL ALONG WINDWARD BIG ISLAND
THIS EVENING. IN 36 TO 48 HOURS ISELLE IS EXPECTED TO REACH THE
WESTERN PERIPHERY OF THE RIDGE AS A WEAK CUT OFF LOW DIGS SOUTHWARD
ALONG THE FORECAST TRACK…RESULTING IN A SLOWING OF THE FORWARD
MOTION THROUGH 72 HOURS. AS THE LOW MOVES SOUTH AND ISELLE WEAKENS…
A NEW RIDGE ALOFT IS FORECAST TO BUILD NORTH OF THE WEAKENING
ISELLE…AND THE FORWARD MOTION WILL INCREASE ONCE AGAIN. THE
UPDATED FORECAST TRACK ONLY OFFERS MINOR CHANGES TO THE PREVIOUS…
AND CLOSELY FOLLOWS THE WELL-PERFORMING CONSENSUS TVCN.

THE INTENSITY FORECAST CALLS FOR ONLY SLIGHT WEAKENING BEFORE
LANDFALL TONIGHT…DESPITE THE FORECAST OF MODERATE NORTHWESTERLY
SHEAR BY SHIPS GUIDANCE. ISELLE REMAINS SOUTH OF A RIDGE ALOFT
CENTERED WEST OF THE MAIN HAWAIIAN ISLANDS AND A RIDGE CENTERED OVER
THE BAJA PENINSULA. A COL…OR WEAKNESS…BETWEEN THESE TWO RIDGES
PROVIDES A LIGHTER SHEAR ENVIRONMENT IN WHICH ISELLE WOULD BE ABLE
TO MAINTAIN THE CURRENT INTENSITY BEFORE LANDFALL…WHEREAS IF
ISELLE WERE TO MOVE WEST OF THE COL AND CLOSER TO THE RIDGE CENTERED
TO THE WEST…THE SHEAR PROFILE WOULD BE MORE DEBILITATING. THE
INTENSITY FORECAST PROBLEM IS THAT GLOBAL MODELS ARE OFFERING
DIFFERENT SOLUTIONS AS TO THE INTERACTION BETWEEN ISELLE AND THE
FLOW ALOFT IN THE SHORT TERM…WITH SOME SOLUTIONS TRACKING ISELLE
AND THE COL WESTWARD IN TANDEM…WHILE OTHERS MOVE ISELLE WEST OF
THE COL AND INTO AN AREA OF STRONGER SHEAR. INTERACTION WITH THE
TERRAIN OF THE BIG ISLAND IS EXPECTED TO WEAKEN ISELLE TONIGHT…
WHILE A SOUTHWARD-MOVING CUT OFF LOW DEVELOPING NORTHWEST OF THE
HAWAIIAN ISLANDS ON DAYS 2 AND 3 WILL BRING STRONGER SHEAR.
INTERACTION WITH THIS LOW IS EXPECTED TO LEAD TO THE DEMISE OF
ISELLE…WITH REMNANT LOW STATUS FORECAST BY DAY 5…CLOSELY
FOLLOWING THE TRENDS OFFERED BY THE SHIPS GUIDANCE.

FORECAST POSITIONS AND MAX WINDS

INIT 07/1500Z 18.5N 150.6W 70 KT 80 MPH
12H 08/0000Z 19.1N 152.9W 65 KT 75 MPH
24H 08/1200Z 19.8N 155.9W 55 KT 65 MPH…INLAND
36H 09/0000Z 20.5N 158.7W 50 KT 60 MPH
48H 09/1200Z 21.0N 161.0W 45 KT 50 MPH
72H 10/1200Z 22.5N 165.7W 40 KT 45 MPH
96H 11/1200Z 24.4N 171.1W 30 KT 35 MPH
120H 12/1200Z 27.0N 177.0W 25 KT 30 MPH…POST-TROP/REMNT LOW

$$

FORECASTER BIRCHARD