CPAC: ISELLE - Post-Tropical

[AFWeather]

Yet the pressures are rising.

Yep. And remember yesterday when the AVN indicated significant weakening, yet surface pressure was found 5mb lower than the estimated intensity along with no decrease in the wind intensity. She certainly isn't making the forecast easy on us.

And for what it's worth, she's now moving WNW finally. Right in line with the current CHPC track.

Good to have you here with us sir. Do you do recon as well?

Seems like Iselle's convection is expanding to the west.

Nope, I'm not with the reserve guys. I'm basically the weatherman for the Army (25 ID) here on Schofield Barracks. I don't have access to any more information than you guys do.

[Chris_in_Tampa]

Didn't the dropsondes support higher?

The dropsnodes verified that something was wrong with the SFMR. And yes, that the flight level winds could be even higher.

In case you missed what I posted earlier:

SFMR estimates are over 10 seconds. For a sonde it is likely much lower. I don't know for certain, but it may be as little as 0.5 seconds.

"Measurements of pressure, temperature, relative humidity, and wind are obtained at 0.5 s [2 Hz] resolution (for certain dropsonde models the wind measurements are only available at 1.0 s [1 Hz] resolution)."

From: http://www.aoml.noaa.gov/hrd/Storm_page ... ormat.html

I don't know what the true value is, that is why I don't officially describe it in my recon system. Sondes can record at different intervals it seems, so it is possible it may not always be consistent. That is why in my recon system I go with a generic disclaimer: "Winds at a particular level are peak winds since a dropsonde only records momentary slices of data at each level as it falls through the atmosphere."

Perhaps someone here knows different.

[Kingarabian]

A bit more south.

[wxman57]

Looks very close to my track. I have it at 65 mph as it passes the southern tip of the island.

[WeatherGuesser]

At 7:00 AM HST, the center of Hurricane Iselle was located at 16.9N 144.9W.

690 miles ESE of Hilo
755 miles ESE of Kailua-Kona
725 miles ESE of South Point
800 miles ESE of Kahului
855 miles ESE of Kaunakakai
830 miles ESE of Lanai City
900 miles ESE of Honolulu

http://i.imgur.com/WnkhZT4.jpg

What is that, twice the size of the islands? Maybe more? In a direct hit, virtually everyone will be affected.

[WeatherGuesser]

We now have Hurricane Warnings in effect.

[supercane4867]

It doesn't matter whether the center passes the southern or northern tip, eyewall will literally covers the whole island

[Yellow Evan]

On a trivia note: Hawaii has not been under a hurricane warning since 1993

[WeatherGuesser]

On a trivia note: Hawaii has not been under a hurricane warning since 1993

And think of the number of people that have moved there or been born since then that have never had this to deal with. Probably millions.

[AFWeather]

So they bumped her from 75 to 80 KT. However, she just crossed the 27C SST isotherm. Her track should keep her in waters 26.5C or higher. She'll actually cross back into 27+C water after the big island.

[Yellow Evan]

So they bumped her from 75 to 80 KT. However, she just crossed the 27C SST isotherm. Her track should keep her in waters 26.5C or higher. She'll actually cross back into 27+C water after the big island.

Yea, I could see it deepening again once that it occurs. But shear will be stronger.

[galaxy401]

981-982 mb on recent pass. Iselle is probably maintaining her intensity.

[NDG]

Love seeing history in the making

[Kingarabian]

981-982 mb on recent pass. Iselle is probably maintaining her intensity.

CPHC has it at 982 for the time being.

[supercane4867]

So they bumped her from 75 to 80 KT. However, she just crossed the 27C SST isotherm. Her track should keep her in waters 26.5C or higher. She'll actually cross back into 27+C water after the big island.

Yea, I could see it deepening again once that it occurs. But shear will be stronger.

Only if the circulation survives 13,803 ft volcano

[galaxy401]

I wonder if gasses from Kilauea volcano will affect the hurricane in any way like with Flossie last year. If so, the changes will probably be minor but it will still be interesting regardless.

[AFWeather]

WTPA43 PHFO 062048
TCDCP3

HURRICANE ISELLE DISCUSSION NUMBER 27
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP092014
1100 AM HST WED AUG 06 2014

ISELLE HAS NOT WEAKENED OVER THE PAST SIX HOURS...AND IN FACT
APPEARS TO HAVE STRENGTHENED A BIT. AIR FORCE HURRICANE HUNTERS
RECENTLY FOUND MAXIMUM FLIGHT LEVEL WINDS OF 85 KT...WHICH SUGGESTS
ABOUT 77 KT WHEN ADJUSTED TO THE SURFACE...AND THE SFMR FOUND
MAXIMUM SURFACE WINDS OF 72 KNOTS. THIS DATA SUGGESTS RAISING THE
ADVISORY INTENSITY TO 80 KT. THE WIND RADII HAVE BEEN ADJUSTED
SOMEWHAT TO BETTER MATCH WHAT WAS FOUND BY RECONNAISANCE...BUT MAY
STILL BE A BIT GENEROUS. ISELLE IS IN AN ENVIRONMENT OF MARGINAL SEA
SURFACE TEMPERATURES OF 26C...BUT THE WIND SHEAR OVER THE SYSTEM IS
CURRENTLY WEAK. A CLEARLY DEFINED EYE FEATURE HAS REDEVELOPED IN THE
INFRARED AND VISIBLE IMAGERY OVER THE PAST 12 HOURS.

THE GLOBAL MODELS AND THE SHIPS GUIDANCE BOTH SHOW THE SHEAR
REMAINING RELATIVELY WEAK THROUGH THE NEXT 24 HOURS...THOUGH THE SEA
SURFACE TEMPERATURES WILL REMAIN MARGINAL. SINCE THERE APPEARS TO BE
LESS OF A WINDOW FOR ISELLE TO WEAKEN SIGNIFICANTLY BEFORE REACHING
THE ISLANDS...WE ARE UPGRADING THE TROPICAL STORM WARNING FOR THE
BIG ISLAND TO A HURRICANE WARNING. THE FORECAST TRACK AND WIND RADII
ALSO NECESSITATE ISSUING A TROPICAL STORM WARNING FOR MAUI COUNTY.
IT IS IMPORTANT TO NOTE THAT REGARDLESS OF WHETHER ISELLE REACHES
THE BIG ISLAND AS A TROPICAL STORM OR MINIMAL HURRICANE...THE
IMPACTS WILL STILL BE VERY SIMILAR.

ALTHOUGH THE SEA SURFACE TEMPERATURES INCREASE ALONG THE FORECAST
TRACK BEYOND 36 HOURS...NORTHERLY WIND SHEAR IS EXPECTED TO INCREASE
SIGNIFICANTLY OVER ISELLE AS AN UPPER LEVEL TROUGH DIGS RAPIDLY JUST
TO THE NORTHWEST OF HAWAII. THIS SHOULD RESULT IN MORE RAPID
WEAKENING IN THE LONGER TERM.

THE FORECAST TRACK PHILOSOPHY HAS NOT CHANGED. ISELLE WILL CONTINUE
TO GRADUALLY GAIN LATITUDE TO THE SOUTH OF A RELATIVELY WEAK
SUBTROPICAL RIDGE SEVERAL HUNDRED MILES NORTH OF THE HAWAIIAN
ISLANDS. THIS FORECAST IS ESSENTIALLY A CONTINUATION OF THE PREVIOUS
TRACK FORECAST.


FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 17.2N 145.9W 80 KT 90 MPH
12H 07/0600Z 17.7N 148.2W 75 KT 85 MPH
24H 07/1800Z 18.3N 151.2W 70 KT 80 MPH
36H 08/0600Z 18.9N 154.3W 65 KT 75 MPH
48H 08/1800Z 19.6N 157.6W 55 KT 65 MPH
72H 09/1800Z 20.7N 163.4W 45 KT 50 MPH
96H 10/1800Z 22.1N 168.3W 40 KT 45 MPH
120H 11/1800Z 23.4N 172.7W 40 KT 45 MPH

$$
FORECASTER R BALLARD

[Kingarabian]

SE quadrant:

Highest Flight Level Wind (30 sec. Avg.): From 206° at 74 knots (From the SSW at ~ 85.2 mph)
Highest Peak (10 sec. Avg.) Flight Level Wind: 77 knots (~ 88.6 mph)
Highest SFMR Peak (10s Avg.) Sfc. Wind: 65 knots (~ 74.8 mph)
Lowest Extrapolated Sfc. Pressure: 981.2 mb (~ 28.98 inHg) <-- which has been reading low

[Blown Away]

Do possible El Niño conditions make conditions more favorable for hurricanes to impact Hawaii??

[Kingarabian]

Do possible El Niño conditions make conditions more favorable for hurricanes to impact Hawaii??

Yes.