CPAC: ISELLE - Post-Tropical

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#1261 Postby Yellow Evan » Fri Aug 08, 2014 3:07 pm

WTPA33 PHFO 081811 CCA
TCPCP3

BULLETIN
TROPICAL STORM ISELLE INTERMEDIATE ADVISORY NUMBER 34A...CORRECTED
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP092014
800 AM HST FRI AUG 08 2014

...BLUSTERY ISELLE PASSING SOUTH OF MAUI COUNTY...


SUMMARY OF 800 AM HST...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...19.4N 157.3W
ABOUT 85 MI...135 KM W OF KAILUA-KONA HAWAII
ABOUT 135 MI...220 KM SSE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...WNW OR 280 DEGREES AT 20 MPH...32 KM/H
MINIMUM CENTRAL PRESSURE...1008 MB...29.77 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES IN WATCHES AND WARNINGS WITH THIS ADVISORY...

NONE.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

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

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS....IN
THIS CASE IN THE NEXT 12 TO 24 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 TROPICAL STORM ISELLE WAS
LOCATED BY AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT NEAR LATITUDE
19.4 NORTH...LONGITUDE 157.3 WEST. ISELLE IS MOVING TOWARD THE
WEST-NORTHWEST NEAR 20 MPH...32 KM/H...AND THIS MOTION IS EXPECTED
TO CONTINUE THROUGH EARLY SUNDAY. ON THE FORECAST TRACK...THE CENTER
OF ISELLE WILL BE PASSING ABOUT 100 MILES SOUTH OF OAHU THIS
AFTERNOON...AND ABOUT 130 MILES SOUTH OF KAUAI TONIGHT.

MAXIMUM SUSTAINED WINDS ARE NEAR 50 MPH...85 KM/H...WITH HIGHER
GUSTS. ADDITIONAL WEAKENING IS FORECAST DURING THE NEXT 48
HOURS...WITH ISELLE EXPECTED TO BECOME A DEPRESSION TODAY...AND
LIKELY BECOMING A REMNANT LOW BY SATURDAY AFTERNOON.

TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 105 MILES...165 KM
FROM THE CENTER. A WEATHER STATION AT KULA ON MAUI RECENTLY REPORTED
A WIND GUST TO 61 MPH...98 KM/H.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1008 MB...29.77 INCHES.


HAZARDS AFFECTING LAND
----------------------
WIND...TROPICAL STORM CONDITIONS WILL GRADUALLY DIMINISH ON THE BIG
ISLAND AND MAUI TODAY. TROPICAL STORM CONDITIONS ARE LIKELY OVER
PARTS OF OAHU TODAY AND KAUAI TONIGHT.

RAINFALL...RAINFALL TOTALS OF 5 TO 8 INCHES...WITH ISOLATED MAXIMUM
AMOUNTS TO 12 INCHES...ARE EXPECTED NEAR THE TRACK OF ISELLE. THE
HEAVIEST RAINFALL WILL LIKELY OCCUR OVER MOUNTAINOUS TERRAIN. THESE
RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AS WELL AS ROCK AND
MUD SLIDES.

SURF...SWELLS GENERATED BY ISELLE ARE PRODUCING VERY LARGE AND
DAMAGING SURF...MAINLY ALONG EAST AND SOUTH FACING SHORES OF THE
BIG ISLAND. THIS DAMAGING SURF WILL DIMINISH LATER TODAY.


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

$$
FORECASTER R BALLARD

CORRECTED TO ADD WIND REPORT FROM KULA ON MAUI.
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#1262 Postby Alyono » Fri Aug 08, 2014 4:10 pm

TWC has showed some severe damage from Iselle in the mountains
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Re: CPAC: ISELLE - Tropical Storm

#1263 Postby cycloneye » Fri Aug 08, 2014 4:17 pm

TROPICAL STORM ISELLE DISCUSSION NUMBER 35
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP092014
1100 AM HST FRI AUG 08 2014

INTERACTION WITH THE BIG ISLAND VOLCANO SUMMITS APPEARS TO HAVE
DONE QUITE A NUMBER ON ISELLE THIS MORNING. VISIBLE SATELLITE
IMAGERY NOW SHOWS A FAIRLY LARGE AREA OF CYCLONICALLY ROTATING
SHOWER BANDS...BUT WITHOUT THE WELL DEFINED CORE STRUCTURE OF A
TYPICAL TROPICAL CYCLONE. THERE ARE A NUMBER OF SMALLER VORTICITY
CENTERS ROTATING AROUND A BROAD CLOUD SYSTEM CENTER...WHICH AIR
FORCE RECONNAISSANCE WAS HELPFUL IN LOCATING JUST BEFORE 1800 UTC.

NOT SURPRISINGLY...RECON FOUND THE MINIMUM CENTRAL PRESSURE IN
ISELLE CONTINUES TO RISE THIS MORNING. HOWEVER...THERE IS A GOOD
DEAL OF MOMENTUM ASSOCIATED WITH THE OUTER VORTEX OF WHAT REMAINS
WITH ISELLE. A SUSTAINED WIND OF 44 KT WAS REPORTED BY PHNY...
LANAI CITY AIRPORT...80 NM NNE OF THE CENTER AROUND 18Z. THE SFMR
RECORDED SOME 40 KT WINDS 70 NM TO THE NW OF THE CENTER AS WELL.
THUS THE ADVISORY INTENSITY WILL BE MAINTAINED AT 45 KT. ALTHOUGH
ISELLE WILL BE MOVING OVER WARMER SSTS OVER THE NEXT SEVERAL
DAYS...THE ENVIRONMENT AS WELL AS THE SEVERE DISRUPTION TO THE INNER
CORE MAKE SIGNIFICANT REDEVELOPMENT UNLIKELY. A DIGGING UPPER TROUGH
OVER THE NORTHWEST HAWAIIAN ISLANDS WILL MAINTAIN STRONG SHEAR OVER
ISELLE. NEVERTHELESS...THE INTENSITY GUIDANCE IS FAIRLY UNANIMOUS IN
KEEPING THE BROADER CIRCULATION A LITTLE STRONGER FOR A LONGER
TIME...AND THE OFFICIAL FORECAST HAS BEEN NUDGED UPWARD TO ACCOUNT
FOR THAT...BUT BELOW THE INTENSITY CONSENSUS.

THE TRACK GUIDANCE CONTINUES TO BE FAIRLY CONSISTENT. WHAT REMAINS
OF ISELLE SHOULD SLOW IN FORWARD SPEED OVER THE NEXT 24 TO 36 HOURS
AS THE SUBTROPICAL RIDGE TO ITS NORTH WEAKENS. BEYOND 36 HOURS...A
NEW HIGH PRESSURE AREA BUILDING TO THE NORTH OF THE CEYLON WILL
CAUSE ISELLE TO SPEED UP. THE REMNANT LOW OF ISELLE IS THEN EXPECTED
TO GAIN LATITUDE FASTER AS IT MOVES AROUND THE SOUTHWEST PERIPHERY
OF THIS HIGH.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 19.5N 158.0W 45 KT 50 MPH
12H 09/0600Z 19.9N 160.1W 40 KT 45 MPH
24H 09/1800Z 20.3N 162.2W 35 KT 40 MPH
36H 10/0600Z 20.6N 164.2W 35 KT 40 MPH
48H 10/1800Z 21.0N 166.8W 30 KT 35 MPH
72H 11/1800Z 21.9N 172.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 12/1800Z 23.2N 177.9W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 13/1800Z 26.9N 176.0E 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
FORECASTER R BALLARD
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Re: CPAC: ISELLE - Tropical Storm

#1264 Postby Iceman56 » Fri Aug 08, 2014 4:18 pm

HurricaneBelle wrote:
wxman57 wrote:Take a good look at the satellite loop above this post. The LLC is way west of Hawaii. It decoupled from the MLC. lt's the MLC that is making landfall on the island now. Center is near where my crosshairs are on the image below. This explains the sudden slow-down of the storm. It didn't slow down, it made landfall and is continuing west. It's the mid level center that is hanging way behind. Note the lower pressures on the west side of Hawaii.


Looks like someone either independently came up with this observation right after your post, or decided to claim it as his own, and got retweeted by Jim Cantore on Twitter:

https://twitter.com/JimCantore/status/4 ... 5034714112


Sorry but this is wrong! This is a terrible misinterpretation of the satellite imagery. We get eddies that form to the lee of the islands the time...ALL the time. This is a result of the channeled flow between the islands. Sometimes you get one or more counterrotating vortices. That low level vorticity center was absolutely NOT the LLCC of Iselle.

You can clearly see that from the various surface wind observations over the Big Island from 12-14Z, and from a loop of the 0.5° velocity imagery from PHWA as the LLCC came ashore.
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Re: CPAC: ISELLE - Tropical Storm

#1265 Postby wxman57 » Fri Aug 08, 2014 4:37 pm

Iceman56 wrote:Sorry but this is wrong! This is a terrible misinterpretation of the satellite imagery. We get eddies that form to the lee of the islands the time...ALL the time. This is a result of the channeled flow between the islands. Sometimes you get one or more counterrotating vortices. That low level vorticity center was absolutely NOT the LLCC of Iselle.

You can clearly see that from the various surface wind observations over the Big Island from 12-14Z, and from a loop of the 0.5° velocity imagery from PHWA as the LLCC came ashore.


I believe that you are incorrect. The plane has verified the LLC is now west of 158 deg. The LLC decoupled from the mid-level center early this morning. In fact, the center that the recon plane found a short while ago was on the eastern edge of the large area of low pressure. It appears they found a small vortex that was rotating northeastward. The LLC is closer to 158.7W rather than 158W. You cannot trust satellite imagery to identify a low-level center. Obs and pressure readings confirmed that the center was well west of Hawaii when the squalls reached the southern part of Hawaii around 12Z. You would not have noticed any weather as the center moved by late last evening, as all the weather was associated with the mid-level center that lagged to the east. That's why the squalls appeared to stall for a while early this morning. They were separating from the LLC. And you cannot use radar imagery to locate the surface circulation, as the Earth is curved and the beam will be well above the surface just a short distance from the radar. Radar was tracking a mid-level center, not the surface center.
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#1266 Postby WeatherGuesser » Fri Aug 08, 2014 4:47 pm

Don't know diddly about the land of pineapples, coconuts and macadamias, so I'd have to defer to someone who lives and works there as to what is normal or unusual. I would imagine normal weather patterns there are somewhat different than most other places.
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Re:

#1267 Postby wxman57 » Fri Aug 08, 2014 5:08 pm

WeatherGuesser wrote:Don't know diddly about the land of pineapples, coconuts and macadamias, so I'd have to defer to someone who lives and works there as to what is normal or unusual. I would imagine normal weather patterns there are somewhat different than most other places.


Tropical cyclones don't behave differently in the Central Pacific vs. elsewhere. The LLC on a system that has decoupled cannot be located by radar or IR satellite. I've been forecasting hurricanes for 35+ years worldwide.

By the way, the CPHC correctly identified the situation in their latest discussion (below). That broad area of low center moved well west of Hawaii by the time the squalls associated with the MLC reached the island about 10 hours ago.

VISIBLE SATELLITE
IMAGERY NOW SHOWS A FAIRLY LARGE AREA OF CYCLONICALLY ROTATING
SHOWER BANDS...BUT WITHOUT THE WELL DEFINED CORE STRUCTURE OF A
TYPICAL TROPICAL CYCLONE. THERE ARE A NUMBER OF SMALLER VORTICITY
CENTERS ROTATING AROUND A BROAD CLOUD SYSTEM CENTER
...WHICH AIR
FORCE RECONNAISSANCE WAS HELPFUL IN LOCATING JUST BEFORE 1800 UTC.
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Re: CPAC: ISELLE - Tropical Storm

#1268 Postby supercane4867 » Fri Aug 08, 2014 5:21 pm

I'd call Iselle a remnant low now

Image
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Re: Re:

#1269 Postby tallywx » Fri Aug 08, 2014 5:23 pm

wxman57 wrote:
WeatherGuesser wrote:Don't know diddly about the land of pineapples, coconuts and macadamias, so I'd have to defer to someone who lives and works there as to what is normal or unusual. I would imagine normal weather patterns there are somewhat different than most other places.


Tropical cyclones don't behave differently in the Central Pacific vs. elsewhere. The LLC on a system that has decoupled cannot be located by radar or IR satellite. I've been forecasting hurricanes for 35+ years worldwide.


What you don't get is that the decoupling didn't occur until the main LLC killed itself over Mauna Loa. You had a broad lee-side eddy that formed from the stronger NE winds that were shooting the gap between the Big Island and Maui (and this eddy is present during particularly strong trade regimes for the same reason). Only when the main LLC killed itself over the Big Island did the lee eddy take over as the new center of the storm.
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Re: CPAC: ISELLE - Tropical Storm

#1270 Postby wxman57 » Fri Aug 08, 2014 5:58 pm

I agree that the decoupling took place after landfall, but that landfall was closer to 06Z not after 12Z. That was a MLC landfall after 12Z. It was around 13Z when we first noticed the broad low well west of Hawaii around which several smaller vortices were rotating. At that time, lowest pressure was on the west side of the Island and the advisory had the center just reaching the coast. Hilo, closest to the advisory position had a 2mb higher pressure than the western side of the island, and winds on the western side of the island were from the SE. The obs didn't fit a center position just making landfall.
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Re: CPAC: ISELLE - Tropical Storm

#1271 Postby tallywx » Fri Aug 08, 2014 6:01 pm

wxman57 wrote:I agree that the decoupling took place after landfall, but that landfall was closer to 06Z not after 12Z. That was a MLC landfall after 12Z.


The (MLC?) circulation appeared pretty dramatic on radar when it came ashore. What was the radar beam height so close to the site (i.e., was it still sampling mid-levels because the dome is on elevated terrain)?
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#1272 Postby TheStormExpert » Fri Aug 08, 2014 6:58 pm

The high elevation and sudden increase in shear did a number on this prior to landfall. Sounds to me like it could have been much worse.
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#1273 Postby Kingarabian » Fri Aug 08, 2014 7:08 pm

Worst is over for Oahu? We didn't get much.
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Iceman56

Re: CPAC: ISELLE - Tropical Storm

#1274 Postby Iceman56 » Fri Aug 08, 2014 7:09 pm

wxman57 wrote:I believe that you are incorrect. The plane has verified the LLC is now west of 158 deg. The LLC decoupled from the mid-level center early this morning. In fact, the center that the recon plane found a short while ago was on the eastern edge of the large area of low pressure. It appears they found a small vortex that was rotating northeastward. The LLC is closer to 158.7W rather than 158W. You cannot trust satellite imagery to identify a low-level center. Obs and pressure readings confirmed that the center was well west of Hawaii when the squalls reached the southern part of Hawaii around 12Z. You would not have noticed any weather as the center moved by late last evening, as all the weather was associated with the mid-level center that lagged to the east. That's why the squalls appeared to stall for a while early this morning. They were separating from the LLC. And you cannot use radar imagery to locate the surface circulation, as the Earth is curved and the beam will be well above the surface just a short distance from the radar. Radar was tracking a mid-level center, not the surface center.


You can believe whatever you like, but you either aren't interpreting the data correctly or you have not looked at key data that clearly shows otherwise. When the eye is only 10 NM from the radar as it was last night, you are not seeing a mid level center in the 0.5° reflectivity and velocity imagery. The beam does rise with height, but it's not at the mid-levels when it's only 10 NM from the radar. Also, you need to go back and look at how the surface winds at all the mesonet stations on the Big Island behaved at the time this LOW level (at or below 1000') radar signature of an eye feature moved ashore. This exercise is left for the student, but I can assure you the strongest SURFACE level winds were cyclonic around the eye feature.

The pressure is ALWAYS lower on the downwind side of a barrier. That is not an artifact of Iselle, that's just plain physics. When easterlies are blowing across the Big Island, the pressure will always be at least a couple of millibars higher at Hilo than at Kona. In fact, the stronger the winds, the greater the pressure difference. We see that every single day here, no fail.

A disorganized low level center did reform west of the Big Island because you have the large remnant vortex from Iselle (which still has plenty of inertia and vorticity that doesn't go away very quickly despite the loss of the core) tracking westbound, but the core LLCC never emerged off the Kona coast.
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#1275 Postby Alyono » Fri Aug 08, 2014 7:50 pm

This debate may be better served in another forum... maybe tropical analysis and not the main Iselle thread
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Re:

#1276 Postby Yellow Evan » Fri Aug 08, 2014 8:23 pm

TheStormExpert wrote:The high elevation and sudden increase in shear did a number on this prior to landfall. Sounds to me like it could have been much worse.


The former enhanced rain and so did the slower than expected motion.
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#1277 Postby JonathanBelles » Fri Aug 08, 2014 8:57 pm

Tonight's Post on Iselle and Julio: http://jonathanbelles.com/2014/08/08/is ... volcanoes/
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Re:

#1278 Postby Equilibrium » Fri Aug 08, 2014 9:28 pm

JonathanBelles wrote:Tonight's Post on Iselle and Julio: http://jonathanbelles.com/2014/08/08/is ... volcanoes/


The 91 mph was that just a gust ? if not it was a cane.

Selected Maximum Winds as of This Morning:

Mauna Kea – 91 mph
Oahu Forest – 72 mph
Kula – 61 mph
Malokai – 57 mph
Hilo Harbor – 56 mph
Kona Int’l – 45 mph
Honolulu – 41 mph
South Point – 33 mph
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Re: Re:

#1279 Postby Yellow Evan » Fri Aug 08, 2014 9:37 pm

Equilibrium wrote:
JonathanBelles wrote:Tonight's Post on Iselle and Julio: http://jonathanbelles.com/2014/08/08/is ... volcanoes/


The 91 mph was that just a gust ? if not it was a cane.

Selected Maximum Winds as of This Morning:

Mauna Kea – 91 mph
Oahu Forest – 72 mph
Kula – 61 mph
Malokai – 57 mph
Hilo Harbor – 56 mph
Kona Int’l – 45 mph
Honolulu – 41 mph
South Point – 33 mph


The 91mph wind was at 14K feet.
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Re: Re:

#1280 Postby Chris_in_Tampa » Fri Aug 08, 2014 9:41 pm

Equilibrium wrote:The 91 mph was that just a gust ? if not it was a cane.


Hurricane:

"A tropical cyclone in the Atlantic, Caribbean Sea, Gulf of Mexico, or eastern Pacific, which the maximum 1-minute sustained surface wind is 64 knots (74 mph) or greater."

From: http://w1.weather.gov/glossary/index.php?letter=h

Even if it was sustained at 74mph on the volcano, it wouldn't count. Higher elevations, even high rises, can experience higher winds. They just don't count toward the advisory wind speeds. (I believe the standard surface wind reporting level is 10 meters. Not sure if that is just the U.S. or the WMO.)
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