iCyclone Chase: ISAAC

[Cory]

Ah, OK. Thanks, Cory. I wonder why it died in the eye. Well, I am 99% sure the highest winds preceded the eye-- the backside was just kinda blah. (Whether KGAO actually sampled those peak, front-side winds is a question, however.)

It may have lost line power during the front of the storm then the backup battery died by the time the eye got there. The backup options for AWOS and ASOS weren't well thought out.

[HurricaneJosh]

It may have lost line power during the front of the storm then the backup battery died by the time the eye got there. The backup options for AWOS and ASOS weren't well thought out.

Ah, that makes sense. Well, next time, we'll have a complete wind trace. I'm berry excited about our new instrumentation choice.

[Cory]

Ah, that makes sense. Well, next time, we'll have a fully wind trace. I'm berry excited about our new instrumentation choice.

[HurricaneJosh]

Gonna get some hawt wind data, babe. Very excited the BASTARD held on.

To others who weren't in on the conversation or following on the iCyclone Facebook Page...

I deployed Cory's BASTARD (the instrument mount that attaches magnetically to the roof of the car) as Isaac approached. This is a newly re-engineered version with a much taller mast. (No, it ain't 10 m, but it's closer. )

As you can see, I picked a location with nice, open exposure, free of any interference (or, as free as you can be in a town). In the eye-- after hours of getting pounded-- I got out of the car and checked the instrument and was pretty pissed to see that the highest gust was 42 kt! Obviously, there was an equipment malfunction, which Cory attributes to water forcing into the impeller.

The big bright side: while the equipment malfunctioned, the BASTARD did not-- it held totally steady and did not budge an inch, despite getting pounded by five hours of eyewall, despite the car shaking, etc. (Nice job with the engineering, Cory! ) So that's awesome-- we know this new, taller mast can withstand very rough conditions.

Given this, Cory has recommended a new instrument-- a traditional three-cup deal that can record at 1-sec intervals and store up to 500K data points!! So I swear to Zeus and Athena, I'm coming back from the next chase with high-res, detailed wind data!

[HurricaneJosh]

Oh, and here's another small item of interest-- a partial barogram showing the pressure bottoming out in the eye and them slowly recovering as the backside moved in. I recorded this at the Lady of the Sea General Hospital on Highway 1 in Galliano. The lowest pressure was 970.0 mb at 7:04 am CDT-- but please note that I didn't start recording until 6:49 am, so it's possible this wasn't actually the lowest pressure (although it looks like it is, because it's still falling a bit at the start of the record).

I calibrated the barometer for 6 ft above sea level-- eyeballed from the hospital parking lot, which was on a very slight knoll.

Why is this only a partial record?

• The instrument was temporarily out of whack after being pounded for so many hours atop the car-- and I only started recording again once it seemed to recover and show reasonable pressures.
  
• I relocated during the eye (from the church parking lot to the hospital), and when you do that, you really have to start a new barogram if you want the data record to have any integrity.
  

Of interest is the very slow recovery of the pressure. Contrast this with my Ernesto barogram, which shows the very rapid recovery you'd expect as a fast-moving microcane speed away.

So, for what it's worth...

[NorthNJwx]

First off, fantastic job, Josh, on yet another chase! It has been a while since I've posted, but I always appreciate your chase threads.

I noticed the discussion on ASOS/AWOS sustained wind averaging periods in this thread and just wanted to clarify something: the ASOS and AWOS stations actually use a 2-minute averaging period - not a 1-minute averaging period. 2-min is the NWS standard. The WMO uses a 10-min average, and the NHC, of course, defines sustained wind as a 1-min average - so it's tough to find any consistency. Adding to the problem, the NDBC buoys seem to all use either 5- or 8-min averaging periods (depending on the station and its exposure), so comparing data between any of these sources can be tough!

Here's a link to a paper I just found (from 1993, when the ASOS was in its infancy, but still relevant) that discusses the 2-min average and alternatives:

http://www.aoml.noaa...ArchiveASOS.pdf

And this is from the NWS website's glossary of definitions:

http://forecast.weat...=SUSTAINED WIND

But, in practice, max 1-min and 2-min winds aren't usually too far apart. I forget what the general conversion factor is (and it's greater, of course, for land exposure than it is for water), but it's pretty small. So, KGAO's max 1-min wind was a bit higher than that already-impressive 50 kt 2-min value, but it's impossible to know by how much. And it's also very likely that a higher sustained wind value was reached in between those 20-min observations, so that makes determining the max sustained wind at an AWOS site in a TC even harder.

[turtlehurricane]

First off, fantastic job, Josh, on yet another chase! It has been a while since I've posted, but I always appreciate your chase threads.

I noticed the discussion on ASOS/AWOS sustained wind averaging periods in this thread and just wanted to clarify something: the ASOS and AWOS stations actually use a 2-minute averaging period - not a 1-minute averaging period. 2-min is the NWS standard. The WMO uses a 10-min average, and the NHC, of course, defines sustained wind as a 1-min average - so it's tough to find any consistency. Adding to the problem, the NDBC buoys seem to all use either 5- or 8-min averaging periods (depending on the station and its exposure), so comparing data between any of these sources can be tough!

Here's a link to a paper I just found (from 1993, when the ASOS was in its infancy, but still relevant) that discusses the 2-min average and alternatives:

http://www.aoml.noaa...ArchiveASOS.pdf

And this is from the NWS website's glossary of definitions:

http://forecast.weat...=SUSTAINED WIND

But, in practice, max 1-min and 2-min winds aren't usually too far apart. I forget what the general conversion factor is (and it's greater, of course, for land exposure than it is for water), but it's pretty small. So, KGAO's max 1-min wind was a bit higher than that already-impressive 50 kt 2-min value, but it's impossible to know by how much. And it's also very likely that a higher sustained wind value was reached in between those 20-min observations, so that makes determining the max sustained wind at an AWOS site in a TC even harder.

No statistical difference out to an averaging time of ~3 minutes, so anything from 1-min to 3-min can be considered approximately the same. Thanks for the correction though, it's convoluted how they report winds every 1-min with a 2-min average.

[Amped]

Omg, thank you for rounding up these data! I was actually wondering exactly that-- what the winds were in Galliano in these other recent events. I assume these data are from KGAO?

KGAO recorded 50 kt gusting to 67 in Isaac-- so that would make the impact greater than Gustav but less than Katrina for that town. Since the station only samples once every 20 mins, you have to assume the peak winds weren't sampled, and the highest winds were probably higher.

I have to say, I'm surprised at how low the Gustav peak wind is. Are you sure that's right? Gustav was kind of a disappointment, but 1) Galliano was at Ground Zero for Gustav and 2) the townspeople I chatted with (we had a lot of time to kill in that eye!) said Gustav was scary and intense. A security-guard dude talked about how his whole house was shaking from the force of the wind, etc.

Not me. It goes along with my theory that weenies at the NWS and in spotter networks have overmeasuring wind speeds and snowfall totals by a factor of 2 since the beggining of their existence.

[turtlehurricane]

Not me. It goes along with my theory that weenies at the NWS and in spotter networks have overmeasuring wind speeds and snowfall totals by a factor of 2 since the beggining of their existence.

So true, if you don't have an anemometer with you it can be easy to mistake a 50-60 mph wind gust for hurricane force, or a hurricane force wind gust for major hurricane force. People don't realize how strong high winds are. I usually don't even try to estimate since bias is impossible to control, there needs to be some basing on at least a damage assessment or radar data, preferably a handheld anemometer.

[Voyager]

So true, if you don't have an anemometer with you it can be easy to mistake a 50-60 mph wind gust for hurricane force, or a hurricane force wind gust for major hurricane force. People don't realize how strong high winds are. I usually don't even try to estimate since bias is impossible to control, there needs to be some basing on at least a damage assessment or radar data, preferably a handheld anemometer.

So true, and personally, I think it's probably pretty easy to overestimate wind of any speed when you don't have instuments and are guessing. Looks can be deceiving with regard to the way the wind (or even a gentle breeze) moves tree leaves, branches, and other objects. Since I have an anemometer now, I realize this fact. In most instances, the wind looks stronger than it actually it.

[Amped]

So true, if you don't have an anemometer with you it can be easy to mistake a 50-60 mph wind gust for hurricane force, or a hurricane force wind gust for major hurricane force. People don't realize how strong high winds are. I usually don't even try to estimate since bias is impossible to control, there needs to be some basing on at least a damage assessment or radar data, preferably a handheld anemometer.

The problem is a lot of ground sensors go down durring hurricanes. And a lot of times recon assumes the dropsonde/sfmr didn't measure the highest winds. So it's anyones guess as to the surface to 950mb reduction rate. A real 75mph measured away from the beach maybe more damaging than thought. DC only had a quick gust to 65mph during the derecho. So who knows. PVD may have been 75mph in the great new England Hurricane while blue Hill was @185.

[Met1985]

Congrats Josh. Great job man. Would be awsome to go along with you in one of your chases.

[HurricaneJosh]

First off, fantastic job, Josh, on yet another chase! It has been a while since I've posted, but I always appreciate your chase threads.

I noticed the discussion on ASOS/AWOS sustained wind averaging periods in this thread and just wanted to clarify something: the ASOS and AWOS stations actually use a 2-minute averaging period - not a 1-minute averaging period. 2-min is the NWS standard. The WMO uses a 10-min average, and the NHC, of course, defines sustained wind as a 1-min average - so it's tough to find any consistency. Adding to the problem, the NDBC buoys seem to all use either 5- or 8-min averaging periods (depending on the station and its exposure), so comparing data between any of these sources can be tough!

Here's a link to a paper I just found (from 1993, when the ASOS was in its infancy, but still relevant) that discusses the 2-min average and alternatives:

http://www.aoml.noaa...ArchiveASOS.pdf

And this is from the NWS website's glossary of definitions:

http://forecast.weat...=SUSTAINED WIND

But, in practice, max 1-min and 2-min winds aren't usually too far apart. I forget what the general conversion factor is (and it's greater, of course, for land exposure than it is for water), but it's pretty small. So, KGAO's max 1-min wind was a bit higher than that already-impressive 50 kt 2-min value, but it's impossible to know by how much. And it's also very likely that a higher sustained wind value was reached in between those 20-min observations, so that makes determining the max sustained wind at an AWOS site in a TC even harder.

Thank you so much-- I'm so glad you enjoy the chases. And thank you for this info about the averaging period for ASOS/AWOS stations-- that is good to know.

No statistical difference out to an averaging time of ~3 minutes, so anything from 1-min to 3-min can be considered approximately the same. Thanks for the correction though, it's convoluted how they report winds every 1-min with a 2-min average.

it annoys me that the wind value remains statistically the same even when you double the sampling period. Grrrr. I feel like we should at least get a few knots bonus when converting to 1-min.

So true, and personally, I think it's probably pretty easy to overestimate wind of any speed when you don't have instuments and are guessing. Looks can be deceiving with regard to the way the wind (or even a gentle breeze) moves tree leaves, branches, and other objects. Since I have an anemometer now, I realize this fact. In most instances, the wind looks stronger than it actually it.

Omg, totally. I've noticed the same thing. That when I've been in a strong wind with an anemometer, the actual measured value is way less than I would expect-- sometimes by as much as half.

Congrats Josh. Great job man. Would be awsome to go along with you in one of your chases.

Hey, thanks, man.

[HurricaneJosh]

The HRD published the wind swath for Isaac, and the over-land values are disappointing, to say the least!

According to this:

• Grand Isle (where the Mayor flipped out and insisted the storm was much stronger than a Cat 1) saw sustained winds no higher than 60 kt.
  
• Galliano (my location) saw sustained winds no higher than 45 kt.
  
• New Orleans saw winds no higher than 45 kt.
  
• Houma saw winds no higher than 35 or 40 kt.
  
• MS saw winds no higher than 40 kt (and only the extreme W end).
  
• AL saw winds no higher than 25 kt.
  

In all cases, however, winds right on the open coast are indicated to be a little higher.

Re: winds in my location... Again, I'm not understanding how KGAO's 50 kt (2-min) doesn't at least bring the 50-kt isotach over that location-- especially given that the highest measured value very possibly doesn't even represent the highest wind at that location (because the instrument was only sampling 50% of the time).

Whatevz.

[gymengineer]

The HRD published the wind swath for Isaac, and the over-land values are disappointing, to say the least!

According to this:

• Grand Isle (where the Mayor flipped out and insisted the storm was much stronger than a Cat 1) saw sustained winds no higher than 60 kt.
  
• Galliano (my location) saw sustained winds no higher than 45 kt.
  
• New Orleans saw winds no higher than 45 kt.
  
• Houma saw winds no higher than 35 or 40 kt.
  
• MS saw winds no higher than 40 kt (and only the extreme W end).
  
• AL saw winds no higher than 25 kt.
  

In all cases, however, winds right on the open coast are indicated to be a little higher.

Re: winds in my location... Again, I'm not understanding how KGAO's 50 kt (2-min) doesn't at least bring the 50-kt isotach over that location-- especially given that the highest measured value very possibly doesn't even represent the highest wind at that location (because the instrument was only sampling 50% of the time).

Whatevz.

Yup- the map is off, especially given land observations at reporting stations that directly contradict the contours. For example: Lakefront Airport--52kt sus/66kt gust, Gulfport Airport--46/61, even New Orleans Intl Airport managed to record 46/65.

[HurricaneJosh]

Yup- the map is off, especially given land observations at reporting stations that directly contradict the contours. For example: Lakefront Airport--52kt sus/66kt gust, Gulfport Airport--46/61, even New Orleans Intl Airport managed to record 46/65.

Good catches, there. Yeah, I just don't get it. If they felt a need to somehow "correct" all these readings downward-- why? These are all airport readings, for god's sake. If you can't take those at face value, what obs can you accept? The Wilma wind swath over FL has similar weirdness-- does not seem to reflect reliable surface obs. I guess I just don't understand the methodology behind these diagrams or what they're actually depicting.

[HurricaneJosh]

Yup- the map is off, especially given land observations at reporting stations that directly contradict the contours. For example: Lakefront Airport--52kt sus/66kt gust, Gulfport Airport--46/61, even New Orleans Intl Airport managed to record 46/65.

Actually... Looking very closely at the map, the isotachs do seem to accommodate the KMSY and KNEW readings-- you'll notice the 50-kt isotach just barely comes ashore to encompass Lakefront Airport (KNEW)-- but yeah, the KGPT and KGAO winds are simply not reflected.

[stormitecture]

How many is this now for you Josh? I think you may actually have chased as many or more than me (nine). Really on a good roll. Wish we could have connected, but I was chasing for business and don't socialize these days during an intercept. But was good to hear you come out.

[HurricaneJosh]

How many is this now for you Josh? I think you may actually have chased as many or more than me (nine). Really on a good roll. Wish we could have connected, but I was chasing for business and don't socialize these days during an intercept. But was good to hear you come out.

Thanks! I don't socialize during chases, so we're all good. Isaac was my 16th hurricane.

[stormitecture]

Thanks! I don't socialize during chases, so we're all good. Isaac was my 16th hurricane.

Jeez. Yeah...I need to stop being picky. Of course my medical issues in 2005 didn't help the stats ;-)

I have to check your site again, see what 16 storms you've hit.

[HurricaneJosh]

Jeez. Yeah...I need to stop being picky. Of course my medical issues in 2005 didn't help the stats ;-)

I have to check your site again, see what 16 storms you've hit.

Did you skip Dean and Karl because you're too "picky"?

My site lists 10 hurricane chases: http://icyclone.com/chases/

I still need to add the Ernie and Isaac accounts, which will make 12 (I'm backlogged a bit). The other 4 'canes (including Bret 1999 and Bob 1991) are pre-2005-- will take more work to put those accounts together.

[Eyewall2005]

Josh do you mind posting links to the radar reflectivity you used on your GR3 radar for your chases? I would like to download them.

Thanks

[Ginx snewx]

Aerial pics and surge maps

http://nwrcwebapps2.cr.usgs.gov/posthurricane/

http://50.17.205.92/Apps/IsaacStormSurgeMapper/IsaacStormSurgeMapper.html#

[HurricaneJosh]

My big project this weekend: working with my editing partner to create the Isaac video. Sooooooo dreading it, as I have a ton of footage to go through. Ugh. Gonna be hell. Can't wait until it's done.

The video should premiere Sunday! Be on the lookout!

[HurricaneJosh]

I'm still working on my Isaac video, which I'm going to post live on Saturday. The editing has been really slow-going!

But in the meantime, I wanted to share the just-released Isaac video by my very good friend, Michael Laca. (His site: http://tropmet.com/.) Michael's a great cameraman and editor, and so this is a Grade-A video essay of Hurricane Isaac's nocturnal assault on downtown New Orleans. The shots are gorgeous and beautifully-composed, and the editing is very tight, building to a nice climax. This is the gold standard of all the Isaac footage I've seen-- just awesome work.

My video is a completely different flavor entirely. I was down in the bayous, in a tiny town, in the darkness, with a hand-held camera, and so the whole vibe is completely different-- rougher and so on. Michael was the City Mouse and I was the Country Mouse for this hurricane. It will be interesting to contrast the settings/styles once mine goes live.

Anyhoo, enjoy this top-notch work. Look for my video on Saturday.

[HurricaneJosh]

Finally—the iCyclone video from the Hurricane Isaac chase is ready!

Although this is just a teaser for the full-length documentary, it stands on its own as a complete video account of Isaac's long, drawn-out assault on the tiny bayou town of Galliano, Louisiana.

This was one of the toughest video-editing jobs I've done in a while. Isaac was a large, slow-moving hurricane that impacted my location for well over 24 hours—a real endurance test! I got back from the chase with well over 4 hours of raw footage—a lot for me—and weeding through it all and shaping it into a coherent, watchable account took time.

What makes this video unique? For several hours (between 12 midnight and 3 am CDT), Isaac's large eye wobbled right over Galliano, so the town went back and forth between the eye and N eyewall. On the ground, this meant alternating periods of calm and storminess—a peculiar experience which you'll see in the video. When the town finally got deep into the eye, in the wee morning hours, the calm lasted a whopping 7 hours—a record for me!

I'll post a complete chase account in the near future. In the meantime, enjoy the video of this very unusual chase!

[Ginx snewx]

Sweet great vid.

[icebreaker5221]

Finally—the iCyclone video from the Hurricane Isaac chase is ready!

Although this is just a teaser for the full-length documentary, it stands on its own as a complete video account of Isaac's long, drawn-out assault on the tiny bayou town of Galliano, Louisiana.

This was one of the toughest video-editing jobs I've done in a while. Isaac was a large, slow-moving hurricane that impacted my location for well over 24 hours—a real endurance test! I got back from the chase with well over 4 hours of raw footage—a lot for me—and weeding through it all and shaping it into a coherent, watchable account took time.

What makes this video unique? For several hours (between 12 midnight and 3 am CDT), Isaac's large eye wobbled right over Galliano, so the town went back and forth between the eye and N eyewall. On the ground, this meant alternating periods of calm and storminess—a peculiar experience which you'll see in the video. When the town finally got deep into the eye, in the wee morning hours, the calm lasted a whopping 7 hours—a record for me!

I'll post a complete chase account in the near future. In the meantime, enjoy the video of this very unusual chase!

Great video Josh! That chase must have been exhausting.

[wxmx]

Nice video Josh. Made me blue, it looks like it was a long time ago since the last chase specimen...and we are still in September. It will be a long winter.

[HurricaneJosh]

Sweet great vid.

Hey, thanks. I was hoping you'd find it interesting, given how much you'd participated in this thread.

Great video Josh! That chase must have been exhausting.

Thank you-- I'm so glad you liked it! And, yeah, it was mega exhausting-- omg! The last few storms I've chased we're fast-moving microcanes, whereas Isaac was the opposite: big, fat, and slooooooow. The front side was especially exhausting-- it went on for hours and I was relieved to finally get in the eye. But then imagine how weird it was to be in the eye for 7 hours. Lolz. The event lasted nearly 36 hours, I'd say.

Nice video Josh. Made me blue, it looks like it was a long time ago since the last chase specimen...and we are still in September. It will be a long winter.

I'm not gonna tolerate this pessimism... yet.

But thank you for liking the video.