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Chasing DON


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LOL, 20 years post will haunt you.

Dude, it's not because of me that New England hasn't had any action for 20 years and probably won't for another 20. :lol:

It was actually a weird honor being in such a totally bizarre f*ck-up of a cyclone. I've never quite seen anything like it.

I think I'm going to rename Don "Houdini".

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If you had been vacationing down there with no idea Don was in the area, would you have had any indication a tropical cyclone had just made landfall? Honest question, as I'm genuinely curious.

No. Absolutely not. Cory and I were just talking about this exact thing, and we agreed we would not have known-- even with or weather equipment. The system made very little impression on the wind, pressure, and precip traces. And how else can one detect a cyclone?

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No. Absolutely not. Cory and I were just talking about this exact thing, and we agreed we would not have known-- even with or weather equipment. The system made very little impression on the wind, pressure, and precip traces. And how else can one detect a cyclone?

I think they just called it a depression for continuity to let everyone know it is fizzling. Really it is dissipated and/or a glorified inverted trough.

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Pressure seems steady now, as it's 1009.3 mb, with light rain and breezes. Big non-event.

What's really bizarre is the current (0015Z) IR image, which has us in the center of the action, under reds. It just goes to show how course IR imagery really is-- because based on that image, you'd think we were at least having heavy downpours right now.

Weird.

Yeah that is the trouble with IR, it only sees the very top of clouds rather than what's beneath, which is what actually counts. Some overhead cirrus can easily show up as red on IR and persist for awhile after the convection that produced it has shut down.

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I think they just called it a depression for continuity to let everyone know it is fizzling. Really it is dissipated and/or a glorified inverted trough.

Totally-- that is our impression as well.

From our standpoint, this didn't even meet depression criteria. Even the barogram lacked the expected signature-- there wasn't much of a drop during the few hours that the center approached us. We'll be sending our data to the NHC. We think it'll be useful for postananylsis, given we were positioned perfectly at the landfall point. We're not aware of any stations situated as well as we were.

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Totally-- that is our impression as well.

From our standpoint, this didn't even meet depression criteria. Even the barogram lacked the expected signature-- there wasn't much of a drop during the few hours that the center approached us. We'll be sending our data to the NHC. We think it'll be useful for postananylsis, given we were positioned perfectly at the landfall point. We're not aware of any stations situated as well as we were.

Well hopefully the trip was worth it in that respect.

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Well hopefully the trip was worth it in that respect.

Well seems like you have some t-showers developing just south of you. the little circulation seems to be on north end of baffin bay ;)

I take that back.. seems to be light...

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The rain band that approached us at Riviera Beach, as reported by Josh:

post-35-0-66365700-1312030309.jpg

Josh playing in the Gulf of Mexico at Mustang Island:

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Some of the really cool colors we saw at sunset, not long before Don's barely-detectable center moved overhead:

post-35-0-21498100-1312030342.jpg

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No. Absolutely not. Cory and I were just talking about this exact thing, and we agreed we would not have known-- even with or weather equipment. The system made very little impression on the wind, pressure, and precip traces. And how else can one detect a cyclone?

Interesting. Hopefully your obs will at least persuade the NHC to make some changes in the post-season.

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The Official iCyclone Autopsy

OK... I just wanted to wrap-up this thread with some final thoughts.

As y'all know, TS Don collapsed in the most spectacular way as it approached the S TX coast Friday night. Several people-- in this forum, on TV, and even at the NHC-- commented that they'd never seen a tropical cyclone disintegrate so suddenly.

To add to this: Cory's and my experience on the ground suggests that the system's disintegration might have been even faster and earlier than operationally believed.

See the maps below-- which show the cyclone's advisory positions and our position in Riviera Beach, at the W side of Baffin Bay. (Cory derived our exact location using a GPS app: 27.289344ºN 97.661698ºW.) As you can see, we were perfectly situated under the operational track and optimally positioned to collect useful data.

A few observations to share:

Flat Pressure Trace

We had two Kestrels measuring the air pressure. The barogram from one of the instruments is shown below. As you can see, the pressure dropped only modestly over the few hours we were at this location-- not the sort of sharp, rapid, V-shaped dip you expect as a healthy tropical cyclone's center passes over you.

Lowest Pressure

Our lowest readings on the two instruments were 1008.0 and 1008.4 mb, respectively. (We calibrated the instruments for our elevation, which was just a few feet above sea level.) Cory believes the sharp dips in the barogram below (for the first instrument) might be glitches due to our handling the instrument during those minutes. After some discussion, we decided to average the two low readings from the two instruments-- therefore, when we turn our data over to the NHC, we'll recommend a low pressure reading at our location of 1008.2 mb at ~9:20 pm CDT. (Cory still has to do some accuracy testing of his instrument tomorrow-- but this is our preliminary value for now. It might change, pending the results of Cory's tests.)

Our data don't totally jibe with the NHC's operational calls. Two issues:

1) Our pressure is a couple of millibars higher than the advisory value of 1006 mb, suggesting the system was even shallower than believed at the time. (Our reading jibes well with a reading of 1009 mb from the Kingsville area, if I remember correctly.)

2) Our low pressure happened way earlier than it should have, according to the advisory positions. We had our low at ~9:20 pm CDT, whereas the 10 pm advisory position had the center still E of us. This suggests that the system was not vertically coherent, and that the pressure center didn't match the radar center and/or wind center (if that even existed).

"Winds" :D

Here's the shocker: we recorded winds no higher than 10 kt! Keep in mind that 1) we were measuring at only 2 m (whereas surface winds are at 10 m), 2) we were sampling every 10 seconds (kind of low-res for wind readings), and 3) the instrument was a good 30 ft back from the open beach, where the wind felt a bit stronger. Even so, the wind data don't even justify a tropical depression. (I should note that gale-force gusts were recorded further up the coast, near Corpus Christi.)

Conclusion

Given the above-- the flat pressure trace, the lack of structural coherence, and the lack of wind-- Cory and I do not feel Don came ashore as a tropical cyclone, but rather, had degenerated to an open trough before reaching the coast.

We'll send our data and obs to the NHC, and we hope it'll shed some light when they conduct the post-season analysis. As harshly lame as this system was, Cory and I are excited that we were able to collect such useful and revealing data in a very isolated area of the coast that did not have any other recording stations (as far as we know). We didn't see a storm, but we get to contribute meaningfully to the scientific discussion-- and that's cool with us. :)

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