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Chasing RINA


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Josh, look at the Cancun radar.

http://smn.cna.gob.mx/radares/cancun/cancun_ultima.php

I'll bet you are now inside the "eye".

Ha ha ha, awesome! :lol:

I thought I might be, because the pressure stopped falling-- I don't think it's gone any lower than 996.5 mb, so no real change in 10 mins or so-- and it's still kind of calm.

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All I'm going on is radar, but it looks like the center is still well offshore.

[edit] I thought I'd also point out that the last NHC stuff I looked at suggested that Rina might essentially just sit there motionless for awhile.

Oh, it's moving. The pressure is up to 1000.0 mb and still rising. By the way, the wind really picked up-- steady over 20 kt, I'd say. I don't think radar is going to give you good position estimates with such a sheared system-- I think surface obs like pressure and wind direction/speed are the way to go.

The NHC's position is off by about 1 hr. The low pressure and calm were at the 10 pm CDT advisory position (which is here) about an hour ago. But it's close enough.

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Well, there definitely was something of a backside to this system. A little after my last post, the wind picked up suddenly and blew hard for an hour. I stood essentially for one hour straight, on a patio near the open beach, holding the Kestrel above my head like the Statue of Liberty from 10:03 pm to 11:09 pm CDT. Keep in mind that the instrument was only 3-4 m above the ground-- not the standard 10 m. The sample rate was once per 30 sec.

The average wind for the entire period was 20 kt. There were extended periods of steady winds over 25 kt, with a peak gust of 33 kt at 10:16 pm. Of course these values would have been higher at the standard 10 m. Not bad, though. It shows there's still a vigorous surface circulation with this system.

There was almost no rain during this backside.

It's calmed down a bit, but winds are still steady at a fresh 15 kt. Pressure just hitting 1005.0 mb and slowly rising. Still some flashes of lightning.

Ready to pack it in.

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Well, there definitely was something of a backside to this system. A little after my last post, the wind picked up suddenly and blew hard for an hour. I stood essentially for one hour straight, on a patio near the open beach, holding the Kestrel above my head like the Statue of Liberty from 10:03 pm to 11:09 pm CDT. Keep in mind that the instrument was only 3-4 m above the ground-- not the standard 10 m. The sample rate was once per 30 sec.

The average wind for the entire period was 20 kt. There were extended periods of steady winds over 25 kt, with a peak gust of 33 kt at 10:16 pm. Of course these values would have been higher at the standard 10 m. Not bad, though. It shows there's still a vigorous surface circulation with this system.

There was almost no rain during this backside.

It's calmed down a bit, but winds are still steady at a fresh 15 kt. Pressure just hitting 1005.0 mb and slowly rising. Still some flashes of lightning.

Ready to pack it in.

Good job Josh. Science! Hey fly up to the Cape, latest Bufkit has sustained 45 gusting to 70, of course you would be standing in snow and 50 degrees colder. Congrats on getting to the center yet again!

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Good job Josh. Science! Hey fly up to the Cape, latest Bufkit has sustained 45 gusting to 70, of course you would be standing in snow and 50 degrees colder. Congrats on getting to the center yet again!

Hey, thanks, Steve. :wub:

Yeah, it was nothing dramatic or impressive-- it was no Jova or Wilma-- but it was gratifying on a science-nerd level.

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Back at the hotel. It's raining again, but there's electricity and I'm just happy to be back in a warm room.

This was a fun little chase. No, of course it wasn't worth coming from California for it-- obviously not-- but, hey, I was here and I made the most of it. Rina sucked but the chase was a success. I wanted to punch the center and that's what I did. I got right in it-- a bull's eye-- and collected what I believe are valuable and relevant data. (Yeah, I'm patting myself on the back-- I gotta do something after coming from California to chase a sheared TS. :lmao:)

It was cool to really observe/document the component parts of a tropical cyclone as it passed right over my location. And unlike Don, Rina actually did still have an intact structure and observable tropical-cyclone components: a sharp pressure dip, a tight wind core (with front side and backside), a central calm bookended by periods of rain/wind, and a sharp directional shift in the wind after the center passed and the pressure started rising. (We had none of these things in Don.) Rina was weakened and hurting, but the "bones" were still in place. There was still structure. And the frequent lightning was a small bonus.

Quick summary of the chase's particulars. (All times are CDT and rounded to nearest 5 mins unless it's the time of actual, recorded data.)

Location & Time

* My exact location was 20.522478N 87.192073W-- right on a waterfront patio in a private community in Palmul.

* I was at this spot from ~8:00 pm to ~11:25 pm.

* The elevation where I kept the barometer was ~10 ft, and the barometer was calibrated (for sea-level readings) using that value. (Note: During the strong winds on the backside, I held the instrument high over my head to take wind readings-- so that may have slightly affected the air-pressure values from ~10 to 11 pm.)

Front Side

* The starting pressure at this location was 1001.5 mb.

* Strong, gusty winds (along with moderate rain) started at ~8:20 pm and went until ~8:45 pm. During this time, the pressure dropped fast.

Center

* At ~8:45 pm, it started to calm, and by ~8:55 pm, it had stopped raining.

* The lull lasted until ~9:25 pm. Lowest pressure during this lull was 996.5 mb, recorded at 9:12 pm.

* The NHC's 10 pm CDT advisory position (20.5N 87.2W) is as close as you can get to my location with coordinates of only one decimal place. But I believe this 10-pm-advisory position is off by ~1 hr (i.e., it's too far S), as I had the lowest pressure (with calm) an hour earlier-- a little after 9 pm. (It could be that the system was vertically tilted, and therefore the recon center fix did not match the surface center.) I'm going to send the NHC these obs, so perhaps they can factor them into the post-analysis.

* My lowest pressure corresponds very nicely with the NHC's 10-pm-advisory pressure (from recon) of 996 mb.

Backside

* Around ~9:20 pm, there was a marked shift in the wind's direction and it was picking up speed again. The pressure was 997.0 mb and rising.

* At ~9:25 pm, the wind became gusty, and it started raining lightly. The pressure was 997.6 mb and rising rapidly.

* The wind increased and became quite strong for an hour, blowing mostly from the SW-- from a little after 10 pm to a little after 11 pm. During this time-- a solid hour-- the average wind speed was 20 kt (sample rate = 30 secs), with frequent, extended periods of steady 25+ kt, and a peak gust of 33 kt (at 10:16 pm). These measurements were taken on a patio on the open beach, so the exposure was pretty good-- however, the instrument's height was only ~4 m, so true winds (at 10 m) were most certainly higher. During this period of strong winds, there was very little rain.

* By ~11:05 pm, the winds were down to 15 kt and slacking.

Other Comments

* There was frequent, brilliant lightning-- both before and after the center passed. (In fact, there was just a flash and a loud clap of thunder here in Playa del Carmen.)

* I saw very little damage on the drive back up from Palmul to Playa del Carmen-- just some downed branches and localized power outages.

I shot no video. I have no desire to dilute my portfolio with tropical-storm footage-- seems kind of lackluster-- so I didn't even turn on the camera. You know what, though? It was kind of cool and liberating to not have to shoot video, and it allowed me to concentrate more on observations. So it was a different kind of chase.

From a weather-nerd/data-collection standpoint, this chase was a lot of fun.

OK, time to find food.

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Rita was weakened and hurting, but the "bones" were still in place. There was still structure. And the frequent lightning was a small bonus.

NHC did it as well in an advisory, maybe changing more than a letter in the future when they retire a storm.

Good chase, for what you had.

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thumbsupsmileyanim.gif

:wub:

They sent my Kestrel back to me, recalibrated, and I should receive it any day-- so I will finally send yours back to you, when I get back to L.A. Thanks again for lending it so generously.

Now I am really glad I didn't go. 45 MPH (although highly sheared) still GROUNDS planes...

Flight #1302 - CANCELLED

Detailed Flight Information

AMERICAN AIRLINES Departing: CUN Cancun 10/28/2011 03:10 PM CANCELLED

Arriving: MIA Miami 10/28/2011 05:50 PM D40 CANCELLED

This WOULD have been my RETURN flight ;-)

Ugh-- yeah, that would be annoying. My flight is tomorrow-- fingers crossed. But if I'm stuck here, no big deal. I have my computer and Internet, and I can work here just as if I'm at home-- so it's no biggie. It's kind of nice out this morning-- calm, with the sun poking through.

Good day all,

VERY excellent write-up, Josh!

Hey, thanks, Chris! :)

NHC did it as well in an advisory, maybe changing more than a letter in the future when they retire a storm.

Good chase, for what you had.

Oops, fixed it. (Good eye. ;))

Thanks for following along-- I know a sheared TS ain't everyone's cup o' tea. :D

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Oh, in the general chase thread, I asked if you could come up with hundreds of thousands of dollars (a raffle?) to outfit a truck with doppler radar. I've seen truck portable (way smaller than the DOW) on a modified one ton pickup truck for only $600,000 on the Discovery 'Storm Chasers' show, and if they can measure doppler velocities in a tornadic supercell, imagine what you can do...

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Oh, in the general chase thread, I asked if you could come up with hundreds of thousands of dollars (a raffle?) to outfit a truck with doppler radar. I've seen truck portable (way smaller than the DOW) on a modified one ton pickup truck for only $600,000 on the Discovery 'Storm Chasers' show, and if they can measure doppler velocities in a tornadic supercell, imagine what you can do...

I'll check it out. It sounds awesome but complicated-- you'd need a real technician to handle that sort of thing, and that's its own area of expertise-- not to mention it's also way over my chase budget! ("Only" $600K? I don't know about you, but I'm a workin' dude. :lol:) This having been said, I wish someone would do that. Landfalls like Jova need to be better documented.

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