9/25/05 REPORT: MS/AL

[Tony Cook]

Hi Brett,

Just to clarify, your screencaps there aren't from the towercam video. They are much closer to the tornado than the towercam was. Those screencaps look like they came from the vantage point of the video shot by Alex Cody, located here:

http://www.tuscaloosanews.com/apps/pbcs.dl...WVUA01/50925006

He was supposedly shooting NW towards Lake Lurleen. Some of the treeline features look the same as those in the screencaps you posted. Nice shot of the velocity couplet, btw.

TonyC

 

[Brett Adair]

Thanks, Tony for clearing that up. I have some wall cloud and funnel pictures to post up. This was the largest outbreak that I can ever remember Alabama experiencing enduced from a tropical cyclone. :shock:

 

[Andrew Khan]

Originally posted by Jason Toft
This is a perfect example of why the size of a tornado cannot become equal to an F-rating, like we were discussing several months ago.

Jason

I do not know if I participated in that discussion, but the Fujita scale has some Major flaws, and inconsistencies. I mean as you know if depends on how well each building was built, and if the tornado occurs in the city orr in a rural area. I mean an actual F5 tornado could occur in a field in some rural countryside, and be rated at F0, because it caused no damage. Now, and F1 could happen in a city and be named an F4-F5. IT's just too flawed, and it's not just measured by wind-speed but as you know, the damage it did.

 

[nickgrillo]

Originally posted by Andrew Khan+--><div class='quotetop'>QUOTE(Andrew Khan)</div>

<!--QuoteBegin-Jason Toft

This is a perfect example of why the size of a tornado cannot become equal to an F-rating, like we were discussing several months ago.

Jason

I do not know if I participated in that discussion, but the Fujita scale has some Major flaws, and inconsistencies. I mean as you know if depends on how well each building was built, and if the tornado occurs in the city orr in a rural area. I mean an actual F5 tornado could occur in a field in some rural countryside, and be rated at F0, because it caused no damage. Now, and F1 could happen in a city and be named an F4-F5. IT's just too flawed, and it's not just measured by wind-speed but as you know, the damage it did.[/b]

That is just how the F-scale was designed...

When a tornado moves through a city, it's gonna recieve an honest rating - Since the actual windspeed of the tornado will make itself more clear. You cannot make a rating scale that is based upon the actual windspeeds, as there is no way of determining that by looking at fields where a tornado hits. It's all about the damage the tornado produces...

 

[Tony Cook]

This is in response to Dave's question earlier about F4/F5 tornadoes in Hurricanes. I took this from here:
http://www.srh.noaa.gov/jax/ghls/ghlstornadofaq.shtml

Q. Is it true that only weak tornadoes occur in association with hurricanes?
A. While most hurricane tornadoes are weak, strong tornadoes do occur and can result in fatalities. In fact, an F3 tornado (158-206 mph) occurred during Hurricane Andrew (1992) at La Place, LA and killed 2 people and an F4 tornado (207-260 mph) touched down in Galveston, TX during Hurricane Carla (1961) and resulted in 8 deaths. Hurricane Agnes (1972) produced 28 tornadoes within Florida, with 11 of F2 or greater strength, resulting in 7 deaths.

So there's at least one instance of an F4 on record from a Hurricane Tornado.

TonyC

 

[Andrew Khan]

I am wondering why it is so rare to get a major tornado from a Hurricane (Bands). I would take a guess that, the storm-scale rotation doesn't have time to mature enough, because in Hurricanes, the rotations/meso's quickly dissipate and initiate.

 

[HAltschule]

Bingo. These storms are usually mini-supercells that spawn for the most part, short lived tornadoes. The fast movement of the parent storms and the moist environment (lack of dry air) all play some role. The bottom line is that the storms are not able to develop a sustained, persistent updraft rotation.

 

[Andrew Khan]

Originally posted by HAltschule
Bingo. These storms are usually mini-supercells that spawn for the most part, short lived tornadoes. The fast movement of the parent storms and the moist environment (lack of dry air) all play some role. The bottom line is that the storms are not able to develop a sustained, persistent updraft rotation.

So, if they obtained dry air into their inflow, then they would get a sustained rotating updraft, which would allow longer lived tornadoes.

 

[nickgrillo]

I'd have to say strong/violent tornadoes are very much possible from some hurricanes (depending on all the dynamics/instability). For instance, there was some very sustained and discrete supercells in southern MS the other day (associated with Rita) - Some of them lasted a solid hour or so, which is more then ample time to drop a F3-F4 tornado.

 

[Dave Gallaher]

Thanks, TonyC, and everyone.

Wow--Hurricane Carla. I rode that one out with my family in SW Houston and that was a lo-ong night. I remember Dan Rather (local in those days) broadcasting from Galveston until power was gone.

We had a hurricane-spawned tornado that crossed Redstone Arsenal in this area in (I think) 1985 that had an impressive upper structure (which was all I could see from my vantage point as it translated very rapidy) that I reported on in the old print version of ST. If I recall, damage was spotty and F-1...

Dave Gallaher
Huntsville, AL

 

[Andrew Khan]

Originally posted by nickgrillo
I'd have to say strong/violent tornadoes are very much possible from some hurricanes (depending on all the dynamics/instability). For instance, there was some very sustained and discrete supercells in southern MS the other day (associated with Rita) - Some of them lasted a solid hour or so, which is more then ample time to drop a F3-F4 tornado.

I would agree with this, because the embedded/discrete supercells are taking on there own structure and leaving the hurricanes at times, which in return makes them just like any other supercell.

 

[HAltschule]

I would agree with this, because the embedded/discrete supercells are taking on there own structure and leaving the hurricanes at times, which in return makes them just like any other supercell.

No, I disagree. They are all associated with the circulation of the tropical system. You have to remember that these tropical systems are huge and its circulation (at least to some effect) spans out hundreds of miles in most cases. The question was why are they rare. And my answer before was that they are rare because they usually don't have persistent, sustained rotating updrafts. This is still my answer. They CAN become these, but most do not because of the reasons I mentioned in my posts above.

 

[Andrew Khan]

What I was saying is that, the initial supercell/storm development/evolution is generated by the tropical/hurricane situation, and therefore plays a great deal in the evolution. But, after this, the supercell can become independent, meaning it can flourish without the hurricanes factors.

 

[Andy Wehrle]

Sorry to be a party pooper guys, but I'd hate to see you get in trouble with the mods. A Map Room REPORTS thread is for firsthand chase reports ONLY. Take the discussion on tropical cyclone supercell forms to Weather Lab.

 

[Brett Adair]

Think about it this way, it is very hard to get tall supercells in a tropical cyclone environment. In a great plains outbreak, you have a ton of dry air spilling in at the mid levels with no moist layer in sight embedded within it. In tropical cyclones, you do. We all know that tropical cyclones are fighters of drier air, otherwise they would decapitate. There are only slivers of very dry air that come in with cyclones. This is a MAJOR factor....therefore it doesn't allow your updraft to be sustained since they are warm core systems. Tornadoes really feed on that updraft which is provided by the cooler air in the upper levels.