The tornado season of 2008: climate change to blame? And, tropical update

By: Dr. Jeff Masters , 5:07 PM GMT on May 27, 2008

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Residents of Parkersburg, Iowa continue to assess damage and clean up from the tornado that killed six people on Sunday. The tornado was rated EF-5, the highest possible rating for a tornado. An EF-3 tornado also hit Hugo, Minnesota on Sunday, killing one person. Only five new tornado reports occurred yesterday, and severe weather is expected to remain relatively low for the next two days. A new storm system is expected to bring an enhanced chance of severe weather to the upper Midwest beginning Thursday. The deaths Sunday push this year's tornado death toll to 110. This makes 2008 the 12th deadliest tornado season since 1950, and the deadliest since 1998, when 130 deaths were recorded. Assuming that the Parkersburg, Iowa tornado was an EF-4 or EF-5, there have been nine violent EF-4 or EF-5 tornadoes this year. This is the most since 1999, when 13 such twisters were recorded. The total (preliminary) number of tornadoes so far this year is 1191. I doubt that we will break the all time record of 1817 tornadoes in a year, set in 2004, but 2008 may vault into second place if we can top 1998's 1424 tornadoes. Could this year's tornadoes be a sign of climate change?


Figure 1. Tornadoes deaths in the U.S. by year since 1950. Year 2008 deaths are as of May 26.

Well, let's be clear that human-caused climate change is occurring, and will significantly affect nearly all aspects of weather and climate in the decades to come. However, many of these changes will be so small or gradual that they will not become detectable until many decades hence, since there is a large natural variability in weather. As I noted in my February blog, Are tornadoes getting stronger and more frequent?, there is new research that predicts that we may see an increase in the severe thunderstorms that spawn tornadoes by the end of the century. However, the computer modeling efforts that predict this rise in severe weather are just beginning, and much more research remains to be done before we can believe these preliminary results.

Will we be able to detect changes in tornado frequency if they occur?
We won't be able to detect changes in tornado frequency due to climate change, unless there is a very large change. We need a technology that can detect all tornadoes, all the time in order to be able to evaluate changes in tornado frequency. Doppler radar can only "see" perhaps 50% of all tornadoes, and many of those it detects never touch down. Thus, we rely on human observers to spot tornadoes, or look for buildings that got in the way of a tornado, using the damage pattern to identify a tornado. If there are no humans around to see a tornado, and if a tornado does not encounter any structures, it will go unrecorded. As the population increases and more buildings are erected, tornado reports will increase. This factor alone can account for the observed increase in total tornadoes since 1950 (Figure 2).

Is there evidence that strong and violent tornadoes are increasing?
Strong tornadoes (EF2 and EF3 on the Enhanced Fujita Scale) and violent tornadoes (EF4 and EF5, or F4 and F5 on the pre-2007 Fujita Scale), which make up less than 25% of all tornadoes, cause a large fraction of the tornado deaths. These storms are less likely to go uncounted, since they tend to cause significant damage along a long track. Thus, the climatology of strong and violent tornadoes may offer a clue as to how climate change may be affecting severe weather. Unfortunately, we cannot measure the wind speeds of a tornado directly, except in very rare cases when researchers happen to be present with sophisticated research equipment. Tornadoes are categorized using the Enhanced Fujita (EF) scale, which is based on damage. So, if a strong or violent tornado happens to sweep through empty fields and never destroy any structures, it will not get a rating. Thus, if the number of violent tornadoes has actually remained constant over the years, we should expect to see some increase in these storms over the decades, since more buildings have been erected in the paths of tornadoes.

However, if we look at the statistics of strong and violent U.S. tornadoes since 1950 (Figure 2), there does not appear to be any increase in the number of these storms. In fact, there appears to be a decrease, although the quality of the data base is probably not good enough to say this with confidence. It appears likely that climate change has not caused an increase in the strongest tornadoes in recent decades. I believe we can blame 2008's nasty tornado season on an unusually far south loop that the jet stream has taken this year over the U.S., thanks to natural variability in the weather.


Figure 2. Total, strong and violent tornadoes in the U.S. by year since 1950. The year 2008 (not pictured) has had 128 strong or violent tornadoes as of May 26, according to Wikipedia.

Possible development in the Western Caribbean or Eastern Pacific late this week
A weak low pressure area (Invest 90E) has developed in the Eastern Pacific off the coast of Guatemala, near 10N 90W. This low has the potential to develop into a tropical depression by the end of the week, according to the UKMET model. Other models, such as the GFS, Canadian, and ECMWF, foresee that this area of disturbed weather will not have time to develop before moving northwards over Central America by the end of the week, bringing heavy rains to the region. Once over land, this low might move over the waters of the Western Caribbean and allow a tropical depression to form, as predicted by the GFS model. The NOGAPS model, in contrast, predicts that a tropical depression will form in the Western Caribbean south of Cuba, with no development in the Eastern Pacific. Given the persistence of these computer models over the past week in developing something in the region, I'd put the odds of a tropical depression forming within 7 days at about 40% in the Eastern Pacific, and at 20% in the Western Caribbean. There is a lot of wind shear predicted to prevail near or over the Western Caribbean late this week and early next week, reducing the odds that any such development could hold together long enough to affect the U.S. Regardless, residents of Guatemala, El Salvador, Honduras, Belize, and southern Mexico can expect heavy rains and possible flash flooding late this week from this system.


Figure 3. Area of disturbed weather over the Eastern Pacific that is forecast by some models to develop into a tropical depression. The NHC Graphical Tropical Weather Outlook is a good tool to track this disturbance.

I'll have an update by Wednesday afternoon.

Jeff Masters

New Hartford (snp4u)
Missing House, if found call Dennis and Carla
New Hartford
New Hartford (snp4u)
car pile up
New Hartford
Supercell near Pratt, Kansas (MikeTheiss)
Nice structure on upercell east of Pratt, Kansas. Photo copyright Mike Theiss.
Supercell near Pratt, Kansas

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338. Dakster
8:29 PM GMT on May 27, 2008
Welp. You guys/gals got your invest. Time to dust off the computers and start the number crunching...

Just in time for NHC to start the daily tropical outlook...

What's the strongest you think 90E or its remants COULD become in the Atlantic?
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337. Michfan
3:37 PM CDT on May 27, 2008
JFV Probably not due to two factors:

Stronger low in the EPAc will pull moisture in from the SW caribbean robbing any disturbance there of it.

Wind shear directly north of the that disturbance is still quite high. There is only a mid to high level circulation associated with it. It hasn't come down to the surface yet.

Bookmark this for all future needs:

http://www.stormjunkie.com/qcklnk.php
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336. cdo
8:37 PM GMT on May 27, 2008
which blob in that Sat pic is it?
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335. Patrap
3:37 PM CDT on May 27, 2008
GOES-12 (3 Channel) Gulf and Tropics (Updated every ~1/2 hour) Link
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334. Beachfoxx
3:36 PM CDT on May 27, 2008
Tabasco,LOL ~ isn't that the red stuff in a bottle thats for wimps from LA?

ROFLMAO & J/K
Member Since: July 10, 2005 Posts: 157 Comments: 29384
333. HurricaneGeek
4:35 PM EDT on May 27, 2008
Here is a good picture of our 90E
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332. Beachfoxx
3:35 PM CDT on May 27, 2008
Deforestation ~ gets my vote... I too have more than a GED!
LOL

So, the tropics are warming up for the season. Is everyone ready??
Member Since: July 10, 2005 Posts: 157 Comments: 29384
330. Patrap
3:35 PM CDT on May 27, 2008
Well.I'll be in Jax from Friday to Tues.

Atlantic Beach watching the Shuttle Go Up.

And Im bringing Tabasco,LOL
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329. smmcdavid
3:34 PM CDT on May 27, 2008
Drak, just tell us again. Reading back a few pages sounds like work.
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327. cdo
8:33 PM GMT on May 27, 2008
ummmm, didn't Dr M's blog entry talk about it? Since he mentioned it in his blog entry, why are yall saying people cant discuss it in a blog that Dr M did!
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326. Patrap
3:33 PM CDT on May 27, 2008
LOL...In this Blog,..we dont suppress any ones views.

Thats a Democracy.
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325. seflagamma
4:33 PM AST on May 27, 2008
back to Invest 90E....
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324. Beachfoxx
3:33 PM CDT on May 27, 2008
Pat,

Watch it... these FL gals been known to bite! LOL
Member Since: July 10, 2005 Posts: 157 Comments: 29384
323. Drakoen
8:33 PM GMT on May 27, 2008
JFV read the last few pages to hear what I think.

Michfan, probably. The NOGAPS 18z will come out after the GFS 18z.
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321. smmcdavid
3:32 PM CDT on May 27, 2008
I know you aren't trying to offend anyone... it's not your style. I do enjoy your posts.
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319. seflagamma
4:31 PM AST on May 27, 2008
Hey Foxx,

so gave up the seista to have fun here for awhile????

MichaelST, thanks! I agree!!!

GSM, I think the deforestation of our land affects us more than polution...just my opinion...and I have more than a GED also.
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318. Michfan
3:30 PM CDT on May 27, 2008
313. MichaelSTL 3:30 PM CDT on May 27, 2008
304. seflagamma 3:26 PM CDT on May 27, 2008
Oh Geeze!!!! how many times in this blog do I have to put a stop to the GW/CC debate while we have an Invest to watch????? Please!! there are plenty of GW/CC blogs out there to debate in!!! Give us a break.


Sorry... some people obviously can't listen and have to make some remark about it (you know who you are)



Your just feeding into it and making it worse. Go to the other blogs with that crap please.

Drak wouldn't the NOGAPS get a better hold of the system in its future runs now that it is an invest?
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317. Patrap
3:30 PM CDT on May 27, 2008
I stand by my levity.Always

And I dont listen to authority very well,especially those in Fla. LOL

But dem Texas Gals really do make me mindful of my presence.
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316. TerraNova
4:30 PM EDT on May 27, 2008
Afternoon JFV.
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315. Beachfoxx
3:27 PM CDT on May 27, 2008
Inyo-

Your post #294 gets my vote for best post of the day! ROFLMAO

Hi everyone!
Member Since: July 10, 2005 Posts: 157 Comments: 29384
312. smmcdavid
3:27 PM CDT on May 27, 2008
Hey Pat, I got my GED...

and now I'm one semester away from having my BS in marine biology. I do know the carbon cycle... and very well I might add.

Be careful what you say.
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311. TerraNova
4:28 PM EDT on May 27, 2008
What are the initiation times for the GFDL/HWRF? I've already forgotten lol.
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308. Patrap
3:27 PM CDT on May 27, 2008
What is the Carbon Cycle ,you ask? Link

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307. Drakoen
8:26 PM GMT on May 27, 2008
302. Michfan 8:25 PM GMT on May 27, 2008
The wind shear is forecast to stick around for a bit in the Caribbean. Im more interested in 90E's track once the other models get ahold of it in their runs like the GFDL and NOGAPS.


Don't know if they will run the GFDL and HWRF today. The NOGAPS 12z is taking this area of low pressure east into the Caribbean.
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306. seflagamma
4:27 PM AST on May 27, 2008
bbl
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305. Michfan
3:25 PM CDT on May 27, 2008
Back to 90E folks!
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304. seflagamma
4:25 PM AST on May 27, 2008
Oh Geeze!!!! how many times in this blog do I have to put a stop to the GW/CC debate while we have an Invest to watch????? Please!! there are plenty of GW/CC blogs out there to debate in!!! Give us a break.
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303. HadesGodWyvern (Mod)
8:24 PM GMT on May 27, 2008
Typhoon 2000 - Philippines

Tropical Cyclone Watch:
===============================

  • Tropical Disturbance 92W (LPA/1010), slowly organizing with mid-level cyclonic turning, but remains weak...located about 260 km. ENE of Casiguran, Aurora (16.6N 124.5E)...packing winds of 30 km/hr, this disturbance will be observed closely for possible development into a Tropical Cyclone in hours or days
  • Member Since: May 24, 2006 Posts: 50 Comments: 45301
    302. Michfan
    3:18 PM CDT on May 27, 2008
    The wind shear is forecast to stick around for a bit in the Caribbean. Im more interested in 90E's track once the other models get ahold of it in their runs like the GFDL and NOGAPS.
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    301. NEwxguy
    8:21 PM GMT on May 27, 2008
    plants remove CO2 in the daytime and put it back at night.
    Member Since: Posts: Comments:
    300. Patrap
    2:39 PM CDT on May 27, 2008
    The Carbon Cycle, for those who got the GED instead.

    Minus the Deer

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    298. Patrap
    3:19 PM CDT on May 27, 2008
    One Man nor Woman...dont rule the roost on the GW Debate.

    But Maybe the "Decider" can Blast a Way thru it ..hes good at that
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    296. seflagamma
    4:19 PM AST on May 27, 2008
    #290, thanks HOG!
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    293. aviifl
    4:16 PM EDT on May 27, 2008
    Hey, wouldn't be wild if we get a major hurricane in south florida in the month of October. That would be a couple of weeks of the presidential election. That also would be another disaster in south florida for the presedential election. Another fiasco
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    292. seflagamma
    4:17 PM AST on May 27, 2008
    #287, Thanks TerraNova!!!
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    291. moonlightcowboy
    3:16 PM CDT on May 27, 2008
    RAMSDIS IR3 WV LOOP
    Member Since: July 9, 2006 Posts: 184 Comments: 29610
    289. JUSTCOASTING
    8:14 PM GMT on May 27, 2008
    thanks newxguy i will pass it on to her
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    288. seflagamma
    4:14 PM AST on May 27, 2008
    didn't someone tell me earlier there is too much wind shear in the Carribean to develope anything there right now??? is is forcasted to calm down a little??
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    Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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