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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387. Drakoen
9:08 PM GMT on May 27, 2008
385. Weather456 9:07 PM GMT on May 27, 2008
The best we can do is watch the situation unfolds.


Yep.
Member Since: October 28, 2006 Posts: 57 Comments: 30832
386. 69Viking
4:04 PM CDT on May 27, 2008
Good afternoon everyone! Talk about a nice Memorial Day weekend in NW Florida! Spent Saturday and Sunday in the boat at Crab Island, missed the Humpback though, good reason to get my radio installed. Anything exciting going on? Time for catch up.
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385. Weather456
5:06 PM AST on May 27, 2008
The best we can do is watch the situation unfolds.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
384. SouthDadeFish
8:59 PM GMT on May 27, 2008
Okay I hear people saying that the EPAC low will suck moisture away from the Caribbean... But I was wondering how much moisture will it really take away because of the current westerly winds. Wouldn't these winds blow more moisture into the Caribbean? Plus the EPAC low is fairly weak and doesn't have that great of a circulation and therefore doesn't pull in an incredible amount of moisture. I could be completely wrong but I just wanted to hear your thoughts on this.
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383. Michfan
4:02 PM CDT on May 27, 2008
The models process them caneman then give tracks. The NHC doesn't officially issue tracks until it becomes at least a depression.
Member Since: September 7, 2007 Posts: 0 Comments: 1747
382. all4hurricanes
9:02 PM GMT on May 27, 2008
C911
I think only computer models give an official prediction of invests. What is the chance the low in the western Caribbean will develop
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381. extreme236
9:01 PM GMT on May 27, 2008
A tropical wave will be interacting with the convection in the Southern Caribbean soon and it will be worth seeing whether that sparks anything.
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380. smmcdavid
4:02 PM CDT on May 27, 2008
Good times...
Link
Member Since: September 20, 2005 Posts: 31 Comments: 2309
379. all4hurricanes
8:58 PM GMT on May 27, 2008
I think invest 90 will become Alma in the east Pacific but thats just my opinion. Nakri looks like it'l form into a cat 1 pretty soon and maybe even a cat 2 at some point and it's not to late for the low just east of the Philippines to form
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378. caneman911
9:00 PM GMT on May 27, 2008
do they issue paths for invests?
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377. IKE
3:58 PM CDT on May 27, 2008
372. captainhunter 3:58 PM CDT on May 27, 2008
Hey Foxx and Ike,

Here's a link about the humpback...


Link



Thanks for that link....jeez that's something!
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376. Beachfoxx
3:59 PM CDT on May 27, 2008
Thanks Cpt.Hunter,

I put the link on my blog just a bit ago. They actually got some good shots of the whale. Wish I had the time to get on the boat and go whale hunting!
Member Since: July 10, 2005 Posts: 157 Comments: 29385
375. IpswichWeatherCenter
8:57 PM GMT on May 27, 2008
[HELLO 90E!]Tropical Weather Update [21:51 BST 27/5/08] EPAC ORANGE ALERT (50-70%)

Hi

We have a Orange alert for East Pacific development today. The alert has turned into the first EPAC Invest......

MORE
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374. DocBen
8:56 PM GMT on May 27, 2008
The Carib blob seems to be drifting eastward. If 90E is drifting westward might they BOTH develop? Is there any sork of high ridge over Costa Rica seperating them?
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373. Beachfoxx
3:56 PM CDT on May 27, 2008
Ike - we are at 86 here too.
Member Since: July 10, 2005 Posts: 157 Comments: 29385
372. captainhunter
8:55 PM GMT on May 27, 2008
Hey Foxx and Ike,

Here's a link about the humpback...


Link
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370. weathersp
4:47 PM EDT on May 27, 2008
90E seems to me moving SSW along the coast of Costa Rica about 150 miles off shore.
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369. IKE
3:53 PM CDT on May 27, 2008
360. Beachfoxx 3:49 PM CDT on May 27, 2008
Hi Ike... looks like the start to an interesting season.

Did you hear about the Humpback Whale off the coast of Destin???

Pat, wish I could be in JAX to introduce you to some real Hot Sauce! Tabasco, for beginne



Think I read something on that out of the NW FL. Daily News.........about the whale.....

86 degrees here in De-funk-iak Springs....
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368. extreme236
8:53 PM GMT on May 27, 2008
90E looked a bit more organized earlier today but the environment is favorable for development.
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367. extreme236
8:49 PM GMT on May 27, 2008
Wind shear over the current disturbance in the southern Caribbean is about 20-30 knots right now. Some decreasing shear is located just north of Panama. The CPC issued their Hazards/Benefits assessment for the next 2 weeks and they still show possible development in the EPAC or SW Caribbean, citing favorable MJO, lower shear (eventually anyway for the Caribbean) and low-level westerly flow.

Link
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366. smmcdavid
3:51 PM CDT on May 27, 2008
361... I knew the answer to this one, but everyone else decided to answer it first. And I was sooo proud of myself.

Aww... lol
Member Since: September 20, 2005 Posts: 31 Comments: 2309
365. Patrap
3:50 PM CDT on May 27, 2008
Does Global Warming Change Hurricane Intensification Rates?

Felix and Humberto Leave A Question Link

These are the facts when it comes to rapid intensification in the Atlantic -- but can we generalize further about them? Jeff Masters, pretty much the chief expert among hurricane bloggers, puts it like this:

No scientist has published a paper linking rapid hurricane intensification rates with global warming. While the cases of Humberto and Felix are certainly unique, the year 1969 also had two storms that were very similar in their intensification rates. A quick look I did at historical intensification rates doesn't show any noticeable trends, and I think that the rapid intensification rates of Felix, Humberto, and Wilma the past three years are not far enough outside the statistical norms that we need to invoke climate change as an explanation. Still, it does leave one wondering, and climate change could be affecting hurricane intensification rates.

But how might it be affecting them? What would the mechanism of action be? Masters doesn't say, but I'm going to assume that he means more heat stored in the ocean creates an environment more conducive to rapid strengthening. But that raises some obvious questions: Is there an upper limit imposed by physics on how fast strengthening can occur? And do our data totally limit us in saying anything more about trends in intensification rates at the current juncture?



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363. HurricaneGeek
4:49 PM EDT on May 27, 2008
361. It is to specify what basin they are in. The numbers go from 90-99 then back to 90 again. The letters never change. 'L' means Atlantic and 'E' means Eastern Pacific =)
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362. Thundercloud01221991
8:50 PM GMT on May 27, 2008
361. caneman911 8:49 PM GMT on May 27, 2008
Why do invest have either a L or a E behind the #
Action: | Ignore User


the L tells you it is in the Atlantic basin and the E tells you it is the East Pacific Basin
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361. caneman911
8:47 PM GMT on May 27, 2008
Why do invest have either a L or a E behind the #
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360. Beachfoxx
3:45 PM CDT on May 27, 2008
Hi Ike... looks like the start to an interesting season.

Did you hear about the Humpback Whale off the coast of Destin???

Pat, wish I could be in JAX to introduce you to some real Hot Sauce! Tabasco, for beginners.

Member Since: July 10, 2005 Posts: 157 Comments: 29385
359. Patrap
3:47 PM CDT on May 27, 2008
Hurricane Adolph 2001
May 25 to June 1 The most powerful hurricane on record during the May in the Eastern Pacific; Category Four Hurricane with winds between 140 and 150 mph; heavy rains to Mexico's west coast; no landfall.
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358. seflagamma
4:45 PM AST on May 27, 2008
lol!

oK, NOW, back to invest 90E ROFLMAO!!!!

I have other things I should be doing here on my once in a life time afternoon to myself at my house and only me and Harley here..but this is so much more fun than actually doing a few chores! LOL
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357. TerraNova
4:39 PM EDT on May 27, 2008
Good afternoon TerraNova! How are you doing today? Hey Terra, do you still think the Carib disturbance has any chance left for development?

I'm doing great, thanks.

I think the Caribbean blob still has a chance, although it is significantly less due to wind shear, lack of moisture, and the possiblity of land interaction like models are hinting at (land interaction is a problem that prevents most extreme SW Caribbean blobs from developing). Of course, again, that's not to say that it doesn't have a chance. If you want my opinion, I think the EPAC low will be the one that ends up developing as the intensity models have it growing to TD/TS strength. This could drown out the Caribbean low but a lot of it depends on proximity.

EDIT: The eventual course of the eastern pacific low is uncertain.

CONDITIONS SUPPORTING DEVELOPMENT- Dry air will not be a problem
- SST's
- Upward MJO pulse
- Low level flow

CONDITIONS INIBITING DEVELOPMENT
- Unfavorable Wind Shear (at the moment)
- Possiblity of land interaction
- Energy will be stolen away by EPAC low (but this depends on where the EPAC low eventually goes)
- Climatology (I know, this isn't a condition but it does help in making a decision)
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356. Patrap
3:44 PM CDT on May 27, 2008
Pacific Stuff,Hurricane wise. Link
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355. Drakoen
8:46 PM GMT on May 27, 2008
Pressure is down to 1006mb.
Member Since: October 28, 2006 Posts: 57 Comments: 30832
354. daws99
3:43 PM EST on May 27, 2008
.
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353. Patrap
3:43 PM CDT on May 27, 2008
Alma in the 70s Comes to Mind I think Press
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352. NEwxguy
8:42 PM GMT on May 27, 2008
holds up a cross,you will not suck me into the GW talk,you will not get me,I will fight.
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351. Patrap
3:43 PM CDT on May 27, 2008
Family kinda Knows each other BF..LOL
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349. Drakoen
8:40 PM GMT on May 27, 2008
The circulation center is current drifting to the east.
Member Since: October 28, 2006 Posts: 57 Comments: 30832
348. Patrap
3:41 PM CDT on May 27, 2008
I cant say..I hear theres a Hit out on me from The BarometerBoB Show, Fla Moderators..LOL

Atlantic Beach area..
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347. IKE
3:40 PM CDT on May 27, 2008
336. cdo 3:38 PM CDT on May 27, 2008
which blob in that Sat pic is it?


It is hard to see...it's easier to see in motion.....

Link
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346. captainhunter
8:38 PM GMT on May 27, 2008
Does anyone have any history on lows forming in the Pacific and making it to the Carribean or GOM?
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345. seflagamma
4:40 PM AST on May 27, 2008
Oh my goodness, Foxx you are on a roll, I will not leave now! LOL!!!!
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344. HurricaneGeek
4:39 PM EDT on May 27, 2008
Looking at the visual loop, it's hard to make out a real define circulation. But it's an invest lol. If you look for it, however, you can see it (better). It's at 10N and 90W. Maybe less convection then what was there earlier from what I see while looking at the loop. Any thoughts, comments?
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343. Beachfoxx
3:41 PM CDT on May 27, 2008
How did I know this was coming??? LOL
339. Patrap 3:40 PM CDT on May 27, 2008 Hide this comment.
Tabasco and Global Warming Link
Member Since: July 10, 2005 Posts: 157 Comments: 29385
341. weatherfromFlorida
8:38 PM GMT on May 27, 2008
330. I am heading to the VAB to see the launch Saturday, Pat, were you heading?
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339. Patrap
3:38 PM CDT on May 27, 2008
Tabasco and Global Warming Link
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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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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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