The tornado season of 2008: climate change to blame? And, tropical update
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
Missing House, if found call Dennis and Carla
Nice structure on upercell east of Pratt, Kansas. Photo copyright Mike Theiss.
Reader Comments
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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)
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
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.
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.
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
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?
Aww... lol
Link
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....
Here's a link about the humpback...
Link
Hi
We have a Orange alert for East Pacific development today. The alert has turned into the first EPAC Invest......
MORE
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!
Hey Foxx and Ike,
Here's a link about the humpback...
Link
Thanks for that link....jeez that's something!
Link
I think only computer models give an official prediction of invests. What is the chance the low in the western Caribbean will develop
The best we can do is watch the situation unfolds.
Yep.
And, I'm trying to get people to read my blog by randomly inserting the link into the conversation... lol.
That, plus the effects of the upward MJO pulse, plus what the tropical wave currently over Western South America will bring with it could make up for moisture lost to the EPAC low, but it depends on how strong the EPAC low gets. A low that hasn't even fully closed off yet won't stand much of a chance against a tropical storm. However, this is something that the models can't agree on and we just need to wait and see how strong the EPAC low gets, where it goes, and how the Caribbean low reacts to it.
Looks like the mid level low in the SW Caribbean is trying to go down to the surface. Looks better now on the vort than it did earlier today. Shear is increasing north of Panama a few hundred miles.
Anticyclone is still in place over the Epac low giving it more of a chance at development. I just see too much flow over the SW Carribean disturbance to see it develop. I think the EPac low is going to hinder if it remains this close to it.
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?
Some of the models a few days ago were actually predicting for two completely separate systems to form. I believe the models have dropped that idea for now, but they may have to resurrect it if the "blobs" keep behaving how they have been. I could imagine two forming at the same time....
sm, I like your blog also; I am all into family just look at my prev blogs! LOL
by the way Foxx, Hgeek and I been posting on your blog so you can have a hammock!
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