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

By: Dr. Jeff Masters , 05:07 PM GMT on Mei 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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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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287. TerraNova
4:12 PM EDT on May 27, 2008
has the EPAC had a depression or storm yet this season? I think they get started before we do don't they?

Nope, not yet. The EPAC season began two weeks ago. Were 90E to develop it would be TD1/TS Alma.
Member Since: Juli 30, 2007 Posts: 76 Comments: 4063
286. seflagamma
4:11 PM AST on May 27, 2008
getting exciting....geeze I have sure missed all of you and getting excited over a possible "invest" for the past 6 mos, LOL...and I am home today so actally have time to blog here and read your comments!!!
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285. Drakoen
8:11 PM GMT on May 27, 2008
279. TerraNova 8:10 PM GMT on May 27, 2008
I'm not entirely convinced that the area in the EPAC will head out to the west or Northwest at least not in the short term.

I agree. Also is the 200 mb anticyclonic circulation over 90E be creating wind shear over the Caribbean?


No. An deep upper level trough is creating the wind shear. ON the water vapor imagery, notice that positively titled area that extends from NE to SW from the Bahamas down into Central America.
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284. atmoaggie
8:12 PM GMT on May 27, 2008
Thanks Dr. Masters. My you all have busy today.

Token GW comment: If you are thoroughly convinced the planet is so horribly effected by your CO2 emissions, then by all means, do something about it. Stop exhaling now. You would still end up emitting CO2, but at least now at a drastically reduced rate. Then you can feel like you did something good.

About the chances for our potential tropical recession(s):
2 storms in the GFS? Seriously?
Check out the competing lows in the 12 Z GFS (yeah, I know its been out forever about now). The GFS Kaleidescope decided it was making forecasts too easy by only developing one jumping about system, so it made 2. See loop here.

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283. NEwxguy
8:10 PM GMT on May 27, 2008
266. JUSTCOASTING 8:00 PM GMT on May 27, 2008
Ok gan i need some help my daughter is doing a final science report on tropical systems and hope to follow one progress,Question the newest invest if you were in that are now in a boat what kind of conditions would be finding out there with just an invest.Would there be large seas or lighting now ?Help if you can
Thanks

If you were in a boat under the invest,you would have choppy seas,thunderstorms to contend with,gusty winds 15 to 25 mph.Not nice weather,but nothing real serious.
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282. WPBHurricane05
4:10 PM EDT on May 27, 2008
looks like our central atlantic tropical wave is about to enter the caribbean Link
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280. seflagamma
4:08 PM AST on May 27, 2008
wow, our first depression of the season...for the atlantic side...has the EPAC had a depression or storm yet this season? I think they get started before we do don't they?
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279. TerraNova
4:08 PM EDT on May 27, 2008
I'm not entirely convinced that the area in the EPAC will head out to the west or Northwest at least not in the short term.

I agree. Also is the 200 mb anticyclonic circulation over 90E be creating wind shear over the Caribbean?
Member Since: Juli 30, 2007 Posts: 76 Comments: 4063
277. smmcdavid
3:08 PM CDT on May 27, 2008
And terra... and in advance anyone else who answers. lol
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276. nash28
4:08 PM EDT on May 27, 2008
Hmmm.. 12z NOGAPS hasn't deviated much over the last few days....

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274. HadesGodWyvern (Mod)
8:08 PM GMT on May 27, 2008

NEW TROPICAL STORM FORECAST TO DEVELOP AFTER 24 HOURS
FORECAST POSITION AT T+ 24 : 9.2N 87.5W

VERIFYING TIME POSITION STRENGTH TENDENCY
-------------- -------- -------- --------
12UTC 28.05.2008 9.2N 87.5W WEAK
00UTC 29.05.2008 9.6N 89.1W MODERATE INTENSIFYING SLIGHTLY
12UTC 29.05.2008 10.3N 89.7W STRONG INTENSIFYING RAPIDLY
00UTC 30.05.2008 11.4N 90.3W INTENSE INTENSIFYING RAPIDLY
12UTC 30.05.2008 12.2N 90.7W INTENSE INTENSIFYING SLIGHTLY
00UTC 31.05.2008 13.5N 90.5W STRONG WEAKENING RAPIDLY
12UTC 31.05.2008 17.5N 92.9W WEAK WEAKENING RAPIDLY
00UTC 01.06.2008 17.8N 93.5W BELOW TROPICAL STORM STRENGTH



THIS INFORMATION IS PROVIDED AS GUIDANCE FOR TROPICAL CYCLONE RSMCS.
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273. smmcdavid
3:06 PM CDT on May 27, 2008
Thanks Michael...
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272. TerraNova
4:04 PM EDT on May 27, 2008
So who thinks we will eventually see a depression from 90E?

All of the preliminary intensity models are showing a tropical storm by 48 hours. Plus the NHC has a 20-50% chance of genesis. I'd say it's very possible the EPAC will see it's first depression. Conditions are much more favorable for tropical genesis in the Pacific than in the Atlantic.
Member Since: Juli 30, 2007 Posts: 76 Comments: 4063
271. Drakoen
8:04 PM GMT on May 27, 2008
I'm not entirely convinced that the area in the EPAC will head out to the west or Northwest at least not in the short term. Looking at the water vapor imagery I see mid to upper level anticyclonic flow in the EPAC but just to the east I see mid to upper level cyclonic flow with the trough in the area. At the surface, High pressure flow only extends out to Lousiana One of the two flows will determine which model is right and which model is wrong.
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270. smmcdavid
3:04 PM CDT on May 27, 2008
I think I'm good... filled up yesterday. This won't already be on the news, will it?
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269. TerraNova
3:57 PM EDT on May 27, 2008
The current models are not in very good agreement past 72 hours or so. The BAMS guidance (meant for weak systems so BAMM and BAMD can be discounted unless this system gets stronger) has the low being pulled northward into Central America. This is the only preliminary model showing eastward motion meaning that it could be an outcast. Notice that the LBAR has the system surviving the cross into the BOC.

(FSU)
Member Since: Juli 30, 2007 Posts: 76 Comments: 4063
268. Thundercloud01221991
8:01 PM GMT on May 27, 2008
263. redrobin 7:57 PM GMT on May 27, 2008
253. GulfScotsman 2:46 PM CDT on May 27, 2008
Can Joe Bastardi single handedly raise your gas Prices $.50 overnight...

stay tuned.

If anyone says a storm is coming toward Houston we will be looking at much more than $.50 a gallon increase!!!!!!!!in gas


Action: | Ignore User


everyone fill up before 6 PM newscast otherwise you will see a jump in gas prices
Member Since: Agustus 1, 2006 Posts: 28 Comments: 3716
267. seflagamma
4:00 PM AST on May 27, 2008
thanks to all who addressed my last post and

253. GulfScotsman 3:46 PM AST on May 27, 2008
Can Joe Bastardi single handedly raise your gas Prices $.50 overnight...


That made me laugh big time! LOL

We just need a nice wet tropical depression to ride up the center of Florida to dump about 4-6 inches of rain in the center of the state all the way up! is that asking for too much?
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266. JUSTCOASTING
7:58 PM GMT on May 27, 2008
Ok gan i need some help my daughter is doing a final science report on tropical systems and hope to follow one progress,Question the newest invest if you were in that are now in a boat what kind of conditions would be finding out there with just an invest.Would there be large seas or lighting now ?Help if you can
Thanks
Member Since: Posts: Comments:
263. redrobin
2:57 PM CDT on May 27, 2008
253. GulfScotsman 2:46 PM CDT on May 27, 2008
Can Joe Bastardi single handedly raise your gas Prices $.50 overnight...

stay tuned.

If anyone says a storm is coming toward Houston we will be looking at much more than $.50 a gallon increase!!!!!!!!in gas

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262. nash28
3:50 PM EDT on May 27, 2008
Wind shear forecasts several days out are like throwing darts blindfolded. The ULH orientation will help determine whether shear drops or not.
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261. smmcdavid
2:54 PM CDT on May 27, 2008
So who thinks we will eventually see a depression from 90E?
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260. Weather456
3:52 PM AST on May 27, 2008
yeah 90E has a good chance of development but I'll watch the caribbean incase it shows something.
Member Since: Juli 24, 2005 Posts: 407 Comments: 19076
256. Drakoen
7:46 PM GMT on May 27, 2008
The circulation in the EPAC is broad but well-defined even enough to create its own low level steering. The wind shear forecast varies with the models and has to do a lot with the upper level high that is current vertically stacked with the system. Where the low tracks is where the shear will be favorable.
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255. tornadofan
7:47 PM GMT on May 27, 2008
Can Joe Bastardi single handedly raise your gas Prices $.50 overnight...

I bet he has invested in Oil Futures. He'll make a fortune with his forecast!
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254. StormHype
7:43 PM GMT on May 27, 2008
Hurricane forecasters monitor possible development
news of the possible development already hitting the news
Reuters


WHOOT WHOOT.... Line's out the door at Home Depot... supply of Tapcons nearly depleated... more at 6pm.
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252. HurricaneKing
3:41 PM EDT on May 27, 2008
Please tell me if this sounds right. It looks like a broad low with one weak spin in the Pacific and another in the caribbean. To me the center of the broad low looks over land between them. Although we have 90e I still wouldn't right the atlantic off. Most of the time the bigger swirl in the whole mess tends to win out. That may be 90e or it may be the other swirl. My personal opinion from a quick glance at the satellite is that 90e is spinning better but the other swirl is bigger.
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251. HurricaneGeek
3:44 PM EDT on May 27, 2008
Gams, you can see here that wind shear is still high in the Carib. Even an 80 knot reading south of Jamaica.
Dr Masters mentioned in his blog as well (wind shear).
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250. TerraNova
3:40 PM EDT on May 27, 2008
NOAA's FTP server has 90E's minimum central pressure at 1007 mb, with maximum sustained winds at 25 mph.
Member Since: Juli 30, 2007 Posts: 76 Comments: 4063
249. crackerlogic
7:32 PM GMT on May 27, 2008
Ok I don’t post much if at all. I just sit back and wait for a chance to surf in Clearwater, but this struck a nerve. Any one that believes man can change the climate has a God complex. I know what you are going to say, what about all the crap going in the air? That is going into our lungs and that will kill us way before global warming. The next thing you are going to say is what about the temp going up on the planet? Well 17% of the temp gages where in Siberia and are no long being used do the collapse of the Soviet Union. This is about the time the temps started to rise. No offence to anyone, you are all smarter than me, just my 2 cents
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248. Weather456
3:32 PM AST on May 27, 2008
That area in the SW Caribbean mentioned by the NHC to be associated with mid-upper level low has surface reflection. The 1800 UTC products at the CIMSS showed increase in low level convergence and vort along with the surface obs being reported this afternoon. QuikSCAT sure choose a wrong time to go down.
Member Since: Juli 24, 2005 Posts: 407 Comments: 19076
247. tornadojames
2:40 PM EST on May 27, 2008
Hurricane forecasters monitor possible development

news of the possible development already hitting the news
Reuters
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246. sporteguy03
7:39 PM GMT on May 27, 2008
Gamma,
90E is stationary or Quasi as the NHC put it, where will it go? Don't know just watch and see.
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245. HurricaneGeek
3:39 PM EDT on May 27, 2008
Also, hurricane23 on post 211 posted. lol
Didn't see that
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244. Drakoen
7:38 PM GMT on May 27, 2008
The models still don't have a good idea of whats going to happen. Thats what I get from reviewing the satellite imagery and latest model runs.
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243. TerraNova
3:37 PM EDT on May 27, 2008
Afternoon everyone.
Member Since: Juli 30, 2007 Posts: 76 Comments: 4063
242. HurricaneGeek
3:36 PM EDT on May 27, 2008
Gams, hi =)
90E, for the East Pacific. 90L means Atlantic. A link on the top of the page that says Tropical/Hurricane, click there and you can see the models so far. Chances are in favor that nothing will get going in to Carib.
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241. Patrap
2:36 PM CDT on May 27, 2008
Global Warming Will Bring Violent Storms And Tornadoes, NASA Predicts Link

ScienceDaily (Aug. 31, 2007) — NASA scientists have developed a new climate model that indicates that the most violent severe storms and tornadoes may become more common as Earth's climate warms./em>
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240. seflagamma
3:34 PM AST on May 27, 2008
Hi SM,
Yes we got to redirect this conversation. I pretty much avoid this blog from Dec - May because of the discussions on here when there are no storms to talk about! LOL

OK, where is 90L going??? into GOM????

will it get mixed in with the swirl in the Caribbean on other side of Cen Am???
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239. hurricane23
3:36 PM EDT on May 27, 2008
TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1605 UTC TUE MAY 27 2008

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN
FROM THE EQUATOR TO 32N...EAST OF 140W.

UPPER RIDGE PROVIDES GOOD UPPER DIFFLUENCE AND OUTFLOW FOR ITCZ
DEEP CONVECTION E OF 95W BUT LACK OF UPLIFTING MECHANISM
PREVENTS CONTINUITY TO CYCLE. ONLY EXCEPTION TO THIS SCENARIO
IS HEALTHY 1008 MB LOW PRES AT 11N91W. WHILE STILL QUASI-
STATIONARY...LOW PRES IS EXPECTED TO DRIFT INTO FAVORABLE
ENVIRONMENT ALOFT CONDUCIVE TO DEVELOPMENT WITHIN 48 HRS AS
LARGE AREA OF WLY WINDS ON S SIDE OF LOW PRES LIKELY TO BRING
PLENTY OF ADDITIONAL WARM TRPCL MOISTURE INTO SYSTEM.
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238. Patrap
2:33 PM CDT on May 27, 2008

National Hurricane Preparedness Week
Link

History teaches that a lack of hurricane awareness and preparation are common threads among all major hurricane disasters. By knowing your vulnerability and what actions you should take, you can reduce the effects of a hurricane disaster. Hurricane Preparedness Week during 2008 will be held May 25th through May 31st.

The goal of this Hurricane Preparedness Web site is to inform the public about the hurricane hazards and provide knowledge which can be used to take ACTION. This information can be used to save lives at work, home, while on the road, or on the water.


Tuesday's Lesson.

High Winds

The intensity of a landfalling hurricane is expressed in terms of categories that relate wind speeds and potential damage. According to the Saffir-Simpson Hurricane Scale, a Category 1 hurricane has lighter winds compared to storms in higher categories. A Category 4 hurricane would have winds between 131 and 155 mph and, on the average, would usually be expected to cause 100 times the damage of the Category 1 storm. Depending on circumstances, less intense storms may still be strong enough to produce damage, particularly in areas that have not prepared in advance. Link
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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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