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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488. TEXASYANKEE43
10:33 PM GMT on May 27, 2008
486

I ain't touchin that
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487. Dakster
10:14 PM GMT on May 27, 2008
Hey Stormw... Good Afternoon. Hope all is well on your end.

Looking forward to your daily synopsis reports.
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486. fire831rescue
10:30 PM GMT on May 27, 2008
Ok, ya'll. I'm tired of lurking. Looks like we have an invest but it's on the wrong side of Mexico. Can't wait for the blog to explode on that one... By the way, anyone know where it's headed?
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485. TEXASYANKEE43
10:27 PM GMT on May 27, 2008
Shear tendency over the Gulf of Mexico shows decreasing shear over the entire gulf


Thanks, that answers my ? for 481.


On another note, our local met in Houston has retired. Does anyone remember Dr. Neal Frank?
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484. extreme236
10:28 PM GMT on May 27, 2008
This is the GFS shear in 48 hours according to the 12Z GFS:



Member Since: August 2, 2007 Posts: 19 Comments: 19234
483. extreme236
10:26 PM GMT on May 27, 2008
Shear tendency over the Gulf of Mexico shows decreasing shear over the entire gulf.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
482. extreme236
10:25 PM GMT on May 27, 2008
18Z at the start shows a 1008 mb low (90E) nothing in the Caribbean at initially. Will have to see if it shows the same consistency as it has with the Caribbean system this run.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
481. TEXASYANKEE43
10:24 PM GMT on May 27, 2008
All I see is a general WNW movement winding up in the BOC by Monday.


Will the BOC have favorable conditions by Mon.?
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480. Drakoen
10:23 PM GMT on May 27, 2008
The NOGAPS 18z is coming out now. I think the GFS and the NOGAPS will be the models to watch.
Member Since: October 28, 2006 Posts: 57 Comments: 29905
479. kingy
10:15 PM GMT on May 27, 2008
Patrap - agreed.

On a practical note I have a modest place in the keys which I avoid staying in during the Hurricane season, the reason is that I can't stand the evacuations which we have seen in recent years. I am paying a crazy 5 figure sum for insurance on this property and I feel less and less safe living in it, I will look at selling up some day. For now, I am lucky enough to have another property in Florida. This one is concrete built with steel window shutters and I will feel confident inside in a cat 1 or 2. Theoretically it would stand a cat 4 but I wouldn't be there to find out. Andrew was enough to teach me to flee a big storm. I don't know too many people that have been thru a cat 4/cat 5 that would repeat the experience
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478. IKE
5:22 PM CDT on May 27, 2008
All I see is a general WNW movement winding up in the BOC by Monday.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
477. extreme236
10:22 PM GMT on May 27, 2008
The GFS wants to develop that CV storm again in about 100+ hours.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
476. extreme236
10:19 PM GMT on May 27, 2008
The GFS apparently has it in for the Yucatan and Belize. Apparently it doesn't think they had enough after Dean last year.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
475. Drakoen
10:19 PM GMT on May 27, 2008
474. IKE 10:19 PM GMT on May 27, 2008
According to the last few runs of the GFS...this disturbed weather(around central America), is going to move WNW over the next 5 days.....


WNW then NNW into the Gulf of Honduras.
Member Since: October 28, 2006 Posts: 57 Comments: 29905
474. IKE
5:18 PM CDT on May 27, 2008
According to the last few runs of the GFS...this disturbed weather(around central America), is going to move WNW over the next 5 days.....
Member Since: June 9, 2005 Posts: 23 Comments: 37858
473. Patrap
5:12 PM CDT on May 27, 2008

468.

Certainly...
Take the opportunity now to Store Fuel for a Possible Evactuation,add some stable mix, and store Properly.
One will be one step ahead of the fray. If a threat develops and one has to bug out.
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472. extreme236
10:12 PM GMT on May 27, 2008
464. Drakoen 10:08 PM GMT on May 27, 2008
I give both the EPAC and the Caribbean area the same chance for development. If anything I would favor the EPAC a little bit more because of climatology


I agree
Member Since: August 2, 2007 Posts: 19 Comments: 19234
471. hurricane23
6:11 PM EDT on May 27, 2008
low level convergence is good and so is upper level divergence in the caribbean infact more so then in the e-pac.

SEE HERE
and HERE

One thing to keep in mind is once high pressure builds more in the upper layers unfavorable conditions may relax a bit.
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470. Drakoen
10:12 PM GMT on May 27, 2008
Look at these surface observations in the Caribbean:
Member Since: October 28, 2006 Posts: 57 Comments: 29905
469. Patrap
5:11 PM CDT on May 27, 2008
UNYSIS 10 Day GFSx valid June 6 0 Zulu Link
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468. kingy
10:09 PM GMT on May 27, 2008
yeah Patrap, that was my business that took a hit. I'm not an oil futures guy however, I retired from the realty business. But given the volatility in oil prices I am sure that a gulf event that affected oil output would impact pump prices.
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467. Drakoen
10:09 PM GMT on May 27, 2008
463. extreme236 10:07 PM GMT on May 27, 2008
From how I interpret the GFS is that 90E moves close to Central America then a low develops in the SW Caribbean and absorbs 90E.


You got it.
Member Since: October 28, 2006 Posts: 57 Comments: 29905
466. kingy
10:02 PM GMT on May 27, 2008
Not sure the doc can claim "Well, let's be clear that human-caused climate change is occurring".

It may be clear to him ....but there are many learned scholars that are equally sure that his statement is not correct and not proven.
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465. juniormeteorologist
10:06 PM GMT on May 27, 2008
i lost my entire links..can i get a link to the gfs model, nogap model
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464. Drakoen
10:07 PM GMT on May 27, 2008
I give both the EPAC and the Caribbean area the same chance for development. If anything I would favor the EPAC a little bit more because of climatology.
Member Since: October 28, 2006 Posts: 57 Comments: 29905
463. extreme236
10:06 PM GMT on May 27, 2008
From how I interpret the GFS is that 90E moves close to Central America then a low develops in the SW Caribbean and absorbs 90E.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
462. moonlightcowboy
5:07 PM CDT on May 27, 2008
GOES experimental DUST LOOP

Yellow areas have the potential for dust, but blowing dust is generally noted by orange and red colors.
Member Since: July 9, 2006 Posts: 184 Comments: 29594
461. Patrap
5:05 PM CDT on May 27, 2008
A billion Dollar Impact wouldnt even come close to Calamity in todays dollars.

The total damage from Katrina is estimated at $81.2 billion (2005 U.S. dollars), nearly double the cost of the previously most expensive storm,


Betsy in 65 was the First Billon Dollar Baby..

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460. Drakoen
10:04 PM GMT on May 27, 2008
454. jphurricane2006 10:04 PM GMT on May 27, 2008
chilling out?

what is it having a smoke or a cocktail? LMAO

EPAC has 90E, what is being said about that?


lol. I tried to be funny...
Member Since: October 28, 2006 Posts: 57 Comments: 29905
459. extreme236
10:05 PM GMT on May 27, 2008
456. Drakoen 10:04 PM GMT on May 27, 2008
Interesting stuff from the EPAC TWD...


Yes, very interesting...
Member Since: August 2, 2007 Posts: 19 Comments: 19234
458. hurricane23
6:04 PM EDT on May 27, 2008
Models are taking this Northeasterly.
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457. Patrap
5:03 PM CDT on May 27, 2008
well guys, the season is hotting up. We have some interesting events underway. No doubt we will get a billion dollar disaster happening somewhere on US soil. Any Gulf storms will hit oil prices like never before.

Gee,..a Oil futures Guy.

Arent you the Guy who posted about your buisness the other day?
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456. Drakoen
10:02 PM GMT on May 27, 2008
Interesting stuff from the EPAC TWD...
Member Since: October 28, 2006 Posts: 57 Comments: 29905
455. hurricane23
6:03 PM EDT on May 27, 2008
Very interesting there 236.
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453. 69Viking
5:00 PM CDT on May 27, 2008
Ok, hitting the road for home. Might check back in later when things at home quite down this evening. Keep an eye on those blobs while I'm gone!
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452. moonlightcowboy
4:51 PM CDT on May 27, 2008
I'm having some fun with the RAMSDIS site, some of their new products and possibly finding a new way to directly link their loaded loops to the comments box, instead of linking the site and having to locate the loop and load it.

RAMSDIS GOES-12 4km VISIBLE LOOP

Member Since: July 9, 2006 Posts: 184 Comments: 29594
450. Drakoen
9:59 PM GMT on May 27, 2008
The GFS just has the Caribbean system chilling out north of Honduras...
Member Since: October 28, 2006 Posts: 57 Comments: 29905
449. kingy
9:58 PM GMT on May 27, 2008
well guys, the season is hotting up. We have some interesting events underway. No doubt we will get a billion dollar disaster happening somewhere on US soil. Any Gulf storms will hit oil prices like never before.
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446. TEXASYANKEE43
9:56 PM GMT on May 27, 2008
Well I think the best example of that TexasYankee would be Gabby, but that was a weird system.



Didn't those other 2 die and reform several times? j/k
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445. extreme236
9:59 PM GMT on May 27, 2008
From the EPAC TWD:

A BROAD AREA OF SURFACE LOW PRESSURE DOMINATES THE SW CARIBBEAN
AND THE E PAC ALONG THE COAST OF CENTRAL AMERICA. SEVERAL
CYCLONIC SWIRLS ARE NOTED WITHIN THIS AREA WITH THE MOST
PRONOUNCED SWIRL NEAR 09N89W...IN THE AREA WHERE OUR MARINE
PRODUCTS HAVE SUGGESTED A SURFACE LOW WOULD DEVELOP. MODEL
GUIDANCE CONTINUES TO SUGGEST THAT THIS LOW PRESSURE WILL
MEANDER IN THIS AREA FOR THE NEXT DAY OR SO...AND PERHAPS DRIFT
NE LATER THIS WEEK. THE UPPER PATTERN DESCRIBED IN DETAIL ABOVE
IS ALSO NOT EXPECTED TO CHANGE DURING FOR THE FIRST 24 HOURS
THEN AN UPPER LOW WILL SPIN UP OVER THE BAY OF CAMPECHE...WHILE
AN UPPER ANTICYCLONE DEVELOPS OVER THE SW CARIBBEAN. THIS WOULD
ALLOW A SURFACE LOW TO MOVE NW ACROSS CENTRAL AMERICA OVER GULF
OF HONDURAS. THE APPROACHING TROPICAL WAVE MAY ADD THE NEEDED
LOW LEVEL VORTICITY TO GET THIS SPINNING. NOTE THAT THE GRADIENT
S OF THIS LOW PRESSURE IS ALREADY SUPPORTING A SW TO W 20 TO 25
KT WIND AND SEAS TO ABOUT 10 FT. THESE CONDITIONS ARE EXPECTED
TO PERSIST S OF THE LOW THROUGH 48 HOURS.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
444. hurricane23
5:59 PM EDT on May 27, 2008
Here are some models for 90E...Ships model brings it to Hurricane Intensity.If you want to view the models GO HERE and hit Guidance.


009
WHXX01 KMIA 271826
CHGE77
TROPICAL CYCLONE GUIDANCE MESSAGE
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
1826 UTC TUE MAY 27 2008

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

EAST PACIFIC OBJECTIVE AIDS FOR

DISTURBANCE INVEST (EP902008) 20080527 1800 UTC

...00 HRS... ...12 HRS... ...24 HRS. .. ...36 HRS...
080527 1800 080528 0600 080528 1800 080529 0600

LAT LON LAT LON LAT LON LAT LON
BAMS 10.0N 90.0W 9.7N 90.3W 9.5N 90.6W 9.5N 90.6W
BAMD 10.0N 90.0W 9.9N 90.0W 10.2N 90.3W 10.7N 90.8W
BAMM 10.0N 90.0W 9.7N 89.7W 9.9N 89.8W 10.4N 89.9W
LBAR 10.0N 90.0W 10.3N 89.8W 11.4N 90.2W 13.1N 91.0W
SHIP 25KTS 32KTS 38KTS 43KTS
DSHP 25KTS 32KTS 38KTS 43KTS

...48 HRS... ...72 HRS... ...96 HRS. .. ..120 HRS...
080529 1800 080530 1800 080531 1800 080601 1800

LAT LON LAT LON LAT LON LAT LON
BAMS 9.6N 90.4W 10.7N 89.7W 12.5N 88.7W 14.9N 88.9W
BAMD 11.5N 91.8W 13.2N 94.2W 14.3N 96.6W 14.1N 99.3W
BAMM 10.9N 90.4W 11.9N 91.2W 12.3N 91.8W 12.5N 92.3W
LBAR 15.3N 92.1W 19.9N 95.2W 22.4N 96.7W 23.1N 97.3W
SHIP 49KTS 56KTS 61KTS 68KTS
DSHP 49KTS 56KTS 61KTS 68KTS

...INITIAL CONDITIONS...
LATCUR = 10.0N LONCUR = 90.0W DIRCUR = 0DEG SPDCUR = 0KT
LATM12 = 10.0N LONM12 = 90.0W DIRM12 = 360DEG SPDM12 = 0KT
LATM24 = 10.0N LONM24 = 90.0W
WNDCUR = 25KT RMAXWD = 200NM WNDM12 = 25KT
CENPRS = 1007MB OUTPRS = 1010MB OUTRAD = 225NM SDEPTH = M
RD34NE = 0NM RD34SE = 0NM RD34SW = 0NM RD34NW = 0NM

$$
NNNN


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443. smmcdavid
4:58 PM CDT on May 27, 2008
Thanks for the info.
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441. extreme236
9:56 PM GMT on May 27, 2008
Well 90E is an invest because it was/is more organized than the Caribbean system and has a deeper low pressure that is at the sfc. The Caribbean system does not have a sfc low apparently however the thing in the Caribbean is almost more impressive in appearance than 90E IMO
Member Since: August 2, 2007 Posts: 19 Comments: 19234
440. extreme236
9:55 PM GMT on May 27, 2008
Well I think the best example of that TexasYankee would be Gabby, but that was a weird system.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
439. TerraNova
5:53 PM EDT on May 27, 2008
If the EPAC and Carib low have basically the same pressure in millibars, why is one an invest and the other not? Is it because of favorable conditions for development?

It's just the GFS that has the two lows nearly identical in strength to eachother...it may not actually be that way. Upon closer inspection, surface charts have the Pacific low at 1006 mb, stronger/deeper than the caribbean low.
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438. weatherboykris
9:54 PM GMT on May 27, 2008
Exactly Adrian. Some people thought we were going to wake up this morning Arthur. These early season storms need days to ferment before any development occurs. Wait and see folks.
Member Since: December 9, 2006 Posts: 125 Comments: 11346

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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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