2011: Year of the tornado. MSP tornado likely EF2

The numbers are getting downright scary.

1162 preliminary tornado reports so far in 2011 in the U.S.

671 average number of tornadoes to date

116 and counting, the number of fatalities in the Joplin, MO tornado

8th deadliest tornado in U.S. history

481 people killed in tornadoes so far in 2011

6 years have produced over 500 tornado deaths since 1875 in USA

58 years since we've seen this many tornado deaths in the USA

The big question: Why?

There are a few atmospheric clues as to why this year is an off the charts tornado producer, but it's hard to reach a clear conclusion.

1) La Nina may play a role in active tornado years, but the tie is not a slam dunk. The explanation in a recent paper from NOAA's Earth Syetem Research Laboratory.

El Niño/La Niña and Tornadoes

--------------------------------------------------------------------------------

"The record setting tornado outbreak during 26-28 April 2011 took place within a global climate context of lingering La Niña conditions (cold phase of the Southern Oscillation). Below normal sea surface temperatures (SSTs) had developed in the prior year over the tropical central Pacific, and though peaking in winter, have persisted into this spring. To the extent that such global ocean conditions may have played a role in the occurrence of this extreme tornado outbreak, there may exist a long-lead capability to alert the public and decision makers of heightened risk for more violent tornado outbreaks over a season for a given geographical region.

What is the current understanding of La Niña effects on US tornado occurrences?

There are suggestions that winter (January-March) tornado counts may change their preferred geographical location depending on the phase of the El Niño/Southern Oscillation (ENSO).11 However, that study's analysis covering 1950-2003 found that neither the frequency of tornado days nor of violent tornado days (days with 5 or more F2+ tornadoes) is affected systematically by the phase ENSO for the US as a whole. A separate investigation that used data for a shorter period of 1950-1992, but covering all seasons, argued that La Niña events increase tornadic activity in the Ohio River Valley and the Deep South during spring, and that La Niña facilitates large tornadic outbreaks and is associated with more destructive storms. It should be recognized, however, that small sample sizes do not permit a robust statistical appraisal for either of these studies."

2) Warmer than average water temperatures in the Gulf of Mexico?

There is some speculation that warm waters in the Gulf of Mexico may be adding heat and moisture to air masses in the southern USA. This may be providing extra fuel to storms in 2011.

3) Climate change link is tenuous:

Again, the report from NOAA's Earth Syetem Research Laboratory.

"So far, we have not been able to link any of the major causes of the (April) tornado outbreak to global warming. Barring a detection of change, a claim of attribution (to human impacts) is thus problematic, although it does not exclude that a future change in such environmental conditions may occur as anthropogenic greenhouse gas forcing increases.

The body of knowledge regarding the possible role played by large-scale climate forcing in tornado outbreaks is rapidly evolving, and constitutes a field of study that must integrate existing expertise in meso-scale meteorology with expertise in global-scale climate dynamics. Likewise, the methods for conducting attribution science also continue to evolve, and advances on the tornado-climate linkages will require modeling capabilities beyond current tools. Despite various limitations in data and tools, it should be noted that applying a scientific process is essential if one is to overcome the lack of rigor inherent in attribution claims that are all too often based on mere coincidental associations."

One thing is clear. A consistent and powerful jet stream is racing across the central USA this spring, and has triggered massive tornado outbreaks. The root causes may be studied for years, but the trend continues.

MSP tornado survey in:

Looks like and EF2. Details here.

PUBLIC INFORMATION STATEMENT

NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN

752 PM CDT MON MAY 23 2011

...SURVEY TEAM ASSESSMENT ON THE NORTHERN TWIN CITIES METRO TORNADO

OF SUNDAY AFTERNOON MAY 22ND...

THE TORNADO THAT HIT NORTH MINNEAPOLIS AND OTHER AREAS WILL BE RATED

EITHER AS A STRONG EF1 OR AN EF2.

THERE REMAIN SOME UNCERTAINTIES IN RATING THE TORNADO THAT HIT

NORTH MINNEAPOLIS...ST. LOUIS PARK...GOLDEN VALLEY...FRIDLEY AND

MOUNDS VIEW AND BLAINE SINCE SOME OF THE FIELD INFORMATION GATHERED

STILL NEEDS TO BE PROCESSED. HOWEVER...IT IS SAFE TO SAY THAT IT

WILL BE RATED AS EITHER A STRONG EF1 OR POSSIBLY AN EF2. THE

TORNADO WAS ABOUT 1/2 MILE WIDE AT ITS WIDEST POINT. IT WAS ON THE

GROUND FOR 6 AND ONE QUARTER MILES IN HENNEPIN COUNTY...PLUS AN

ADDITIONAL 8 MILES ACROSS ANOKA AND RAMSEY COUNTIES AS THE TORNADO

WENT THROUGH PARTS OF FRIDLEY...MOUNDS VIEW...AND BLAINE.

Next outbreak on the way:

It looks like yet another severe tornado outbreak is firing off today in the Southern Plains. This time the cities under the highest risk will be Oklahoma City, Tulsa, Wichita and yes, Joplin, Missouri.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0754 AM CDT TUE MAY 24 2011

VALID 241300Z - 251200Z

...THERE IS A HIGH RISK OF SVR TSTMS OVER PARTS OF OKLAHOMA AND

KANSAS...

...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK AREA

FROM N TX N/NEWD INTO PARTS OF AR AND MO...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE ABOVE AREAS

FROM S CNTRL TX THROUGH THE MID MS AND OH VLYS INTO NEW

ENGLAND...THE MID ATLANTIC STATES AND NC...

...SYNOPSIS...

...TORNADO OUTBREAK EXPECTED OVER PARTS OF THE SRN AND CNTRL PLNS

AND OZARKS LATER TODAY INTO TONIGHT...

We could easily add several dozen more tornadoes to the 2011 count today.

Let's hope this time no major cities take a direct hit.

PH