Why weather played a role in bin Laden raid; Tornado records smashed

We’re learning that weather played a critical role in the timing (and potential success) of the dramatic raid that lead to the death of Osama bin Laden.

The mission to capture or kill bin Laden was scrubbed on Saturday night/early Sunday due to bad weather in Pakistan. A front blew through the area with high winds and there were thunderstorms in the area, forcing the military to scrub the mission Saturday night.

Take a look at hourly weather conditions at nearby Islamabad late Saturday night. As you can see wind gusted over 34 mph and thunderstorms were reported nearby for several hours Saturday night.

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Hourly observations from Islamabad show why high winds and thunder scrubbed the mission Saturday night. (Click images to enlarge)

Winds also shifted direction rapidly Saturday afternoon in Islamabad.

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When you combine wind shear, high winds over 30 mph and thunderstorms in the area you can see why the helicopter landing and mission was scrubbed Saturday night/early Sunday morning.

Sunday Night: “Perfect weather” green lights the mission

Sometime around midnight Sunday night/ Monday morning a team of helicopters lifts off from the deserts of eastern Afghanistan and headed for Abbotabad.

The sky is clear and moonless, and the weather conditions are ideal for the pilots to drop in from above, undetected until the sound of rotors fills the sky in Abbotabad at 12:55 am local time.

Not only are skies clear, the air is calm with no wind at ground level. Haze is reported at nearby Islamabad with visibility reported at 2.5 miles. This may have been a critically beneficial factor in favor of U.S. Special Forces that night.

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Hourly observation from Islamabad, Pakistan within one hour of the raid.

Visibility of just 2.5 miles meant the helicopters were invisible to the naked eye above 12,000 feet as they flew in, but visibility was good enough for the pilots to have clear sight of the compound as they dropped out of the sky from above to land in nearly perfect weather conditions.

The timing of the raid was also likely chosen by the phase of the new moon on May 3rd. The dark, moonless sky another factor working in stealthy favor of the surprise attack.

Somewhere in the U.S. Government (probably the Air Force) there are some very happy meteorologists today. They likely gave the advice to scrub on Saturday night, and the green light to go on Sunday night based on an excellent weather forecast.

The rest is history.

April 27, 2011: Biggest tornado outbreak in U.S. history:

Speaking of history, we’ve lust lived through the biggest single tornado outbreak on record in the USA.

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Tracks of rotating tornadic supercells on April 27th.

NOAA has tallied the numbers, and it turns out last week’s tornadic outburst set multiple records

April 25-28, 2011, Tornado Outbreak Statistics

NOAA’s preliminary estimate is that there were 362 tornadoes during the entire outbreak from 8:00 a.m. EDT April 25 to 8:00 a.m. April 28, 2011.

During the 24-hour period from 8:00 a.m. EDT April 27 to 8:00 a.m. EDT April 28, The National Weather Service (NWS) estimates there were a total of 312 tornadoes.

The largest previous number of tornadoes on record in one event occurred from April 3-4, 1974, with 148 tornadoes.

NWS Weather Forecast Offices issued life-saving tornado warnings, with an average lead-time of 24 minutes. NWS issued warnings for more than 90 percent of these tornadoes.

Expert analysis by NOAA Research and the National Weather Service of the fatality information indicates that at least 350 people were killed during the entire outbreak from 8:00 a.m. EDT April 25 to 8:00 a.m. April 28. There were 340 fatalities during the 24-hour-period from 8:00 a.m. April 27 to 8:00 a.m. April 28.

The April 26-28 period had the most people killed by tornadoes in a two-day period since April 5-6, 1936, when 454 people were killed, mostly in Tupelo, Mississippi, and Gainesville, Georgia.

April 27, 2011, is the deadliest single day for tornadoes since the March 18, 1925, tornado outbreak that had 747 fatalities across 7 states (including the Tri-State Tornado).

The Tuscaloosa-Birmingham (EF4) tornado during the April 2011 event caused at least 65 fatalities. This tornado had a maximum width of 1.5 miles and a track 80 miles long.

These are the most fatalities from a single tornado in the United States since May 25, 1955, when 80 people were killed in a tornado in southern Kansas with 75 of those deaths in Udall, Kansas.

The deadliest single tornado on record in the United States was the Tri-State tornado (Mo., Ill., Ind.) on March 18, 1925, when 695 died.

Ongoing (preliminary) List of Tornadoes by EF Rating (EF3 to EF5):

EF5: 2

EF4: 11

EF3: 21

Note: All numbers are based on combined NOAA and historical research records and current fatality estimates. The historical research records extend back to 1680.

April 2011: Most “tornadic” month ever recorded

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Month of April 2011 (and record monthly) Tornado Statistics

NWS’s preliminary estimate is that there have been more than 600 tornadoes thus far during the month of April 2011.

The previous record number of tornadoes during the month of April was 267 tornadoes set in April 1974.

The previous record number of tornadoes during any month was 542 tornadoes set in May 2003.

The average number of tornadoes for the month of April during the past decade is 161.

The overall monthly average number of tornadoes for the past decade is 106.

2011 Year-to-Date (and record annual) Statistics

NWS’s preliminary estimate is that there have been 881 tornadoes so far this year.

The previous yearly record number of tornadoes was set in 2004 with 1,817.

May is historically the most active month for tornadoes.

The overall yearly average number of tornadoes for the past decade is 1,274.

Is Minnesota next?

It remains to be seen whether the tornadic trends of Spring 2011 will continue and migrate north. There are still signs of a pattern change starting about May 15th that could lead to more tranquil weather in the Midwest.

In the mean time, enjoy the sun today and most of Wednesday, before our next shot of rain moves in Wednesday night.

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Shot of rain Wednesday night into Thursday could be a soaker.

Overall, weather trends are finally looking more like “spring has sprung” in the Upper Midwest.


  • SSHumble

    This is outstanding work. I wish every city had weather coverage as in depth as you provide for the metro.

  • Brooke White

    Yesterday my mother reminded me of a tornado ‘fact’ that I frequently heard as a child: that a reasonably sized water body (lake) could affect a tornado’s path (i.e. a tornado can’t cross water or the tornado will ‘skip’ over the water body). I’ve found online tornado FAQ’s dispelling this myth but I can’t find any information on where this myth came from or on the science of tornado-water body interaction. Do you have any thoughts on this?

  • Paul Huttner

    Thanks Humble!

    Hi Brooke:

    I recall hearing that the Minnetonka tornado in May 1965 crossed Carsons Bay and sucked up a lot of water which may have disrupted the funnel.

    I don’t know if this is suburban legend, but I agree that tornado’s parent thunderstorm circulations are generally too big to be disrupted by water.

    Waterspouts occur frequently in oceans around the world.


  • Brooke White

    Thanks for the information, Paul!