I just attended the annual meeting of the American Institute for Conservation which met on the topic - Disaster Preparedness, Response, and Recovery".  You can contact the AIC at:  [log in to unmask] or at (202) 452-9545 to get a list of publication materials that are available.

I would suggest that you first get a structural engineer to do an assessment and report on the structural integrity of your building - this will give you an overall assessment of the areas of the building that are likely to collapse during either a tornado or severe thunderstorm with straight-line winds.  You need to be aware of what collections and archival materials are near windows, doorways, etc. and perhaps mitigate that ahead of time.

In a disaster the absolute priority is human safety.  You should have an evacuation plan and you should drill on a regular basis.  If disaster does strike, then you will not be allowed back into the structure for some time, until the police, fire, and FEMA people are done - and, if the building is structurally unsound, it may be a matter of weeks before it can be made safe for entry.  Duplicate copies of all important records should be maintained in several places off-site, as well as copies of your disaster plan, phone tree, list of recovery specialists, and an extra depot of recovery supplies.
Do not expect to have power or running water.  Do not throw anything away - many objects, artifacts, and archival materials can be saved!

Lastly, talk to your insurance adjuster and get a risk assessment for your locale and institution.  The chances are that you have a far greater threat from fire, flood, and HVAC emergencies during construction then you ever will from a random tornado.  80% of disasters in cultural institutions happen during construction!  Know thy risks!

Cheers!
Dave

David Harvey
Associate Conservator,
Metals & Arms
The Colonial Williamsburg Foundation
P.O. Box 1776
Williamsburg, Virginia  23187-1776  USA
Voice:   757-220-7039
E-Mail:  [log in to unmask]