Here are the changes which are scheduled to go into effect on March 15, 2010:

New Special Weather Statement Policy: The old short term forecast will be replaced by special
weather statements. Here are the details of the change:

Special Weather Statements are used to convey short-term weather and impact information
of importance to our customers that (1) is insufficient to justify issuance of a warning or
advisory or (2) provides information in the convective pre-warning mode. Essentially this
product serves the function of the old short-term forecast (NOW) with two important
differences: (1) it is much more widely disseminated and receives more attention than the
NOW, and (2) the threshold for SPS issuance is higher than the NOW, thus only information
of significance is passed on to the user.

The Special Weather Statement is a short-fused product (~1-4 hours) and is not a
replacement for the Hazardous Weather Outlook (HWO). Where the HWO focuses on more
general outlook conditions for the next 7 days, the SPS should focus on detailed forecast
information for the next ~1-4 hours. The SPS will either deal with specific storms and the
immediate downstream impact, or over a larger area concerning thunderstorm trends and
potential impacts.

After one year, we decided to discontinue the Significant Weather Advisory. The information
contained in a very similar format under the Special Weather Statement.

The Special Weather Statement shall be issued:

Thunderstorms

o Use as a pre-warning tool to provide a heads-up of impending severe weather, e.g., counties
downstream of severe thunderstorms not yet in a warning.
o Hail less than warning criteria, e.g., ½ inch- 7/8 inch
o Wind less than warning criteria, ~40-57mph
o Lightning of unusually great intensity or any thunderstorm forecast to hit a significantly
exposed population (e.g., college football game).
o A favorable landspout environment.

Winter Weather

o Precipitation events (snow or ice) sufficient to impact travel but below advisory/warning
criteria.
o Blowing/drifting snow sufficient to cause a travel hazard but below advisory/warning criteria.
o Wind chills near but not in criteria early or late in the season (~-10 to -20°F).

Other

o Heat indices only briefly in criteria in time and/or space (<3hrs, scattered coverage), or near
but not in criteria.
o Dense fog (or smoke or haze) not sufficiently widespread and/or long-lasting enough to justify
an advisory (<3hrs, scattered coverage).


Max hail/wind tag on Severe Thunderstorm Warnings: On the bottom of our severe
thunderstorm warnings and statements we will included the maximum hail and/or wind value we
expect for that particular warning.
.
Tornado Emergencies: This is NOT a new warning type! It is a high-impact call-to-action for
high end tornado events. If your county is ever under one of these, you can expect major
damage, fatalities and a really bad day! Here is our tornado policy:


Definition:

A TORNADO EMERGENCY means that significant, widespread damage with a high likelihood of
numerous fatalities is expected to continue with a strong and violent tornado. A tornado
emergency is not a new warning product, but a new, visible and high impact call-to-action.

Intended Purpose:

To motivate and provide a sense of urgency to persons in the path of this storm to take
immediate shelter in a reinforced structure that offers maximum protection from destructive
winds.

To communicate to state, local, and county officials and emergency responders that they
should prepare for immediate search and rescue operations.

To communicate the need to prepare for immediate medical emergencies, evacuation
measures, and emergency sheltering.


Format:

A statement in the third bullet of the warning

A headline at the top of the Severe Weather Statement that states, “…TORNADO EMERGENCY
FOR [GEOGRAPHIC AREA]…” The “tornado emergency” would be issued predominately in
Severe Weather Statements since it is highly likely that a tornado warning would be in effect.

Criteria:

A large and catastrophic tornado has been confirmed and will continue (A radar signature
alone is not sufficient)

It is going to have a high impact and/or affect a highly vulnerable population (Historically, this
probably has happened once every 10 years in our CWA.)

Numerous fatalities expected

The Warning Team and Event Coordinator/Shift Supervisor has approved its issuance

If a Tornado Emergency headline is included:

The definition of a tornado emergency must be included in the warning/statement

An official Weather Event Overview must be conducted and led by the warning meteorologist
with input from the on-duty staff after the event

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Thanks to Mike Cox for forwarding this information to Iowastorms.