The National Weather Service has officially adjusted the severe weather criteria for reporting hail… Previously, hail of 0.75 inches or larger was considered severe and would prompt a severe thunderstorm warning. Now to assist with reducing the amount of severe thunderstorm warnings and more accurately advise of severe weather, severe hail size is now increased to 1.0 inches. The change takes effect on January 5, 2010 for all regions in the USA.
To: subscribers: NWS partners…users and employees
Subject: National change in minimum hail size criterion
for issuing Severe Thunderstorm Warning /svr/
and severe weather statement /svs/ products
effective January 5 2010Effective Tuesday January 5 2010 at 0001 coordinated Universal time
/UTC/…all NWS weather forecast offices /wfos/ will operationally
change the minimum hail size criterion used to issue Severe
Thunderstorm Warning /svr/ and severe weather statement /svs/
products from 3/4 inch /penny/ diameter or larger hail to 1 inch
/quarter/ diameter or larger hail.No change is being made to the svr and svs product wind criterion
of wind gusts equal to or in excess of 50 knots /58 mph/.A public information statement /pns/ soliciting comments regarding
this change was issued September 23 2009 /use lowercase/:http://www.Weather.Gov/os/notification/pns09_1_inch_hail.Txt
NWS received 63 comments in response to the pns…54 of which /86
percent/ supported this change. A web Page will be created to
address all comments since some comments indicated a need for
additional outreach. This web Page will be available by December 15
2009 and will be publicized via another pns.NWS reviewed all comments before deciding to change minimum hail
size criterion for svr and svs products.Central and western region wfos currently issue svr and svs
products experimentally using the 1 inch /quarter/ diameter or
larger hail size criterion /use lower case/:http://www.NWS.NOAA.Gov/om/notification/scn09-19hail_change.Txt
and
http://www.NWS.NOAA.Gov/om/notification/scn09-36wr_hail_exp.Txt
These wfos will continue to issue 1 inch /quarter/ hail size
criterion products experimentally through January 4 2010. All NWS
wfos will adopt the new criterion operationally on January 5 2010.For further information regarding this change please contact:
John T ferree
fire and public weather services branch
120 David l. Boren Blvd suite 2312
Norman OK 73072
John.T.Ferree@noaa.GovOr
mark Fox
warning and coordination meteorologist
National Weather Service Fort Worth Texas
3401 northern cross Blvd
Fort Worth Texas 76137
mark.Fox@noaa.Gov
National service change notices are online at /use lowercase/: http://weather.Gov/os/notif.Htm
