Severe Local Storm Watch(SEL, WWUS9)
Definition
A severe local storm watch, issued by the Storm Prediction Center in Norman, OK, is used when the risk of a hazardous weather (severe thunderstorms and/or tornados) has increased significantly, but its occurrence, location, and/or timing is still uncertain. It is intended to provide enough lead time so that those who need to set their plans in motion can do so.
Each watch refers to rectangle (example - Either side of a line from Tulsa, OK to Columbia, MO) or parallelogram (North-South or East-West of a line...) with an average area 25,000 square miles. Reasonable effort is made to have each public watch independent of any previously issued watch. However, subsequent severe storm watches that overlap existing watch areas do not alter the valid period of the earlier watch, except when specifically stated in the new issuance. Watch anchor points lie within the watch area and distances from reference points should be expressed to the nearest 5 statute miles.
 |
 |
 |
| Either side of a line... |
East-West of a line... |
North-South of a line... |
Each watch is numbered sequentially, beginning with number 1 for the first issuance of each calendar year and contains information for the general public, marine, and aviation interests in discrete, sequential sections. The text begins with the most serious type of severe weather expected (tornado/severe thunderstorm) followed by the area(s) affected. Funnel clouds are not be mentioned.
Also included is...
- other watch information that identifies any watches in the same geographical area that are being replaced or canceled by this new watch,
- hail size (in inches, except in tornado watches associated with hurricanes),
- turbulence,
- surface wind speed in knots,
- maximum height of thunderstorm tops (in hundreds of feet),
- estimated direction and speed of thunderstorm cell movement. (The format is "Mean Wind Vector DDDFF," where DDD is the direction the storm is moving FROM (to the nearest 5°) and FF the wind speed to the nearest 5 knots.), and
- a discussion of the meteorological reasoning (parameters and factors) that support the watch issuance and forecast for severe weather.
Example
:370,0990 400,0981 400,0955 370,0963:WWUS9 KMKC 261710
MKC WW 261710
KSZOOO-270100-
BULLETIN - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 390
NATIONAL WEATHER SERVICE KANSAS CITY MO
1210 PM CDT FRI MAY 26 2000
.A...THE NATIONAL SEVERE STORMS FORECAST CENTER HAS ISSUED A TORNADO
WATCH FOR
PARTS OF CENTRAL AND EASTERN KANSAS
EFFECTIVE THIS FRIDAY AFTERNOON AND EVENING UNTIL 800 PM CDT.
THIS IS A PARTICULARLY DANGEROUS SITUATION WITH THE POSSIBILITY OF
VERY DAMAGING TORNADOES. ALSO LARGE HAIL...DANGEROUS
LIGHTNING...AND DAMAGING THUNDERSTORM WINDS CAN BE EXPECTED.
THE TORNADO WATCH AREA IS ALONG AND 65 STATUTE MILES EAST AND WEST
OF A LINE FROM 45 MILES EAST SOUTHEAST OF MEDICINE LODGE KANSAS TO
45 MILES NORTHEAST OF CONCORDIA KANSAS.
REMEMBER...A TORNADO WATCH MEANS CONDITIONS FAVOR TORNADOES AND
SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. PERSONS IN
THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING WEATHER
CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE WARNINGS.
.B...OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES SEVERE
THUNDERSTORM WATCH NUMBER 388. WATCH NUMBER 388 WILL NOT BE IN
EFFECT AFTER 100 PM CDT.
.C...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND
ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO
75 KNOTS. A FEW CUMULONIMBUS WITH MAX TOPS TO 600. MEAN WIND
VECTOR 23040.
.D...LINE TOWERING CUMULUS DEVELOPING FROM SOUTHWEST OF CNK TO
BETWEEN RSL AND SLN AT MOMENT. EXPECT RAPID THUNDERSTORM
DEVELOPMENT WITHIN NEXT HOUR ALONG DRY LINE/COLD FRONT WITH
SUPERCELLS AND TORNADO DEVELOPMENT LIKELY.
.E...OTHER THUNDERSTORMS...CONTINUE WW NUMBER 389. WW LIKELY TO BE
REQUIRED WITHIN NEXT HOUR OR TWO OVER PORTIONS OF WESTERN AND
CENTRAL OK. WW LIKELY TO BE REQUIRED LATER THIS AFTERNOON OVER
PORTIONS OF EASTERN KS AND WESTERN MO.
...JOHNS |
|