thumb|Tornado Watch issued prior to the [[2025 Somerset–London tornado.]]

A tornado watch (SAME code: TOA) is a statement issued by weather forecasting agencies to advise the public that atmospheric conditions in a given region may lead to the development of tornadoes within (or near) the region over a period of several hours. In addition to the potential for tornado development, thunderstorms that develop within the watch area may contain large hail, strong straight-line winds, and intense rainfall and/or flooding, all of which may pose a similar damage risk as the attendant tornado threat.

A watch must not be confused with a tornado warning, and encourages the public to remain vigilant for the onset of severe weather, including possible tornadoes. A tornado watch does not mean a tornado has been observed or will occur, just that favorable conditions increase the likelihood of such storms happening, and may be issued several hours ahead of the formation or arrival of potentially tornadic thunderstorms.

Definition

A tornado watch indicates that atmospheric conditions observed in and close to the watch area have created a significant risk for the development and intensification of severe convective thunderstorms capable of producing tornadoes, and are normally issued in advance of the onset of severe weather. If severe weather actually does occur, a severe thunderstorm warning or tornado warning would then be issued. Residents and travelers in the watch area are advised to immediately undertake safety preparations ahead of the arrival of severe weather. A tornado watch is not required for a warning to be issued; tornado warnings are occasionally issued when a tornado watch is not active (i.e., when a severe thunderstorm watch is active or if conditions for tornadic development are not expected to be substantive enough to require a watch), if a severe thunderstorm has a confirmed tornado or developed strong rotation. A tornado watch can replace an existing severe thunderstorm watch, if not merely a portion of it, if conditions that were originally considered marginally conducive, if at all for tornadic development have evolved to permit a greater risk of tornado formation.

Although the risk of tornadoes is emphasized as the primary hazard, depending on storm cell intensity, the probability exists for other hazardous phenomena exceeding regional severe criterion to occur: severe thunderstorms that develop within the watch area will also pose a likelihood of producing large hailstones, intense straight-line winds that can produce serious structural damage equivalent to a lower-category tornado over a comparatively broader areal swath, intense lightning, torrential rainfall and/or flash flooding caused by high rainfall accumulations. A tornado watch therefore implies that it is also a severe thunderstorm watch.

When a tornado watch is issued, people within the region of expected tornado threat are advised to review safety precautions in the event they must seek immediate shelter in a basement, cellar, safe room or a sturdy above-ground room in the center section of a home or building (such as a bathroom or closet) when a tornado warning or severe thunderstorm warning is issued for their area. Residents are also advised to monitor conditions ahead of the developing weather situation, and keep abreast of warnings and updated storm information through local broadcast media, weather radio, weather app alert notifications, SMS notifications and/or automated emergency phone calls. Where present, tornado sirens and local police or fire department dispatch units are also used as an outdoor warning system in the event of a tornado or particularly intense non-tornadic thunderstorm in some tornado-prone regions.

Regional basis

United States

thumb|right|300px|Map of average annual tornado watches in the United States between 2006 and 2025.<br>

In the United States, tornado watches are issued by the Storm Prediction Center (SPC), a national guidance center of the National Weather Service (NWS), for areas of the lower 48 states where atmospheric conditions favor the development of tornadoes and accompanying severe thunderstorms. Although watch issuances for those states are exceedingly rare as their respective climates are less favorable for the kind of convective conditions capable of tornadogenesis, responsibilities for issuing tornado watches covering Alaska and Hawaii are respectively handled by local NWS forecast offices in Fairbanks, Anchorage and Juneau, Alaska, and Honolulu, Hawaii. Watches are typically valid for six to nine hours (extending if necessary as long as 12 hours during tropical cyclones or other unusually steady-state or slow-moving severe weather events) after the time of issuance, and are intended to precede the first reported tornado by two hours and the first report of severe hail or wind by one hour. SPC watch boxes—termed because the approximate watch area is represented in weather maps as a quadrilateral for aviation purposes—are usually outlined in the approximate delineation of x miles north and south, or east and west, or either side of a line (perpendicular to the center line) from y miles direction of city, state, to z miles another direction of another city, state (e.g., "50 miles either side of a line from 10 miles northeast of Columbia, South Carolina to 15 miles south-southwest of Montgomery, Alabama"). Geographic coverage of tornado watches (which ranges from on average, encompassing portions of one or more states) vary based on the size of the land area under threat, the duration of severe weather risk, and the forward motion of the parent storm system and associated surface boundaries.

In situations in which the SPC has outlined a “high risk” or high-end “moderate risk” of severe convective storms within and near the watch area, the intensified wording "particularly dangerous situation" (PDS) can be added into the watch product to highlight high forecaster confidence that atmospheric conditions support the development of multiple strong to violent tornadoes (rated EF2–EF5 on the Enhanced Fujita Scale) capable of significant damage, if not total destruction of property and severe injury or death from the intense winds and projectile debris, as well as the possibility of destructive straight-line winds and hail from the parent supercells. (Tornadoes occurring in these situations may develop during the storm's maturation stage under typical low-level mesocyclonic tornadogenesis, or by accelerated mesocyclonic maturation generated early in the thunderstorm's development from sufficient wind shear and very high convective available potential energy [CAPE] values.) PDS tornado watches—which, based on SPC watch issuance averages between 1996 and 2005, account for ~3% of all tornado watches issued per year in the U.S.—usually suggest the likelihood of a major tornado outbreak, although they can be issued if a significant threat exists of isolated intense tornadoes. The SPC (then the National Severe Storms Forecast Center) conceived the PDS verbiage for use in tornado watches in 1981; it was applied to a public tornado watch product for the first time—encompassing portions of northern Texas and southern Oklahoma—during the outbreak of April 2, 1982. (The indicated threat would be verified, with seven of the 14 significant (F3+) tornadoes observed that day—four rated F3, two rated F4 and one rated F5—occurring within the watch area.) In subsequent years but in earnest since 2011, the SPC and the National Weather Service have applied PDS verbiage to other watch and warning types (including tornado warnings, severe thunderstorm watches and warnings, flash flood warnings and red flag warnings) to emphasize an exceptionally high risk to life and property.

SPC meteorologists utilize WarnGen software integrated into the National Centers Advance Weather Interactive Processing System (N-AWIPS) and/or the SPC Product Generator (PRODGEN) to generate the watch statement, which is disseminated through various communication routes accessed by the media and various agencies, on the internet, to NOAA satellites, and over NOAA Weather Radio. Local NWS offices concurrently issue Watch County Notification (WCN) messages that list subdivisions within their designated area of responsibility that the office has considered to be in the initial watch; WCN messages—which the SPC uses as the basis for their Watch Outline Update product—are updated to denote changes to the watch by local WFOs, which are provided responsibility for adding or removing counties/subdivisions from the watch, extending its time of expiration, or cancelling the watch entirely if conditions no longer support a severe weather threat (if atmospheric conditions have become less conducive to form tornadoes or were insufficient for tornadic development compared to earlier forecast analysis). The SPC updates Watch Outline Updates at least on an hourly basis to incorporate changes made by the accordant WFOs in their Watch County Notification messages. Unlike the box/subdivision structure of watches issued by the U.S. Storm Prediction Center, tornado watches issued by the Meteorological Service are issued strictly for groups of census subdivisions, often covering a total area that is relatively smaller than tornado watches in the U.S.). Watches are disseminated to the public through broadcast and online media outlets (including local television stations and The Weather Network/MétéoMédia), and Weatheradio Canada; depending on regional office discretion, the watch may require activation of the National Public Alerting System (Alert Ready) () and feeding provincial alerting systems (such as Alberta Emergency Alert and SaskAlert) to distribute the alert to local broadcast media and cellular phones.

Example products

Example of a tornado watch

<pre>SEL9

URGENT - IMMEDIATE BROADCAST REQUESTED

Tornado Watch Number 269

NWS Storm Prediction Center Norman OK

715 PM EDT Fri May 16 2025

The NWS Storm Prediction Center has issued a

  • Tornado Watch for portions of

Far Eastern Indiana

Central and Eastern Kentucky

Western and Central Ohio

Western West Virginia

  • Effective this Friday night and Saturday morning from 715 PM

until 300 AM EDT.

  • Primary threats include...

Several tornadoes and a couple intense tornadoes likely

Widespread damaging winds and isolated significant gusts to 80

mph likely

Scattered large hail and isolated very large hail events to 3

inches in diameter likely

SUMMARY...Multiple intense supercells will likely persist this

evening and into the early overnight hours as they move eastward in

a very favorable environment. Strong tornadoes appear likely with

any sustained/mature supercells, along with very large hail up to

2-3 inches in diameter. Widespread damaging winds also appear likely

with one or more clusters that are forecast to develop later this

evening. Peak gusts may reach 70-80 mph.

The tornado watch area is approximately along and 85 statute miles

east and west of a line from 25 miles north northwest of Columbus OH

to 45 miles southwest of London KY. For a complete depiction of the

watch see the associated watch outline update (WOUS64 KWNS WOU9).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

REMEMBER...A Tornado Watch means conditions are favorable for

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.

&&

OTHER WATCH INFORMATION...CONTINUE...WW 262...WW 263...WW

264...WW 265...WW 266...WW 267...WW 268...

AVIATION...Tornadoes and a few severe thunderstorms with hail

surface and aloft to 3 inches. Extreme turbulence and surface wind

gusts to 70 knots. A few cumulonimbi with maximum tops to 600. Mean

storm motion vector 26040.

...Gleason</pre>

Example of a Watch Outline Update

Below is another example issued by the Storm Prediction Center.

<pre> BULLETIN - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH OUTLINE UPDATE FOR WT 559

NWS STORM PREDICTION CENTER NORMAN OK

1100 PM CST FRI DEC 10 2021

TORNADO WATCH 559 IS IN EFFECT UNTIL 500 AM CST FOR THE

FOLLOWING LOCATIONS

ILC003-027-047-051-055-059-065-069-077-081-087-121-127-145-151-

153-165-181-185-189-191-193-199-111100-

/O.NEW.KWNS.TO.A.0559.211211T0500Z-211211T1100Z/

IL

. ILLINOIS COUNTIES INCLUDED ARE

ALEXANDER CLINTON EDWARDS

FAYETTE FRANKLIN GALLATIN

HAMILTON HARDIN JACKSON

JEFFERSON JOHNSON MARION

MASSAC PERRY POPE

PULASKI SALINE UNION

WABASH WASHINGTON WAYNE

WHITE WILLIAMSON

INC051-125-129-147-163-173-111100-

/O.NEW.KWNS.TO.A.0559.211211T0500Z-211211T1100Z/

IN

. INDIANA COUNTIES INCLUDED ARE

GIBSON PIKE POSEY

SPENCER VANDERBURGH WARRICK

KYC007-033-035-039-047-055-059-075-083-101-105-107-139-143-145-

149-157-177-219-221-225-233-111100-

/O.NEW.KWNS.TO.A.0559.211211T0500Z-211211T1100Z/

KY

. KENTUCKY COUNTIES INCLUDED ARE

BALLARD CALDWELL CALLOWAY

CARLISLE CHRISTIAN CRITTENDEN

DAVIESS FULTON GRAVES

HENDERSON HICKMAN HOPKINS

LIVINGSTON LYON MARSHALL

MCCRACKEN MCLEAN MUHLENBERG

TODD TRIGG UNION

WEBSTER

MOC017-031-133-157-201-111100-

/O.NEW.KWNS.TO.A.0559.211211T0500Z-211211T1100Z/

MO

. MISSOURI COUNTIES INCLUDED ARE

BOLLINGER CAPE GIRARDEAU MISSISSIPPI

PERRY SCOTT

ATTN...WFO...PAH...LSX...</pre>

Example of a Watch Status Message

<pre>STATUS REPORT #1 ON WW 68

VALID 261425Z - 261540Z

SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 ESE PNS

TO 30 N DHN TO 15 E ATL.

..SPC..03/26/09

ATTN...WFO...TAE...FFC...</pre>

See also

  • Severe weather terminology (United States)
  • Tornado Warning
  • Severe Thunderstorm Watch

References

  • Current Watches