Watch / Warning / Advisory Criteria
- WFO Mobile -
Watch / Warning / Advisory Criteria for Issuance WMO / AWIPS Headers
Tornado Watch Issued when observed and/or expected atmospheric conditions support the formation of tornadic storms within the next 6 hours. Coordinated issuance between the Storm Prediction Center and NWS Mobile. WWUS20 KWNS / SEL(1-5)
Tornado Warning
Issued when observational data (NEXRAD doppler weather radar or credible field storm spotters) indicate a tornado is forming or has developed over a county (or portion of a county).  Issued for short, near term periods (0.5 to 1.5 hours).   WFUS54 KMOB / BHMTORMOB
Severe Thunderstorm Watch
Issued when observed and/or expected atmospheric conditions support the formation of severe thunderstorms within the next 6 hours.  Coordinated issuance between the Storm Prediction Center and NWS Mobile.  The National Weather Service considers a thunderstorm to be severe if it produces hail at least 3/4-inch in diameter, winds of 58 mph or greater, or a tornado.   WWUS20 KWNS / SEL(1-5)
Severe Thunderstorm Warning Issued when observational data (NEXRAD doppler weather radar or credible field storm reports) indicate the formation of severe storms over a county (or portion of a county).   Issued for short, near term periods (0.5 to 1.5 hours).   The National Weather Service considers a thunderstorm to be severe if it produces hail at least 3/4-inch in diameter, winds of 58 mph or greater, or a tornado. WUUS54 KMOB / BHMSVRMOB
Flood Watch
Issued when a potential of significant flooding (or life threatening flash flooding) exists within the next 12 to 24 hours.   WGUS64 KMOB / BHMFFAMOB
Flash Flood Warning
Issued when observational data (NEXRAD doppler weather radar or credible field storm reports) indicate very heavy rain sufficient to produce rapid flash flooding, or flash flooding is already occurring or is apparently imminent (as with a dam break).  Issued for short, near term periods (1 to 4 hours generally). WGUS54 KMOB / BHMFFWMOB
Urban / Small Stream Flood Advisory
Issued when observational data (NEXRAD doppler weather radar or credible field storm reports) indicate rainfall sufficient to cause nuisance flooding of poorly drained urban or small streams.  Issued for short, near term periods (1 to 4 hours generally). WGUS84 KMOB / BHMFLSMOB
(issued under the Flood Statement header)
Coastal Flood Watch
Issued when strong winds blowing onshore results in above normal tides and an increased risk of coastal flooding within the next 12 to 24 hours.  Coastal flooding occurs when tidal waters along the coast inundate the shoreline...damaging piers, homes, berms, and coastal roadways.   WHUS44 KMOB / BHMCFWMOB
Coastal Flood Warning
Issued when coastal flooding becomes imminent or is expected within the next 12 hours.   Coastal flooding occurs when tidal waters along the coast inundate the shoreline...damaging boats, piers, homes, berms, and coastal roadways. WHUS44 KMOB / BHMCFWMOB
Tropical Storm Watch
Issued by the NWS/National Hurricane Center when tropical storm force winds (39 to 73 mph) are possible over the coastal areas within the next 36 hours.  Coordinated issuance between NHC and NWS Mobile.   WTNT(1-5) KNHC / TCPAT(1-5)
Tropical Storm Warning
Issued by the NWS/National Hurricane Center when tropical storm force winds (39 to 73 mph) are possible over the coastal areas within the next 24 hours.  Coordinated issuance between NHC and NWS Mobile. WTNT(1-5) KNHC / TCPAT(1-5)
Hurricane Watch
Issued by the NWS/National Hurricane Center when hurricane force winds (74 mph and above) are possible over the coastal areas within the next 36 hours.  Coordinated issuance between NHC and NWS Mobile. WTNT(1-5) KNHC / TCPAT(1-5)
Hurricane Warning
Issued by the NWS/National Hurricane Center when hurricane force winds (74 mph and above) are expected over the coastal areas within the next 24 hours.  Coordinated issuance between NHC and NWS Mobile. WTNT(1-5) KNHC / TCPAT(1-5)
Inland Tropical Storm Watch
Issued when sustained winds of 40 to 73 mph (associated with landfalling tropical systems) are possible over inland areas within the next 24 to 36 hours. WWUS74 KMOB / BHMNPWMOB
Inland Tropical Storm Warning Issued when sustained winds of 40 to 73 mph (associated with landfalling tropical systems) are possible over inland areas within the next 12 to 24 hours. WWUS74 KMOB / BHMNPWMOB
Inland Hurricane Watch Issued when sustained winds of 74 mph or greater (associated with landfalling tropical systems) are possible over inland areas within the next 24 to 36 hours. WWUS74 KMOB / BHMNPWMOB
Inland Hurricane Warning Issued when sustained winds of 74 mph or greater (associated with landfalling tropical systems) are possible over inland areas within the next 12 to 24 hours. WWUS74 KMOB / BHMNPWMOB
Special Marine Warning
Convective (thunderstorm based) winds over the coastal waters of 34 knots or greater within the next 1 to 3 hours. WHUS54 KMOB / BHMSMWMOB
Small Craft Advisory (marine)
Synoptic (large scale) prevailing winds over the coastal waters of 20 to 33 knots, expected or occurring within the next 12 to 24 hours. FZUS54 KMOB / BHMCWFMOB
(issued as a headline in the Coastal Waters Forecast product)
Gale Warning (marine)
Synoptic (large scale) prevailing one minute winds over the coastal waters of 34 to 47 knots, or frequent gusts in excess of 34 knots, expected or occurring within the next 12 to 24 hours. FZUS54 KMOB / BHMCWFMOB
(issued as a headline in the Coastal Waters Forecast product)
Storm Warning (marine)
Synoptic (large scale) prevailing winds over the coastal waters of 48 knots or greater expected or occurring within the next 12 to 24 hours. FZUS54 KMOB / BHMCWFMOB
(issued as a headline in the Coastal Waters Forecast product)
High Surf Advisory
Issued anytime heavy wave action in the surf breaker zone provides for significantly rough conditions at the beaches.  These high surf conditions pose a greater risk for the loss of life to recreational swimmers (due to significantly increased deadly rip current potential), as well as an increased potential for significant damaging beach erosion.  Issued when the conditions are expected (or observed to be occurring) within the next 12 to 24 hours .   WHUS44 KMOB / BHMCFWMOB
Wind Advisory
Issued when sustained wind over land areas (lasting one hour or frequent gusts) of 25 to 39 mph are expected within the next 12 to 24 hours.  These winds are not associated with thunderstorms. WWUS74 KMOB / BHMNPWMOB
High Wind Watch/Warning Issued  when sustained wind over land areas (lasting one hour or frequent gusts) are expected to be 40 mph or greater within the next 12 to 24 hours.  These winds are not associated with thunderstorm or tropical systems. WWUS74 KMOB / BHMNPWMOB
Winter Storm Watch
Issued for a potential of significant wintry precipitation (with amounts of a 1/4 inch or more of ice, or 2 inches or more of snow, or a 1/4 inch or more of sleet over the forecast area)...generally within 24 to 36 hours of the expected event.     WWUS44 KMOB / BHMWSWMOB
Winter Storm Warning
Issued for a greater potential of a significant mixed wintry precipitation event (1/4 inch or more of ice, 2 inches of snow, or a 1/4 inch or more of sleet over the forecast area)...generally within 24 hours.    WWUS44 KMOB / BHMWSWMOB
Heavy Snow Warning
Issued when 2 inches or more of snow are expected to fall within the next 12 to 24 hours. WWUS44 KMOB / BHMWSWMOB
Ice Storm Warning
Issued when 1/4 inch or more of ice accrual on exposed surfaces is expected within the next 12 to 24 hours. WWUS44 KMOB / BHMWSWMOB
Winter Weather Advisory
Issued when a mixture of light freezing drizzle(<1/4 inch accrual), freezing rain (<1/4 inch accrual), sleet(<1/2 inch accumulation), or snow (1/2 to less than a 2 inch accumulation) is expected within the next 12 to 24 hours. WWUS44 KMOB / BHMWSWMOB
Snow Advisory
Issued when a light accumulation (1/2 inch to less than 2 inches) of snow is expected within the next 12 to 24 hours. WWUS44 KMOB / BHMWSWMOB
Freeze Watch/Warning
Issued when light freezing temperatures are expected to pose a threat  to new growth at the start and end of the growing seasons (spring and fall)...or after an extended period of unusually warm weather.  Issued mainly for agricultural and gardening interests.  Watch for 24-48 hours in advance of event...Warning 12-24 hours in advance.  WWUS74 KMOB / BHMNPWMOB
Hard Freeze Watch/Warning
Issued when deep freezing temperatures (less than 26 degrees for at least 5 hours) are expected within the next 12 to 24 hours.  This type of freeze is characterized as a "hard freeze"...posing a threat to exposed water pipes, farm equipment,  automobile radiators, livestock, etc.
Watch for 24-48 hours in advance of the event...Warning 12-24 hours in advance.
WWUS74 KMOB / BHMNPWMOB
Frost Advisory
Issued when a frost is expected at the start and end of the growing seasons within the next 12 to 24 hours.  Frost can occur at temperatures of 33 to 36 degrees in light wind and clear sky conditions.  Mostly issued to alert the potential of frost burn on sensative outdoor plants. WWUS74 KMOB / BHMNPWMOB
Wind Chill Advisory
Issued when the wind chill is expected to fall to zero degrees Fahrenheit (or below) for 3 hours or more (within the next 12 to 24 hours).  Alerts the public to an increased risk of frost bite and rapid damage to exposed skin surfaces. WWUS44 KMOB / BHMWSWMOB
Excessive Heat Watch Issued for potenial of an excessive heat event occurring within the next 24 to 48 hours.  Excessive heat events are those when the heat index rises to at least 110 F...and the minimum air temperature has not gone (or is forecast to not go) below 80 degrees for at least a 48 hour period.  If the heat event appears to be more likely to verify at the Advisory criteria (see below)...then a Watch is not generally issued. WWUS74 KMOB / BHMNPWMOB
Excessive Heat Warning Issued for excessive heat events occurring within the next 12-24 hours where the heat index rises to at least 110 F...and the minimum air temperature has not gone (or is forecast to not go) below 80 degrees for at least a 48 hour period. WWUS74 KMOB / BHMNPWMOB
Heat Advisory
Issued for excessive heat events occurring within the next 12-24 hours when the heat index rises to at least 108 F...and the minimum air temperature has not gone (or is forecast to not go) below 78 degrees for at least a 48 hour period. WWUS74 KMOB / BHMNPWMOB
Dense Fog Advisory
Issued when dense fog (with visibility less than a quarter mile) covers a significant area.  Issued for a period within the next 6 to 18 hours generally.  Widespread dense fog can pose a significant travel problem (delays, hazards) to motorists as well as those navigating on inland waterways (rivers, bayous, etc).   WWUS74 KMOB / BHMNPWMOB

10/24/05 - Jeff Garmon, NWS Mobile


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