significant weather alert
A significant weather alert is issued when doppler radar indicates a strong thunderstorm is producing small hail or high winds under severe thunderstorm criteria. It does not necessarily account for lightning or flooding.
The National Weather Service issues a significant weather alert if hail size in a thunderstorm is less than 3/4 inch (20 mm) in diameter, and/or winds less than 58 miles per hour (90 km/h) or greater. These are mainly used in the NWS's southern region headquarters (SRH).
This forecast product was created in the early 2000s, and is sometimes a precursor to a severe thunderstorm warning. Many versions of the First Warning broadcast weather alert system have begun including significant weather alert into their systems, however, these systems usually classify such an advisory under the terms "Heavy T-Storms", "Heavy Storms" or "Strong T-Storms".
This product is not an actual official product, instead it is issued as a special weather statement. Special weather statements are also used for any type of weather approching watch/warning/advisory level. Many offices do not use significant weather alert, instead issue normal special weather statements mentioning much of the same text used in a significant weather alert.
Here is an example of a significant weather alert:
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE TALLAHASSEE FL 925 PM EDT SAT AUG 11 2007 ...A SIGNIFICANT WEATHER ALERT IS IN EFFECT FOR LEE COUNTY... UNTIL 1015 PM EDT AT 920 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM NEAR LEESBURG...MOVING SOUTH AT 15 MPH. PEOPLE IN LEE COUNTY...INCLUDING THE CITY OF LEESBURG...SHOULD MONITOR THE WEATHER SITUATION CLOSELY. LISTEN FOR POSSIBLE WARNINGS AND BE PREPARED TO TAKE APPROPRIATE ACTION SHOULD SEVERE WEATHER THREATEN. PEA SIZE HAIL...AND WINDS 30 TO 40 MPH ARE EXPECTED WITH THIS STORM. THIS STORM IS CAPABLE OF PRODUCING TORRENTIAL DOWNPOURS WHICH MAY CAUSE LOCALIZED FLOODING OF STREETS AND LOW LYING AREAS...AND IS ALSO PRODUCING FREQUENT TO NEARLY CONTINUOUS CLOUD TO GROUND LIGHTNING. MOVE INDOORS IMMEDIATELY! LIGHTNING IS ONE OF NATURES NUMBER ONE KILLERS. REMEMBER...IF YOU CAN HEAR THUNDER...YOU ARE CLOSE ENOUGH TO BE STRUCK BY LIGHTNING. $$ 12-WATSON
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