Significant Weather Advisory 

A significant weather alert, also called a significant weather advisory, is issued when doppler weather radar indicates a strong thunderstorm is producing small hail or high winds whose strength does not reach severe thunderstorm criteria. It does not necessarily account for lightning or flooding.

Contents

History

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".

Criteria

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).1

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 approaching 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.

Example of a significant weather alert

The following example of a significant weather alert was issued by the Tallahassee, Florida National Weather Service on August 11, 2007.2

 
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

See also

Severe weather terminology (United States)

References

  1. ^ "What is a "Significant Weather Alert"?". NWS Peachtree City, Georgia. Retrieved on 2008-03-09.
  2. ^ WATSON (August 11, 2007). "SPECIAL WEATHER STATEMENT". NWS - Tallahassee, Florida. Retrieved on 2008-03-09.

External links