Wind Speeds and Alert Levels
The following table that correlates the various wind speed alert levels:
|Wind Speed||Maritime Alert||Land Alert||Tropical Cyclone Alert||Beaufort|
|25 – 38 mph
(22 – 33 knots)
|Small Craft Advisory||Wind Advisory||Wind Advisory or Small Craft Advisory||
|39 – 54 mph
(34 – 47 knots)
|Gale Warning||High Wind Warning||Tropical Storm Warning*||
|55 – 73 mph
(48 – 63 knots)
|Storm Warning||High Wind Warning||Tropical Storm Warning†||
|74 – 110 mph
(64 – 99 knots)
|Hurricane Force Wind Warning||High Wind Warning||Hurricane Warning||
|Over 110 mph
|Hurricane Force Wind Warning||Extreme Wind Warning||Hurricane Warning and Extreme Wind Warning‡||
* Tropical Storm Warning flags and lights will always be displayed the same as Storm Warning flags and lights.
† A tropical storm with winds in this range is sometimes referred to as a “severe tropical storm”.
‡ The Extreme Wind Warning is issued shortly before the eyewall makes landfall.
Below is a tale of the NWS Wind Categories and their corresponding Beaufort Wind Speeds categories and conditions:
|Wind Category||Beaufort No.||Wind speed||Conditions|
|25 to 31 mph
(40 to 50 km/h)
|Large branches in motion; whistling in telephone wires.|
|32 to 38 mph
(51 to 62 km/h)
|Whole trees in motion; inconvenience felt walking against wind.|
8 – 9
|39 to 54 mph
(63 to 88 km/h)
|Twigs break off trees; wind generally impedes progress. Tropical storm criteria begin.|
10 – 11
|55 to 73 mph
(89 to 117 km/h)
|Damage to chimneys and TV antennas; pushes over shallow-rooted trees. Severe thunderstorm criteria begin (58 mph (93 km/h)).|
12 – 13†
|74 to 112 mph
(118 to 181 km/h)
|Peels shingles off roofs; windows broken if struck by debris; trees uprooted or snapped; mobile homes severely damaged or overturned; moving cars pushed off road. Hurricane criteria begin.|
14 – 16†
|113 to 237 mph
(182 to 381 km/h)
|Roofs torn off houses; cars lifted off ground; trees defoliated and sometimes debarked. Major hurricane criteria begin.|
† Beaufort levels above 12 are non-standard in the United States. Instead, the Saffir-Simpson Hurricane Scale (Category 1, Category 2, etc.) is used.
The following Marine Wind Alert Messages are issued by the National Weather Service (NWS):
A Small Craft Advisory is issued for the coastal waters when winds of 25-33 knots and seas 10 feet or higher are occurring or forecast.
A Small Craft Advisory may also be issued when sea or lake ice exists that could be hazardous to small boats. There is no precise definition of a small craft. Any vessel that may be adversely affected by Small Craft Advisory criteria should be considered a small craft. Other considerations include the experience of the vessel operator, and the type, overall size, and sea worthiness of the vessel. There is no legal definition of "small craft". The Small Craft Advisory is an advisory in Coastal Waters and Nearshore forecasts for sustained winds, frequent gusts, or sea/wave conditions, exceeding defined thresholds specific to geographic areas.
Note: A Special Marine Warning is issued whenever a severe local storm or strong wind of brief duration is imminent and is not covered by existing warnings or advisories.
A Gale Watch is issued when there is an increased risk for a gale force wind event, meaning sustained surface winds, or frequent gusts, of 34 to 47 knots (39 to 54 mph), but the occurrence, location, and/or timing of the event is still uncertain.
A Gale Warning is issued for coastal, offshore, and high seas areas when winds of 34 to 47 knots (39 to 54 mph) not associated with a tropical cyclone are occurring or forecast.
A Storm Warning is issued for coastal, offshore, and high seas areas when winds between 48 knots (89 km/h, 55 mph) and 63 knots (117 km/h, 73 mph) are occurring or predicted to occur and not associated with a tropical cyclone are occurring or forecast.
If the winds are associated with a tropical cyclone, a Tropical Storm Warning will be substituted for the Storm Warning and less severe Gale Warning.
A Hurricane Force Wind warning is issued when sustained winds or frequent gusts of 64 knots (118 km/h, 74 mph) or greater are either being observed or are predicted to occur. The winds must not be directly associated with a tropical cyclone, or a Hurricane warning will be issued.
In U.S. Maritime Warning Flag Systems, two red square flags with a black square taking up the middle ninth of each flag is used to indicate a Hurricane Force Wind Warning (The use of one such flag denotes a Storm warning or a Tropical Storm Warning).
Note: An Extreme Wind Warning (EWW) is a warning issued when a landfalling hurricane is expected to bring winds of 100 knots (115 mph, 185 km/h, 51 m/s) to a specific location. The warning is issued just prior to when the strongest winds of the eyewall are expected to impact an area. The warning is to be issued for the smallest area possible, and be valid for times of two hours or less.
This warning was developed in response to confusion resulting from the landfall of Hurricane Katrina. NWS offices in Jackson and New Orleans/Baton Rouge issued 11 tornado warnings for areas that would not experience an actual tornado, but would experience extreme wind speeds commonly associated with tornadoes. The extreme wind warning is now expected to be used in these situations.
The following Blowing Dust Alert Messages are issued by the National Weather Service (NWS):
A Dust Storm Warning is issued when blowing dust is expected to reduce visibility frequently to 1/4 mile or less, generally with winds of 25 mph or more.
Texas South Plains Area
The prevalent months for a Dust Storm Warning to be issued for a dust storm originating from the Texas South Plains area is during the months of October through June - the least likely being the summer months of July through September.
The prevalent months for a Dust Storm Warning to be issued for a dust storm originating from the desert Southwest of Arizona is during the months of July through September, which are the general months of monsoonal winds for the area.
A haboob is a type of intense dust storm.
A Blowing Dust Advisory is issued when strong winds and considerable blowing sand or dust reducing visibilities. This advisory can be issued when a gust front or other strong wind blows loose sand and dirt.
- NOAA – NWS Directives System – NDS 10-3 Marine and Coastal Weather Services: http://www.nws.noaa.gov/directives/sym/pd01003curr.pdf
- NOAA – Beaufort Wind Scale: http://www.crh.noaa.gov/images/iwx/publications/Beaufort_Wind_Chart.pdf
- NOAA – NWS – Marine Forecasts: http://www.nws.noaa.gov/om/marine/cwd.htm
- Image Source: http://www.erh.noaa.gov/okx/images/coastal.jpg [Accessed July 16, 2013]
- NOAA – National Weather Service Weather Forecast Office – Norman, OK – Watch, Warning and Advisory Criteria: http://www.srh.noaa.gov/oun/?n=spotter-wwa-definitions