How to find the wind speed at an address on a date

Step 1: the nearest airport stations

Airport weather stations are the main source of measured wind. The Automated Surface Observing System (ASOS), run by the NWS, the FAA and the Defense Department, has more than 900 U.S. sites. Find the two or three closest to the property and pull the hours around the storm.¹⁵

• Height: federal standards call for 10 m (32.8 feet), with some variance; typical ASOS sensors sit at 33 or 27 feet (1998 user's guide).¹⁶
• Sustained wind: a 2-minute average of 24 five-second averages.^16,17
• Gusts: the highest 5-second average on older cup sensors; the sonic sensors that replaced them from 2003 to 2005 use the highest 3-second running average, the WMO gust standard, and report more gusts (2003 NWS notice).^16,17
• Peak wind: scheduled hourly reports add the highest wind above 25 knots since the last hourly report. The Iowa Environmental Mesonet parses it, with its time, from the PK WND remark, but does very little quality control.^16,6

NCEI's Local Climatological Data (LCD) adds the daily fastest sustained wind (held at least 2 minutes since 1994) and the raw METAR text, in local standard time with no daylight saving.⁴

For a claim or lawsuit, NCEI certifies LCD PDFs, which can be ordered for litigation, and fees may apply; Storm Events reports are certified by sending search results to ncei.orders@noaa.gov.^3,5,9

Step 2: storm reports and damage surveys

Storm reports show whether the NWS logged damaging wind near the property that day, measured or estimated. SPC Storm Reports list preliminary, thunderstorm-related local storm reports from NWS offices back to June 1, 1999; each date runs from 1200 UTC to 1159 UTC the next day. The list likely misses some reports and leaves out any that arrived more than 10 days late.^7,8

The NCEI Storm Events Database holds the official, final NWS Storm Data from January 1950 and takes a few months to compile. Its wind events:^9,7

• Thunderstorm Wind: convective winds of 50 knots (58 mph) or more, or any speed that causes a fatality, injury or damage; filed by county.^18,10
• High Wind: non-convective sustained winds of 35 knots (40 mph) for 1 hour or more, or gusts of 50 knots (58 mph) or more (higher in some mountains); filed by forecast zone.^18,10
• Each event has a magnitude in knots and a code: MG measured gust, EG estimated gust, MS measured sustained, ES estimated sustained.^10,18

When speeds are estimated from damage, the preparer weighs the age, construction and exposure of what was damaged; damage alone does not automatically imply 50 knot winds.¹⁸

Where the NWS surveyed damage, Damage Assessment Toolkit points carry a location, dates, damage, degree of damage, rating (EF number, or TSTM or Wind) and wind speed. The data is preliminary; official statistics are in Storm Data.^12,11

EF scale winds are damage-based estimates of 3-second gusts, not the same wind as station observations. Its 28 damage indicators include strip malls, warehouses, metal building systems and apartments of 3 stories or less.¹⁹

Step 3: the URMA wind grid over the address

URMA (UnRestricted Mesoscale Analysis) fills the space between stations. It is NOAA's hourly surface weather analysis, with 10 m wind speed, direction and gust on a 2.5 km (1.6 mile) grid over the lower 48 states, with files from January 28, 2014, on NCEI and NOAA's Amazon Web Services bucket.¹

It runs 6 hours after analysis time to catch late observations and is the NWS analysis of record for verifying forecasts. It blends observations into a first guess from the HRRR and NAM models, so it is an analysis, not a measurement.^20,1

For hurricanes: best tracks and station tables

NHC's HURDAT2 best track lists each Atlantic storm's position, maximum winds and central pressure every 6 hours from 1851 to 2025, and its size from 2004.¹³

• Maximum sustained wind is the highest 1-minute average wind in the storm at 10 m with unobstructed exposure, in knots.¹⁴
• Wind radii, from 2004 on, give the farthest reach of 34, 50 and 64 knot winds in each quadrant; landfalls are marked L.¹⁴

Tropical Cyclone Reports add station tables; Harvey's gives sustained winds as 2-minute averages on land and 8-minute at buoys unless noted.^13,21

Station coverage can miss the worst of a storm. In Harvey, NHC wrote, the northeastern quadrant came ashore in an unpopulated, unmonitored area and the maximum winds were probably not sampled by any anemometer; an instrument near Copano Bay failed before the highest winds arrived.²¹

Limits of every record

• Station spacing: a 2024 SPC study lists average spacing of 44 km (27 miles) for ASOS and AWOS, 35 km (22 miles) for the West Texas Mesonet and 30 km (19 miles) for the Oklahoma Mesonet.²
• Downburst size: in simulated downbursts, severe winds covered about 10 square km (4 square miles) or less for about 5 minutes on average, and a typical mesonet's chance of measuring a severe gust was about 1%.²
• Exposure: a sheltered station can read lower than the open wind.
• Averaging times: EF scale 3-second gusts, NHC 1-minute winds and ASOS 2-minute winds are not the same wind, so compare like with like.^19,16,14
• Time zones: LCD uses local standard time and Storm Events usually does; SPC, NHC and the damage toolkit use UTC.^4,10,8,14,12