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Snow Measurements. NOAA/NWS Current Standard Observing Practices ASOS, Snow Paid and Snow Spotters. Thomas Townsend Regional Observations Program Manager NWS Central Region May 25, 2011. Snow Measurements. A short history LCD record stations Snow Paid observers ASOS NWS Spotters.
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Snow Measurements NOAA/NWS Current Standard Observing Practices ASOS, Snow Paid and Snow Spotters Thomas Townsend Regional Observations Program Manager NWS Central Region May 25, 2011
Snow Measurements • A short history • LCD record stations • Snow Paid observers • ASOS • NWS Spotters
Snow MeasurementsA little history • For many years up until the Modernization of the National Weather Service in the early and mid 1990’s the NWS Offices measured snow at the four synoptic times and at midnight, producing high quality records at about 230 Local Climatological Data (LCD) stations. • The FAA Flight Service Stations also measured snow at the four synoptic times and at midnight, producing high quality records at many more Local Climatological Data (LCD) stations. • Bringing the total to about 273 LCD station.
Snow Measurements • Following ASOS commissioning and the movement of NWS away from many LCD airports and taking of aviation observations and augmentation of ASOS, the NWS struggled to fill the LCD snow records using volunteers and cooperative data, etc. • The NWS closed half of offices and moved about half of the remaining 122 offices off of airports. • Estimated data was not allowed into the observation record (Data is data). • Aviation Service Levels were negotiated between the FAA the Air Transport Association, FAA contract observers at A and B level stations provided 6-hourly snow depth reports and snow increase remarks at all Aviation Service Level A and B locations. Snowfall was no longer a requirement at aviation stations.
Snow Measurements2002-03 Winter Season: Major Snowstorms/Customer Ire • Boston – • A snowfall of 27.6 inches was measured at Logan Airport from Feb. 16-17, 2003. If accurate, this would be a new 24-hour Boston snowfall record. 41.6 inches of snow was measured for February, a new monthly record. • Snowfall measurements were taken on a non-standard slatted wood bench approximately four feet from a 3-story high building. The prevailing strong northeast winds (22 MPH with gusts to 39 MPH) during the storm likely resulted in inflated snowfall totals as the downwind site likely received deposition from wind blown roof snow. Snow depths were also likely reduced by the exposure and strong winds. • BALTIMORE/WASHINGTON • A four day snowfall total of 28.2" was measured at BWI resulting in a reported all-time record snowstorm total. The hourly observations imply that hourly snowfall was reported. However, the Committee was unable to confirm this fact in addition to determining the representativeness of the snowfall observing site.
Snow Measurements • There had been a loss of about 50 percent of the snowfall data since automation of surface observations at LCD airport locations. LCD snowfall data have, for decades, provided the nation with the bulk of its near real-time 6-and-24 hourly snowfall observations. • Following the winter of 2002-2003, a snow team was formed under the Extremes Committee of the NCDC to form recommendations to the NWS Corporate Board Operations Committee. • For winter 2003‑2004, NWS requested the FAA to add snowfall measurements and other parameters to their observation requirements at LCD locations, where possible and supported establishment of NWS "Snow Paid" Contracts where LCD sites still lacked snowfall data.
Snow MeasurementsToday • Nearly all NWS Offices measure and record snowfall and snow depth at the four synoptic times and midnight, and use the data to prepare Daily and Monthly Climate Records. • FAA Contract observers at about 60 locations observe and record snowfall and snow depth at the four synoptic times and midnight, and use the data to prepare Daily and Monthly Climate Records. • NWS has secured the services of individuals and businesses at most remaining LCD locations observe and record snowfall and snow depth at the four synoptic times and midnight, and use the data to prepare Daily and Monthly Climate Records.
ASOS • All LCD ASOS locations • replaced Heated Tipping Bucket (HTB) with All Weather Precipitation Accumulation Gauge (AWPAG) • Added a 8 ft double Alter shield during the last year
Snow MeasurementsSupplemental Observations • Various class of supplemental snow observers are trained and used by NWS offices across the nation. • Most offices use CoCoRaHS observers. • Some other sources: • Some “Storm Spotters” in the SKYWARN program also receive snow observation training by NWS and are used for winter weather data • UCOOP stations - Unofficial cooperative stations receive NWS training and call in reports. • Chicago Area Snow Team (CAST) has been in operation for several years. There are about 10 observers currently. These observers are NWS trained. • North Dakota State Water Commission/Atmospheric Resources Board (ARB) network of observers – 91 snow observers trained by the state. • Central Illinois - Significant Weather Observation Program (SWOP) trained by NWS. • Colorado Avalanche Information Center (CAIC) and La Sal Avalanche Center information regularly. These folks are considered snow experts in areas including observing, forecasting, snow pits/swe, avalanche monitoring and control, etc.
Snow Measurements CoCoRaHS network has become a great value to the NWS
Snow Measurements • Supplemental observers generally observe and report snowfall and snow depth once daily – in the morning. • Offices locally keep a contact list and metadata for these reporters • NWS occasionally calls the observers for spot reports during a snow storm
