National Weather Service United States Department of Commerce

Mostly Sunny, Breezy and Pleasantly Cool

Cool and dry air will continue to pour into Michigan today on the heels of gusty northwest winds. Highs today will be only in the upper 60s to lower 70s, followed by chilly lows tonight in the mid 40s to lower 50s. These readings are about 10 degrees below normal for this time of year. Read More >


What equipment does a Cooperative Station use?

A cooperative weather observer uses different equipment dependant on the type of station he or she is at. Typically, and at a minimum, all observers have a rain gage with a few having a thermometer. Observing sites are placed in one or more of the following networks:

  • The "a" network is the basic climatic network of the NWS, and specifically support climatological operations, and are the backbone of the Nations Climatic database. These sites observe 24 hour maximum and minimum temperatures and 24 hour precipitation totals. Included in the "a" network are stations in the historical climatology network (HCN), which must have at least 80 years of records.
  • The "b" network is specifically designed to support hydrologic operations and are used primarily to support hydrologic operations. These sites always report 24 hour precipitation totals with many also take river level readings.
  • The "ab" sites support both Climatological and hydrological programs of the NWS.
  • The "c" stations were setup to act as meteorological sites and to supplement the "a" and "b" network.These sites support the issuance of warnings and forecasts programs.

All sites play important roles in the daily operations of the National Weather Service.

Temperature and Temperature Shelters

Cotton Region Shelter Some cooperative observers use the Cotton Region Shelter (CRS) to record maximum and minimum temperature data. A CRS is typically a wooden structure with louvered sides, a slotted bottom and solid top. It is usually made of pine, painted white, and sits atop a wooden or metal base, 5 to 6 feet above the ground. Some shelters have an electric fan in it to allow for better circulation during light wind conditions.

Thermometers used in a CRS are two basic types: Alcohol and Mercury. Alcohol thermometers are used to record the minimum temperatures. Minimum thermometers have a small bar embedded in the liquid which is pulled down the tube as the temperature falls. As the temperature warms again and the liquid moves back up the tube, the bar remains at the "minimum" which allows the observer to read the lowest temperature.

Mercury thermometers are used to record the maximum temperature. Maximum thermometers have a small break near the base of the well of liquid at the bottom of the thermometer. So as the temperature falls from the high, this break in the liquid keeps the liquid in place at its high point. The observer then twirls the thermometers in a rack which rejoins the mercury or sends the bar back to the top of the liquid, resetting them for another days recording.


Electronic Temperature Equipment
MMTS unit Another and newer type of thermometer is the Maximum Minimum Temperature System or MMTS. An MMTS is an electronic thermometer not too different from the type you buy at the local electronics store. The MMTS is a thermistor housed in a shelter which looks similar to a bee hive. This design is similar in functionality to the CRS.
Currently the MMTS requires a cable to connect the sensor with the display. Future plans call for wireless devices which would eliminate many of the problems currently associated with the cabled systems.


Precipitation Gauges
There are several types of gages used but the two basic types are recording and non-recording.
Standard Rain Gauge The most common is the non-recording gauge called a Standard Rain Gauge (SRG). Typically the SRG is a metal cylinder with a funnel on top and a plastic measuring tube in the middle. The measuring tube can handle up to 2.00 inches of rain before overflowing into the larger outer cylinder. During the winter, the observer removes the funnel and inner tube and allows the snow to collect in the outer tube. The observer then melts the snow and measures it, getting an accurate water equivalent to report.


Fisher/Porter gauge Another type of precipitation gauge is the recording gauge. The most common type is the Fisher/Porter (F&P) gauge, developed by the Belfort instrument Company. The Fisher /Porter gauge (as the one pictured below) is designed to work for many years in remote and harsh environments.
The F&P gauge weighs the precipitation it collects in a large metal bucket. This bucket sits atop a mechanism which converts the weight of the water into the measuring unit of inches and then, every 15 minutes, punches holes in a paper tape, recording the amount of precipitation. In the winter months the bucket is filled with anti-freeze which allows snow and ice to melt and be accurately measured. The observer removes the tape once a month and sends it to the local NWS Office. After reviewing the data the tape is sent to the National Climatic Data Center for archiving.


Snowfall and Snow Depth
Observers also report the amount of snow and the depth of newly fallen and existing snow. This can be a difficult task, especially in windy conditions. Observers must use experience and the guidelines provided by the NWS.
In some instances snowfall measurement is an estimation at best. To help the observer, a snowboard may be used. The snowboard is simply a piece of plywood, typically 3 feet square with a ruler attached in the middle. The snowboard sits in an open space and as the name implies, is covered with snow. The observer then measures the amount of newly fallen snow every 6 hours, brushing off the "old" snow when finished.

Communications and observations
There are several methods available to the CWO to send data to the NWS. Some observers call information to the office using a toll free number. Others use a programmable telephone or a PC based program. The newsest and most preferred method is via a web based reporting system. All the observer provided data is coded in a special format which NWS computers can read and decipher, allowing the viewing of this data both graphically and in a tabular format.


The Coop weather observer plays an extremely important part in the role of the National Weather Service. The data they collect are used in a wide variety of applications: Agriculture, Industry, city planning, litigation, and studies about long term climatological events such as El Nino and La Nina. Coop observers are truly unsung heros who's dedication needs to be celebrated and their efforts sung from the heights.