National Weather Service Skywarn (Questions and Answers)
What is SKYWARN?
Operation SKYWARN is a plan sponsored by the National Weather Service (NWS), employing volunteer weather observers for reporting destructive storms or other severe, unusual, or abnormal weather conditions. Amateur radio operators, generally operating through local organizations, are ideally equipped to contribute to the SKYWARN program.
How Does SKYWARN Work?
When severe weather is predicted, National Weather Service personnel alert pre-designated amateur radio volunteers to respond to the two meter amateur station installed at the NWS office. One or more repeaters having coverage in the target area are selected, and NWS personnel specify the starting time for the SKYWARN net.
At the beginning of the net, the net control operator outlines the situation and tells field observers what data the forecasters are asking for. Then the net is polled for the specified information. If appropriate, a forecaster may question one or more observers directly.
Usually, it takes only a few minutes to collect the necessary information. The process may be repeated every fifteen minutes or every half hour depending on NWS operational needs, until the threat has passed.
What Kinds of Information Will Be Requested?
This depends on the nature of the weather emergency. For starters, each report should include the call sign of the observer, his or her location, and the time of the observation. Other requested information might include wind speed and direction, presence of hail, rate and type of precipitation, outside air temperature, etc. (more about this later).
SKYWARN training is available to various groups. This training teaches you to recognize particular danger signs, estimate wind speed by interpreting tree motion, and so on. But you can help even without formal training. Just listen carefully to instructions, and provide as many of the requested items as you are able.
Generally, the forecaster wants you to describe what you see in plain English. However, accuracy is important! For example, if a temperature reading is called for and you don't have access to a thermometer, don't guess! Just say, "temperature unavailable."
What Use is Made of SKYWARN Reports?
The primary objective of the SKYWARN program is to identify hazardous weather early enough to warn the public. Thus, the Weather Service is particularly interested in tracking severe storms which are approaching densely populated areas.
Although we have few tornadoes compared to other parts of the country, we're not immune. Each year brings a few tornadoes and destructive storms to our area. If a tornado were to touch down in a densely populated neighborhood, the toll in injuries and property damage could be high.
The National Weather Service has a wide range of information sources with which to detect hazardous weather. But their equipment has limitations. For example, one of the primary weather radars in southern New England is located at Worcester. The radar's beam is directed up at a slight angle. Thus, when it "sees" a thunderstorm cell out by Springfield, it's really looking at precipitation well above the ground. It can't "see" what is happening on the ground.
Here's a specific example. Suppose the forecaster spots three such cells near Athol on the radar. Observers in one cell report high winds and hail one half to one inch in diameter, while reports from observers in the other cells indicate relatively benign conditions. The forecaster may then focus on the dangerous cell, asking additional questions to ascertain the speed and direction of travel of the cell. If the cell appears to observers to be travelling toward Fitchburg, and increasing rather than decreasing in intensity, the forecaster will issue a severe thunderstorm warning for northern Worcester County and place the warning on NOAA Weather Radio, etc.
In another scenario, one of our infamous winter storms may bring a mixture of rain, freezing rain, and snow to the area. Direct observations may help forecasters to pinpoint the location and movement of the rain/snow line. This information, in turn, is used by highway and emergency services departments to prepare action plans for dealing with the weather.
How Much Advance Warning Does the National Weather Service Provide When a SKYWARN Net is Called Up?
That's an interesting question. The Northeast is affected by competing weather systems from several sources. For example, some of our winter storms result when wet air from the Gulf and Atlantic collide with much colder, dry air from Canada. The relative strengths of the two systems may determine whether we get rain, freezing rain, snow, or clear weather. It's like watching a baseball game. Although you can measure the performance of the players and teams, sometimes, "It ain't over till it's over."
In the summertime, many of our thunderstorms come from eastern New York state. But, under some conditions, cells may form literally over our heads just minutes before unleashing their fury on us down below.
Our severe thunderstorm and tornado watches come not from Boston or Worcester, but from Kansas City. There, at the National Severe Storms Forecast Center, a sophisticated high-tech system monitors real-time weather data from many sources, issuing watches when conditions are favorable for severe weather in any given area. Usually, these alerts provide an hour or two of advance notice, and are often the basis for activating the SKYWARN system.
How Do Amateurs Know on Any Given Day Whether There is Likely to be a SKYWARN Net?
Well, in the winter, it's easy. Anytime there is a hint of snow, the media get into the act in a big way. But, SKYWARN nets in the winter are a rare occurrence. Sudden severe weather during the winter is rarely a surprise.
During the summer, we may or may not have any advance warning. But there are secret code words to watch for in the daily forecast. Anytime a forecast says, "Possible thunderstorms which may contain hail or strong winds," the forecasters are entertaining at least a possibility of severe weather. Nothing may ultimately develop, but the mention of hail and/or strong winds should have the prudent SKYWARN operator thinking about packing an extra battery for the HT in his or her lunchbox, and keeping an ear to the local repeater and NOAA Weather Radio.
THUNDERSTORM TIPS FOR SKYWARN OBSERVERS
Here's some detailed information about the kind of information likely to be requested by the NWS in a summertime SKYWARN operation.
First, it's important to note that although April to October is considered our thunderstorm season, conditions favorable for producing thunderstorms - even tornadoes - can develop any time of year in the Northeast. So it pays to be aware of the weather forecast. You might want to save this article for future reference.
SKYWARN nets will usually be activated whenever a severe thunderstorm watch is issued for the local area. The following format is likely to be used for SKYWARN reports:
1. Identity (call sign) of observer
2. Observer's location
3. Time of observation
4. Wind speed
5. Rate of rainfall
6. Presence of hail
7. Location and direction of storm
1. Call sign. Self-explanatory.
2. Location. Be precise, but remember that the forecaster may not be familiar with every subdivision and hamlet within the area. If you're in the country, specify your location relative to a recognizable town, e.g., one mile north of Barre.
3. Time of observation. In most cases, the word "currently" suffices. If your observations are ten or fifteen minutes stale, give the actual time for your observation in local time, 24 hour format. Don't say, "The temperature ten minutes ago was 28...". That forces the net control operator to look at the clock and calculate the time of the observation. Instead, YOU look at the clock and do the calculation and say, "The temperature at 3:35 p.m. was 280."
4. Wind speed. The forecaster is primarily concerned with winds in excess of 40 miles per hour. If you have a wind gauge, or know how to estimate wind speeds, give your estimate in miles per hour. Otherwise, use an appropriate English word, e.g., light or moderate, to describe the wind. Also, be sure to report wind damage such as small limbs down or trees down.
5. Rate of rainfall. Again, if you have a rain gauge, you may be able to provide a numerical value. But most of us will use the terms light, moderate, deluge, etc. Heavy rain indicates a strong downdraft within a thunderstorm. Your description may help the forecaster pinpoint your exact location relative to what is seen on the radar screen.
6. Presence of hail. This is a very important element to report. Hail is produced in severe storms with strong updrafts. Although not as dangerous as a tornado, a severe thunderstorm may last much longer than the average thunderstorm and cause considerable damage. Also, the size of hail should be reported, because it is a very good indication of the severity of the thunderstorm.
7. Location and direction of storm. You can estimate your distance from a thunderstorm by measuring how long it takes for the thunder to reach you. Remember that sound requires about five seconds to travel a mile. If you have a good view to the horizon, you may also be able to judge a storm's position relative to landmarks that can be pinpointed on a map. Every SKYWARN observer should know where the compass points are at your usual observing position.
The following are danger signs, which should be reported immediately. If one of these danger signs is observed, break into the net using the words, "Break, emergency traffic." When recognized, calmly give your call sign, location, and a BRIEF summary of your observation. Keep your transmission short, then stand by so the forecaster can question you further as to details.
Note: The first rule of emergency communications is to protect yourself. Ensure your own safety first; then and only then, communicate your observations.
Danger Sign #1. FUNNEL CLOUDS. A funnel cloud extends from the base of towering cumulus (thunderhead) or cumulonimbus (mature thunderstorm) clouds. It may or may not reach the ground. If the funnel cloud comes in contact with the ground, it then becomes a tornado. However, many harmless clouds are funnel shaped. Don't be fooled by an impostor. A true funnel cloud will exhibit (in the words of the Spotter's Guide) "organized and sustained rotation about a nearly vertical axis."
Danger Sign #2. HAIL greater than half inch in diameter. Hail of greater than penny size is indicative of a severe, damage-producing thunderstorm and should be reported immediately.
Danger Sign #3. WINDS greater than 40 miles per hour. At 30 mph, entire trees are in motion. At 40 mph, twigs break off trees and walking is difficult. At 55 mph, damage to chimneys and antennas may be observed. Damaging winds, whether associated with a tornado or a severe thunderstorm, should be reported immediately. Note that in our area, we have lots of large old trees that sustain damage in moderate winds. Generally, such incidents are not critical in weather terms.
Danger Sign #4. FLOODING. If you live in an area prone to flooding, torrential downpours and/or evidence of actual flooding should be reported immediately.
This discussion of SKYWARN procedures is just a brief overview. The National Weather Service has a number of free publications available for SKYWARN volunteers. Also, NWS forecasters periodically conduct training sessions specifically oriented to amateur observers and ham radio operators.
NOAA Weather Radio Frequencies
|Worcester||162.550 MHz||Providence||162.400 MHz|
|Boston||162.475 MHz||Eastern New York|
|Camp Edwards||162.550 MHz||Albany||162.550 MHz|
|Hartford||162.475 MHz||Marlboro||162.425 MHz|
|New London||162.550 MHz|