Spotters play vital role in confirming electronic weather data

NWS

David Floyd, a meteorologist from the National Weather Service in Goodland, conducted a severe weather identification class in McCook Tuesday evening, and encouraged people to become "storm spotters" for the Goodland weather station.

Floyd said it is important for meteorologists to correlate what spotters are seeing first-hand with what meteorologists are seeing electronically at the station. For example, Floyd said, "Doppler radar is sometimes darned good at estimating the size of hail ... and sometimes it's not so good. We want to hear from our spotters."

Meteorologists used to believe, Floyd said, that a rotating supercell had at least a 50 percent chance of producing a tornado. With Doppler, they've learned that only 10 to 15 percent of those supercells have that likelihood. Doppler radar is a very good tool, but it still has its limitations. Floyd said. "It cannot tell us whether a tornado is on the ground. It doesn't have the resolution to see that," he said. "Radar does not always detect weather tornadoes."

"There's a lot going on in the lower one mile of the atmosphere that doesn't always show on radar," Floyd said. "We need spotters."

Floyd said the reports made by storm spotters are used not only to help weather officials issue watches and warnings for imminent storms and potential danger, but also in follow-up statements and to verify the validity of the watches and warnings issued. "We'll match the warnings we issued with spotters' reports," Floyd said.

In a storm spotter training session in the basement of the McCook Public Library Wednesday, Floyd taught 40-50 weather-watchers about thunderstorms and cloud formations that are present only when there's a storm.

THUNDERSTORM CLOUD FORMATIONS

Depending on the number of "cells" within a thunderstorm formation, all storms can be divided into four categories: single cell, multi-cell clusters, multi-cell line or squall line, and supercells. Supercells are intense, well-organized and long-lived, Floyd said, and 90 percent of the time produce some type of severe weather.

Every storm has to have updraft -- air moving up and into cloud towers -- and downdraft -- severe winds, rain and hail, Floyd said. It is at the base of the storm's updraft -- where the air is flowing up and into the cloud towers -- that tornadoes are produced.

Storms that are spinning and rotating, or indicating "barbershop pole" motion, are particularly threatening, and need to be watched very closely, he said. "A rotating storm has a 90 percent chance of producing severe weather."

ACCESSORY CLOUDS

"The clouds underneath storm formations are different than the clouds you see day-to-day," he said. "The cloud structures under storms are only there because there's a storm."

Floyd calls these cloud structures "accessory clouds," and they indicate the possibility of severe weather:

* Shelf cloud -- A horizontal shelf-like cloud associated with a storm's outflow, a rapid temperature drop, strong wind or wind abruptly changing direction. "This cloud is just screaming 'Outflow!'," Floyd said.

* Roll cloud -- Horizontal "tubes" of clouds, sometimes rolling slowly as it moves, associated with a storm's outflow. Not as common as shelf clouds.

* Scud cloud -- Detached, wind-blown cloud fragments. "Foolers" that just hang around storms and are often mistaken for other types of clouds and/or tornadoes. "These are just blowin' where the wind blows," Floyd said.

* Wall cloud -- An abrupt lowering of a storm's updraft base caused by the uptake of rain-cooled air. "These are significant clouds," Floyd said. This cloud is attached to the bottom of a storm's updraft and rotates as it sucks air in and up. An intense, well-organized wall cloud very often precedes a tornado, he said.

* Tail cloud -- A rapid low-level, well-organized inflow and uplift into a wall cloud. "This looks like a stinger, pointing into the storm," Floyd said.

* Beaver tail -- Long, flat clouds at the same level as the updraft base, marking a well-organized inflow into a storm. "A beaver tail is associated with the most organized, intense updraft," Floyd said.

"Funnels and tornadoes have to have updraft above them," Floyd said. "Rapid updraft and spinning are significant stuff."

Trained spotters are asked to report all wall clouds, funnels and tornadoes. They are also asked to report ponding (deep, standing water), flooding (rapidly moving water), hail that is dime-sized or larger, and winds estimated at 60 miles an hour and more.

"Do not report lightning," Floyd said. "But do respect it. Lightning is the spotter's No. 1 enemy." Check out: lightningsafety.noaa.gov

Spotters can report by calling their county sheriff's offices or the NWS office at (800) 272-7811. They can also log onto internet at http://weather.gov/goodland/storm.htm

"eSPOTTER"

The "eSpotter" program provides trained spotters and local emergency management officials with a direct link to report critical severe weather information: http://www.crh.noaa.gov/espotter

Spotters will log into the Web server, generate a severe weather report, then submit it to the NWS office. Within seconds, a banner will flash at the NWS office indicating that a new report has arrived. In addition, the NWS will have the ability to send messages to spotters.

Spotters wishing to participate in this program must supply names and e-mail addresses to the Goodland office. Contact Floyd at: david.l.floyd@noaa.gov