WHY.......?

by Rusty Kapela
Warning Coordination Meteorologist
NWS Milwaukee/Sullivan-MKX

WHY do N-W-S meteorologists need severe weather reports from weather spotters during a severe weather episode?

They need to know what the storms are doing at ground level. The Doppler Radar cannot detect what is happening at the ground...it was designed to look into the heart of storm clouds, and their surroundings, to detect wind currents and other storm-structure clues that suggest a storm is or will become severe. Ground-truth spotter reports allow meteorologists to correlate what they see on radar with what is actually happening. In some cases, the storm may "look" severe on Doppler radar, but in reality, it isn't. The reverse is true, as well. Consequently, the meteorologist is learning in real-time. By the way, a storm is severe if it produces hail at least 3/4 inch in diameter, and/or damaging winds at least 58 mph, or a tornado. These are known as severe weather events. Flash floods are another classic severe weather event.

WHY do N-W-S meteorologists need severe weather reports days or even weeks after the end of a severe weather episode?

NWS meteorologists want to know two basic things...

1. did they "cry wolf" too many times, that is, did they over-warn or issue warnings that were not needed /False Alarm Ratio - FAR/
2. did they issue the warnings prior to the actual occurrence of severe weather events, /Probability of Detection - POD/.

The greater the lead time of the warnings, the greater the chances that people can seek shelter. Ideally, meteorologists want to minimize the FAR and maximize the POD. The presence or absence of severe weather events allows meteorologists to assess the effectiveness of their warning service to the general public, and make necessary changes in future severe weather episodes... such as "hit it harder", or "hold back" on the warnings.

WHY does the N-W-S need to know the exact time and location of severe weather reports such as toppled trees and power lines, damaged buildings, flooded or washed out roads, etc.? The WCM's, or their designee, are required to file monthly, detailed storm report, "Stormdata", for their part of Wisconsin. This report contains the exact time(s) and locations of all hazardous weather events and associated damage or impact. Besides the large hail, wind damage, and tornado events, meteorologists also need information on funnel clouds, waterspouts, dust devils, blizzards/whiteouts, flash floods, road washouts, dam failures, urban/small stream flooding, rainfall amounts, snow accumulations, lightning strikes/fires, non-thunderstorm high winds, freezing rain/drizzle, icy roads, dense fog, and injuries/deaths due to extreme cold, excessive heat and all of the above "events." Obviously these reports will help meteorologists determine the effectiveness of their watch warning service. In addition, an accurate "Stormdata" database allows Emergency Managers to more readily assess the weather hazards in their county, or local municipality, and plan for future mitigation.

WHY does the N-W-S need to know the time, place and number of people injured or killed, and the monetary value of damages caused by severe weather incidents?

The N-W-S includes, in its monthly "Stormdata", information on the number of injuries and deaths, and damage amounts that were directly- related to various weather hazards/events. These numbers are incorporated into NWS messages that are disseminated on computer wire services to the media, businesses, government agencies, and the general public. "Stormdata" reports from all states are then compiled into a national publication which is available to anyone. Emergency managers can utilize the "Stormdata" reports to produce a weather hazard analysis for their county or local area. Insurance companies, construction and industrial companies, and university researchers use "Stormdata" publications in a variety of applications pertinent to their areas of expertise. Last, but not least, "Stormdata" information is used by computer programmers to improve the software programs that run the WSR-88D Doppler radar system!

WHY do the National Weather Service (NWS) Warning Coordination Meteorologists (WCM's), and other meteorologists, conduct spotter training classes for Emergency Managers, amateur radio operators, county sheriff departments, local police departments, firefighters, 911 dispatchers, emergency and medical services personnel, county highway departments, public works departments, and other volunteer spotter organizations?

Since the NWS's Doppler radar cannot detect what kind of a weather hazard is occurring at the ground, it needs ground-truth reports from "weather spotters." All of these people and organizations constitute the weather spotter networks that are "activated" just prior to severe weather episodes. In order for weather spotters to pass onto the NWS accurate and timely severe weather reports they need information on what to look for, and how to differentiate between the real and false severe storms, funnel clouds, tornadoes, etc. As with anything else, if one wants to be an effective spotter, they must attend several spotter classes. The last thing anyone wants is a false severe weather report that triggers a needless warning. Conversely, if a NWS meteorologist receives reliable spotter information that indicates a storm is not severe, then they will avoid the issuance of a needless warning. Besides the WCM's providing training, other experienced severe weather spotters conduct spotter training within their respective organizations. In other words, we're all in this together.

The basic related answer to all the above WHY's is that the NWS has been mandated by law to issue timely and accurate watches and warnings for all types of weather hazards in order to minimize the loss of life and property. Simply said, the NWS cannot do it alone. It needs the help of many different people and organizations in order to accomplish its #1 mission of minimizing the loss of life and property due to weather hazards. Consequently, the NWS is deeply indebted to all of the individuals and organizations who contribute to the watch/warning program.