SOUTH SHORE SKYWARN GROUP

South Eastern Massachusetts

SKYWARN OBSERVER'S GUIDE
REVISED 09/24/99

Safety Precautions!

When acting as a spotter, always remember that your safety is most important. During a thunderstorm with lightning, stay in your covered vehicle with the windows up and door shut.

Do not try to outrun a tornado in your car. Get out of your car and curl up into a ball in a ditch or ravine in a location that will be as free of flying debris as you can, but be aware of localized flooding. Keep your head covered and eyes closed.

Above all else, use common sense and don’t take unnecessary risks.

NEVER place yourself in any danger when reporting Severe Weather!
We need you, and thank you for your help!

Please include the following items in all your SKYWARN reports:

WHAT: Describe event.

WHERE: Direction, and distance from known location, plus movement, and speed of condition being observed.

WHEN: EXACT time of event.

BY WHOM: Spotter name (plus callsign if Ham radio operator), and location.

WHAT TO REPORT

ONLY REPORT OBSERVATIONS,
NOT INTERPRETATIONS!!!

• Funnel clouds
• Tornadoes
• Wall clouds (confirmed or suspected)
• Mama clouds
• Roll clouds
• Shelf clouds
• Waterspouts
• Report ANY KIND of thunderstorm activity during the winter months.

• • Report time of observation
  • Location
  • Direction of motion
    

• Downburst Winds
• Wind damage to buildings
• Wind damage to trees (large limbs broken off)
• Wind speeds of 35 mph or greater
• In non-thunderstorm events... report winds in excess of 50 mph or greater.

• • Report time of observation
  • Location
  • Estimated wind speed
  • Estimated wind direction
    

• Hailstones of any size (initial report).

• • Report time of observation
  • Location
  • Size of hailstones -- Measure if possible, report largest size, most common size, and depth of coverage. For size reference use pea, marble, dime, quarter, golfball, baseball, softball.
    

• Lightning strikes to people
• Lightning strikes to animals
• Lightning strikes causing building damage

• • Report time of strike
  • Location
  • What was struck
  • If a person was struck, report what person was doing, age, & sex
    

• Flooded streets
• Standing water in buildings
• Water over the banks of creeks and streams
• Rainfall rates of 3 inches per hour or greater... and any rainfall totals at the end of a storm event.

• • Report time of observation
  • Location
  • Depth of standing water (if possible)
  • Actual rainfall rate (if possible)
    

• SNOW - Report three (3) inches of snow or snow falling at the rate of one (1) inch per hour.

• ICING - Report glazing of roads and attempt to measure how thick the ice accumulation is where appropriate... along with any damage reports.

• ANY other pertinent reports that may be regarded as a threat to life and property, including power outages.

Always record and report the time of your observation

Always identify yourself

If a SKYWARN net has been activated in your County then report your observations to your Net Control Station.

If no SKYWARN net has been activated in your area, then you may report your observations on the District SKYWARN frequency, or by phone to your local emergency management office, law enforcement agency, or the National Weather Service.

The GENERAL PUBLIC should contact their local law enforcement agency during times of severe weather, NOT the National Weather Service.

Notes:

When spotting for wall clouds, funnel clouds, tornadoes, and waterspouts the key is always to look for rotation! Often, scud clouds are mistaken for funnels or tornadoes because they may form beneath the parent thunderstorm and appear to touch the ground. Just remember... with scud there will be no rotation.

When estimating wind speed feel free to use the Beaufort Wind Scale provided in this guide (condensed below). Study the description of the Effects Observed and choose the appropriate wind speed range from the table. Report the speed in miles per hour or in knots. DO NOT REPORT THE BEAUFORT FORCE NUMBER. This will likely send the meteorologists at the National Weather Service scurrying for reference books, wasting valuable time.

ESTIMATING WIND SPEED
25-31 - Large branches moving. Whistling in overhead wires.
32-38 - Whole trees moving. Inconvenience in walking against wind.
39-46 - Small branches (twigs) break. Impedes walking.
46-54 - Slight structural damage. Larger branches, and weak limbs may break.
55-63 - Moderate structural and tree damage.
64 and above - Heavy to severe tree, and structural damage.

When reporting wind direction remember that meteorologists always do things backwards. The wind direction reported is ALWAYS the direction from which the wind is blowing. For example, if you report the winds as Southerly at 10 mph, that means the winds are coming from the south blowing to the north.

When reporting hail, use the common references that are used by the National Weather Service. That is, describe them as pea-sized (1/4 inch), marble-sized (1/2 inch), dime-sized (3/4 inch), quarter-sized (1 inch), golfball-sized (1 3/4 inch), baseball-sized (2 3/4 inch) (arggghhhh... let’s hope you never have to report that)!!!

When assessing wind damage, remember that most wind damage is done by straight-line winds, not by tornadoes. With straight-line wind damage, all the damage will look like it diverges (moves outwards) from a single point possibly in several directions. With tornado damage, destruction is generally along one direction, debris along the ground is twisted or has spiral characteristics, and often small arcs where the top-soil has been removed are visible.

If a person is struck by lightning take appropriate action to ensure immediate aid is given. A person retains no electrical charge after being struck, so it is safe to touch that person. This means CPR can be administered immediately if necessary.

SPOTTER RULES AND CLUES

1. Always have a safe place nearby to protect yourself from wind and/or hail.

2. Cars are a safe place from lightning, but NOT from tornadoes.

3. Moving water is powerful, it only takes a slight current to push a vehicle off the road.

4. Large hail often falls just in advance of a tornado, especially large ones.

5. Tornadoes generally move toward the NORTHEAST at 25 to 35 MPH when associated with fronts, and squall lines but CAN travel at 70 MPH.

6. The first gust of wind to reach you from a thunderstorm is frequently the strongest.

7. WALL CLOUDS form on the rain free base often 15 to 20 minutes before the tornado occurs.

8. A rain free base denotes the storm's updraft area, a place to watch closely.

9. Overshooting tops are an indicator of a very strong storm.

TORNADOES usually form in the trailing edge of a thunderstorm. Wind speeds can reach 300 MPH in "MAXI" TORNADOES. Conventional radar can't see a tornado... it only sees the rain, and hail.

Direct Reporting to NSSL in Project Verify

Thanks to the Internet you can participate in Project Verify (NSSL Severe Weather Reports Database). To help NWS/NSSL fine tune the 88D radars they need information about Tornadoes, Hail, Thunderstorm Winds and Thunderstorms. For more information click here.

The Spotter’s Observation Kit

Consider keeping the following equipment handy:

• Weather radio (It’s nice to be able to keep up with weather warnings.)

• Communications radio for reporting your observations (When you see severe weather, you’ve got to report it!)

• Raincoat with hood (Stay dry!)

• Flashlight (In case you can’t see when it gets dark!)

• Binoculars (So you can tell whether that cloud is really rotating!)

• Camera or Camcorder (So that a permanent record can be made of your observations. Pictures and video are the BEST form of training for other spotters.)

• Compass (For estimating the wind direction -- remember...that’s the direction the wind is coming from!)

• Your SKYWARN Observer’s Guide (So you can remember all this stuff!)

Some Meteorological Terms

ANVIL

The top portion of a mature thunderstorm that has the appearance of having been "blown off".

ARC CLOUD

Also sometimes called a shelf cloud. This is usually the dark, ominous looking cloud formation the precedes the passage of a squall line or multicell thunderstorm formation. It is formed as warm moist air overrides cool downdraft winds at the leading edge of the thunderstorm (the gust front).

CELL

The basic thunderstorm, which consists of one updraft and one downdraft.

DEBRIS CLOUD

Area of dust, sand, and debris that forms near the ground at the base of a tornado.

DOWNBURST

A small area of rapidly descending air beneath a thunderstorm. Downburst winds hit the ground and spread out, often at speeds in excess of 100 mph. See also downdraft, macroburst and microburst.

DOWNDRAFT

Area within a thunderstorm where the predominant air motion is downward. Where there is precipitation there will always be a downdraft. Downbursts are localized areas within the downdraft of very rapidly descending air.

FUNNEL (CLOUD)

Generally the funnel is a visible tornado that hasn’t yet reached the ground. Funnels consist of water droplets that have condensed due to the rapid temperature and pressure changes in the vicinity. Also called condensation funnel.

GUST FRONT

The area near the leading edge of a thunderstorm where downdraft winds hit the earth’s surface and spread out. The gust front is the leading edge of the spreading winds. The gust front is usually found just below or very near the arc cloud.

HAIL

Large ice chunks that grow within the thunderstorm until they are too heavy to be supported by the mechanics within the storm. Large hailstones fall at speeds greater than 100 mph.

INFLOW

Area of a thunderstorm where air from the surrounding environment is "sucked up" into the thunderstorm updraft. The inflow area is always void of precipitation and the cloud bases are dark and flat.

MACROBURST

A downburst with a diameter of greater than 2.5 miles.

MAMMATUS

Downward protruding "bumps" usually on the underside of the anvil of a thunderstorm. Mammatus ("Mama") clouds are indicative of extreme turbulence.

MICROBURST

A downburst with a diameter of 2.5 miles or less.

OUTFLOW

That portion of the thunderstorm where the downdraft winds hit the surface of the earth and spread out.

OVERSHOOTING TOP

A protruding cloud area above the usually smooth anvil of a mature thunderstorm that indicates the presence of an intense updraft.

SCUD (CLOUD)

Clouds that appear to have broken off beneath the base of a thunderstorm. Scud (fractus) clouds often may reach to near the ground and can be easily mistaken for a funnel.

SHELF CLOUD

See Arc Cloud.

TAIL CLOUD

Scud-type cloud that forms near the base of a wall cloud and protrudes almost parallel to the earth toward the main precipitation shaft of the thunderstorm.

TORNADO

Rotating area of strong winds and rapid pressure change that sometimes forms in conjunction with a severe thunderstorm.

UPDRAFT

The area within the thunderstorm where the predominant air motion is upward.

VAULT

An area of dry clear air that often forms between the main precipitation shaft and the rain-free base wall cloud.

WALL CLOUD

A rotating cloud that forms beneath the base of the thunderstorm behind the main precipitation shaft where some of the inflowing air and outflowing air meet and mix. Tornadoes, if they occur, will appear to drop out of the wall cloud.

WATERSPOUT

A weak tornado that forms over warm water. The formation mechanisms for waterspouts are different from those of land tornadoes, and waterspouts may form during relatively calm-looking weather

Source: Meteorology, William L. Donn, 1975, McGraw-Hill, Inc., New York.

Source: Meteorology Today, C. Donald Ahrens, 1991, West Publishing Company, St. Paul.

SPOTTER TRAINING WEB SITES:

Introduction To Observation Weather Techniques

NOAA Quest Series VORTEX

NOAA Severe Storms Spotter Guide Online

NSSL Educational Information

Severe Weather Safety - NWSFO Norman, OK

Spotter Guide - NWSFO Norman, OK

Cloud Boutique - PSC Meteorology Program

Selected Internet Resources For The Beginning Storm Chaser

Storm Spotters Guide - Guide To Meteorology (UIUC)

Storm Track's Storm Chase Guide

Weather Glossary For Storm Spotters

Basic Weather Skills via FSU

Meteorology Online Guides

The Forecast Factory

Back to SKYWARN home page.