NWS Jacksonville » Skywarn™ Spotter Information » Skywarn™ Spotter Guide


 Hail Size Reference Chart
Hail Diameter (Inches) Reference Object
0.25 Pea
0.50 Mothball
0.75 Penny
0.88 Nickel
1.00 Quarter
1.25 Half Dollar
1.50 Ping Pong Ball
1.75 Golfball
2.00 Hen Egg
2.50 Tennis Ball
2.75 Baseball
3.00 Teacup
4.00 Grapefruit
4.50 Softball
Red indicates severe criteria


 Beaufort Wind Speed Estimate Scale
Beaufort Description Wind Speed Observations
MPH Knots On Land On Water Surfaces
0 Calm 0 0-1 Calm. Smoke rises vertically. Waters are mirror smooth.
1 Light Air 1-3 1-3 Smokes drift indicates wind direction. Still wind vanes. Waters have a ripple.
2 Light Breeze 4-7 4-6 Wind is felt on face, leaves rustle, wind vanes begin to move. Small wavelets, crests glassy, no breaking.
3 Gentle Breeze 8-12 7-10 Leaves and small twigs constantly move, light flags are extended. Large wavelets, crests begin to break, scattered whitecaps.
4 Moderate Breeze 13-18 11-16 Dust, leaves and loose paper lifted, small tree branches move. Small waves (1-4 ft) becoming longer with numerous whitecaps.
5 Fresh Breeze 19-24 17-21 Small trees in leaf begin to sway. Moderate waves (4-8 ft) taking longer form, many whitecaps, some spray.
6 Strong Breeze 25-31 22-27 Larger tree branches moving, whistling in wires. Larger waves (8-13 ft), whitecaps common, more spray.
7 Near Gale 32-38 28-33 Whole trees moving, resistance felft walking against wind. Mounting sea (seas heaps) (waves 13-20 ft), foam streaks off of breakers.
8 Gale 39-46 34-40 Twigs break off of trees, resistance felt walking in wind. Moderately high waves (13-20 ft) of greater length, edges of crests begin to break into spindrift, foam blown in streaks.
9 Strong Gale 47-54 41-47 Twigs break off of trees, wind impedes walking. High waves (20 ft), sea begins to roll, dense streaks of foam, visibility affected by spray.
10 Storm 55-63 48-55 Damage to TV antennae, large branches break off trees. Very high waves (20-30 ft) with overhanging crests, sea white with dense blown foam, heavy sea roll, visibility impaired.
11 Violent Storm 64-73 56-63 Widespread damage. Signficant tree damage.
Exceptionally high waves (30-45 ft), foam patches cover the sea, poor visibility.
12 Hurricane 74+ 64+

Major damage.

73-112 mph: Roof surfaces peeled off, windows broken, trailer homes overturned.

113+ mph: Roofs blown from houses, weak buildings and trailer homes destroyed, large trees uprooted, train cars blown off tracks.

Storm waves (> 45 ft), air filled with foam and spray, sea completely white, visibility bad.
Red indicates severe criteria

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