Sherburne County ARES/RACES

           
 SHERBURNE  COUNTY  SKYWARN

Updated:Saturday January 10, 2009

 
 

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Operations
Estimating

 

Weather Report Estimating

Measured reports are preferred over estimated reports, as they are generally more accurate. However, sometimes it's hard to estimate properly under severe weather conditions. Over-estimating is as bad or worse than under-estimating storm conditions.

Here are guidelines for estimating in your reports.

Hail Size

Pea Size        1/4"
Dime Size       1/2" (Minimum reportable size)
Penny Size     3/4"
Nickel Size     1"
Golf Ball Size  1-3/4"
Baseball Size  2-3/4"

Snow Intensity

Light            Visibility > 1/2 mile.
Moderate      Visibility > 1/4 mile but <= 1/2 mile.
Heavy          Visibility <= 1/4 mile.

Rain Intensity

Light            Less than 0.2"/Hr.
Moderate      0.2" to 1.0"/Hr.
Heavy          1.1" to 2.2"/Hr. (Minimum reportable rain)
Very heavy   2.3" to 4.5"/Hr.
Intense        4.6" to 7.1"/Hr.
Extreme      More than 7.1"/Hr.

Wind Speed (Miles Per Hour)

0 (Calm) Smoke rises vertically
1-3         Smoke drifts but windvanes do not move
4-7         Wind felt on face, leaves rustle
8-12       Small twigs in motion
13-18     Dust raised, loose paper raised, small branches move
19-24      Small leafy trees move, crested wavelets form on water
25-31      Large branches in motion, whistling in wires
32-38      Whole trees in motion, inconvenience felt walking against wind
39-54      Twigs break off trees
55-72      Damage to chimneys, pushes over shallow rooted trees
72-112    Peels surface off roofs, windows broken, trailer homes overturned
113-157  Roofs torn off houses, trailers destroyed, large trees snapped and uprooted
158 +     Severe damage, cars lifted off ground (life passes before your eyes)

 

Beaufort Wind Scale

Beaufort
Number
Wind Speed
(MPH)
Description
0
<1
Calm; smoke rises vertically.
1
1-3
Direction of wind shown by smoke drift; wind vanes unaffected.
2
4-7
Wind felt on face; leaves rustle; wind vanes move.
3
8-12
Leaves and small twigs in constant motion; wind will extend a flag.
4
13-18
Raises dust, loose paper; small branches move.
5
19-24
Small trees with leaves begin to sway; crested waves form on inland waters.
6
25-31
Large branches in motion; whistling heard on telephone wires; umbrellas difficult to control.
7
32-38
Whole trees sway; walking into wind becomes difficult.
8
39-46
Twigs break off trees; cars veer on roads.
9
47-54
Slight structural damage occurs (roof shingles may blow away, etc.)
10
55-63
Large trees uprooted; considerable structural damage.
11
64-72
Widespread damage.
12
73 +
Hurricane force; widespread damage.

 

 

As a volunteer organization, Sherburne County Skywarn welcomes any suggestions you might have to help us serve you better.

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