Weather and Natural Phenomena

Temperature		Wind Speed		Other
Freezing and Boiling points of water Convert between Fahrenheit and Celsius Approximate conversion		Old Beaufort Scale - land Old Beaufort Scale - sea New Beaufort Scale		Earthquakes Other

Temperature

Temperature scale	Freezing point of water	Boiling point of water	Degrees between the two
Fahrenheit	32 deg F	212 deg F	180
Celsius	0 deg C	100 deg C	100
Kelvin	273.15 K	373.15 K	100
Rankine	491.67 deg Ra	671.67 deg Ra	180
Réaumur	0 deg Ré	80 deg Ré	80
Rømer	7.5 deg Rø	60 deg Rø	52.5
Newton	0 deg N	33 deg N	33
Delisle	150 deg De	0 deg De	-150

The usual symbol for temperature is ° (as in 20° C), but I'm not sure if all browsers will display that!

The old way of measuring temperature in Britain was Fahrenheit. Even when Celsius became the official way of measuring temperature, for example in weather forecasts, the forecasters still gave the Fahrenheit as well for many years. Even today, they sometimes give Fahrenheit to emphasise a particular extreme temperature. The rather odd figure for freezing point in Fahrenheit (32 deg F) is because 0 deg F is the temperature that brine (salt and water) freezes. That was the coldest the inventor, Fahrenheit, could reliably reproduce in his laboratory. The 180 gap was chosen because it has lots of factors. It can be divided by 2, 3, 4, 5, 6, 9, 10, etc.

The old name for Celsius was Centigrade. They are exactly the same values. The original scale invented by Celsius had the same size degree, but went the other way, so 100 degrees was freezing and zero degrees was boiling.

Kelvin is another way to measure temperature, used by scientists. 0 K is absolute zero, the coldest temperature that is theoretically possible (and impossible to achieve), which is -273.15 degrees Celsius. One degree in the Kelvin scale is the same step as one degree Celsius. Similarly Rankine starts at absolute zero as 0 deg Ra, and one degree in the Rankine scale is the same step as one degree Fahrenheit.

The other scales are historic ones and no longer used. The Réaumur scale used to be used in Europe, particularly in France and Germany, but was eventually replaced by the Celsius scale. Monsieur René de Réaumur proposed it in 1731. Rømer is a disused temperature scale named after the Danish astronomer Ole Christensen Rømer, who proposed it in 1701. It is similar to Fahrenheit in that the freezing point of brine is zero. Isaac Newton devised his scale around 1700. He invented the word 'thermometer' for an instrument to measure it. The Delisle scale was invented in 1732 by the French astronomer Joseph-Nicolas Delisle, and recalibrated in 1738. It remained in use for almost 100 years in Russia. Like the original Celsius, it goes the 'wrong' way.

The BBC programme QI (which stands for Quite Interesting) has pointed out that Briritsh people tend to use Celsius when talking about cold temperatures ("It was minus four last night.") but Fahrenheit for hot temperatures ("The temperature must be in the nineties today.") It is quite true. It somehow doesn't seem as impressive to talk about "the high twenties" (deg C) as a hot temperature or "twenty five" (deg F) as a cold temperature. This could be because a temperature in the twenties is ambiguous - both Celsius and Fahrenheit occur in Britain, in cold winters and hot summers (all right - we have a temperate climate!) It is also true that you can detect a ten degree Fahrenheit difference of temperature. A summer day in the seventies is distinctly cooler than a summer day in the eighties. To talk of "low twenties" and "high twenties" doesn't give the same distinction. On the other hand, it is definitely gratifying to high-light below freezing as negetive. Body temperature is also more impressive as Fahrenheit ("I have a temperature of over a hundred!")

Talking of which, an important fact is that normal body temperature in Fahrenheit is 98.6 deg F, and in Celsius, it is 37 deg C. I am NOT going to give it for the other scales!

There are other cases of mixed units. In volume, the British drink pints of beer and milk, yet all other liquids are sold by litre (fruit juice, wine, water, petrol, etc.) We measure small lengths in millimetres, but large distances in miles. We measure our food in kilogrammes and ourselves in stone and pounds. Either we are very stupid, or very clever!

Accurate conversion of temperature (2 methods) between Fahrenheit and Celsius
Fahrenheit to Celsius	Celsius to Fahrenheit	Fahrenheit to Celsius	Celsius to Fahrenheit
Fahrenheit Subtract 32 Multiple by 5 Divide by 9 Gives Celsius	Celsius Multiple by 9 Divide by 5 Add 32 Gives Fahrenheit	Fahrenheit Add 40 Multiple by 5 Divide by 9 Subtract 40 Gives Celsius	Celsius Add 40 Multiple by 9 Divide by 5 Subtract 40 Gives Fahrenheit

The second method takes more steps, but has a pleasing symmetry. It comes from the completely useless piece of information

-40 deg C = -40 deg F

A correspondent has added these pleasing palindromes (reversals):

16 deg C = 61 deg F
28 deg C = 82 deg F

Approximate Fahrenheit and Celsius conversion

The problem with accurate conversions is that the calculations can be hard to do unless you have a calculator handy. Anyway, the answer tends to have decimals in, whereas most of us just want to know whether tomorrow's weather forecast is hot or cool! So here is a very rough approximation, within 5 deg C.

Fahrenheit	Celsius
32 deg F	0 deg C
40 deg F	5 deg C
50 deg F	10 deg C
60 deg F	15 deg C
70 deg F	20 deg C
80 deg F	25 deg C
90 deg F	30 deg C

Another way of doing this -

To convert from Fahrenheit to Celsius:
Subtract 30 and divide by 2.

To convert from Celsius to Fahrenheit:
Multiply by 2 and add 30.

I give the accurate value for the freezing point of water, because I am a gardener, so I think that frosts are IMPORTANT!

If you find the above table too hard to memorise, then remember that 70 deg F is 20 deg C, and this is a comfortable indoor room temperature. For temperatures above or below that, remember that 5 deg C is (roughly) 10 deg F. So 50 deg F (cool) is 10 deg C, and 90 deg F (hot - for Britain!) is 30 deg C.

The Beaufort scale was devised in 1805.

Old Beaufort Scale of Winds (Land)

Force	Wind	Effect on land	Speed miles per hour
0	Calm	Smoke raises vertically	Less than 1
1	Light air	Direction shown by smoke but not by wind vanes	1-3
2	Light breeze	Wind felt on face; wind vanes move	4-7
3	Gentle breeze	Leaves and twigs in motion; wind extends light flag	8-12
4	Moderate breeze	Raises dust, loose paper and moves small branches	13-18
5	Fresh breeze	Small trees in leaf begin to sway	19-24
6	Strong breeze	Large branches in motion; whistling in telegraph wires; difficulty with umbrellas	25-31
7	Moderate gale	Whole trees in motion; difficult to walk against wind	32-38
8	Fresh gale	Twigs break off trees; progress impeded	39-46
9	Strong gale	Slight structural damage occurs; chimney pots and slates blown off	47-54
10	Whole gale	Trees uprooted and considerable structural damage	55-63
11	Storm	Widespread damage, seldom experienced in England	64-75
12	Hurricane	Winds of this force only encounted in tropical revolving storms	More than 75

This was copied from an old reference book. Note that it confidently states that you don't get hurricane force winds except in tropical revolving storms, and even force 11 is seldom found in England. Global warming seems to be proving that wrong. But I find the descriptions vivid, and you can use them today to estimate wind speed.

Old Beaufort Scale of Winds - Sea

Force	Speed in knots	Conditions
0	<1	Calm, sea like a mirror.
1	1-3	Light air, ripples only.
2	4-6	Light breeze, small wavelets (0.2m). Crests have a glassy appearance.
3	7-10	Gentle breeze, large wavelets (0.6m), crests begin to break.
4	11-16	Moderate breeze, small waves (1m), some white horses.
5	17-21	Fresh breeze, moderate waves (1.8m), many white horses.
6	22-27	Strong breeze, large waves (3m), probably some spray.
7	28-33	Near gale, mounting sea (4m) with foam blown in streaks downwind.
8	34-40	Gale, moderately high waves (5.5m), crests break into spindrift.
9	41-47	Strong gale, high waves (7m), dense foam, visibility affected.
10	48-55	Storm, very high waves (9m), heavy sea roll, visibility impaired. Surface generally white.
11	56-63	Violent storm, exceptionally high waves (11m), visibility poor.
12	64+	Hurricane, 14m waves, air filled with foam and spray, visibility bad.

Wave heights quoted are approximately those that may be expected in the open sea. In enclosed waters the waves will be smaller and steeper. Fetch, depth, swell, heavy rain and tide will also affect their height, and there will also usually be a time lag between any increase in the wind and the consequent increase in the sea.

New Beaufort Scale of Winds

The new scale has no names below Force 8, and they are slightly different anyway. The descriptions no longer exist. But the numbers and wind speeds are the same, except for force 12. I thought originally that this was a misprint in my reference book, but have since been informed that winds of hurricane strength had already been redefined as 115 KPH in the metric system by the time the new scale came out, which is 72 mph.

Force	Wind	Speed miles per hour
0		Less than 1
1		1-3
2		4-7
3		8-12
4		13-18
5		19-24
6		25-31
7		32-38
8	Gale	39-46
9	Severe gale	47-54
10	Storm	55-63
11	Violent storm	64-72
12	Hurricane force	More than 72

Earthquakes

It may seem strange to put this on a weather page, but the descriptions are rather like the old Beaufort Scale, so I thought they belonged together.

Mercalli	Description	Effect	Richter
1		detected only by seismographs	< 3
2	feeble	just noticeable by some people	3 - 3.4
3	slight	similar to passing of heavy lorries	3.5 - 4
4	moderate	rocking of loose objects	4.1 - 4.4
5	quite strong	felt by most people even when sleeping	4.5 - 4.8
6	strong	trees rock and some structural damage is caused	4.9 - 5.4
7	very strong	walls crack	5.5 - 6
8	destructive	weak buildings collapse	6.1 - 6.5
9	ruinous	houses collapse and ground pipes crack	6.6 - 7
10	disastrous	landslides occur, ground cracks and buildings collapse	7.1 - 7.3
11	very disastrous	few buildings remain standing	7.4 - 8.1
12	catastrophic	ground rises and falls in waves	> 8.1

Other

Wales as a unit of rainfall
Wales is well known as a unit of area (as in "a giant iceberg as big as Wales") - see Length and Area for details. However, I have also heard of it as a unit of rainfall. Some rain forest was described as being "three times as wet as Wales".

The Misery Index - I couldn't resist this one!
The Misery Index was suggested in correspondence to the Times as a classification of the discomfort endured during a wet English summer. In this index, the balmy air and blue sky of the Mediterranean are indicated as 100. Values below 30 call for immediate emigration to escape from the grey skies and continuous rain in Britain.

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