Weatherbadger's blog

Weather forecasts in 1943 vs 2012

weatherbadger — Sun, 19 Feb 2012 21:59:36 +0000

Recently I’ve been dipping into an old book. The Weather by George Kimble and Raymond Bush, published in 1943. Nearly 70 years old, the chapters on forecasting show some interesting signs of ageing, but great parallels with weather forecasting today. Here is a snippet.

CHAPTER X Further Outlook
At the present time no reputable meteorologist will commit himself to a really definite forecast for more than forty-eight hours, and for more than a limited area. He may give you a “further outlook” extending four or five days ahead, but usually only if a High is well established somewhere near the British Isles and air-mass conditions are likely to remain unchanged: even then he will couch it in fairly general terms. The reason he is unable to project his forecast any further is, broadly speaking, because his physical knowledge represents such rough and simplified approximations to the actual state of affairs that any conclusions drawn from them can be made to harmonise with experience only for a brief period of time.

This chapter continues with a discussion of the use of statistics behind forecasts – basically how climatological information was used in forecasting. Of course, this was before the use of computers to model the weather, so the meteorologists had to bash away with their relatively few observations, statistical rules of thumb, meteorological theory, experience and a pencil to project a weather forecast.

For a forecaster today, this “meteorological theory/experience” includes elements behind the output of the atmospheric models we get on our computer screens. This helps modify/interpret this computer output appropriately to produce a forecast.

in 2012 there is potentially an amount of numerical/statistical analysis as a forecaster: e.g. verifying previous forecasts, looking at climatic data for a region, analysing the output of an ensemble model. Some of that (not the ensemble stuff) will have applied back then. So all in all, I’d say the job requirements are fairly similar to now as they were then. With a more female, less pipe-smoking persuasion.

Finally, whilst we’re thinking back, the relative lack of technology really makes me appreciate the brains behind the forecasting for the 1944 Normandy landings even more.

Hmmm, a bit somber that one. Thoughts/no spam on a postcard please.

Making snowflakes

weatherbadger — Sat, 04 Feb 2012 09:07:07 +0000

My minibadger likes to make snowflakes by cutting a folded up a sheet of paper with scissors (and dropping the bits all over the kitchen floor.) I like snowflakes made by taking a mass of moist air and chilling it to make ice crystals then sticking these crystals together as they fall to the ground.

Yesterday, I heard the weather chap on the radio say that the snow today would be “light and no good for snowballs”. I thought this sounded fishy, as I’ve spent the last part of the week looking at the weather models trying to decide whether we’ll be getting rain or sleet overnight. Surely if the snow is borderline turning to rain/sleet it’s going to be wet/sticky “snowballs/snowman” snow?

Not being a snow expert I revised some snowflake science. Looking at the temperatures associated with the weather front expected over the UK today, we’ll have a temperature ascent warm enough to make the ice crystals “sticky”. This means that they will coalesce more as they fall to earth, making larger flakes – better for snowballs.

Conversely if the temperatures are too low, then the crystals don’t stick together so much, and you end up with dry powdery snow, which is less dense than average.

Speaking of density, the ratio of water content to snow indicates whether you have powdery snow or wetter snowball/snowman snow. An average is around 10:1 snow to water. So 10cm of snow comes from 1cm of water. Wet snow can have a ratio of 5:1, (1cm water -> 5cm snow) whereas dry powdery snow will have a higher ratio (e.g. 1cm water -> 20cm snow). The weather model was showing around 12mm of rain falling over Oxford tonight, but giving a snow cover of 80mm. This ratio of 7:1 suggests wettish snow. Once the snow has fallen, overnight temperatures may mess things up, but I reckon keep your carrots at the ready for tomorrow morning.

Incidentally, I wondered whether the myth that Eskimos have hundreds of words for snow is true. Wikipedia says it isn’t.

Enjoy the snow if you can. Let me know if you get any snow, and if it’s powder or slush, or something in between.

Why is it so cold?

weatherbadger — Tue, 31 Jan 2012 20:33:14 +0000

An air mass is a large volume of air, which acquires temperature and water vapour content characteristics based upon those of the region over which it moves/is situated.
There are 6 types of airmass affecting the UK, such as “Tropical Maritime” and “Arctic”. These greatly influence the type of weather we get here. If you ask a weather forecaster where the air has/will come from they should be able to give you an idea of the sort of weather to expect. At present we’re receiving “Polar Continental” air from the east. This has travelled thousands of miles from northern Russia, and is dry and very cold.
Because it’s winter in the northern Hemisphere, there has been relatively little sunlight to warm this air mass up along its journey from Russia (taking in Eastern Europe on the way) so the UK gets the left overs of a Siberian winter. Without the furry hats and vodka hangovers.
At present the air has taken a more southerly track than would normally be associated with a Polar Continental airmass, skirting over the NE Mediterranean. But because it’s so blooming cold (northern Greece and Turkey are below zero C) and there’s nothing to warm the air up on the way, the UK gets our lovely cold snap.

Please wrap up will you? That’s what Mrs Badger said this morning when I told her about my blog.

First blog post!

weatherbadger — Tue, 31 Jan 2012 00:15:10 +0000

Greetings to my first Weatherbadger blog post!

After years of Tweeting and posting links on Facebook I’ve decided it’s time to go in house and put some more ramblings on the Weatherbadger website. We’re going to ditch the “site news” page, which hadn’t been updated for ages anyway, and put a bit of effort into writing some interesting weather related stuff here. Hopefully you’ll want to come back regularly and comment (I believe you have to register or something first) if you want.

I do aim to focus on the weather, but as I’m a badger, I reserve the right to mention other things which interest me. The layout/design still needs work, but it’s all about the words right?

Right, enough for now – I’m going to have another look at the plummeting temperatures.