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Home Port: Welcome to Old Weather => The Science: What You're Doing This For => Topic started by: philip.brohan on April 15, 2011, 12:04:48 pm

Title: The weather in 1.85 characters.
Post by: philip.brohan on April 15, 2011, 12:04:48 pm
[I wrote this really as a blog post (http://blogs.zooniverse.org/oldweather/2011/04/the-weather-in-1-85-characters/), rather than a forum entry - I suspect most of the forum regulars already know more about the weather codes than I do - Philip].

My desk in the Met Office is some way from a window, but if I peer across the heads of a few colleagues I can see that the weather outside is, well, disappointing: A gloomy day, with the sky filled with mottled grey clouds from horizon to horizon (though at least it's stopped raining). Here in the UK we're famously obsessed with talking about the weather, but sailors would have no time for such waffle: Following an example set by the famous Admiral Beaufort (http://en.wikipedia.org/wiki/Francis_Beaufort) they record the current weather in a terse code (http://forum.oldweather.org/index.php?topic=161.0), and today's weather in Exeter would be simply 'o' (overcast), or perhaps 'oc' (overcast cloudy) if they were feeling extravagant.

The weather code system has evolved quite a bit since Beaufort's day, and it's a powerful and concise way of recording notable weather events. The basic code records the amount of cloud in the sky, and ranges from 'b' (clear sky or mostly so), through 'bc, and 'c' to 'o' (overcast). These are by far the most common codes, but you can add to them to record many of the various nastys the atmosphere can inflict on you - there are codes for rain, snow, hail, gales, squalls, fog etc.

This means that the longer the code recorded in a logbook, the worse the weather was (or at least the more exciting it was). The longest code I've found in the logs completed so far is 'ocpqrlt' (overcast, clouds, showers, squalls, rain, thunder and lightning) from HMS Bacchante, at Dakar at midnight on 31st August 1917 (http://oldweather.s3.amazonaws.com/ADM53-34661/ADM53-34661-018_1.jpg). (Thanks to captain richbr15, lieutenant dazedandconfused, and the crew for patiently typing all that in). This sort of detail, however, is rarely necessary, and, on average, the logs only need 1.85 characters to record the current weather.

I'm excited by the weather codes because they offer a new opportunity to test our climate models. In principle, if we know the surface pressure and temperature (also in the logs, of course) our models should tell us where it's clear, where it's cloudy, where it's raining, and even about thunderstorms and squalls. In practice it's not quite as easy as that, partly because our computers are not yet powerful enough to run atmosphere models that are detailed enough to resolve small features like thunderstorms and squalls; but even so I look forward to learning more about the accuracy of our cloud and rainfall models. So please keep entering the weather codes - we need the ordinary records of cloud cover as well as the unusual events.

Since I started writing this the rain has come back, so I should modify my current weather report to 'or'; but improvement is in sight - the forecast for this weekend is for 'bc' (broken cloud), maybe even 'b' (little or no cloud) at times. The designers of the weather codes were uninterested in particularly fine weather, so there's no way of encoding 'glorious sunshine' for example ('gs' would be gales and snow). Still I wish you all as much 'b' as you care for, except for a dose of 'r' (rain) for anybody praying for it.

Title: Re: The weather in 1.85 characters.
Post by: Bunting Tosser on April 15, 2011, 12:51:57 pm
Oo, sounds like a pat on the back.
Thank you, p.b. Good of you to take time away from organising good weather for "The Wedding" (hope it doesn't suffer as a consequence - or it'll be The Tower for someone).

Now if I can just find the 0.85 key, I'll get back to work.

Best wishes,

Title: Re: The weather in 1.85 characters.
Post by: Caro on April 15, 2011, 05:36:07 pm
Thanks Philip. Ah weather codes; we love 'em.  ::) ;D
Title: Re: The weather in 1.85 characters.
Post by: Kathy on April 15, 2011, 06:15:22 pm
I find that I want a complete weather station - wind, pressure, etc  (the trashcan scale is fine as far as it goes, but I'd like to be more specific  ;D), because I now automatically use the code when thinking about my local weather and I'm thinking (Heaven help me!) that it would be interesting to note down my own local readings-

I am becoming Old Weather's monster - (its alive, alive!)

Kathy W.

(PS - who thought up Old Weather? - I guess that is whose monster I have become  ;D)
Title: Re: The weather in 1.85 characters.
Post by: Tegwen on April 15, 2011, 06:16:32 pm
Just for the sake of completion we also had ocprqlt on HMS Clio


Title: Re: The weather in 1.85 characters.
Post by: mapurves on March 22, 2013, 10:56:49 pm
Seen on the Concord at 5:00 p.m. 26/07/1892 at New London, Connecticut, and also with seven characters: bcmpqlt