In message , Adrian D. Shaw
writes

Felly sgrifennodd Paul Hyett :

Absolute Drought - A period of 15 consecutive days without rainfall of
more than 0.01" (0.2mm)

That's an ineresting definition.

I got it from my old copy of Guinness Weather Facts & Feats.

So a period of 30 consecutive days without
rainfall of more than 0.03", and that occurring 10 days ago, is not an
absolute drought?

The first 20 days of that period would be, but the 0.03" would reset the
counter.

This is of interest to me as I was recently thinking of ways to put up
descriptive words on my weather pages such as "raining", "dry", "very dry"
and "parched", according to the weather. I realised that it is more than
just calculating when the last rain fell. Also to be taken into account
are the amounts that have fallen, when it fell, and also the temperature
(as the term "drought" suggests to me lack of water; if there's no
evaporation then there is no drought).

It seems to me that the definition should contain a formula something like

for each day 15, allow (day of drought)*some constant, maybe temperature
dependent mm of precipitation for absolute drought

and should probably be a fair bit more complex than that. An absolute drought
could therefore be broken by a little rain, then reinstated if it continues
dry for a certain period. This seems logical and sensible.

See http://homepage.ntlworld.com/booty.weather/FAQ/AF.htm
--
Paul Hyett (change 'invalid83261' to 'blueyonder' to email me)