I've been wondering for years what relevance the number has after a PROB fog. It doesn't matter operationally whether it's PROB 10 or PROB 90. If there's any probability of fog or other phenomena reducing the visibility below the alternate criteria, or whatever the exact AIP wording is, you need an alternate.
So why don't we ditch the number entirely and make it just PROB, meaning there is some probability, so gas it up?
Or, even better, remove the term PROB entirely. If there is a chance of deteriorating weather during a certain period just forecast it as such. It makes the TAF/ TTF shorter, which makes it easier to read, and makes no operational change as far as flight crew are concerned.
Last edited by DirectAnywhere; 19th Jun 2013 at 05:39.