When you use the word 'pressure', you mean an increase in 'true wind speed' with no directional change or?
When the wind is ahead of the beam (e.g., beating on on a close reach), a "simple" gust will move the apparent wind direction more FORWARD, in addition to increasing the apparent wind speed. A "simple gust", for this purpose is no change in true wind direction, only true wind speed.
'Pressure' in a sense is a different concept that is harder to explain because it's multi-faceted (or somewhat ethereal to describe objectively).
- If you're describing the cumulative load on the sails, as resisted by the hull and control surfaces in terms of "heeling angle" (for example), that might be a different description.
- In that case, were you saying: Head off to maintain about the same angle of heel. If you can't do that, then you'll have to i) reduce sail, ii) ease the sails, in some combination, or iii) yield to greater angle of heel.
- Is that what you meant, Jackdaw?
When I (and most racers I suppose) say 'pressure', it means general airflow against the sail. The MANNER in which this can increase can vary:
It can be freshening breeze, a general increase in overall pressure
It can be a wind line, a localized increased pressure due to a topographic feature or a squall
It can be a puff, which along with added pressure might be a lift or knock, depending on what side of it you're on
Calling the type of pressure change can help the crew deal with what is about to happen.
'sustained wind-line in 3...2...1'
'big puff, looks like a knock (left side while on port tack) in 3.. 2... 1... building...'
At some point for all boats, an increased level of general pressure will call for reduced sail area.