Veering slowly and losing its identity….

The other Thursday evening the weather forecast, on the app appropriately named Windy,  was very clear; there will be a gale in Lyme Bay on Saturday.  It had been predicting this for some days, then as if by some miracle, on Friday morning it had ‘ softly and suddenly vanished away’.

it looked something like this. This is actually hurricane Erin which is about to make the weather a bit dodgy for the last week of the summer hols!

While it is not unusual to occasionally have strong winds and rain during an English summer , what was striking about the last week is the unpredictability and the duration of the weather patterns.  A long periods of high pressure created endless easterlies, not our favourite direction on this part of the coast. This broke with the arrival of an enormous depression in the North Atlantic which sent a series of weather fronts whipping across the West Country bringing strong W and SW winds.  The afore mentioned gale was a small depression spinning around this.

We rely heavily on the weather forecasts to plan our day to day activities and when these are so erratic it makes our lives just that little bit more difficult. Last week the five day forecasts, which are usually pretty reliable, where changing significantly as close as 24hrs ahead. This does create a challenge for the skipper when passage planning and can be confusing for our passengers who might wonder why we are in harbour when the weather looks favourable or why we are rushing to the next safe haven rather than sauntering under sail in a gentle breeze. 

There are reasons for this uncertainty which are very complex and nerdy but if I understand it with my miniscule knowledge of meteorology it’s something like this.  The temperature of the N Atlantic was 5 degrees above the average for June that means a lot of extra water vapour entering the atmosphere, when this condenses it means huge amounts of additional energy entering the weather systems creating dramatic anomalies.  The slow equalisation of the artic and tropical air masses slows the jet stream allowing more undulations which stay in place for longer. Bigger slow moving systems both high or low.  I still don’t understand however how a full gale can simply disappear in 24 hrs.

We obviously have criteria for when we can sensibly sail between ports and when we should hunker down for the day. The simplest is wind strength, but this must be considered in relation to direction and duration.  A force 5 gusting 6 is pretty manageable when sailing across (reaching) or with the wind (running) but is too much when sailing towards the wind (beating). If the direction is offshore or the wind is new (less than 6 hrs duration) then the waves will be manageable but if the wind is onshore and persistent the waves could reach over 1.5 m which could be untenable. If the tidal stream is running against the wind the waves get steeper and the progress can be much slower and very uncomfortable, so no fun for anyone. Then if there are frail or motion sensitive passengers on board, we might temper our decisions to suit them. Conversely a fit and experienced group might allow us a bit more flexibility. So, there is no simple go/don’t go criteria but a complex and sometimes intuitive calculation. Ultimately we strive to work with rather than against the rhythms of nature as explained at https://www.snark.limited/our-philosophy