Weekend weather analysis

Libby goes over the charts from the weekend and has a look at what could be in store for the next five days

The weekend was dominated by a large scale high pressure system centred over Denmark. With no associated frontal system we were provided with dry, clear conditions and air temperatures above average (though the wind chill factor meant it felt a lot cooler). The wind direction in the Solent came from 045˚ and 120˚ while the wind strength varied from 12 knots to 25 knots across the weekend.

Saturday started with an average of 15 knots from the east north east (~ 065˚) with the forecast increase in pressure, expect around 11am, arriving early. By 10 am the wind strength had increase to an average of 20-24 knots with gusty conditions providing maximums of 30 knots. The increase in wind strength was more than expected. Looking at analysis synoptic charts ripples in the synoptic high pressure system can be seen making the isobars slightly closer and providing a greater wind strength. The wind steadied at around 080˚ and 18 knots by midday and by late afternoon decreased to 12-15 knots as expected in the forecast.

Sunday saw very similar conditions with a small reduction in the average wind strength to between 15-18 knots with gusts peaking at 22 knots. The wind direction was around 090˚ to 110˚ across the day while the wind strength decrease gradually from 2pm to an average of 8 knots. The forecast was for only 12 knots with the wind veering slightly towards the south east and an increase in wind strength expect across the afternoon. The wind pressure was again stronger than forecast with no signs of a sea breeze or a thermal enhancement the forecast wind strength was dependant on interpretation of the isobaric gradient on the synoptic chart forecasts. As with Saturday the slight ripples in the isobars that cause the changes in wind strength were also present in on Sunday’s forecast chart.

Along the eastern shore of Southampton Water convergence was occurring producing a stronger a band of wind as well as towards a 10 degree back in the wind direction. As the distance from the shore increase and in the more open water of the Solent the wind veered towards 20 degrees and the wind strength became steadier.


Outlook
The weekend ahead will see the high pressure system that dominated this weekend and the rest of week finally shifting as deep low pressure system forms over the Atlantic and pushes towards the UK.

Saturday will have winds of about 10 knots from a south easterly direction from the end of the high pressure system.

Sunday should see stronger winds from the southwest as a deep low pressure centre approaches.

Dependant on the speed of the system Sunday could be wet with winds up at 20 knots or dry with winds around 12 knots. Keep an eye on www.ecmwf.int long term forecasts over the next couple of days and then check out the 5 day forecast from the Met. Office at www.westwind.ch

Look out on Friday morning for Libby's detailed weather forecast for the weekend.