Heat lows, light winds and tricky Hyeres conditions

It has been a very tricky week here in Hyeres not just for the sailors but also for me as a forecaster. As a venue it is probably one the hardest to forecast for and for the sailors to interpret. It is often said that no two days are the same but here that can really seem like the case - just when you think you have sussed it you haven't.

This morning we were greeted to a beautiful mill pond and an outlook for the day that didn't look promising with generally less than 06 KT from the E and possibly even some showers.

By 1000 the wind had filled in and then built to a peak of 10-12 KT on some courses, not quite what was planned but considerably better. This allowed the racing to be completed in some reasonable conditions ahead of the final medal race tomorrow. I am sure many were please about this as some races drifted to a close yesterday in <05 KT with wind direction varying for 090-170.

Why is Hyeres so testing? Predominantly it is due to its location, rather than a nice piece of straight coastline which makes sea breeze development relatively simple it is complicated by the Peninsula and the islands offshore.
Coupled with that the region to the NW of the area heats up very quickly and create a low pressure system- commonly called a 'heat low', an example below. This effects the gradient wind which drives the surface conditions. Here in Hyeres it acts to enhance E to ESE conditions but in the process makes for often unstable conditions until established.