Tuesday, September 10, 2019

Shear Wave

6,600' over Post Mills on Sunday
Sunday mark the beginning of wave season in New England.  It was kind of windy, thermals were generally weak, cloud base was low and the clouds sort formed streets (perpendicular to the wind).  The first 2 hours of my flight I tried to thermal to cloud base and then look for wave.  Most of the time was spent trying to get to cloud base in the weak thermals and avoiding the strong areas of sink.  Since the wind was out of the northwest, when I got to cloud base I would try to move toward the northeast (mistake) and generally found sink.

I found a strong thermal over Rich Starr's house (I guess there's a lot of hot air around there) that took me to cloudbase over the east ridge and from there I was able to transition to wave at about 5,000'.  When I looked around I noticed I was on the southwest side of the cloud street and the glide computer said the wind was 280 degrees at 20 kts.  Below 5,000' the wind was 320 degrees at 10 kts.

I think what was happening was there was cloud street that runs perpendicular to the wind (320 to 140 degrees).  The thermals push up into the inversion at 5,000' and forms a "ridge".  The inversion layer is moving at 20 kts from 280 degrees and hits the "ridge" at a 40 degree angle and has to go up and over the "ridge" forming the shear wave (see cloud street wave).

While the OLC points and the maximum altitude were unremarkable, it was a really fun flight.