Calm at surface, smooth at 3,000 up with winds

[Leo O'Farrell]

This is a weather question. Yesterday, doing a dusk out night return from Oakland to O88 (Rio Vista where the fuel is cheap) it was smooth at 3,500 heading East, with a strong headwind. On the descent into the delta airport next to an ever growing windfarm, the air was rough and turbulent all the way to the surface.

Experienced the same on climb out, then smooth from 3,000' all the way up to 4,500'. Turning the nose of the Cessna to KOAK, picked up a lot of speed, at least 25 knots.

Is this considered an inversion, or wind shear?

Back at Oakland did my night currency pattern work, and it was quite calm and dark before moonrise.

 

[EdFred]

I would say the wind farm was messing with the air.

 

[Ianovic]

Setting sun over delta makes all sorts of little sinkers. The waterways are fairly stable temp wise, while the farmland heats throughout the day and cools immediately when the sun sets. An hour or more after sunset it's smooth as silk unless there's wind. It is frequently breezy in rio vista when it's calm elsewhere. Gotta love $5.00 a gallon avgas.

 

[EdFred]

Setting sun over delta makes all sorts of little sinkers. The waterways are fairly stable temp wise, while the farmland heats throughout the day and cools immediately when the sun sets. An hour or more after sunset it's smooth as silk unless there's wind. It is frequently breezy in rio vista when it's calm elsewhere. Gotta love $5.00 a gallon avgas.

Talk about becoming acclimated.

 

[MAKG1]

Yeah, I experienced that, too.

I clocked a 35 knot northeast wind near Gilroy, at 3500 feet, and it was calm at the surface. That got me to Salinas with a 150 knot ground speed in an Archer.

Not very turbulent, either, despite there being 4000 foot mountains upwind. Just a bump or two. On the return at 4500, it was smooth as a baby's bottom, but really slow....85 knots ground speed.

It got a bit bumpy descending over Prunedale, but I would hesitate to even call it moderate turbulence. I got no turbulence at all on the following climbout (but I climb faster than I descend in that aircraft at low altitude, so I was at altitude well before the Prunedale hills). The wind tapered off smoothly over San Jose; no turbulence on descent.

 

[Sac Arrow]

I'm pretty sure that "wind shear" is only a result of convective activity. It's not abnormal to see large changes in the direction and speed of the wind as you climb out in clear air. Especially in that region because the coastal mountains cause big deflections of offshore winds.

 

[sacbluesman]

I've flown into O88 more times than I can remember. That airport is a menace with the winds. I've been told that the winds are due to the topography however I've never been concerned enough to really pay attention.

 

[gismo]

I've flown into O88 more times than I can remember. That airport is a menace with the winds. I've been told that the winds are due to the topography however I've never been concerned enough to really pay attention.

I've encountered a lot more turbulence with wind interacting with nearby terrain and obstructions than with wind changes over altitude.

 

[Silvaire]

Yes that is common windshear and I've experienced it around here often (I'm out of C83) Sometimes it will be dead calm on the surface with a steady 25 or 30 kt wind above 1500 or 2000 feet. Flying is smooth other than a few bumps as you transition through the layers or unless you try to do a fly-by of Mt Diablo after which it's like going over a waterfall. Done that a few times

 

[CaptLabrador]

Very Few of my landings at O88 have been without the little bumps on the way in. Its the delta creating all kinds of different heating patterns out there. Great airport for xwind training on the short north-south runway.