RASP Winds

Wind charts on the RASP.

On average, I have found the RASP wind charts to be reliable the vast majority of the time.  I’ve been able to count on them to accurately forecast the winds that I eventually encounter.  I find the surface wind most helpful in  predicting where i will find the thermal lift, if it is that kind of day, or the wave lift, if is THAT kind of day.

Let’s take a concrete example of my flight on Feb 24, 2018.  This was an example of wave lift and ridge lift, accurately forecsted by RASP, and I relied on that forecast.  The flight report was posted to the Forum – see:

On the day of the flight I reviewed the RASP for the last time.  At 8:35 AM  I posted the following:

Good wave climb (Stonyford/ St John area) to 14,000 (higher if you have oxygen) is possible, but just in one spot.

Cruise south, come home on the ridge.
Good ridge fcst for running the ridge back (and down again to bessa towers in the afternoon.

My flight plan was based upon this chart “Vertical Velocity and Wind at 700mb”:


The dashed line you see on the 700 mb chart above is computer generated based upon the greatest average upward vertical velocity within the area depicted in this fcst area.

You can see it is drawn from somewhere north of Round Valley (west of Yolla Peak) to about Woodland

The cross section of the lift along that line is called the “Wind Parallel Section”

Simple to read now that it is explained.  Wind is from left to right, at distance point “0” that is north of Round Valley, and distance point 100 that is approximately Woodland, Ca. the two hills are the ridge north of Gravelly on the left, and Snow Mountain to the right of it.  The ground gets lower as you get closer to Woodland.

The dark red indicates the vertical velocity of the air, on the downwind side of Snor Mtn is going up at about 300 cm/second, which equates to about 600 feet per minute (6 Kts) up!

The surface wind chart indicates calm air (blue spot) when in the wind shadow of Snow Mtn and indicates a stead wind coming across the cortina ridge from Lake Berryessa up to 3 Sisters.


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