Dr. Jack's ETA foracast validates Friday

To celebrate the Spring Equinox, I hauled the Nimbus to Boulder, Colorado
yesterday for the year's first flight.

The 21Z ETA Blipmap forecast looked strange to say the least and I wasn't
convinced that it was accurate. The blipmaps showed a strong subsidence
over the mountains just west of Boulder and 5 - 6 knot lift on the plains to
the east - just the reverse of the usual Boulder conditions. ETA also
showed a "V" shaped high cloud cover extending to the NE. Surface winds
were predicted to be light from the west and the B/S parameter was low and
the shear value high signifying strong turbulence and difficulty centering
thermals.

Driving into Boulder at about 10AM the "V" shaped cloud deck was exactly
where Dr. Jack said it would be. The 12:45 launch was very turbulent
resembling wave rotor but the glide computer showed only 5 - 11 knots of
wind from the west. Several attempts to tow west were met with 5 - 8 Knots
down while still on tow - not good when towing into steeply rising terrain.
I got tired of the pounding and released at 2000 AGL just west of the
airport and contacted broken lift. Scratching to stay airborne I drifted
east into stronger lift. Once east of the airport, I contacted steady 6
knots exactly as forecast. The lift topped out at 14,000, as forecast.
Several attempts to glide upwind into the mountains were met with strong
sink and I retreated to the east. Throughout the flight the turbulence
remained strong and the lift difficult to center. Scattered Cu's formed but
they were badly torn up and gave strong evidence of the pervasive shear.

On all forecast parameters, I give Dr. Jack an A+ for the March 19 21Z ETA
forecast.

Bill Daniels