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Plowshares & Convergence
updated 12/2004

There are different types of convergence. The convergence in the Antelope Valley is different than Plowshares.

At Plowshares, the relatively cold and heavy marine air is pulled up the valley by the thermal generated inland low. The marine air drives under the relatively warmer and lighter desert air. Out in the valley, the convergence moves upriver like a sea breeze front, lifting the desert air in front of it. As you get further upriver, the marine air may advance only so far and can be held off by the NE flow coming off the San Joaquin Valley. It's still better to be on the desert side of the east / west convergence line. A valley like the Santa Clara will produce a more typical sea breeze front because it usually draws all the way up the river toward the desert (Santa Anna days can be an exception).

In the Antelope Valley convergence the marine side has less of a temperature differential and doesn't act like the plowing sea breeze fronts. It's a NW / SW convergence with desert on both sides. You run downwind along the line. One of the problems at Plowshares is the route is perpendicular to the convergence, so if you want to stay in it you have to wait for it.

On days with good temperature dynamics, you don't need the convergence, but thermals are like the chicken and egg thing. Convergence will assist thermals, and thermals create convergence. A high plateau like Lockwood Valley will often create a convergence because the lift is so good it will draw in from all directions.

If you launch early at Plowshares, you may need to look west for the convergence. The convergence will usually move, and you have to move with it or you'll get caught on the wrong side. If the drift is already from the west at launch, then you need to look to the east, but that takes you away from retrieval.

Since the Plowshares convergence is a variation of a sea breeze front, it works best in the spring and fall when the diurnal flow (daily drain and fill) is balance back and forth. The launch at Plowshares is also in a venturi where the valley route to the ocean necks down. It seems to be more influenced by the pressure gradients than the winds aloft, however, the winds aloft may coincide with the pressure gradients. When you have high pressure subsistence (descending air mass), the drain seems to accelerate offshore through the narrow end of the valley.  An inland low will suck the marine air in early.

If you move upriver with the convergence at Plowshares, a hang gliders speed advantage is negated because even a paraglide can outrun it. With speed to spare, the hang gliders have been running down the range and then bridging across the valley on the convergence line.

The north flow coming down from the Big Valley splits near the junction of 33 and 166. It then follows the rivers and flows toward Pine from the NW and toward New Cuyama from the NE. Sometimes the west will push through past New Cuyama late in the day, but will often be held off by the stubborn NE. If you can get around the corner at Santa Barbara Canyon, you usually pick up a tail wind.

Theoretically, you can take the deep route, stay out of the valley influence, and avoid the east flow. If you do, its best to have your boots broken in, plenty of water and power bars, disposal gear, and do it on a Saturday so you won't be late for work on Monday. You can also go OTB past Cottonwood and try Hurricane Deck, or go directly to San Rafael Peak if your getting high and the drift is from the north.

Convergence comes in variations including scale. Look for it behind West Bowl, over the Monastery, and crossing Ramero Saddle on a north day. Control your focus, stay flexible, adjust your task to harmonize with the day, and you can bridge across from Santa Paula Peak to Malibu.

SD

copyright 5/29/01