The acceleration was caused by a shortwave trough embedded within strong southwesterly mid-level flow.

The river continues its southwesterly flow through Skagit County and outlets into Samish Bay in Puget Sound.

But for a month and a half we were in a pattern where we had consistent southwesterly flow that was drawing mild air.

Meandering, the storm started to turn northward under the steering currents of a southwesterly flow associated with an approaching mid-level trough.

Later that day Noel accelerated northeastward in the southwesterly flow ahead of an approaching trough.

Passing east of Socorro Island, the storm turned north and shortly thereafter north-northeast due to southwesterly flow over northwestern Mexico.

The pattern of air flow is so common that the winds have scoured a straight path in the ground, marking its southwesterly flow.

As it slowly turned to the north, southwesterly flow from a large trough over the central United States increased wind shear over the hurricane.

In addition, strong southwesterly flow gradually decreased convection around the center.

An environment of weak wind shear in the wake of the typhoon allowed a new area of low pressure to form within the southwesterly flow on May 21.