Frances Dynamics

[Sanibel]

The "stair-stepping" wobbles were caused by the storm weakening. When Frances brick-walled into the ridge she hit a synoptic inhibitor that stopped the free flow of her cyclonic engine. Her tail pipe was clogged so to speak.

Because of this confining of her energy transfer mechanism she backed up and spread the energy further out. The storm expanded - as seen in her progressive warming cloud tops and widening form.

The stair-stepping happens because pulses of deep energy don't flow evenly into the backing-up core cycle. Like a mis-timed engine, these imbalanced deeper pulses swing out into the deep bands near the core. When one side contains a deep pulse it pulls the eye that way. This imbalance displays how the eye fails to maintain its gravity axis in a storm like this with a challenging synoptic border ahead of it keeping it in check. Frances had a widely-spead low pressure pan. This was a signaling feature of such a disabled storm.

Frances was expanding because her energy had to go somewhere, so it went out into her bands like a storm winding down instead of up. So, the Gulf Stream actually did enhance her in a relative way. If not for the Gulf Stream she probably would have lost intensity as she approached Florida. She didn't. She didn't because the Gulf Stream kept her at 105mph with its input. It also kept the explanded energy in her widened bands higher. That explains the 125mph gusts so far from the center...