Re: Jim's updates
Posted by Tim_NC on 12/30/2010, 3:06 pm
Adding extra-tropical storms to the list eh? Hmmm....

While I applaud the modification, I can't help but wonder how an extra-tropical Low makes the list.

The evolution of an extra-tropical Low is similar to a tropical Low; after all, a Low is basically still a Low no matter where it is.

Basic Extra-tropical Low Evolution:

Stage 1: It starts as a "wave" in the isobars.

Stage 2: The first isobar closes off; we have a Low (= a TD.)

Stage 3: More isobars close off; we have a Gale (= a mild TS.)

Stage 4: More isobars close off; we have a Storm (= a strong TS.)

Stage 5: More isobars close off; we have "Hurricane Force Wind Warning" (= a Cat 1 Hurricane.)

Question: which of the above stages "count"?

COMPLICATIONS:

1.) Measuring a Low only by its pressure can be misleading. Wind speeds in Lows are greatly affected by the proximity and strength of Highs. A solitary Low moving up the coast struggles to build a wind field; but if a Low encroaches on a High the wind field intensifies rapidly.

2.) Hit? Near hit? I wonder how this would be defined. The wind, temperature, and precipitation fields of an extra-tropical Low are quite bizarre when compared to a Tropical Low. And then there's the Center itself. Developing Lows have gigantic, weather-free centers that shrink in size only as the faster-moving cold front gains ground on the slower-moving warm front. The more mature a Low, the more compact the weather-free center.

(A full, tight, top-to-bottom center only forms at full maturity, when the cold front catches the warm front causing an "occlusion." At this stage there's no escaping the storm's ferocity.)

The "geographical effects" felt from these Lows have little in common with their tropical cousins. In fact, in regard to their centers the effects may be opposite. If you want the least impact from a developing Low....just have its center pass directly overhead! (Because you will spend the maximum time in its large weather-free center.)

When the Mid-Atlantic Coast was savaged by the "Great Atlantic Coastal Storm" in March 1962, the center of that stationary complex (dual) Low was hundreds of miles off the coast.

The point of all this is to make note of how difficult it is to put these Lows into a box.

Oh...that reminds me. I would offer that a Tropical "brush" might be determined by the storm's strength. For example X miles for a TS; Y miles for a hurricane; and Z miles for a major hurricane.

If I keep on writing I'm going to confuse myself to death....so I'll end here.

Tim in NC

P.S. The recent nor'easter had no High in its vicinity. If it had, the snow would have extended well inland, and coastal winds would have been higher.
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Jim's updates - CypressTX, 12/28/2010, 2:53 pm
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