Tuesday, August 23, 2011

Irene Day One

I have previously written about my morning routine. When I log onto the internet, the first page that opens is the National Hurricane Center with its Atlantic map where it tracks tropical disturbances that have the potential to develop into tropical depressions, tropical storms and hurricanes. These disturbances often begin as major systems leaving North Africa for the Cape Verde Islands and appear on satellite images as broad areas of cloud and rain. NHC assigns a percentage probability that the disturbance will become a tropical cyclone within a rolling 48 hours.

On Monday, NHC predicted that Tropical Storm Irene would become the season's first Atlantic hurricane. It did. As it tracks west past the Dominican Republic (likely drowning Haiti in the process), it will push through the Turks and Caicos into southeastern Bahamas. From there, the various models used by NHC began to diverge. NHC prediction accuracy diminishes rapidly beyond 48 hours. On one extreme, models showed Irene becoming a Major Hurricane (Cat 3 or stronger) over the central Bahamas before landfall in southern Florida where it would recoil as a Tropical Storm travelling up the west coast of Florida. On the other extreme, Irene would stay just east of Florida as a Major Hurricane drawing energy from the hot Gulf Stream waters with landfall somewhere between Georgia and North Carolina. A cold front over the southeast together with the influence of the Gulf Stream might have pushed Irene to sea before she rounded Cape Hatteras.

As of yesterday, Irene is forecast to reach us in North Carolina, in whatever form, on or about Saturday.

As of this morning, the models have a better aligned consensus. Irene will become a Cat 3 hurricane today or tomorrow. Her forecast path shows landfall around Myrtle Beach, South Carolina, passing us to the west. While that may sound promising, it puts us in the most dangerous quadrant for wind.

How do we prepare? (This question was more interesting yesterday when I drafted this blog and there were more variables still up in the air.) First, we track her, reading the NHC Forecast Discussion in addition to the regular Public Advisories.And we look for continental systems that could influence Irene's course. For instance, yesterday there was the above-mentioned cold front dropping down from the north that could have blocked her northward motion. (Now there is a breach in that front through which Irene will be able to continue north.)

Second, we begin to consider our options under different scenarios. To oversimplify, we consider the following:
  1. Tropical Storm or weak Cat 1 Hurricane passing east of us. We keep the boat in the marina with doubled lines.
  2. Strong Cat 1 or weak Cat 2 direct hit. We might move the boat up one of the creeks and secure her with multiple anchors.
  3. Strong Cat 2 or higher, even if passing to east. Haul out.
Our challenge is that all the known factors as well as the forecast factors can change daily if not with each Public Advisory. As I learned with Hurricane Earl last September, a good strategy at 10AM may be a bad strategy at 11AM when the advisory is published. (And it may be good again when the next advisory comes out.)

For now, we watch, wait and begin to plan without knowing the actual timing or how powerful the storm will be when we begin to feel the leading edge winds or how high the storm surge will be when it passes (high water or low?).

Having written all of the above yesterday, I am sad to say that there is less doubt about Irene's course and strength today than many storms I have followed. Barring another significant factor that changes her path, Irene looks to hit us beginning Saturday with the eye passing early AM Sunday. Because she will landfall in North Carolina as a Major Hurricane, we will likely haul out. After all, this is our home, not just a weekend toy.

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