Irene rakes the coast; 65 million in path; NYC rare direct hit?

Here we go.

The hurricane scenario may have dreaded is unfolding this weekend along the east coast.

1km visible image of Irene Friday from NASA Aqua/MODIS satellite

Let's break down some of the many facets of Irene.

Sheer size of Irene the biggest factor:

Irene's sheer size may be the biggest factor is how much damage she eventually does. As many as 65 million people lie in the storms path. Hundreds of thousands of trees may be knocked down from the Carolinas to Maine. Power may be cut to tens of millions.

Storm track:

Hurricane Irene is tracking right along the east coast, and the huge storm is effecting millions in the most densely populated area of the USA.

The suite of spaghetti models continues to be remarkably consistent taking Irene through eastern North Carolina and right along the Jersey Shore into New York City.

A direct hit from a category 1 Hurricane Irene in New York City looks likely at this point.

Even if the center of Irene misses New York, the storm is so large that hurricane force winds (or at least gusts) are almost certain along the entire coast from the Carolina's to New York.

Intensity:

Irene showed signs of dry air intrusion and slight weakening Friday. To my eye however, the CDO with Irene seem to be in up cycle...and further strengthening can't be ruled out before Irene reaches the Carolina coast Saturday.

There are two main reasons why intensity is becoming somewhat of a secondary consideration at this point.

1) The storm is so large that hurricane force wind gusts will be felt over a huge area.

2) The wall of water moving north with Irene (storm surge) is already in motion, and will arrive and flood low lying coastal areas regardless of Irene's eventual intensity at landfall.

New York City: Effects of a direct hit?

There are many scenarios regarding a direct hit of even a Category 1 hurricane on New York City. Not many are good. Here are some of the possible impacts and considerations.

-Storm surge Flooding: Depending on exact storm track, various scenarios put storm surge of 3 to 7 feet along the Jersey Shore and into the New York Harbor system. Add wave up to 9 feet on top of that surge, and you may have significant coastal flooding.

The effects of flooding into New York remain unclear, and potentially dangerous. This kind of scenario doesn't happen often...and the fact is we really don't know how severe the damage and flooding from storm surge will be in New York.

Wind Damage:

So what happens when hurricane force winds batter the tall buildings in New York City? The fact is again, we don't know how extensive the damage will be.

One thing to consider is the increase in wind speeds with height above ground. As you reduce friction above ground, wind speeds will increase.

With category 1 winds of 75+ mph at the ground, you may have category 2 winds of 100mph 10 stories up!

You will also get an increase in wind speeds with the wind tunnel effects between buildings. There could be significant damage to skyscraper windows this weekend, and potentially showers of glass to the streets of New York City.

There are good reasons why mass evacuations are ordered for large areas. We are now living through one great big bad weather experiment!

PH