Tuesday, May 4, 2004

2004 HURRICANE SEASON PRELIMINARY FORECAST

This forecast is based in part on the research of Dr. William Gray of Colorado State University, who has been issuing annual hurricane intensity forecasts for the past 21 years.

Dr. Gray's initial forecast for this season:
- Number of Hurricanes 8
- Hurricane Days: 35 (days that all tropical systems will be classified as at least Category 1)
- Intense Hurricanes: 3 (tropical systems which will meet or Exceed Category 3 with winds 111 mph +
- Intense Hurricane Days: 8 (days that hurricanes will be classified as Category 3)

Overall U.S. coast hurricane landfall probabilities

1) Entire U.S. coastline - 71% (average for last century is 52%)

2) U.S. East Coast Including the Florida Peninsula - 52% (average for last century is 31%)

3) Gulf Coast from the Florida Panhandle westward to Brownsville - 40% (average for last century is 30%)

4) Expected above-average major hurricane landfall risk in the Caribbean

Factors contributing to the expected above-average hurricane risk this season:
(as taken from Dr. Gray's website)

A. February 2004 Sea-surface temperatres off the Northwestern European Coast

Warm sea surface temperatures off the northwest coast of Europe correlate quite strongly with warm sea surface temperatures across the entire North Atlantic Ocean. A warm North Atlantic Ocean indicates that the temperature-salinity circulation is likely stronger than normal, the subtropical high near the eastern Atlantic is weaker than normal and consequently trade wind strength across the Atlantic is also reduced. Weaker trade winds induce less upwelling which keeps the tropical Atlantic warmer than normal. This pattern tends to persist throughout the spring and summer implying a warmer tropical Atlantic during the hurricane season which is an enhancing factor for developing tropical waves.

B. February 2004 Sea Level Pressure in the Southeast Pacific

High sea level pressure in the eastern Pacific south of the equator indicates a positive Southern Oscillation Index (SOI) and stronger-than-normal trade winds across the Pacific. Increased trades drive enhanced upwelling off the west coast of South American that are typical of La NiƱa and hurricane-enhancing conditions. Cool sea surface temperatures are associated with these higher surface pressures that tend to persist throughout the spring and summer thereby reducing vertical wind shear over the tropical Atlantic and providing more favorable conditions for tropical cyclone development

WHAT IT ALL MEANS?

1. Warmer than average temperatures and lower than normal air pressure will persist in the Atlantic.
2. Weak high pressure in the Atlantic creates weak trade winds, which allow strong storms to migrate to the coast.
3. Lack of warm water off South America coast reduces upper air wind flow, which is necessary to "blow" storms out to sea once they approach the U.S. East Coast.

WHAT IS THE PREDICTION FOR THE MID-ATLANTIC COAST?

Here's how I will break it down:

Texas to Louisiana: I think there is a high risk of a landfalling hurricane by August due to weak steering winds up above.

Louisiana to Miami: Lesser chance of hurricanes striking this area for the same reason... most storms are going to have a westward track, thus sparing the west coast of Florida to New Orleans.

Miami to Charleston, SC: I believe there is an equally high risk of a major hurricane landfall (Category 3) in this region by late September, when conditions are most favorable due to warm water.

Charleston, SC to Cape May, NJ: Persistent warm water in the western Atlantic and lack of a cold spring will enable a near-major hurricane (Category 2) to make landfall in this region between late August and mid-September.

Cape May, NJ to Maine: This region may experience one or two landfalling tropical storms late in the season, by October, if steering currents in the Atlantic remain weak.

WILL THERE BE ANOTHER ISABEL?

Based on these indications, I believe there is an equal chance that the Mid-Atlantic will experience the direct or side effects of a major hurricane before September 10. The situation this year may be similar to what happened in North Carolina in 1996, when 3 hurricanes followed similar paths on or along the coast.
With weak steering currents, it is more likely that tropical systems this year will approach the coast from a diagonal path as Isabel or Hugo (in 1989) did, instead of "curving" up the coast.

If you live in a low-lying area that was affected by Isabel, you should spend time this spring and summer thinking about what changes you should make to your property to prevent damage from occuring again were there to be flooding, high winds or heavy rain.

Remember that Isabel, though very destructive, missed traveling directly up the Chesapeake Bay by a mere 50 miles. Were that to occur, a strong Category 2 storm (winds 110 mph) reaching the mouth of the Bay, and maintaining access to the Bay's warm waters... it is not inconceivable that major cities such as Richmond, DC and Baltimore would experience sustained winds at hurricane force (74 mph+) as well as a storm surge in excess of 5 feet. Damage would be, on our terms, catastrophic. With hundreds of thousands of trees down, disruption to schools would last two weeks. The cleanup would take months, if not years in some areas. And this is not an exaggeration, this is what we lucked out at missing due to Isabel's altered path.

Be scared? No. Be Prepared? Yes. You have 4 months to get ready. If this forecast turns out wrong, I will be pleased. Let's hope it does.
5/4 EVENING COMMENT: "Looks like we've made it...."
- Barry Manilow

Yes, that takes some of you back a few years I'm sure.

What I'm referring to is the weather for the week ahead and into the weekend. (Hmm.. big surprise there, since this is a weather forecast site.)

The front has passed, the High pressure has arrived, and this is why I love this time of year:
- Each day is getting a little warmer (theoretically)
- Each day there is a little more light (later sunset, earlier sunrise)
- Each day features a little more green, flowers, etc.
- Each day is one more closer to summer vacation!

SO we are in for another nice stretch of good days... I think all the way through the weekend. Yes, some scattered showers and thunderstorms may interrupt some on Saturday, but the warmth will counteract any rain that falls.

Wednesday to Friday: Warmer, less wind, more sun. Highs near 80 by Friday in Baltimore, in the 70's in PA. No rain in sight.

Saturday to Monday: Still warm Sat and Sun until the next front passes. As you would expect the heat will build a little each day, as will the humidity. So I think we will see low 80's all the way through to and including Monday. However, I don't think we'll see a return to the sticking, wring-out-your-shirt humidity we say last week. This is a cooler, drier pattern, so it will take longer for the high to "moderate" and start pumping that Gulf/Atlantic moisture in.

Things will deteroriate by Wednesday, and possibly another vigorous cold front will smash on through. But you know what is waiting on the other side of it... Another round of sunny weather!

So enjoy this time of year, cause it looks like so far we made it without the occurance of any long-drawn out wet, rainy weather produced by stationary fronts.

Next post will be early next week as we see if this pattern will hold on or be replaced by something else.