WTOC Hurricane Center ... 2006 Outlook - WTOC-TV: Savannah, Beaufort, SC, News, Weather & Sports

Will 2006 Be Another Active Hurricane Season
Or More Importantly, Active For Us?

By Patrick Prokop, Meteorologist, WTOC-TV

A Dry Spring

As we close out the season of spring, one must ponder as to what is in store for those “Tropical months” that lie ahead. March , April and May have been extremely dry over our area this spring with only 40% of normal rainfall. (This is with the average of five stations in Chatham County of: the airport, WTOC, Coffee Bluff, Downtown and Tybee). Normal for the three month period is 10.57 inches with the average of the five station totaling only 4.25 inches. The official rain value, which is the one gauge at the airport, was only 2.83 inches for the period which is a scant 27% of normal. However, the long range outlook from the Climate Prediction Center of the National Weather Service is hinting at normal or even above normal rainfall for our area during the summer months ahead. Could this mean a shift in the wind currents allowing more tropical system to move our way?

Normal Rainfall Patterns

Traditionally, most of our annual rains accumulate during the warm humid months of June through September where each month's average is between 5 to 7 inches, as compared to around 3 inches per month during the winter season. November is even less with averages around 2 inches. This above average forecast is hinting at an influx of additional tropical activity.

Prevailing Winds

Savannah is located in a geographical region in which our weather is split, with the winter season under the influence of the "Prevailing Westerlies". These west to east flowing winds in the mid and upper level of the atmosphere causes weather system to advance from the west coast to the east coast bringing in cold fronts and low pressure system to our area from the middle of the country or Gulf of Mexico. The Gulf of Mexico systems bring most of our winter rains, but this year, have been low in frequency, hence the dryer than normal rainfall so far for this year. During the summer months, the large high pressure system in the central Atlantic, known as the "Bermuda High Pressure System" migrates northward. During the winter months, while the center of this high is south of our latitude (32 degrees north), the counterclockwise circulation around it, produce those "Westerly" winds (winds blowing from the west to east). But as the high drifts northward during the summer, the center of circulation passes to our north resulting in the bottom side of the circulation to flow into our area. These "Easterly" winds flow from east to west and bring in weather from the sub-tropical and tropical Atlantic into our region during that time.

These winds are also known as the "Trade" winds. Sailing companies in the 15th through the 19th centuries use wind to power their vessels across the ocean and used these wind currents to deliver their trades, hence the name. Vessels would leave from Southern Europe or Northern Africa and sail across the Atlantic to the Americas within the easterly winds currents. As they arrive in the West Indies, they would turn their vessels northward to flow up the east coast, eventually making it to New York and Boston. From there, they picked up the "Westerlies" and sail back to Europe across the north Atlantic.

It was doom and gloom for any sea captain who navigated his fleet of ships into the core of the large Bermuda high pressure system as he would lose the power of the wind and be stranded in the area known as the "Doldrums" or "Horse latitudes". One of the reasons for this name is because vessels in this area could spend days, or even weeks just drifting in the middle of the Atlantic with their precious supply of fresh drinking water slowly being consumed. Any livestock, particularly horses, were sacrificed in order to save the water for human consumption and the livestock was tossed overboard, hence the name, "Horse latitudes." Another explanation is at these latitudes, when at shore, they would hitch their vessels to horses to pull them up the coast until they would get back into favorable winds. (Believe what you will).

The Steering Winds ... The Circulation of the Bermunda High

It is these same winds that dictate the flow of tropical weather systems that approach our area. Last year, the Bermuda high pressure was a bit stronger than usual and the western edge extended past our coast and entered into the Gulf of Mexico. This drove numerous tropical systems into the Gulf and then forced them northward into the southern Mississippi Valley and the Florida panhandle. If the high was even stronger, it would have driven the storms into Texas and Mexico or even Central America (and a few did wander south of Texas into the Mexican and Central American coasts). If the Bermuda high pressure system is weak, tropical system would curve northward before reaching the east coast of the US. This is usually accompanied by the "East Coast Trough" which is a strong SW to NE flow of winds over the east coast of the US. When this trough is present, no storms would make landfall in our area and most curve northward and remain out at sea. (This same trough aided the sailing vessels to travel up the coast where they eventually would pick up the westerlies and head home to Europe.)

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Then you have the difference of the two scenarios where the Bermuda high is not too strong or too weak and the "East Coast Trough" is non existent. This is the time to BEWARE. It is during this pattern when tropical system are most apt to pass over our area and it could be anything from a tropical wave to a full fledge hurricane. Lately, we have seen the strong Bermuda high and the weak Bermuda high. Both of these patterns steer storms away from our coast.

The Big Question

So the question; "Will this be an active storm season" or more appropriately, "Will this be an active storm season for us"? The results will be determined on the position and intensity of the Bermuda high pressure system when storms are roaming the tropical seas.

The prediction from the tropical team of Dr. William Gray of Colorado State University is calling for 17 named storms. The prediction from NOAA is 13-16 named storms. Last year was the most active ever with 27 named storms, normal is 10. The prediction for this year is not to be as active as last year, however, with a prediction of possible 17 named storms, it appears it will be another stressful season. Oh, one more thing, the prediction for last year's storm season was for 15 named storms.

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