Sunday, May 20, 2012

Wake-Up! It's Hurricane Season

The official start of the 2012 hurricane season is not until June 1, but Mother Nature decided to start it a little early.  Tropical Storm Alberto formed Saturday afternoon off the coast of South Carolina.  It was centered at that time about 140 miles east-southeast of Charleston, South Carolina with maximum sustained winds of 45 mph.  A ship report indicated that it was a little stronger shortly after the official release and it was bumped up to 60 mph.

Image Credit: NEXSA
Satellite photos showed a tight circulation yesterday morning with convection west of the center.  It stated that way much of the day and the photo to the left shows the storm as of early afternoon before the first advisory was released.  The center of the storm was just under the high clouds with good convection near the center.  Click on the image to see an enlarged view.

The system was drifting to the southwest at about 3 mph, but it began moving west-southwest at about 5 mph overnight.  The movement was largely the result of a high pressure system over the eastern U.S.

Most of the rain and higher winds were well offshore, but a Tropical Storm Watch was issued for the low country of South Carolina as a precaution due to the closeness of the storm.  There is some concern that the immediate coast could see tropical storm force winds.
Initial computer model forecasts indicated that the storm would move slowly southwest, then meander, and eventually move off to the northeast.  That continues to be the forecast from the early guidance this morning (see the forecasts below).

Early track guidance from the computer models Sunday morning.  Click on the image for an enlarged view.  Image Credit: NCAR.
Alberto is expected to maintain its intensity and slow down today.  The system will likely meander tonight off the coast of Georgia and South Carolina.  It should begin to move northeast tomorrow and gradually increase its forward speed becoming post-tropical in a few days.

There will be impacts to the South Carolina coast.  The immediate coast will see stronger winds, but they should be below tropical storm force except in a few gusts.  Waves will be higher and there may be some erosion.  Showers will move inland occasionally until the system begins to move to the northeast.  The rain will move offshore once that begins.

A Sign?

Does this indicate that the upcoming season is going to be active?  Probably not, although the National Hurricane Center will issue its forecast on Thursday and the Tropical Meteorology Project at Colorado State University will update their forecast on Friday, June 1.

Image Credit: NOAA/NESDIS.
Alberto formed on the tail end of a cold front from a low pressure system that was stalled off the coast.  Sea surface temperatures near the Gulf stream were marginal, but it was able to acquire tropical characteristics.  However, the temperatures were not anything unusual for this time of year.

The chart to the right shows sea surface temperatures as of May 18 (click on the image to see an enlarged view).  A temperature of 26C is usually necessary for tropical cyclone development.

Storms forming in May are rare, but not unheard of.  Usually they form in the Caribbean Sea or Gulf of Mexico and move north.  If Alberto had formed in this area, it might be a sign of a busy season ahead.  However, it formed on the tail end of a stalled front which is a random event and not a sign of things to come.