Tuesday, June 4, 2013

Is Andrea About To Form?

Early Start

Hurricane season began June 1st and by all accounts it is expected to be an active season.  Is the season about to get underway?  It seems the computers think so.  The vast majority of the computers have been indicating that something could form in the Gulf of Mexico this week.

There was an area of disturbed weather extending from the Yucatan Peninsula northeast into the Gulf of Mexico Monday evening.  Moisture was streaming north from the western Caribbean Sea.  No indications of development have been noted over the past 24 hours.

However, computer models suggest that thunderstorm activity will be on the increase today into Wednesday.  The latest Regional Precision Model (RPM) has a circulation forming in the Gulf north of Yucatan on Wednesday.  The system would then move north curving northeast into the Apalachee Bay on Thursday.

The 72-forecast valid Thursday evening at 00z June 7, 2013.  Click on the image for a larger view.  Image Credit: WSI.

The above model has the system coming onshore late Thursday afternoon and moving northeast toward coastal South Carolina.  That is where the heaviest rainfall would occur.  It could be breezy for the coastal sections, but the system is not expected to be very strong.

Rainfall will likely be the biggest issue with this system.  The European model has well over an inch of rain possible for the Midlands will higher amounts toward the coast.  This model likewise has the system moving out of the Gulf and through the coastal areas of South Carolina.

The ECMWF surface forecast valid Friday evening at 00z June 8, 2013.  Click on the image for a larger view.  Image Credit: WSI.

The timing of this system could be off owing to the fact that it hasn’t developed yet.  There is also some uncertainty on the track.  This will be important for rainfall.  The system must track through the coastal areas inland if the Midlands are to see significant rain.  If the system tracks along the immediate coast or just offshore, then rainfall will likely be light.

It appears from a consensus of the computer models that passage through South Carolina is likely to be on Friday.  Locally heavy rains and flooding are more likely in the coastal areas of South Carolina and North Carolina.

If the computer trends continue and the system develops into a tropical storm, it would be named Andrea.  It may become a tropical storm by Thursday moving inland later that day.  This system is not likely to form in a hurricane, but could still be a problem for the eastern Gulf coast northeast into the coastal Carolinas.

In Its Wake

The weather is likely to improve over the weekend as the system moves up the eastern seaboard.  The chance for rain will diminish, but the high humidity could remain.  Conditions are likely to allow the heat to build early next week.  This combined with the humidity is likely to bring very uncomfortable conditions to the Midlands.  The heat index may become important by the middle of next week for the first time this summer.

All of this has factored into the seven day forecast.  There will likely be refinements in the forecast as events unfold.  However, there is good confidence in the broad picture.  Thus prepare for rain at the end of the workweek and then prepare for a build-up of heat and humidity next week.

The seven-day forecast for Columbia, SC made on Monday, June 3, 2013.  Click on the image for a larger view.  Image Credit: WLTX-TV.