Saturday, August 18, 2012

Tropics Continue To Perk Up

Gordon, at the top of the graphic below, is now a hurricane in the middle of the Atlantic. It will cross the Azores over the next day or so, bringing gusty winds and rains to the island chain as it works towards Europe. It will gradually weaken as it encounters a gradually more unfavorable environment but it could produce some heavier showers in Spain in five to six days.

Closer to home, Helene is near the Mexican coastline of the Gulf of Mexico as a very weak tropical storm and will spread inland today. However, rains associated with the system could linger near the coastline along the Gulf into next week.

For our interests, the item in the bottom circle may be of more interest.  This low pressure center may become Isaac in a few days' time as it pushes westward through the Central Atlantic.  It is days away from impacting anyone on this side of the world but it will steadily push westward, buoyed by the mid level subtropical ridge and guided west through the tropical Atlantic.  It *should* intensify slowly over the next few days and could be a tropical storm early next week.

There's a pretty steep difference between the GFS and Euro regarding intensity and location in about five days' time.  The GFS (top map in the graphic below) suggests a strengthening system approaching the Caribbean Islands' by Wednesday, while the Euro (bottom map) has a weak tropical wave pushing through the Caribbean.  The Euro, in fact, in last night's run does not develop this system at all while the GFS takes "Isaac" and pushes it very close to Antigua and some of the smaller Leeward Islands before taking the storm between Bermuda and the US.

The difference between the two is likely based in the rapid pace of the Euro's depiction. The Euro pushes this system along so quickly that it can never organize vertically in the atmosphere. The surface low is pushed out ahead of any weak mid level circulation center. This was seen in Ernesto (which took longer than advertised to become a hurricane) and also in TD 7/Helene (which didn't become a tropical storm until it almost crossed the Bay of Campeche in the Gulf.

Other "tropics" computer modeling also suggest that the low in the tropical Atlantic will push west as the subtropical ridge holds firm, getting closer to the Leeward or Windward Islands on Tuesday or Wednesday. If the faster paced modeling wins out, we will see this system likely remain weak.  In its wake resides another tropical system that's about to come off the African coast as well.