Monday, July 08, 2013

Watching Chantal

Tropical Storm Chantal formed last night in the central parts of the Atlantic Ocean and is located a good distance to the east of the Caribbean Islands. However, it is quickly moving west and west-northwest at around 25 mph, which is a pretty fast pace for a tropical cyclone and the impacts from Chantal will begin to reach the Caribbean Islands late tonight and early Tuesday, mostly in the form of squalls of rain and wind.

Model guidance suggests a steady west-northwest track for at least the next three days before some guidance tries to turn this system to the north in response to an upper trough that nudges across the eastern half of the US.  The operational GFS and Euro have waffled around a bit with track, shifting from a Caribbean-centric track on Sunday to one that traverses north of the islands on the early morning runs this morning.

A few items to talk about with regards to the storm over the coming days.  First, the presence of dry air out ahead of the storm system as it pushes west and northwest. This could slow some of the development of the storm should the circulation ingest some of the surrounding dry air around the storm.  This is something to keep an eye on as this system develops.  You can see the plentiful dry air out ahead of the storm until the Caribbean.

Second, the potential track.  Should the system push west-northwest through the Northeast Caribbean the question of land interaction rears its head.  Land will also prevent the storm from strengthening due to causing friction and disrupting the center of circulation within the storm.  Also, most guidance is varying widely on the final track with this system.

Also, some models do indicate the possibility of wind shear becoming a factor with the storm late this week. This isn't a lock but there is some possibility of it occurring as the upper high in the Caribbean pushes farther west and a bit of wind shear develops between the upper high's circulation and that of an upper trough in the Atlantic.  If Chantal takes a more northern track, the possibility of wind shear impacts will increase.  Add to this the potential impact of land interaction should the system cross over the Caribbean islands and Chantal has some obstacles to potential strengthening ahead.

All of those negatives may prevent this system from getting too cranked up.  That said, the atmosphere beyond the dry air issues over the next three to four days is relatively favorable so continued organization and strengthening with this system does seem plausible...although the dry air may slow the rate of intensification a bit.   The question turns into what happens this weekend and into early next week with a trough that may set up across the East Coast or inland...does this system, if it remains weak, stay south of that trough or does the storm system get pulled towards it and to the north and towards Florida or the Gulf?  There are still a lot of questions to be this point, our risk is low from this system at this point in terms of direct impact.