Tropical Update 8/15/11
Tropical Storm Gert
Gert is a 60mph tropical storm and is passing east of Bermuda this afternoon. Gert will turn more to the northeast later today and move out to sea. The only suspense left with Gert is to see if he becomes our first Atlantic hurricane of the season.
According to Dr. Ryan Maue’s site http://coaps.fsu.edu/~maue/tropical/the accumulated cyclone energy index is only at 11.8 units through this morning for the year. The typical normal amount through this time period is 14. Thus even though we are well ahead of schedule for named storms with 7, we have yet to see a hurricane and thus the low ACE number.
Some of the left most models do pass close to eastern Newfoundland in a few days, so that will have to be watched.
This system has been around for several days and until recently has shown very little intention of getting its act together. However over the last 12 hours or so the convection has intensified and the system looks more healthy than it has since it first emerged from Africa.
In looking at surface obs and ship obs in just east of the Islands, I see pressures of around 1011mb and no indication yet of a close circulation.
The global models want to keep this system weak and on a due west coast into Central America. This may be because the system is so weak it is steered by the low level flow and also gets partially absorbed into a monsoonal trough in the southwest Caribbean. The 12z NHC simple hurricane models take the system further north into the western Caribbean Sea near Jamaica and just east of the Yucatan. The 12z intensity models show steady strengthening with this system becoming a hurricane in 3-4 days. The new 12z HWRF is coming in as I write this and it looks to be taking a track similar to the 12z simple NHC models.
If this system can develop into a depression or tropical storm in the next couple of days, it will likely end up where the HWRF and NHC models have it in the northwest Caribbean Sea by the end of the week. If the system is very slow to develop and may plow into Nicaragua or Honduras in a couple of days. The global models show a trough in the southeast US late this week which will have to be watched to see if it weakens the ridge enough to allow this system to gain latitude and possibly move into the Gulf by this weekend, assuming it is a cyclone. Beyond that though, the models also seem to want to rebuild a ridge over Texas and the southern Plains which may steer anything in the Gulf towards Mexico. However, the pattern over the US is going to favor frequent troughs into the Great Lakes and eastern US for mid to late August, so we can’t simply write off any storm this far off.
There is a very nice looking tropical wave off of Africa today. The global models all track this feature westward this week with the ECMWF and GFS showing development. The latest run of the 12z GFS takes the storm into the Caribbean, Gulf, and into New Orleans. The 00z ECMWF had the system further north moving to around 22N/62W in 10 days.
This is of course meaningless this far out. The pattern appears to be heading towards a ridge in the west and a mean trough near the Mississippi River Valley as we head into late August. At the same time a western Atlantic Ridge (Bermuda High) may be stronger than normal and stretch west towards the east coast. If this is the pattern that develops, this will strongly favor systems that stay far enough south threatening the southeast coast, Florida, and the eastern Gulf. So this is a dangerous jet stream pattern, if realized, we are heading into for the heart of the hurricane season.