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Tropical Weather Outlook

By: MAweatherboy1 , 12:11 AM GMT on August 09, 2012

We're definitely to that time of year now. Hurricane season is nearing its peak, and after a quiet July we have already seen two storms one week into August. There are three main features tonight. The first of those is Tropical Storm Ernesto. Ernesto spent most of its life failing to live up to expectations, but that all changed yesterday as Ernesto strengthened significantly from a moderate tropical storm to nearly a Cat 2 hurricane prior to landfall on the Yucatan Peninsula. Ernesto is now emerging into the Bay of Campeche. It weakened quite a bit over land as would be expected, but it retained a solid overall structure so it should strengthen some in its short time over the BOC. Its current maximum sustained winds are 50mph as of the National Hurricane Center's 8PM EDT intermediate advisory. It is moving W at 7 mph, and this general motion with a bend more to the WSW should continue until dissipation over Mexico on Friday. As Figure 1 shows, Ernesto will not be over water long, so I don't see a second peak any higher than 65mph.

Figure 1: Visible loop of Ernesto, showing how it is now emerging over water once more.

The second feature being watched is Invest 92L. 92L is currently located about 950 miles W of the southern Cape Verde islands according to the National Hurricane Center. The NHC is giving it a 50% chance of development in the next 48 hours. 92L's window of opportunity is short, as SHIPS indicates wind shear will increase to 20 or more knots beyond 48 hours. Even now conditions are not ideal as there is a good deal of dry air in front of the system. Nonetheless, organization has improved today, so some development is possible. I think's its pretty much a coin flip on whether it happens or not, so I'll play it safe and side with the NHC and give 92L a 50% chance of development in the next 48 hours.

Figure 2: Invest 92L. Deep convection is less than impressive, but structure is improving.

The third and final area of interest tonight is a vigorous tropical wave over Africa that will be emerging over the far eastern Atlantic in less than 2 days. There are more questions than answers with this system. The most aggressive model for development has been the GFS, with the ECMWF also showing some development. There have been a lot of inconsistencies however, especially in the GFS. Runs from a couple days ago were fairly consistent in showing this wave becoming a powerful hurricane and threatening the East Coast. Recent runs have been much more inconsistent, with the last 4 runs showing a Southeast storm, a Northeast storm, an out to sea storm, and nothing at all on the most recent run. Based on what a powerful wave this is I do think we will see development, and I still believe there is a good chance this system will end up being a Cape Verde hurricane. However, I think the most likely scenario for this storm is a recurve out to sea. I consider myself pretty good at reading between the lines on the models. The 6z GFS showed a big storm for the Northeast, but by the end of the run the dominant high pressure system had backed way off to the east. The generally more reliable 12z run painted a very accurate potential scenario in my opinion as it backed the high up enough to allow for a recurve with room to spare for the US. 18z tonight was not at all accurate with intensity in my opinion but once again had the idea of moving the high back. In addition, the GFS ensemble means and individual members have been showing the high moving back. So while the GFS has shown a lot of landfalling or nearly landfalling systems, I think it will begin to become more consistent in showing a recurve. The ECMWF did not pick up on development as fast as the GFS, but it has now and it is also showing the high getting pushed way back, maybe even a little too far, allowing for storms to recurve very early on. The UKMET and NOGAPS have also shown signs of the high weakening and/or pushing back. Making predictions for so far out is risky, but I have higher than normal confidence for a long range forecast that the overall pattern this year will favor recurving storms for anything that forms around or before 40W. This means that the biggest threat for US landfalls will come from storms forming in or close to the Caribbean and in the Gulf of Mexcio. Of course, the models could flip back and end up keeping the high where it is or the high could weaken and move back briefly before building back in, but I just don't see that right now. While I;m on the subject of long range predictions, I think my forecast of 12 named storms this year is pretty much on track, or it may be just slightly too low. I think we could easily see Gordon, Helene, and Issac in the rest of this month, then Joyce, Keith, and Leslie in September, and one or two more storms in September or October. It definitely looks like our biggest threat will be from home grown systems.

Thank you as always for reading. I'd love to hear your thoughts on what you think the year's dominant pattern will end up being. Enjoy the rest of your week!

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

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1. GeorgiaStormz
12:18 AM GMT on August 09, 2012
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About MAweatherboy1

Average 20 year old weather nerd. Plymouth State University Meteorology, Class of 2018. NOAA Hollings scholar. Summer 2016 intern at NWS Boston.

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