98L to affect the leewards but not horribly strong; Watching Caribbean in long range

Please note that these tidbits do NOT reflect the official forecasts of the National Hurricane Center, and should not be taken as such. While tropical cyclones exist in the Atlantic, the official NHC forecasts will be posted in the lower part of this blog. Please refer to those when making decisions, and heed the advisories and evacuation statements of your local National Weather Service Office.

If you can, playing the video in HD makes it much easier to see things. The video will play in low quality by default. If HD quality isn't available, then it will be in a few minutes. Let me know if you have problems with the video, and please feel free to ask me any questions regarding what I talk about in these tidbits, or about the weather in general. You can post in either of my blogs or on Youtube. I will do my best to answer. Thanks for stopping by!

Find me on Youtube          Find me on Facebook (also on Twitter)



We have a new invest in the central Atlantic, designated 98L. This is an area of monsoonal low pressure which is exhibiting excellent mid-level rotation in a consolidated area of thunderstorm activity. The surface circulation is not quite closed yet, and is lacking pure northerly winds on the western side and pure southerly winds on the eastern side. This is a typical monsoonal convergence pattern. It appears likely that the circulation will eventually close off and make 98L a tropical depression, and I wouldn't be surprised to see it declared one within the next day or two. Environmental conditions look favorable for development during the next couple of days, but as 98L approaches the leeward Antilles, wind shear will probably increase in the face of an upper trough north of the Caribbean which is forecasted to stay in place for at least the next week. This may keep 98L in check similar to how Maria struggled, and at this point it would seem hard for 98L to attain hurricane status. However, wind shear forecasts 5-7 days out are a bit uncertain, and the islands should closely monitor 98L's progress.

As alluded to above, steering currents should carry 98L in the general direction of the leeward Antilles islands. Puerto Rico and Hispaniola may get some more rain from this system, and that's the last thing that Puerto Rico needs after all of the rain they have had so far this season. Even without a big wind event, the rain alone could be devastating. 98L would likely continue northwest into the Bahamas area ahead of an upper trough over the eastern United States, which will likely recurve it eventually. At this point I still wouldn't expect 98L to be getting very strong, and some global models even dissipate it. As far as any threat to the U.S. goes, I wouldn't worry too much about it right now until we see what it looks like in the northeastern Caribbean.

Looking ahead....we're still watching the western Caribbean, southern gulf, and Bahamas area in the long-range. My original target time period of September 15th-25th is proving to be too early, and the development window may be shifting right into the first week of October now, so my timing was a bit off. However, the logic of why development is likely to occur eventually in this pattern still stands, and although we will have to climatologically turn our eyes towards the Caribbean during October anyway, I think that this pattern means there is an above-normal chance of development occurring. The MJO coming back is probably the last ingredient that we need, and it is forecasted to come back to the Caribbean within 15 days. The ensemble means still show a very wet Caribbean with very low pressures in 12-15 days, illustrating the need to be on the watch.

We shall see what happens!

Tropical Atlantic Visible/IR2 Satellite (click image for loop):



Atlantic Tropical Surface Analysis:



200mb Vertical Velocity Potential (green areas represent upward motion associated with the MJO):