Complicated forecast for 99L, easy one for 90L

Convection or thunderstorm activity has increased substantially over night with 99L. You can also see here that invest area 90L is well on its way to becoming a tropical depression.

Convection or thunderstorm activity has increased substantially over night with 99L. You can also see here that invest area 90L is well on its way to becoming a tropical depression.

As I mentioned yesterday in my blog post, it looks as though invest area 99L will continue to struggle and not be much of an issue for land areas anytime soon. However, the recent development of convection or deep thunderstorms suggests that perhaps things are changing, even if only a little bit right now.

The very latest info from the NHC indicates that development chances are going up slightly – now up to 50% in the five day time frame. It appears the warmer sea surface temperatures and a better overall environment are slowly playing in to favor of this system developing.

One aspect that I cannot get over is the large size of the overall envelope of energy with 99L. It is not a small, weak and fragile tropical wave. It’s quite the opposite in fact with a large area of circulation and deep precipitable water profile. What this means is that this feature is not just going away despite the marginal conditions in the atmosphere. As we have seen in the over night hours, convection actually began to increase and persist with 99L and this morning, the satellite shot indicates continued slow organization. If this continues, we may have something to deal with in the coming days as it moves generally WNW towards the Caribbean Sea. Interests in the northern Leeward Islands, Puerto Rico and Hispaniola need to monitor 99L closely. At the very least, it could bring periods of heavy rain and gusty winds as the week progresses.

5 day tropical weather outlook grpahic showing the likely development areas and tracks for 99L (orange) and 90L (red)

5 day tropical weather outlook grpahic showing the likely development areas and tracks for 99L (orange) and 90L (red)

The longer term outlook for 99L is tough to call right now. So much is based on whether or not it goes on to fully develop in to a tropical depression or a storm. Generally speaking, the weaker and shallower in the atmosphere a system is, the farther west it tracks under the low level flow pattern. For now, the NHC is showing a potential track area extending up in to the Bahamas by later this week. There are some indications that the track could be farther south but we will have to wait and see about that. Very warm water temps await this system and if conditions improve aloft, it could be an interesting week ahead with not much time to prepare should this threaten land areas from Florida northward to the Carolinas. While this is not indicated by any particular solid forecast right now, it goes without saying that the closer this gets to the U.S. the shorter the time frame for reacting will be.

As for the short term, I want to emphasize again that this large wave energy should bring heavy rain and squalls to portions of the Caribbean Sea over the next few days. Do not count 99L out just yet. It’s late August, water temps are very warm and we have a large system heading westward. Let’s not get caught off guard.

Meanwhile, what should become the season’s next hurricane, and a strong one at that, is developing in to a tropical depression right now far out in the eastern Atlantic.

The NHC should begin advisories on TD7 later today. The model guidance is in excellent agreement that it will strengthen quickly in to TS Gaston and eventually become a hurricane. I see nothing to suggest that this will ever affect land but it will add to the seasonal ACE score, something that is tracked to help size up the quality of the storms/hurricanes that form.

In the eastern Pacific, a pair of disturbances well off the coast of Mexico both have a shot to develop as they move west to west-northwest out in to the open Pacific. No other areas of concern are seen over the next several days for Pacific Mexico or the Baja peninsula.

I’ll have more here in my daily video discussion. Also, you can follow all of my updates using our app, Hurricane Impact, available in the App Store. This blog, social media posts, video updates and field mission reports/data all goes in to the app. We’ve had it since 2012 as a great way to keep up with HurricaneTrack.com info while on the go. Search “Hurricane Impact” on the App Store.

M. Sudduth 8:15 AM ET Aug 22

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About Mark Sudduth

Greetings! I am Mark Sudduth, the founder and editor of HurricaneTrack.com. The site began in 1999 as a way to post info concerning tropical storms and hurricanes for any interested visitors. Little did I know how big it would become in the years since. Now, we have millions of visitors from all over the world who have come to rely on the site as a no non-sense, tell it like it is resource for all things hurricane related. We are supported by a combination of corporate sponsors and our loyal Client Services members who subscribe to premium content on our sister site, premium.hurricanetrack.com. I am married with six energetic and intelligent children and live in southeast North Carolina. I graduated UNC-Wilmington in 1995 with a BA in Geography and have studied the effects of hurricanes on our society ever since.
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