Copious amount of moisture for parts of Southeast but no development seen with 92L

Radar image showing the large amount of rain across portions of the Southeast

Radar image showing the large amount of rain across portions of the Southeast

There is an awful lot of rain spreading across portions of the Southeast this morning but it’s not associated with the disturbance in the Gulf of Mexico – at least not directly.

Looking at satellite imagery, it is easy to tell that 92L has not become any better organized over night. The energy is not focusing around the weak low pressure center and continues to be spread out. As long as this continues, the system will not develop.

The pattern we’ve seen in place across the Southeast for the past several days will persist through the weekend with a change finally coming early next week. The front hung up across the area will fade and a return to a more typical summertime pattern will ensue. However, all of the rain that has fallen and that is still coming presents a problem to consider for later on: what if we get a tropical storm or hurricane landfall in this area over the next few weeks? I am concerned about the flood risk for the Southeast should a tropical cyclone pay a visit. So far, there’s not been any risk of that since Alberto back in June. We are coming up on the peak time of the season and there is a lot of talk in the hurricane forecasting world of a busy period coming up as the overall pattern seems to be heading towards one more conducive for development. We’ve seen a lot of rain across a good deal of the Southeast this summer. Rivers will be swollen and the ground saturated. Let’s hope this is not a set-up to a major flood event as we progress through the peak of the season.

In the east Atlantic, Erin remains a weak tropical storm as it fights the dry air still in place. This is not much of a surprise and I think it won’t be too much longer until we see the dry air ease up and the real meat of the season kicks in. In fact, another strong tropical wave is emerging from the coast of Africa now with potential for development over the next several days. At least for now, there are no threats for land areas to worry about.

I’ll post another update this evening concerning 92L and the rest of the tropics.

M. Sudduth 8:57am ET August 17

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Erin of no concern, 92L has small window of opportunity to develop while the pattern begins to look very busy

Model plots for 92L in the southwest Gulf of Mexico

Model plots for 92L in the southwest Gulf of Mexico

There’s a lot to talk about this Friday so let’s get right to it.

First up, TS Erin continues to track WNW over the open waters of the east Atlantic but it is really beginning to struggle against the dry air. Add to this the fact that water temps where Erin is are marginal for supporting deep convection and the future of the storm does not look good. It won’t matter as Erin is forecast to move farther out in to the Atlantic, away from any land areas, and never be of concern.

Meanwhile, 92L has a small chance this weekend to become a tropical depression or weak tropical storm in the Gulf of Mexico. Upper level winds are not very supportive for development but, depending upon the track of the low, it could encounter an environment that would allow for some strengthening.

This system is complex and not typical of a potentially developing mid-August tropical system. Most of the heavy weather is located to the north and east of the center and is not wrapping around with distinct banding like we see in a more classic tropical storm structure. This should keep what ever strengthening that does manage to take place at a minimum.

Computer model guidance suggests a track towards the western Gulf of Mexico but I am not so sure that anything would be left to reach land. Most of the more advanced models break the system up over the next few days with minimal impact to land. Maybe we can get a little moisture to move over to Texas where they could use the rain – we will just have to wait and see.

ECMWF forecast for the MJO showing a very favorable pattern evolving over the next few weeks

ECMWF forecast for the MJO showing a very favorable pattern evolving over the next few weeks

The upcoming pattern looks very active as we head towards the end of the month and in to September. We have seen a very notable lack of upward motion or MJO activity in the Atlantic for the past several weeks. This has resulted in quite a bit of sinking, dry air across the tropics and we’ve seen the results of that with anemic tropical storms and no hurricanes forming. It looks like that will change in the coming weeks. The reason is the forecast for the MJO or Madden-Julian Oscillation which is looking more favorable for the Atlantic as we progress through the next several weeks. This should result in a dramatic uptick in activity across the Atlantic with the chance of seeing a hurricane develop as well. It will take a few more days for the pattern to evolve but the signs are pointing to a very busy end of the month and especially September.

I’ll post another update concerning 92L early this evening.

M. Sudduth 8:05am ET August 16

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No worries of development from 92L as Erin forms in east Atlantic

TS Erin track map over the eastern Atlantic

TS Erin track map over the eastern Atlantic

It looks like the disturbance in the Caribbean Sea, also known as invest 92L, will amount to pretty much nothing – at least in terms of tropical cyclone development. There is still a copious amount of deep tropical moisture associated with the system but it is not concentrated around a common area of low pressure. The energy is spread out over too large an area for 92L to really come together which is precisely what the more reliable global models have shown the past few days – especially the ECMWF.

The NHC still gives the system a high chance, 60%, of development once it reaches the southern Gulf of Mexico some time this weekend. Looking at upper level winds and other factors, I do not see this system doing much. The main issue will be continued heavy rain for portions of the northwest Caribbean, including the Yucatan peninsula. Beyond that, I see little to worry about as we approach the weekend.

Meanwhile, TS Erin has formed in the far eastern Atlantic from TD #5. The deepest convection lies to the south of the center with quite an impressive moisture feed streaming in from the southwest. Erin is expected to slowly strengthen as it moves generally WNW over the open Atlantic.

Ocean heat content map with Erin plotted

Ocean heat content map with Erin plotted

Right now, Erin is located in an area of fairly low ocean heat content. The forecast track takes the storm over a region of less ocean heat content where only the surface of the ocean is warm enough to support tropical cyclones. Once the circulation agitates the water, it could weaken the system some or at least slow down the intensification process. If Erin can survive past 50W longitude, then ocean heat content values increase dramatically and it could have a chance to strengthen once again.

The other issue will be fairly dry mid-level air still lurking around in the deep tropics. Should Erin lose its connection to the high dewpoint airmass to its southwest, which is helping to feed the convection now, then this too could hamper Erin’s ability to strengthen. All in all, the environment is not all that conducive but it’s not terribly negative either. It will be interesting to see if Erin can survive longer than Dorian or Chantal before it. With it being mid-August now, one would think that climatology would kick in and allow for longer lasting Cape Verde tropical cyclones.

The forecast track bends Erin back to the west with time, mainly due to the anticipated weakening of the storm. This would make it shallower in the atmosphere and thus the lower level flow would be the primary steering mechanism – like a small sailboat versus a larger one with a huge sail to catch any wind that may be out there. Erin is many days away from affecting the Lesser Antilles if were going to do so at all.

The remainder of the tropics are quiet and this finally includes the east Pacific. I’ll have more here this evening.

M. Sudduth 9:16am ET August 15

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