92L has the spin but lacks the organized convection

Vorticity chart showing the spin (red blob) associated with 92L in the Gulf of Mexico

Vorticity chart showing the spin (red blob) associated with 92L in the Gulf of Mexico

A quick post about 92L this evening. As you can see by the 850mb vorticity map that I have included here, the system has the spin or vorticity that it needs to thrive. What’s lacking is organized deep convection wrapping around this spin. Without the convection wrapping around the center of circulation, which is clearly seen in satellite imagery, the low pressure area will remain fairly weak.

The shear values are not too strong but apparently are just strong enough to displace the main area of showers and thunderstorms off to the east and north of the center. Until and unless this shear lets up more, 92L won’t develop much despite sitting over very warm Gulf of Mexico water.

Computer guidance points towards Texas or northern Mexico but this is for the center. The worst weather, for now at least, is located well away from the center. It’s possible that Texas could see some beneficial rain from this system but how much and where is tough to say right now. The low should move steadily off to the west or west-northwest over the weekend.

We’ll see what the NHC says about this feature tonight and then see how it looks tomorrow morning. The Hurricane Hunters can get out there fairly quickly if need be should things look more interesting in the morning. For now, it’s something to watch but poses no major threat of impact over the weekend.

I’ll post more here in the morning.

M. Sudduth 4:35pm ET August 16


Erin Now a Depression, Gulf System Disorganized

As of 11:00AM this morning, most of the deep thunderstorm activity with what is now Tropical Depression Erin has vanished.  The culprit is dry air sitting over the majority of the tropical Atlantic, which has essentially put a lid on convective development – much like throwing a glass of cold water in a boiling pot of water.  Here’s a water vapor image, showing what is left of Erin and the stable environment out in front of the former tropical storm:

Tropical Storm Erin and the Atlantic

Tropical Depression Erin (pink arrow) and the dry environment ahead as seen in Water Vapor imagery


Meanwhile, closer to home, a low level swirl has emerged into the southwest Gulf of Mexico.  This is what is left of the tropical system we’ve been watching over the last few days.  Again, dry air and strong upper level winds have created an unfavorable environment for development in the Gulf, even though a distinct low-level swirl can be seen in visible satellite imagery:

Visible image of 92L in the Gulf

Tropical disturbance in the Gulf of Mexico as of Friday morning. Note the low level swirl, free of thunderstorm activity.


As long as the environment continues to be hostile like this, it will be very difficult for either system to get better organized.  However, since the Gulf system is close to land – it will continue to be monitored for signs of development over the next few days, and recon is standing by to fly into the system if necessary.

Looking forward a few days, the large-scale environment is about to change across the tropical Atlantic.  A large-scale atmospheric wave called the MJO (or, Madden-Julian Oscillation), is expected to move into a phase which will enhance upward motion in the Atlantic next week.  Generally speaking, this creates an environment with less dry-air, lower surface pressures and more shower and thunderstorm activity across the deep tropics.

As noted in the latest update from Colorado State University, it is possible we will see one or more systems develop in the second half of August as we quickly approach the peak of the Atlantic hurricane season.

M. Watkins – Friday, 12:31PM EDT 8/16/2013


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