We have three “invests” in the Atlantic this evening, all of which may develop. Lets first focus on Invest 90L, out on the eastern Atlantic:
http://img523.imageshack.us/my.php?image=invest90dr5.jpg
Currently there appears to be a weak swirl just to the east of the heaviest convection. So, this system is not terribly well organized but if convection continues to fire as it is now the circulation will organize more and further intensification will occur. But, is the environment favorable for this?
http://img523.imageshack.us/my.php?image=eastatlanticshearsl9.png
http://cimss.ssec.wisc.edu/tropic/real-time/europe/winds/wm7shr.GIF
Currently, shear is fairly low over the system, 10-15 knots. This will not accelerate development but it is low enough to allow further slow development, if other factors contribute:
http://img515.imageshack.us/my.php?image=sstspp7.png
Currently, it is over marginal SSTs for development, 27-28 degrees Celsius…again…this will not cause rapid development but will not prevent it from slowly occurring if other factors fall in place.
http://img127.imageshack.us/my.php?image=saldd2.png
http://cimss.ssec.wisc.edu/tropic/real-time/wavetrak/winds/m8split.html
As you can see, Invest 90L is riding just out ahead of a very strong burst of the SAL (Saharan Air Layer). This, will also prohibit rapid development, however, this system is moving quite quickly so may stay just ahead of the SAL. So, right now all factors are marginal development, so I am calling for slow development. I believe this system may become a depression as early as Sunday and probably will by Monday.
As for where this thing will go, there is a strong subtropical ridge to the north of it. This will steer it to the WNW over the next few days. Once it gets near the Bahamas by Thursday, it will start approaching a large weakness in the ridge due to a large trough over eastern North America. This should allow this system to curve out to sea, perhaps near Bermuda but away from the US, if it does develop. More on future strength:
Down the road, it appears that this invest may encounter higher shear due to a band of sub tropical jet stream energy on the southern side of a large ridge, perhaps again slowing any development.
http://img127.imageshack.us/my.php?image=futurelowlevelsteeringstn9.png
As you can see on the above image from the GFS (which doesn’t even have the system at this point) that the flow will be very brisk from the ESE at the mid levels near where the system will be around this time. This could very well tear the system apart. Right now, the few models that have run on this are showing a strong TS/weak Hurricane by Thursday. Right now, I do not know that this will come to fruition. I am calling for slow development to a weak tropical cyclone (TD/weak TS) through Tuesday, but then a halting of development and perhaps a weakening thereafter through at least Friday. To be honest, I do not know if this will be around next weekend. So, to me this is a watch and see just incase but don’t expect anything big system.
The next invest on our list is Invest 91L in the northern Gulf of Mexico. This one is much closer to home and bears watching:
http://img127.imageshack.us/my.php?image=invest91pb1.jpg
Over the last few hours, a weak spin has been evident on the visible satellite, near or possibly under the deep convection. This system is not what I would call on the verge of becoming a depression, but is over a fairly good environment for strengthening and already has deep convection and some kind of at least mid level, if not low level circulation.
http://img515.imageshack.us/my.php?image=westatlanticshearyg5.png
http://cimss.ssec.wisc.edu/tropic/real-time/atlantic/winds/wg8shr.GIF
As shown above, this system (which is associated with an old frontal boundary) is under low shear, 5-10 knots. This is favorable for development. However, it should be noted that there is an upper low near Cuba. This is causing higher shear to the southern portion of the system and may restrict outflow to the S-SE quadrants of the system.
http://img515.imageshack.us/my.php?image=sstspp7.png
Invest 91L is also over warm waters, 28-29 degrees Celsius. This is also favorable for development. There are a couple of inhibiting factors though, both of which can be seen on water vapor imagery:
http://img515.imageshack.us/my.php?image=gomwvxu2.png
The upper low mentioned above is causing some shear on the southeastern quadrant of the system. This may slow development some. This upper low may also limit outflow for the rest of the weekend. But, the upper low should get out of the way by Monday. There is also some very dry air to the north of the system. This is also limiting outflow to the northern quadrant of the system. This will likely not go away at all over the next few days. So, the environment is marginal for development currently, but will become more favorable by Monday, but some dry air may still be a problem over the coarse of this systems lifespan. So, I believe slow organization will continue through Sunday, perhaps into a depression as early as Sunday evening. After Sunday, there is no reason why slow to perhaps moderate intensification won’t occur until Tuesday, when this system will run into Texas. So, I expect a moderate tropical storm (perhaps as strong as 50-55 knots) by the time this hit Texas on Tuesday. As for where exactly it will go, there is a decent ridge to the NW of this invest. This ridge will slide east over the next couple days. This should steer Invest 91L to the SW in the short term, then to the west late Sunday through Monday, and then as the ridge becomes farther east of the system by Tuesday, a turn more to the NW seems logical. This would put landfall somewhere between Corpus Christi and Houston Tuesday afternoon. I will have a full projected path once this thing is named.
http://img515.imageshack.us/my.php?image=invest99bz1.png
As for Invest 99L (above) it has a well-defined LLC, but there is no deep convection, because this thing is encountering very dry air and increasing shear. No development is expected as this system continues to the WNW over the few days.
