ATL: HERMINE - Post-Tropical - Discussion

[Florida1118]

Starting to believe that the ECMWF is right about this wave. Seems to lack any convection and that is with it being attached to the ITCZ still. It has a nice circulation but I can now see why ECMWF is slow to develop this and by the time it develops it runs into Hispaniola.

Not sure how you're deciding that now. It's gonna be a long couple days if we cancel and hype an invest over and over depending on what the convection looks like during the current hour. It's gonna take it's time; even the GFS only showed this as a broad low for the next few days.

[Hurricaneman]

This was never expected to do much the next few days but its after 3 days where this gets going

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[Weatherboy1]

I'm just glad we have some long-tracked potential systems to watch for a change. As I always annoy my wife by saying when it comes to these things way out in the Atlantic: "We'll know more in 36/48/72 hours" (about where it's heading, whether it will even become a named storm, etc.) Haha!

[LarryWx]

Looking at the 20 6Z GEFS members, virtually all of them wait til about Tuesday, when it is near 50W, to develop at all. Subsequently, nearly all 20 develop this between 50W and the Lesser Antilles Tue-Wed. That makes this more worrisome because an earlier development would normally mean a better chance to be a fish storm.

[Bocadude85]

Starting to believe that the ECMWF is right about this wave. Seems to lack any convection near the center and that is with it being attached to the ITCZ still. It has a nice circulation but I can now see why the ECMWF is slow to develop this and by the time it develops it runs into Hispaniola. If it develops like the GFS shows it could be trouble but right now I would not bet against the ECMWF winning this model battle (lol yes a battle of models).

I have noticed that as of late the Euro will show development initially and then back off on development for a few days and then suddenly the model will start showing development again.

[tarheelprogrammer]

Starting to believe that the ECMWF is right about this wave. Seems to lack any convection near the center and that is with it being attached to the ITCZ still. It has a nice circulation but I can now see why the ECMWF is slow to develop this and by the time it develops it runs into Hispaniola. If it develops like the GFS shows it could be trouble but right now I would not bet against the ECMWF winning this model battle (lol yes a battle of models).

I have noticed that as of late the Euro will show development initially and then back off on development for a few days and then suddenly the model will start showing development again.

Ridge is stronger on the ECMWF correct?

[Blown Away]

At this point, the best analogs are away from land, but there are some legends that came from where 99L is now...

[LarryWx]

http://i67.tinypic.com/xqcehv.jpg
At this point, the best analogs are away from land, but there are some legends that came from where 99L is now...

As I see it, the problem in using these analogs is that they are already TC's near 99L's position. With 99L not progged to become a TC for several days by the GEFS and not at all by the Euro op., these analogs are likely biased to recurve too far to the east since earlier developers tend to recurve sooner.

[Blown Away]

TAFB not predicting much latitude gain or suggesting a Tropical Cyclone through 72 hours...

[tarheelprogrammer]

 https://twitter.com/RaleighWx/status/766680062011682816

[terstorm1012]

agree with that twitter post. If this one stays weak, it'll be one to watch after it enters the Caribbean.

[Blown Away]

WunderBlog®
Dr. Jeff Masters
99L is Set to Strengthen
By: Bob Henson , 4:35 PM GMT on August 19, 2016

Keeping an eye on 99L
Located about 500 miles southwest of the Cape Verde Islands, 99L is a large but disorganized tropical wave, with a broad zone of scattered convection. The wave is located close to 10°-15°N and 30°W and is heading westward. 99L’s low latitude, and the lack of northward component to its motion, means that it is well positioned to head toward the Caribbean. An upper-level ridge to the northwest of 99L should keep it on a low-latitude path for the next several days, and models are in strong agreement that 99L will continue on its general westward trek, which could put it in the vicinity of the Lesser Antilles by around the middle of next week. The track forecast becomes more uncertain by that point, and it’s too soon to tell which parts of the island chain might be affected.

Wind shear is expected to remain fairly light along 99L’s path (10-15 knots), and SSTs should remain in the 28-29°C range over the next several days. Both of these factors favor development of 99L. In its 8 am EDT tropical weather discussion, NHC gave 99L only a 10% chance of development by Sunday, but a 50% chance by Wednesday. The discussion noted another wave coming off Africa over the weekend that has a 30% chance of development by Wednesday.

Figure 4. Steering flow at the 200-mb level, about 40,000 feet above the surface, will help keep Invest 99L moving generally westward for the next several days. Wind speeds are colored in knots; multiply by 1.15 to obtain wind speed in mph. 99L and Fiona are indicated as low-pressure centers (“L”) around 30°W and 45°W, respectively. Image credit: tropicaltdibits.com.

Nearly all of the ECMWF and GFS ensemble members keep 99L below tropical storm strength for at least the next several days, with the GFS ensemble suggesting that 99L could intensify in the 4- to 5-day period. A word of caution, however: although the ECMWF and GFS are among the top-performing models for tropical cyclone track forecasts, they are much less skilled at predicting intensity, especially for periods less than 5 days. The best-performing model for intensity over the last several years has been the HWRF, as we discussed in our May post on hurricane intensity prediction. Both the 00Z and 06Z Friday runs of the HWRF model intensify 99L to tropical storm strength over the weekend and to hurricane strength as soon as Tuesday or Wednesday. The IVCN, a blend of several high-performing models, also projects that 99L could reach hurricane strength by early next week.

Climatology favors the development of long-track hurricanes in the deep tropical Atlantic during late August. Given the favorable conditions at hand, we will need to watch 99L very closely.

I edited it for 99L... The whole article can be found here: https://www.wunderground.com/blog/JeffM ... rynum=3389

[Weatherboy1]

Well, 99 is WAAAYYYY far out there and isn't even a TD yet - and as others pointed out, most models aren't doing anything in terms of development until the wave gets further west. So we're purely in the speculation zone so far. I would definitely keep an eye on the GENERAL pattern off the coast in the next couple days of modelling though. If the models tend toward a stronger Bermuda high/east coast ridge, then we're not looking at a clear recurve candidate (my opinion of course)

[Hammy]

Looks like it's falling apart today if anything--it's too connected with the ITCZ and appears that it's now dealing with dry and stable air as well.

[wxman57]

There's a good bit of moisture & energy associated with 99L, even though the convection is currently not there. I think there's a good chance it'll blow up as it nears the eastern Caribbean around next Tue-Wed. Could be a TS threat to the NE Caribbean next Wed-Thu-Fri. Beyond then, somewhere between Brownsville, TX and Bermuda is my best guess.

[gatorcane]

Hey Wxman57, thanks for narrowing it down

One thing is pretty certain, if we have something like the GFS is showing in the 12Z run, this board will be packed perhaps even new records will be set for number of active users online.

[cycloneye]

A tropical wave located about 600 miles southwest of the Cabo Verde
Islands is producing a disorganized area of cloudiness and shower
activity. Development, if any, during the next couple of days
should be slow to occur as the system encounters a dry and stable
air mass. After that time, environmental conditions are expected to
become more conducive for development, and a tropical depression
could form early next week while the system moves westward at about
15 mph across the tropical Atlantic Ocean.
* Formation chance through 48 hours...low...10 percent
* Formation chance through 5 days...medium...50 percent

[Blown Away]

There's a good bit of moisture & energy associated with 99L, even though the convection is currently not there. I think there's a good chance it'll blow up as it nears the eastern Caribbean around next Tue-Wed. Could be a TS threat to the NE Caribbean next Wed-Thu-Fri. Beyond then, somewhere between Brownsville, TX and Bermuda is my best guess.

Oh boy, when Wxman57 commits to the Brownsville to Bermuda prediction I take notice...

[Alyono]

even though the EC has had its genesis issues this year, partially due to its resolution, I would say development is no better than 50/50. With all of the cyclones and upward motion in the WPAC, how favorable will the Atlantic really be? I'm torn between something impacting the islands, and this being a figment of the imagination of the MU/CMC

Even NOGAPS dropped this at 6Z

[tatertawt24]

http://i67.tinypic.com/xqcehv.jpg
At this point, the best analogs are away from land, but there are some legends that came from where 99L is now...

What the hell is Christine?