ATL: KAREN - Models

[LarryWx]

ECMWF ensemble 00z

5/51 US landfall = 10% (TD to Cat 1 - strongest member 90mph, average landfall @192 - 216 hours) -> 1 more member most likely will also make landfall after 240 hours
2/51 Cuba landfall = 4% (TD)
Approximately half of the members make and survive the initial turn West, but most of them sort of sit around and slowly disappear after that. Most of the members that don't turn West do so because the system already dissipated before it could. Approximately 10 (20%) of the members don't make the turn at all. That last number is comparable to yesterday's 12z ensemble.

https://i.imgur.com/2dvuS17.png

Actually, 3 more made US LF, 2 in Gulf and 1 at Vero. So, that’s how I got 8.

[chris_fit]

Any changes on the 06Z EPS Larry? I see the 06 Euro has no major changes

[kevin]

ECMWF ensemble 00z

5/51 US landfall = 10% (TD to Cat 1 - strongest member 90mph, average landfall @192 - 216 hours) -> 1 more member most likely will also make landfall after 240 hours
2/51 Cuba landfall = 4% (TD)
Approximately half of the members make and survive the initial turn West, but most of them sort of sit around and slowly disappear after that. Most of the members that don't turn West do so because the system already dissipated before it could. Approximately 10 (20%) of the members don't make the turn at all. That last number is comparable to yesterday's 12z ensemble.

https://i.imgur.com/2dvuS17.png

Actually, 3 more made US LF, 2 in Gulf and 1 at Vero. So, that’s how I got 8.

Yes, you're right I'll edit my post.

[LarryWx]

Any changes on the 06Z EPS Larry? I see the 06 Euro has no major changes

Not too different although I see a good bit higher number of weak members (1000-1004 mb) to go with about the same number of stronger ones. As far as Conus threats, it is impossible to say because it goes out only to 144 and none have had a chance to hit that soon.

[chris_fit]

Actually looks like quite an uptick in activity on the 06 EPS..
.

[SoupBone]

So I've been away, but I'm hearing that the current thinking is that Karen might not survive due to a cold front dropping in?

What models are showing this, and where can I subscribe to their newsletter?

[LarryWx]

Actually looks like quite an uptick in activity on the 06 EPS..
.
https://i.imgur.com/zE3V390.jpg

https://i.imgur.com/REv30H6.jpg

As I said, there was quite an uptick on the 6Z in members in the weak (1000-1004) range. Regarding 996-1000 and 992-996, I see an increase on my source on the 6Z vs 0Z of only one each. So, only a slight uptick there (that’s why I said about the same number of stronger ones) and still not that many. My source doesn’t have as many stronger members as your map shows for some reason. For example, my source shows 9 sub 1,000 whereas yours shows 13. Also, my source shows 4 sub 992 whereas yours shows 6. Maybe your map and mine aren’t apples to apples?

[Jr0d]

So I've been away, but I'm hearing that the current thinking is that Karen might not survive due to a cold front dropping in?

What models are showing this, and where can I subscribe to their newsletter?

The EURO is showing the front in about 208 hours out, the GFS about the same.

The thinking this morning is the ULL to the west of Karen will contribute to shear, then leave a weakness in the ridge that will slow/stall Karen and may even pull her north before she makes it far enough west to be a threat to the Bahamas or SE CONUS.

[wx98]

I think it’s been said before, but the two things the global models always seem to miss (possibly because they aren’t on a fine enough scale) are short-term intensity blowups and the inevitable ridge weakness somewhere near the east coast. That being said, it does seem like the models could be on to something with that ULL getting pulled north instead of retrograding W or SW, which would end up with a sheared Karen slowing again near or east of the Bahamas and then getting pulled north in the weakness. We will see what happens, but it’ll be hard for this to get all the way to Florida.

[LarryWx]

The latest ICON (12Z) is back to totally merging Karen and Jerry from what I can tell before moving the entire weak thing west. It is also further N than recent runs.
Edit: it later stalls and never gets close to the CONUS.

[blp]

I am still looking at this because what I have seen in the past is whenever you have a High building in most cases will create a favorable environment. I think the NHC is totally correct in taking a cautious approach on the intensity. We need to wait until the High builds in and Jerry gets out of the way to get a better picture. IMO, there is something about this year with the models and the intensity forecasting that just seems off in terms of showing more hostility than reality.

[ronjon]

I have a feeling when this system is done that a lot of people (including me) will have ended up wasting lots of time obsessing over model runs for nothing - the system will either degenerate into a wave or head OTS or both. The globals are on to something that will prevent Karen from ramping up.

[Gums]

Salute!

A cold front that was poorly modeled has saved us several times here in the Panhandle
Opal was nearing cat V but the front came thru faster than modeled, so she weakened by LF and increased forward speed. Still a very strong storm, and we were "tree removal paradise" for contractors, heh heh.

Hoping for a typical fall front now, and it could help many others on our coasts.

Gums sends....

[Jr0d]

I think it’s been said before, but the two things the global models always seem to miss (possibly because they aren’t on a fine enough scale) are short-term intensity blowups and the inevitable ridge weakness somewhere near the east coast. That being said, it does seem like the models could be on to something with that ULL getting pulled north instead of retrograding W or SW, which would end up with a sheared Karen slowing again near or east of the Bahamas and then getting pulled north in the weakness. We will see what happens, but it’ll be hard for this to get all the way to Florida.

Climatology gives Karen a slim chance to make it to Florida, the models give it a low to moderate chance. Overall I would give it very low to low odds of making it to Florida, but still significant enough to watch closely,~10 to maybe 15% chance.

It seems like forecasting an ULL is big wild card in a lot of these scenarios. In my amateur opinion they are difficult to forecast, yet crucial to the track and intensity therefore they add much uncertainty.

Overall I think the threat of a SE CONUS strike has gone down significantly, but not enough to write Karen off as a threat. Once/if the west to wsw turn happens and how fast it moves will be the 2 of the most important variables.

Even though the GFS and EURO keep Karen weak, there is too much uncertainty to say that is written in stone.

[blp]

Trending stronger so far.

[LarryWx]

12Z UKMET: inititialized about 35 miles too far N (21.6N instead of 21.1N); moves her further east (all the way to 58.4W) and then dissipates her at 96:

TROPICAL STORM KAREN ANALYSED POSITION : 21.6N 65.0W

ATCF IDENTIFIER : AL122019

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 25.09.2019 0 21.6N 65.0W 1008 30
0000UTC 26.09.2019 12 23.9N 64.0W 1008 28
1200UTC 26.09.2019 24 26.2N 63.1W 1008 26
0000UTC 27.09.2019 36 27.9N 61.2W 1009 24
1200UTC 27.09.2019 48 28.5N 59.5W 1008 30
0000UTC 28.09.2019 60 29.5N 58.4W 1009 27
1200UTC 28.09.2019 72 30.1N 59.5W 1010 22
0000UTC 29.09.2019 84 29.7N 61.6W 1010 23
1200UTC 29.09.2019 96 CEASED TRACKING

[cycloneye]

Trending stronger so far.

https://i.ibb.co/jLrp0xZ/gfs-z850-vort- ... -trend.gif

To let you know that moved your post from the Karen discussion thread to this one.

[LarryWx]

12Z GFS at 138 hits that brick wall well offshore FL that many models have been seeing.

Edit: And then she starts moving W again though weak. Moderate shear along most of the path.

Edit: Then later she (very weak) recurves just E of the Bahamas. And then she degenerates to a wave.

[Jr0d]

I noticed that the GFS starts to drop Karen and strengthen a low South of Cuba around 192 hours. It could be overdoing that low, when the energy it sees could be centralized with Karen, that is the more bullish outlook.

It is also forecasting a good amount of shear over Karen as it moves west, if Karen goes further south or the westerly jet is further north, it will make a huge difference with intensity. Anything like that over 120 hours out is highly uncertain however.

I am willing to say if Karen does not make it to Florida by Friday, Oct 4th it will not make it. Once again the speed will be a crucial player.

As I will keep saying, until Karen makes the west turn we will have a highly uncertain long range forecast. Looping storms are notoriously difficult for both intensity and track.

[jconsor]

 https://twitter.com/yconsor/status/1176920742719631361