ATL: LAURA - Post-Tropical - Discussion

[Extratropical94]

These are the ASCAT passes Aric referred to. You can nicely see the monsoon trough axis meandering around 12N

[Frank2]

What we're seeing this morning just isn't that impressive - at least Isaias had a very pronounced circulation. This looks more like typical ITCZ convergence. My old coworkers would not be that impressed at this point.

Also, on the WV a cutoff low is developing NE of Puerto Rico, so that would be very good news as far as the system not encountering a suitable environment. ULL's are the one wild card even the seasonal forecasts cannot predict - they come and go, but ULL's sure make a big difference when it comes to what a hurricane will not be able to do...

Frank

[TheStormExpert]

https://i.imgur.com/mcKjWgp.jpg
8pm LAST NIGHT
https://i.imgur.com/GUAetWC.jpg
8AM TODAY

As of 8am the NHC has really slowed down 98L in the 5 day window compared to 8pm last night, only makes it to @60W in 5 days... That makes me think the current modeling that shows 98L flying all the way to the EGOM in 7-8 days may not be what the NHC is thinking as of this morning...

I don’t think they slowed it down. They’re probably expecting the development window to come in within the next few days.

[Aric Dunn]

Here is a full mashup of the ASCAT passes.

lets just say we will be waiting a little longer for development..

and any precise tracks from the models are moot right now. lol

looks like there will be erratic motion while this mess tries to consolidate.

could end up being flung more NW if the east lobe take hold

or if the west lobe starts to take hold it may lag behind and dip a little to wsw while the east lobe rotates around..

Just have to wait and see now.

[msbee]

Good morning everyone
what are your thoughts on what effects thus will have on the northern Caribbean islands ?
I know its too early to tell but I would appreciate your thoughts. thanks

At the very least, some heavy rain and gusty wind Friday night and Saturday as it passes, quite possibly as a 40-50 mph TS. If it passes to your north then you won't get much wind.

Thanks. will keep watching

[EquusStorm]

Definitely an energetic mass but yeah 70 on the 2-day is probably pretty generous until it can really consolidate. Of course we want things to deepen out here to drag them a little north away from everyone so a continued slow sloppy organization could increase at least the flood threat for someone in the northern Caribbean...

[wxman57]

You can't put out a 7-day track forecast saying "a general WNW motion" (that's pretty obvious). A 7-day track requires precise lat/lon points, intensity, and wind radii. Throwing out all model guidance isn't a solution. The GFS/Euro and ensembles came into much better agreement with the 00Z run. They're both indicating building high pressure to its north as it passes the NE Caribbean Fri PM/Sat. That could drive the center right across the DR & Cuba Sun/Mon rather than allow a track toward/into the Bahamas. Such a track would keep it week, likely a depression if/when it reaches the Gulf early next week.

Another possibility is that the high to the north Fri/Sat is weaker, allowing a track north of the Greater Antilles and toward the Bahamas. This would allow for a much stronger storm system threatening Florida or the SE U.S. Coast north of Florida early next week. Maybe even a northward turn off the coast.

Unfortunately, I cannot put 2-3 different tracks on my forecast. Current consensus is across the Greater Antilles, so that's the best choice to start with.

you just gave a right extreme and left extreme and went down the middle.. otherwise known as a "Cone of Uncertainty"

this, of course, is barring any major rotational interaction ( Fujiwara of sorts) between the two features for which models historically fail at every time and would potentially cause drastic shifts if the overall position of both features. So again until the two features fates are resolved and a single-center is established, anything other than a WNW motion for the next 48 hours is futile.

Also having precise lat/lon points inside the "cone" is not required. it is by convention only.

No, I gave two possibilities - a track over the Greater Antilles (DR/Cuba) or a track north into the Bahamas. Consensus is weaker and farther south. UKMET & ICON are stronger and into the Bahamas.

When we issue a forecast we don't just draw a cone and say it may be "somewhere in there - you figure it out to our clients". That cone should be eliminated, anyway, as it's useless for indicating current track uncertainty since it never changes. We have to provide precise track points at least every 12 hrs (every 3-6 hours near land). Each point has max sustained wind and gusts per quadrant with wind radii in all four quadrants. There is no luxury in deciding to only issue a 48-hr track because we're not 100% confident. Million-dollar decisions are going to be based on the track. Does a refinery plan to shut down (very, very expensive & dangerous)? Are the tens of thousands of workers offshore in the northern Gulf going to be evacuated? We don't deal with the general public. Specifics are required.

So, where is the center next Tuesday afternoon, say 3pm CDT? How strong will it be then? How large will it be? How far out will 39, 58, and 74 mph winds extend 7 days from this afternoon? You can't just say "I'm not sure - maybe here, maybe there". That's what we have to predict as forecasters. If we're wrong, we may lose some important clients, or they would at least think of our service as less valuable.

[HuracanMaster]

Between microscopic Gonzalo, gargantuan-sized Isaias wave, and now this two-headed monster, this has been the weirdest season in memory

Monster season, my thoughts precisely.
Imagine if a dual vortex storm were to form from this ala fujiwara effect but stable interaction between the 2 centers, crazy?

Sent from my SM-G975U using Tapatalk

[cycloneye]

Great view here on visible.

https://realearth.ssec.wisc.edu/?produc ... HyT53X_Kk#

[Aric Dunn]

Great view here on visible.

https://realearth.ssec.wisc.edu/?produc ... HyT53X_Kk#

Real Earth is my favorite. a lot of fun features. They are still working on improvments though.

[plasticup]

Maybe it's not my place, but I think Aric and wxman57 need to hug it out and have a beer. I don't like see mommy and daddy fighting.

[Cpv17]

Maybe it's not my place, but I think Aric and wxman57 need to hug it out and have a beer. I don't like see mommy and daddy fighting.

I don’t see how you could accurately predict where a storm will be and how strong it’ll be 7 days out like he mentioned. Maybe I misinterpreted it. No one can do that. Not even the best of the best.

[sma10]

You can't put out a 7-day track forecast saying "a general WNW motion" (that's pretty obvious). A 7-day track requires precise lat/lon points, intensity, and wind radii. Throwing out all model guidance isn't a solution. The GFS/Euro and ensembles came into much better agreement with the 00Z run. They're both indicating building high pressure to its north as it passes the NE Caribbean Fri PM/Sat. That could drive the center right across the DR & Cuba Sun/Mon rather than allow a track toward/into the Bahamas. Such a track would keep it week, likely a depression if/when it reaches the Gulf early next week.

Another possibility is that the high to the north Fri/Sat is weaker, allowing a track north of the Greater Antilles and toward the Bahamas. This would allow for a much stronger storm system threatening Florida or the SE U.S. Coast north of Florida early next week. Maybe even a northward turn off the coast.

Unfortunately, I cannot put 2-3 different tracks on my forecast. Current consensus is across the Greater Antilles, so that's the best choice to start with.

you just gave a right extreme and left extreme and went down the middle.. otherwise known as a "Cone of Uncertainty"

this, of course, is barring any major rotational interaction ( Fujiwara of sorts) between the two features for which models historically fail at every time and would potentially cause drastic shifts if the overall position of both features. So again until the two features fates are resolved and a single-center is established, anything other than a WNW motion for the next 48 hours is futile.

Also having precise lat/lon points inside the "cone" is not required. it is by convention only.

No, I gave two possibilities - a track over the Greater Antilles (DR/Cuba) or a track north into the Bahamas. Consensus is weaker and farther south. UKMET & ICON are stronger and into the Bahamas.

When we issue a forecast we don't just draw a cone and say it may be "somewhere in there - you figure it out to our clients". That cone should be eliminated, anyway, as it's useless for indicating current track uncertainty since it never changes. We have to provide precise track points at least every 12 hrs (every 3-6 hours near land). Each point has max sustained wind and gusts per quadrant with wind radii in all four quadrants. There is no luxury in deciding to only issue a 48-hr track because we're not 100% confident. Million-dollar decisions are going to be based on the track. Does a refinery plan to shut down (very, very expensive & dangerous)? Are the tens of thousands of workers offshore in the northern Gulf going to be evacuated? We don't deal with the general public. Specifics are required.

So, where is the center next Tuesday afternoon, say 3pm CDT? How strong will it be then? How large will it be? How far out will 39, 58, and 74 mph winds extend 7 days from this afternoon? You can't just say "I'm not sure - maybe here, maybe there". That's what we have to predict as forecasters. If we're wrong, we may lose some important clients, or they would at least think of our service as less valuable.

Besides the 7 day forecast points and quadrant wind radii, do you also submit an NHC-type forecast discussion to your clients? Hopefully yes, as this would give an opportunity to convey messages such as 'uncertainty is a bit higher, given unusual genesis scenario ... etc'?

[Aric Dunn]

It is looking more and more likely that we will get 99L out of the eastern system at some point..

Very rare for two systems to form this close.

I think a couple seasons ago in the pacific it happened. and you saw the crazy model runs with that..

expect the same here. except these two systems are similar sized.

[wxman57]

https://i.imgur.com/mcKjWgp.jpg
8pm LAST NIGHT
https://i.imgur.com/GUAetWC.jpg
8AM TODAY

As of 8am the NHC has really slowed down 98L in the 5 day window compared to 8pm last night, only makes it to @60W in 5 days... That makes me think the current modeling that shows 98L flying all the way to the EGOM in 7-8 days may not be what the NHC is thinking as of this morning...

I notice that, too, but I don't think the NHC is indicating a slower track. It's a non-commital forecast. That's not a possible 5-day path. They're not required to indicate the 5-day path on that graphic. They're not sure, so they're only indicating the part where they have more confidence. Five days from now, it may be over the Bahamas or Cuba.

[Aric Dunn]

It is looking more and more likely that we will get 99L out of the eastern system at some point..

Very rare for two systems to form this close.

I think a couple seasons ago in the pacific it happened. and you saw the crazy model runs with that..

expect the same here. except these two systems are similar sized.

So this is a merger type of Fujiwhara.. but some times one system or the other gets flung off..

should be interesting.

https://twitter.com/RyanMaue/status/889507072693469185?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E889507072693469185%7Ctwgr%5E&ref_url=https%3A%2F%2Fwww.wwltv.com%2Farticle%2Fnews%2Flocal%2Frare-sight-2-hurricanes-to-battle-it-to-the-death%2F289-459592135

https://twitter.com/i/status/889507072693469185

[gatorcane]

We don’t need models to tell us conditions are not particularly favorable over the MDR east of the Lesser Antilles. You can clearly see the upper low in the center of the Atlantic and a lot of dry stable air. Models do look to be picking up on that and are delaying any significant development:

http://rammb.cira.colostate.edu/ramsdis ... display=24

[Aric Dunn]

Cant wait for models to ingest this binary interaction going on.. things about to get funky..

[wxman57]

It is looking more and more likely that we will get 99L out of the eastern system at some point..

Very rare for two systems to form this close.

I think a couple seasons ago in the pacific it happened. and you saw the crazy model runs with that..

expect the same here. except these two systems are similar sized.

I'd like to see your 7-day forecast on two systems interacting. It's easy when you can just propose something but don't have to follow through with a 7-day forecast for clients. Clearly, there are two separate systems now. However, models indicate a merger in a couple of days. It's better to keep it simple and have one feature to track, as was done with Cristobal earlier this year.

[wxman57]

Besides the 7 day forecast points and quadrant wind radii, do you also submit an NHC-type forecast discussion to your clients? Hopefully yes, as this would give an opportunity to convey messages such as 'uncertainty is a bit higher, given unusual genesis scenario ... etc'?

The track is a very small part of the forecast, which includes a discussion and site-specific forecasts for individual client locations, which guides clients through the activation of the various phases of their hurricane response plans. I see that we already have conference calls being scheduled for today and tomorrow. Going to be a busy next 2 months.