ATL: FLORENCE - Models

[tolakram]

Can one of the pro-mets or more experienced posters explain to me what keeps Florence off shore instead of plowing inland and landfalling in the NC/VA/MD areas in the latest GFS and Euro runs?

It gets caught in the steering currents around the periphery of the high pressure which would steer the storm north instead of west.

Thanks. So I assume if that high pressure receded some it would steer farther off shore, and likewise, if it extended onto land Florence would be blocked and forced West?

RL3AO had a good post about this a few pages back. http://www.storm2k.org/phpbb2/viewtopic.php?p=2700168#p2700168

In addition, the skill of the individual models at this range is not all that high. The NHC uses a blend of a bunch of models.

[TheDreamTraveler]

It looks like the FV3 GFS shows it gets caught under the ridge and pushed west instead of feeling the weakness.

[PavelGaborik10]

Going to be an interesting week or so of model watching. I'm buckled up.

[weathaguyry]

As much as some people on here are worried about models potentially shifting south to Florida, I am very uneasy about this here in NY, if this ends up slowing down off the east coast due to complex steering currents, and creates persistent east winds farther north, it will generate devastating storm surge for myself on Long Island in the back bays, as well as for New Jersey and the Delmarva, so this storm has the potential to be dangerous for many, regardless of exactly how far south it makes it, and definitely needs to be watched by all on the East Coast!

[wxmann_91]

The continued turn into the ridge on the GFS later hours is puzzling. I wouldn't put too much stock into it. Especially with the UKMet doubling down on it's westward motion. My thoughts at this time are that the Outer Banks and possibly the SC coast are going to have to deal with this one. At this time I'm thinking points further South (FL/GA) will be ok. The Ukie may change my mind on that though if it continues its current trend.

SFT

Hasn’t the UKMET always had a left bias?

Yeah, and it's busted horribly before. But people tend to remember its major coups (Matthew 2016 and Irma last year near Florida). It's not a terrible model, but I wouldn't take its outlier solution too seriously.

[Cpv17]

Can one of the pro-mets or more experienced posters explain to me what keeps Florence off shore instead of plowing inland and landfalling in the NC/VA/MD areas in the latest GFS and Euro runs?

It gets caught in the steering currents around the periphery of the high pressure which would steer the storm north instead of west.

Thanks. So I assume if that high pressure receded some it would steer farther off shore, and likewise, if it extended onto land Florence would be blocked and forced West?

The positioning and strength of the high will ultimately tell the story where Florence is going if it misses the trough in a few days, unless it interacts with another trough after the first one, but right now that’s not looking likely. Basically, the stronger the high pressure is, the greater chance it has at making landfall vs going ots. If there’s a huge blocking high over the NE that extends down toward the Virginia’s/Ohio Valley then it very well could go further west and points south of there would be in trouble. It’s too far away in time right now for models to accurately predict the strength and the position of these high pressures.

[LarryWx]

The continued turn into the ridge on the GFS later hours is puzzling. I wouldn't put too much stock into it. Especially with the UKMet doubling down on it's westward motion. My thoughts at this time are that the Outer Banks and possibly the SC coast are going to have to deal with this one. At this time I'm thinking points further South (FL/GA) will be ok. The Ukie may change my mind on that though if it continues its current trend.

SFT

Hasn’t the UKMET always had a left bias?

Yeah, and it's busted horribly before. But people tend to remember its major coups (Matthew 2016 and Irma last year near Florida). It's not a terrible model, but I wouldn't take its outlier solution too seriously.

12Z UKMET Florence:

LEAD CENTRAL MAXIMUM WIND
VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS)
-------------- ---- -------- ------------- -------------
1200UTC 05.09.2018 0 21.6N 45.5W 998 49
0000UTC 06.09.2018 12 22.7N 47.6W 1001 55

So, the actual NHC location's latitude as of 5 PM EDT, 22.7N, is already at the same latitude as this UKMET's 8 PM EDT position. And the longitude at 5 PM EDT was only 46.6W or a full degree east of the UKMET's 8 PM position or near the assumed UKMET's 2 PM EDT position. Translation: just as is the case for the 12Z EPS mean, Flo is currently north of the 12Z UKMET track by a nontrivial amount, a hopeful sign for a down the road safe recurve.

[AutoPenalti]

Something interesting I noticed while checking the archives and obviously it's not the same for every pattern but at around 43 W, roughly where Florence is at now disregarding the latitude, the GFS on September 2nd 00z, showed a OTS solution with a trough that was digging down from the midwest, at the 06Z model run on the same day, GFS began to trend west, it skirt the OBX, trough was less pronounced but was enough to avoid any kind of landfall. At the 18z the track was pretty much similar to the 06Z but one thing that stood out at the end of the run was that Irma made a turn to the west hitting the NY/Maine area and merged with the front.

The next day at 00Z-06Z the pattern remained roughly the same, with an impact to the OBX at the end of the run. At 12Z the GFS had Irma make a W turn late in the run and was targeting the Carolinas, a SW shift from the September 2nd runs. The 18Z runs was inching closer and closer to the FL/GA area but still recurved and hit the Carolinas. It was a notable shift W from the prior runs.

On September 4th, the game changed completely. The 00Z run had landfall in Miami-Dade. The trough was less pronounced and the ridge was even stronger than what was forecast 2 days prior which meant an adjustment with a continued W track towards Cuba before finally feeling the edge of the ridge.

The same went with the Euro, at the same timeframe (September 2nd, 00Z). Around this time, the ridge was a bit stronger than what the GFS showed but was well away from FL. The ensembles as well agreed that this would be an impact to the Carolinas and OBX, the GFS and Euro came into agreement during the 2nd and 3rd days.

So, just to summarize all this, if the GFS and Euro have been showing OTS solutions and more recently a hit in the NE, chances are there may well be continued W shifts or vice-versa with OTS solutions and anything can change between now and 5 days. Something I just wanted to point out before anything is set in stone.

[Hurricaneman]

I’d say those upper air sampling’s are going to be important in a few days,

[caneseddy]

The continued turn into the ridge on the GFS later hours is puzzling. I wouldn't put too much stock into it. Especially with the UKMet doubling down on it's westward motion. My thoughts at this time are that the Outer Banks and possibly the SC coast are going to have to deal with this one. At this time I'm thinking points further South (FL/GA) will be ok. The Ukie may change my mind on that though if it continues its current trend.

SFT

Hasn’t the UKMET always had a left bias?

Yeah, and it's busted horribly before. But people tend to remember its major coups (Matthew 2016 and Irma last year near Florida). It's not a terrible model, but I wouldn't take its outlier solution too seriously.

Also, last season UKMET for several days kept Jose heading west towards Florida while every model said out to sea, until eventually it caved..just food for thought (not to say it should be discounted)

[Hurricane Andrew]

Hasn’t the UKMET always had a left bias?

Yeah, and it's busted horribly before. But people tend to remember its major coups (Matthew 2016 and Irma last year near Florida). It's not a terrible model, but I wouldn't take its outlier solution too seriously.

Also, last season UKMET for several days kept Jose heading west towards Florida while every model said out to sea, until eventually it caved..just food for thought (not to say it should be discounted)

If you bring up the GFS, there is a sharp line in outcomes before and after (after including) yesterday's 18z run. Food for thought as well.

At any rate, perhaps this storm has finally dragged me back to the world of tropics watching.

I don't really know how I feel about that, lol.

[LarryWx]

For the first time in awhile for a GEFS, it appears the 18Z GEFS has no members hitting anywhere south of upper SC with a TS+.

[AutoPenalti]

For the first time in awhile for a GEFS, it appears the 18Z GEFS has no members hitting anywhere south of upper SC with a TS+.

[b0tzy29]

As much as some people on here are worried about models potentially shifting south to Florida, I am very uneasy about this here in NY, if this ends up slowing down off the east coast due to complex steering currents, and creates persistent east winds farther north, it will generate devastating storm surge for myself on Long Island in the back bays, as well as for New Jersey and the Delmarva, so this storm has the potential to be dangerous for many, regardless of exactly how far south it makes it, and definitely needs to be watched by all on the East Coast!

Same here. Live on the water South Shore Long Island. These latest model runs certainly have my attention. Even without a direct hit, my area is very susceptible to a tide 1-2 feet above normal from a full moon, let alone a sub 980 monster just off the coast.

[Blown Away]

Can't deny that most of the GFS & EPS/Euro ensembles keep Flo away from CONUS, Bermuda still a close call no matter what.

[toad strangler]

Can't deny that most of the GFS & EPS/Euro ensembles keep Flo away from CONUS, Bermuda still a close call no matter what.

18z GEFS very fishy. Except Bermuda of course

[Kazmit]

Can't deny that most of the GFS & EPS/Euro ensembles keep Flo away from CONUS, Bermuda still a close call no matter what.

Yeah, I've noticed that most of the GFS and Euro runs the past few days have been grazing us. I'm keeping a close eye on it.

[otowntiger]

Can't deny that most of the GFS & EPS/Euro ensembles keep Flo away from CONUS, Bermuda still a close call no matter what.

Definitely good news. The trend today is definitely looking better and better.

[Aric Dunn]

Can't deny that most of the GFS & EPS/Euro ensembles keep Flo away from CONUS, Bermuda still a close call no matter what.

and then they will switch back . then back again.. blah blah..

[Happy Pelican]

As much as some people on here are worried about models potentially shifting south to Florida, I am very uneasy about this here in NY, if this ends up slowing down off the east coast due to complex steering currents, and creates persistent east winds farther north, it will generate devastating storm surge for myself on Long Island in the back bays, as well as for New Jersey and the Delmarva, so this storm has the potential to be dangerous for many, regardless of exactly how far south it makes it, and definitely needs to be watched by all on the East Coast!

Same here. Live on the water South Shore Long Island. These latest model runs certainly have my attention. Even without a direct hit, my area is very susceptible to a tide 1-2 feet above normal from a full moon, let alone a sub 980 monster just off the coast.

Ugh. This needs to trend OTS.