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WxWatcher007

Major Hurricane Florence

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Just now, olafminesaw said:

There's a lot of moving pieces, but a stable enough/strong enough ridge to drive Florence into the East Coast seems unlikely to me. With the trend being a more northern track in the short/medium range, it makes it a lot more of a thread the needle situation for Florence to get caught under the ridge.

As I said yesterday, I understand this argument from a climo standpoint. But in reality, if Florence misses the first weakness in a few days, it all comes down to the strength and placement of the developing ridge. It seems that even the GFS has caught onto the idea of Florence missing the first weakness and then it comes down to the amplitude of the Ohio Valley trough. I think it's actually quite an easy forecast as far as tropical forecasting is concerned. Basically we should know by Monday if the system is going OTS, maybe sooner.

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54 minutes ago, NJwx85 said:

As I said yesterday, I understand this argument from a climo standpoint. But in reality, if Florence misses the first weakness in a few days, it all comes down to the strength and placement of the developing ridge. It seems that even the GFS has caught onto the idea of Florence missing the first weakness and then it comes down to the amplitude of the Ohio Valley trough. I think it's actually quite an easy forecast as far as tropical forecasting is concerned. Basically we should know by Monday if the system is going OTS, maybe sooner.

The models that mostly missed the first trough always kept florence considerably weaker. In fact none of them had her as a hurricane. The fact she is so much stronger than modeled early gives the recurve models the upper hand as they had her stronger earlier.

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32 minutes ago, shaggy said:

The models that mostly missed the first trough always kept florence considerably weaker. In fact none of them had her as a hurricane. The fact she is so much stronger than modeled early gives the recurve models the upper hand as they had her stronger earlier.

It seems the 12z GFS trended back towards Florence escaping via the first weakness in the trough. If that happens of course it's game over.

It will be interesting to see if the Euro trends back towards missing the initial trough.

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55 minutes ago, NJwx85 said:

It seems the 12z GFS trended back towards Florence escaping via the first weakness in the trough. If that happens of course it's game over.

It will be interesting to see if the Euro trends back towards missing the initial trough.

It's certainly a possibility. Euro went with an escape through that weakness last night. However, given the GFS tends to overdo deepening, that might contribute to Flo's poleward movement. We'll just have to see what shear and dry air do to it over the next few days.

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Surprise

Hurricane Florence Tropical Cyclone Update
NWS National Hurricane Center Miami FL       AL062018
250 PM AST Tue Sep 04 2018

...FLORENCE CONTINUING TO STRENGTHEN...

Recent satellite imagery indicates that Florence has continued to
intensify during the past few hours, and maximum sustained winds
have increased to 85 mph (140 km/h). This increase in intensity
will be reflected in the forecast issued with the 500 PM AST (2100
UTC) advisory package.


SUMMARY OF 250 PM AST...1850 UTC...INFORMATION
---------------------------------------------------
LOCATION...20.0N 42.7W
ABOUT 1265 MI...2035 KM ENE OF THE LESSER ANTILLES
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...WNW OR 300 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...984 MB...29.06 INCHES

$$
Forecaster Brennan/Berg

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1 hour ago, Hoth said:

It's certainly a possibility. Euro went with an escape through that weakness last night. However, given the GFS tends to overdo deepening, that might contribute to Flo's poleward movement. We'll just have to see what shear and dry air do to it over the next few days.

The 12z Euro still found the initial weakness, but it actually shows quite the parade of storms behind Florence. It also keeps Florence around in weak stirring beyond day 8 and it's possible that a Southern track could commence at that time given it's placement to the East of the massive building ridge.

ecmwf_z500_mslp_atl_11.png

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Forming an eye fast., it will easily make CAT 3 tomorrow if it can maintain this trend.

Edit: Higher shear looks like it will kick in tomorrow. But it will relax a bit by day 3.

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By 162 hours the trough is already pulling out of the Ohio valley and a ridge is building along the entire East coast. Pressure is in the 920’s.

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4 minutes ago, NJwx85 said:

00z GFS continues the trend of missing the weakness. Looks to get stuck under the ridge by day 6.

Just the slightest bit of ridging where the weakness was before makes all the difference.

gfs_z500a_watl_fh126_trend.thumb.gif.1039f53e9060814821e4bf6aeab86587.gif

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20 minutes ago, NJwx85 said:

GFS also has Florence down to 933mb by 144 hours.

The area near Bermuda maybe the most favorable spot in the basin.  Not much of a steering flow, but you can see a near perfect anticyclonic outflow pattern.

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12 minutes ago, NJwx85 said:

That sneaky trough over Quebec tries to pull it North, otherwise it was headed for the Carolinas.

It is a lot less sneaky if you look at the 200mb wind field. 

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18 minutes ago, NJwx85 said:

Anyway an interesting and troublesome run for some.

Needs to be a few hundred miles south of the GFS track for it to be a serious threat IMO.....there might be 1 or 2 storms ever to get that far north that far east and still threatened the US with a direct landfall.  Though I suppose there is a first time for everything,

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Euro has also come way back west.....big hurricane too...obviously the next run will change but this is the first real hit any model has had other than scraping the OBX with Florence....

ecmwf_mslp_uv850_seus_10.thumb.png.9af66c6ca71bc0cca87ed8354bd3ef34.png

 

 

 

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00Z EPS show a wholesale change as well. >70% of members have it missing the trough and getting trapped under the ridge. Of course, it's possible that it simply recurves close to the coast, but the probability of a land strike has gone up.

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Euro has the storm at 1000MB by 00z tonight.  Going to need some fast weakening today for that to happen.

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CI up to 5.4adj/5.9 raw. That's 99kt. Pretty impressive looking hurricane now. Especially impressive given the relatively marginal conditions. There's about 15-20 knots of shear and SSTs are 26-27C. The shear increases slightly to around 20 knots over the next 3 days but so do the SSTs. That may not be enough to weaken it substantially, given how well it's done

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11 minutes ago, Amped said:

Euro has the storm at 1000MB by 00z tonight.  Going to need some fast weakening today for that to happen.

Yes, however it's still a vertically deep system. That won't affect steering changes nearly as much as if it had say -- decoupled the vortex, which would allow it to exclusively follow the low level trades. The earlier runs had shown a weak, shallow system that made intensity more of a factor in determining track. This is no longer the case.

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55 minutes ago, csnavywx said:

Yes, however it's still a vertically deep system. That won't affect steering changes nearly as much as if it had say -- decoupled the vortex, which would allow it to exclusively follow the low level trades. The earlier runs had shown a weak, shallow system that made intensity more of a factor in determining track. This is no longer the case.

+1.  Even our local met this morning said that Florence's path would be dictated by her strength.  The GFS shows a very strong system and yet has its day 5 position very close to where the Euro does.  If anything, a stronger system will build the mid layer ridge a bit over the Atlantic.  The differences after day 5 come down primarily to to the strength and orientation of the east coast ridge.

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6 hours ago, SnoSki14 said:

Ukmet is one of the best performing tropical models we have and often leads the way so I'm not surprised the gfs/euro are picking up on the west track.

Wasn’t it the only model at 60 hours last year which had Irma missing MIA and FLL and going into the Keys?  I seem to remember it being heavily discounted and then most of the EPS members in one run jumped way southwest 

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