ATL: HUMBERTO - Models

[LarryWx]

The American models seem to be on their own while every other model recurves up the east coast

But note that the GFS and Legacy are both trending east now even though they're still far to the west of the non-American runs.

[Steve]

CMC sort of splits the difference and goes up Florida.

https://www.tropicaltidbits.com/analysi ... 91212&fh=6

[Evil Jeremy]

CMC sort of splits the difference and goes up Florida.

https://www.tropicaltidbits.com/analysi ... 91212&fh=6

West of the 00z, East of yesterday's 12z

[ronjon]

The American models seem to be on their own while every other model recurves up the east coast

But note that the GFS and Legacy are both trending east now even though they're still far to the west of the non-American runs.

Not really - GFS has been pretty consistent the last several runs - the big difference is they keep the system weak. Time will tell. CMC trended west - NAM and NAVGEM similar to GFS. So far the only model to really ramp up development is the Euro and ICON. We'll have to see if the Euro sticks to its guns for the 12z run.

[Evil Jeremy]

The American models seem to be on their own while every other model recurves up the east coast

But note that the GFS and Legacy are both trending east now even though they're still far to the west of the non-American runs.

Not really - GFS has been pretty consistent the last several runs - the big difference is they keep the system weak. Time will tell. CMC trended west - NAM and NAVGEM similar to GFS. So far the only model to really ramp up development is the Euro and ICON. We'll have to see if the Euro sticks to its guns for the 12z run.

UKMET ramps it up as well while recurving. It does seem intensity and organization in the next 48 hours is the key difference between the model camps.

[Craters]

There's been a flurry of posts in the last page or two that use the word "progressive," which can be interpreted in more than one way. Can somebody explain how the word is being used here in the context of models, patterns, trends, etc? Or are there subtle differences depending on what "progressive" is describing?

Thank you...

[chaser1]

1) Weak and broad = S. Florida rain and west into the GOM
2) Organized and Strengthening = remain east of Florida and possible risk to South & North Carolina
3) The CMC sort of splits the difference and perhaps brings a "last second" T.D. to develop between W. Palm Beach and Vero

My guess on the odd's of either occurring are:
1) 10%
2) 60%
3) 30%

[chaser1]

There's been a flurry of posts in the last page or two that use the word "progressive," which can be interpreted in more than one way. Can somebody explain how the word is being used here in the context of models, patterns, trends, etc? Or are there subtle differences depending on what "progressive" is describing?

Thank you...

In terms of potential storm tracks and the models, "progressive" typically is referring to the overall pattern over North America (and W. Atlantic). More specifically, a large blocking high pressure area over the central U.S. and seemingly semi-stagnant trough off the U.S. east coast would NOT suggest a progressive pattern. Meanwhile, a fast moving zonal flow across the northern latitudes may move a new trough that drops down from the Great Lakes but this trough is moving to the east within that flow pretty quickly. This is what would be referred to a primarily "progressive flow" where every few days a new trough might enter the picture, but then move east and high pressure build back in. IIt is possible to have a progressive pattern where the troughs are deep and farther to the south, but in Summer high pressure ridging is more dominant over the Southern U.S. so troughs of low pressure tend to not be as strong and far south as they become toward Fall and Winter.

[Michele B]

12z GFS still with an Eastern GoM solution, someone is going to bust big time here!

I don't get it!

HOW can they over- or underestimate the ridging by so much as to make a couple hundred mile error like that?!?

Isn't the development of ridging a pretty straightforward thing? I mean, the jet stream and the associated "fronts" pretty much make it obvious where a HIGH or LOW pressure system is and where it will be going, don't they?

[DioBrando]

wat

[Evil Jeremy]

12z GFS still with an Eastern GoM solution, someone is going to bust big time here!

I don't get it!

HOW can they over- or underestimate the ridging by so much as to make a couple hundred mile error like that?!?

Isn't the development of ridging a pretty straightforward thing? I mean, the jet stream and the associated "fronts" pretty much make it obvious where a HIGH or LOW pressure system is and where it will be going, don't they?

Nothing in weather is "pretty straightforward". Or "obvious".

[DioBrando]

heh

[Cat5James]

1) Weak and broad = S. Florida rain and west into the GOM
2) Organized and Strengthening = remain east of Florida and possible risk to South & North Carolina
3) The CMC sort of splits the difference and perhaps brings a "last second" T.D. to develop between W. Palm Beach and Vero

My guess on the odd's of either occurring are:
1) 10%
2) 60%
3) 30%

1) the 12Z CMC shows landfall well below WPB... it’s more like North Miami/South Broward.
2) 10% for the So. FL scenario seems very low given the wave has not yet started to strengthen/develop.

[SFLcane]

12Z HWRF trends south and is into SFL as a moderate TS.

[Hammy]

12z GFS still with an Eastern GoM solution, someone is going to bust big time here!

I don't get it!

HOW can they over- or underestimate the ridging by so much as to make a couple hundred mile error like that?!?

Isn't the development of ridging a pretty straightforward thing? I mean, the jet stream and the associated "fronts" pretty much make it obvious where a HIGH or LOW pressure system is and where it will be going, don't they?

You can see on satellite and surface where the upper and lower fronts and troughs and highs are, but the 500MB isn't so easy to see on satellite or any visual data (hence why the soundings are used) and it seems like these tricky cases, it's the mid-level highs and lows that the models are struggling with so much.

[Emmett_Brown]

12z GFS still with an Eastern GoM solution, someone is going to bust big time here!

I don't get it!

HOW can they over- or underestimate the ridging by so much as to make a couple hundred mile error like that?!?

Isn't the development of ridging a pretty straightforward thing? I mean, the jet stream and the associated "fronts" pretty much make it obvious where a HIGH or LOW pressure system is and where it will be going, don't they?

You can see on satellite and surface where the upper and lower fronts and troughs and highs are, but the 500MB isn't so easy to see on satellite or any visual data (hence why the soundings are used) and it seems like these tricky cases, it's the mid-level highs and lows that the models are struggling with so much.

And, the steering of a TC results from the sum of all steering forces at all levels of the atmosphere. Also, the depth (or should I say height) of the storm's circulation can determine whether high, mid or low level steering currents have the most influence.

[Craters]

There's been a flurry of posts in the last page or two that use the word "progressive," which can be interpreted in more than one way. Can somebody explain how the word is being used here in the context of models, patterns, trends, etc? Or are there subtle differences depending on what "progressive" is describing?

Thank you...

In terms of potential storm tracks and the models, "progressive" typically is referring to the overall pattern over North America (and W. Atlantic). More specifically, a large blocking high pressure area over the central U.S. and seemingly semi-stagnant trough off the U.S. east coast would NOT suggest a progressive pattern. Meanwhile, a fast moving zonal flow across the northern latitudes may move a new trough that drops down from the Great Lakes but this trough is moving to the east within that flow pretty quickly. This is what would be referred to a primarily "progressive flow" where every few days a new trough might enter the picture, but then move east and high pressure build back in. IIt is possible to have a progressive pattern where the troughs are deep and farther to the south, but in Summer high pressure ridging is more dominant over the Southern U.S. so troughs of low pressure tend to not be as strong and far south as they become toward Fall and Winter.

Ah -- that makes sense! Thanks, Chaser!

[sma10]

Interestingly, with the ICON, UKmet, and to some extent EURO solutions, 95L becomes so strong and so slow moving, that we may have to begin to integrate its movement with how future 96L evolves.

In other words, 95L may very well be the deciding factor in where next week's system ends up, as well.

[ronjon]

12z HWRF - weak tropical storm into Ft Laud - migrates NW up the center just east of Tampa to Crystal River and then north bound into Georgia.

https://www.tropicaltidbits.com/analysis/models/?model=hwrf&region=95L&pkg=mslp_wind&runtime=2019091212&fh=75

[jasons2k]

Just a reminder we have a discussion thread for discussion. Let’s keep this focused on the models please - thanks.