ATL: IRMA - Models

[Hammy]

Interestingly the NAM

This is where I stopped reading.


In all seriousness. Don't use the NAM for anything other than entertainment. Don't try to assign trends to it. Don't try to wonder if it's the start of a shift.

Maybe not the start of a shift so much as the west shifts have stopped. The NAM was also shifting west today with the rest of the models.

NAM seems to go back and fourth every run or two, it did the same with Harvey as well.

[DESTRUCTION5]

Here is the trend GIF for the synoptic setup. While it’s not good for forecasting TC track, it IS good at the 500mb longwave pattern inside 48 hours and is picking up on something for such a big change. Notice the trough in the NE is much slower and less progressive.

NAM is like that toy phone you give to a 2 yr old. Looks real but in reality is just for entertaiment or looking for the 0 degree line in winter.

[alienstorm]

There is a couple of interesting items here:
1 - Trough is slower in lifting out
2 - Shortwave digs further SE and seems to connect with longwave.
3 - Irma moves WNW up to Andros Island which is further north than the ECMF, GFS UKMET have it going thus the pull and northward turn happens further north

[Steve]

Looks like the NAM runs tonight are coming in east. Why are they doing that? What is the set up to make them do this now?

Run it at 500mb. The trough is weakening and lifting out, but the upper low that has been dropping down from Montana (now in Nebraska) comes in a little farther east and is enough to connect with trough, and they both link up sort of with the trough retreating east. NAM doesn't cut the NE trough off completely but it's trapped by the Canadian high instead of retreating toward Iceland and it causes Irma to come up farther East. It could be somewhat reasonable, but I think it's overdone. NAM is good with this stuff sometimes, sometimes it isn't.
https://www.tropicaltidbits.com/analysi ... 0&ypos=386

What I would further recommend you do is run the Water Vapor Loop and compare to what the 500mb run above shows. And that goes for any model at 500 because you can usually see how things are going to break. Sometimes you need to go to 350 or 300 or even 200. But in this case, it's pretty clear between the 500 and the WV.
http://www.ssd.noaa.gov/goes/east/natl/flash-wv.html

Hope that helps explain it.

[Nimbus]

Here is the trend GIF for the synoptic setup. While it’s not good for forecasting TC track, it IS good at the 500mb longwave pattern inside 48 hours and is picking up on something for such a big change. Notice the trough in the NE is much slower and less progressive.

NAM is like that toy phone you give to a 2 yr old. Looks real but in reality is just for entertaiment or looking for the 0 degree line in winter.

I was looking at the water vapor imagery for clues and noticed that Katia seemed to be holding that trough back. Could be something that all the 00Z runs pick up on?

[Pughetime12]

NAM out to sea? Wow

[invest man]

Here is the trend GIF for the synoptic setup. While it’s not good for forecasting TC track, it IS good at the 500mb longwave pattern inside 48 hours and is picking up on something for such a big change. Notice the trough in the NE is much slower and less progressive.

NAM is like that toy phone you give to a 2 yr old. Looks real but in reality is just for entertaiment or looking for the 0 degree line in winter.

I was looking at the water vapor imagery for clues and noticed that Katia seemed to be holding that trough back. Could be something that all the 00Z runs pick up on?

The water vapor loop looks like it has 2 lows moving down 1 in Nebraska and 1 further m of it diving se . I just can't see a nw then hooking west in these models. Just doesn't seem reasonable with everything moving the way it is!

[Steve]

Those upper lows are probably only going to reinforce the trough that has brought all the great weather here. Those ULLs are a drop in the bucket of the high pressure that will force it west later.

[Nimbus]

NAM is like that toy phone you give to a 2 yr old. Looks real but in reality is just for entertaiment or looking for the 0 degree line in winter.

I was looking at the water vapor imagery for clues and noticed that Katia seemed to be holding that trough back. Could be something that all the 00Z runs pick up on?

The water vapor loop looks like it has 2 lows moving down 1 in Nebraska and 1 further m of it diving se . I just can't see a nw then hooking west in these models. Just doesn't seem reasonable with everything moving the way it is!

OK I see it now that spin moving SE into Kansas should be a digging long wave.

[Hammy]

I was looking at the water vapor imagery for clues and noticed that Katia seemed to be holding that trough back. Could be something that all the 00Z runs pick up on?

The water vapor loop looks like it has 2 lows moving down 1 in Nebraska and 1 further m of it diving se . I just can't see a nw then hooking west in these models. Just doesn't seem reasonable with everything moving the way it is!

OK I see it now that spin moving SE into Kansas should be a digging long wave.

Is that what's behind the sharper westward turn at day 4-5?

[Nimbus]

The water vapor loop looks like it has 2 lows moving down 1 in Nebraska and 1 further m of it diving se . I just can't see a nw then hooking west in these models. Just doesn't seem reasonable with everything moving the way it is!

OK I see it now that spin moving SE into Kansas should be a digging long wave.

Is that what's behind the sharper westward turn at day 4-5?

All these impulses are rotating around a node of the polar vortex up in Canada.

[Otown_Wx]

NHC just move the 11 PM track slightly westward in central Florida going pretty much over downtown Orlando.

[pcolaman]

Curiously waiting for next model runs.

[bamajammer4eva]

I think the important thing is the fact that the NAM shows the energy over the N Central Gulf Coast has trended westward each run over the past 3 runs. Isn't this what draws Irma northward??

[Nimbus]

I think the important thing is the fact that the NAM shows the energy over the N Central Gulf Coast has trended westward each run over the past 3 runs. Isn't this what draws Irma northward??

I thought it was the erosion of the western edge of the ridge?

[Blown Away]

NHC track on W side of all the spaghetti model guidance... Basically the NHC saying we only need the Euro...

[txwatcher91]

I think the important thing is the fact that the NAM shows the energy over the N Central Gulf Coast has trended westward each run over the past 3 runs. Isn't this what draws Irma northward??

It’s the trough over the NE that pulls it N. It’s slower and deeper, breaks the ridge down quicker. If other models don’t show this then it’s just a bad run of the NAM. It was a significant shift from its prior runs so either some new data was infested tonight or it’s just not handling things right.

[SunnyThoughts]

Gfs rolling out, let's see what it has to say this time.

[bamajammer4eva]

I think the important thing is the fact that the NAM shows the energy over the N Central Gulf Coast has trended westward each run over the past 3 runs. Isn't this what draws Irma northward??

I thought it was the erosion of the western edge of the ridge?

Yes thats true though I thought the cause of that erosion was an Alabama SW. I looped the GFS earlier today and it looked like a system over Alabama pulled Irma towards it and ate the storm. NAM makes it look like the NE trough is eroding the ridge.

[Blown Away]

00z GFS 30 hrs... Slightly NE of 18z... HP tad weaker...