ATL: ARTHUR - Post-Tropical - Discussion

[tolakram]

For intensification, the primary concern is the front approaching from the west. With the SW to NE flow it's in a perfect spot to act as strong ventilation for the outflow and could, I say could, lead to more rapid intensification that if it wasn't there.

How rapid is the big question, if rapid at all.

Zoom 2 live IR view. You can see the front approaching and Arthur growing in size.

http://wwwghcc.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20CONUS&lat=31&lon=-79&info=ir&zoom=2&width=1000&height=800&quality=95&type=Animation&palette=ir1.pal&numframes=10

Personal Forecast Disclaimer:
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Time_Zone]

Thanks . I didn't expect this storm to likely skip hop and jump from 70 to 80+ mph within hours. I expected it to hold steady for a good day or so. That only makes me wonder if it could exceed the current predicted landfall intensity. We'll see what the next update says from the NHC.. like many times before, even though something blatantly is stronger, the NHC doesn't like to acknowledge that right away.[/quote]

It hasn't. One poster speculated he thinks he may have. Personally. I'm thinking maybe 75 MPH. I see no way it goes above 80 by the time recon is there. Knowing Arthur he could very well still be the same intensity.

[Hammy]

Looking at how much the radar is degrading in the last hour now I'm thinking maybe 65mph. The eyewall has splintered and it looks at least in the short term that it's feeling the effects of some westerly shear.

[Aric Dunn]

although limited.. there has clearly been some increase in moisture into the system.. recon very likely to find a 75 to 80 mph ...

[Time_Zone]

Looking at the latest water vapor loop dry air appears to be suddenly abating...Why? Or am am I seeing things?

[chaser1]

'Ol Arthur tryin' to make a name for himself, huh? Looks like yesterday near its maximum point of organization, with the difference being that the LLC isnt running ahead of it mid level center, but catching up to it. The main envelope appears to have possibly temporarily stalled (deepening?), and if the LLC does become embedded and an outflow channel does develop, then his training wheels might come off in a pretty big way.

One other thought; if Arthur has slowed temporarily in response to deepening, that may prove a blessing to the N.C. Outer Cape. Any delayed northward motion could prove to be just the extra few hours needed for the mid level flow to begin pushing Arthur Northeastward and possibly skirting south and east of actual landfall. Obviously the farther north Arthur gets prior to a N.E. motion, the harder it'll be to recurve prior to landfall.

[tolakram]

Live WV loop: http://wwwghcc.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20CONUS&lat=31&lon=-79&info=wv&zoom=2&width=1000&height=800&quality=95&type=Animation&palette=wv2.pal&numframes=10

[Aric Dunn]

Looking at the latest water vapor loop dry air appears to be suddenly abating...Why? Or am am I seeing things?

though it s possible to decern mid level from upper level in a normal WV loop.. most of what you see is not having any part in it..

[Aric Dunn]

ok..... recon...

[ConvergenceZone]

Interesting tidbit in the latest discussion just posted:

" the center of the guidance envelope has again shifted a little westward
toward the North Carolina coast.The GFS has made a rather
significant shift since the previous run, and it now brings the
center of Arthur across eastern North Carolina. The new forecast
track is shifted a little closer to the coast, but it will stay in
the center of the guidance envelope to the east of the GFS."

[HurriGuy]

what the heck??? faulty equipment right when passing through???

[Jevo]

0z Euro is West of previous run as well.. Unfortunately we only get 24 hour plots from the free sites, but this run is showing 978mb approaching E-NC and the OBX

http://i.imgur.com/GNMgOHP.gif

[Aric Dunn]

what the heck??? faulty equipment right when passing through???

not sure but they were flying at 9 to 10 k feet not AF level at all..

[ConvergenceZone]

0z Euro is West of previous run as well.. Unfortunately we only get 24 hour plots from the free sites, but the last run is showing 978mb approaching E-NC and the OBX

http://i.imgur.com/GNMgOHP.gif

Yea, I wouldn't be shocked if when all is said and done that the center moves right along the coast before it moves further out to sea.....I wouldn't be surprised at all...

[Alyono]

EC is around 967 as it makes its closest approach to the Outer Banks

dont have the scaled winds yet, but it looks to be around 95-100 KT using the raw winds

[Time_Zone]

EC is around 967 as it makes its closest approach to the Outer Banks

dont have the scaled winds yet, but it looks to be around 95-100 KT using the raw winds

I highly doubt it gets anywhere near 100 KTS

[ncweatherwizard]

For intensification, the primary concern is the front approaching from the west. With the SW to NE flow it's in a perfect spot to act as strong ventilation for the outflow and could, I say could, lead to more rapid intensification that if it wasn't there.

How rapid is the big question, if rapid at all.

Zoom 2 live IR view. You can see the front approaching and Arthur growing in size.

http://wwwghcc.msfc.nasa.gov/cgi-bin/get-goes?satellite=GOES-E%20CONUS&lat=31&lon=-79&info=ir&zoom=2&width=1000&height=800&quality=95&type=Animation&palette=ir1.pal&numframes=10

Personal Forecast Disclaimer:
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Eh...it's not really ventilation of the outflow that causes the strengthening, but you've basically got the right idea. QG dynamics will tell you that divergence occurs in the upper troposphere ahead of an upper level trough because the winds in a trough are subgeostrophic (and the winds in the downstream ridge are supergeostrophic). So the winds exiting the trough are faster, and you horizontally advect more mass out of a region ahead of a trough than you advect in. Coincidentally, this is also the area where you often see strong SW winds aloft, which causes the cirrus outflow to expand over a large area. But it is really the large-scale divergence and vertical motion in the upper-troposphere that allows the strengthening. This process is baroclinic enhancement of a tropical cyclone.

[Alyono]

what the heck??? faulty equipment right when passing through???

not sure but they were flying at 9 to 10 k feet not AF level at all..

Huh? AF ALWAYS flies at 10,000 ft at night for strong TS or canes

[Alyono]

EC is around 967 as it makes its closest approach to the Outer Banks

dont have the scaled winds yet, but it looks to be around 95-100 KT using the raw winds

I highly doubt it gets anywhere near 100 KTS

what reasoning do you have?

[HurriGuy]

More deep convection fired up on east side with new frame.