ATL: INVEST 98L - Discussion

[OuterBanker]

Did I just see the llc relocate under the cdo? Maybe this thing will pull a surprise.

[ozonepete]

It's certainly making a run at intensifying. Pulsing up and down right now with the usual two or more centers fighting it out. The very favorable upper level outflow is clearly helping the convection to keep bursting.

[ozonepete]

Did I just see the llc relocate under the cdo? Maybe this thing will pull a surprise.

Looks like there were two centers along around 73 degrees west, with one north of 30 and one south of 30. The southern one has dissipated and the northern one looks to be doing pretty well at the moment. A lot of lightning there. This would of course amount to a center relocation or consolidation to the north or northwest of where it looked to be earlier.

[northjaxpro]

Invest 98L is looking better than when I posted a couple of hours or so about it. It does appear that convection is either expanding on the western side of the system or the suspected surface low level circulation did get tucked underneath the hot tower cell from a few hours ago.

The system definitely is as organized as I have seen it to this point. I hate to say this, especially given what the people in coastal North Carolina just went through with Florence, but everyone from the North Carolina coast northward need to pay attention to the developments of 98L this week.

[Ken711]

Would this likely develop into a tropical storm or potentially a hurricane?

[ozonepete]

Would this likely develop into a tropical storm or potentially a hurricane?

It's got a 40% chance from the NHC right now. I'd give it a 60% chance. We just have to keep watching it.

[OuterBanker]

The POD states tomorrow at 2:30 edt recon. They just might want to push that back because of its proximity to the US coast and current appearance.

[emeraldislenc]

I agree

[GCANE]

Dark grey represents ice.
Hasn't been dissipating all morning.
Should expand the tropopause higher in elevation.
Likely for stacking and spinning up the vorts due to conservation of angular momentum.
Could come quickly.

[cycloneye]

2 PM TWO:

A broad area of low pressure located about 450 miles
south-southeast of Cape Hatteras, North Carolina is producing
disorganized showers and thunderstorms. Environmental conditions
are expected to become slightly more conducive for development
during the next day or so while the system moves west-northwestward
to northwestward. By Tuesday night and Wednesday, upper-level winds
are expected to increase, limiting the chances for additional
development, while the system moves northward near the southeastern
United States coast.
* Formation chance through 48 hours...low...50 percent.
* Formation chance through 5 days...medium...50 percent.

[ozonepete]

GCANE what band is that satellite image on?

[GCANE]

GCANE what band is that satellite image on?

1.6um
Band 5

[GCANE]

Winds picking up, closest buoy
Station 41002
31.760 N 74.840 W (31°45'36" N 74°50'24" W)

['CaneFreak]

Hi all,

I had a question. Does it appear to anyone else that Invest 98L may come into the right entrance of the jet streak over the OH Valley and Mid-Atlantic tomorrow? I was just looking at the latest upper air observations and it appears that a secondary Jet streak is now setting up over OH/KY as of the 12Z upper air observations. Is anyone else seeing this jet streak and have any comments on any implications that this may have on the forecast? Thanks!

0Z 9/24 250 mb Upper Air Observations:

12Z 9/24 250 mb Upper Air Observations:

[GCANE]

Pretty much right on the edge of Leslie kicking in a poleward outflow channel.
With the convection firing more northward, it could happen.

[ozonepete]

Hi all,

I had a question. Does it appear to anyone else that Invest 98L may come into the right entrance of the jet streak over the OH Valley and Mid-Atlantic tomorrow? I was just looking at the latest upper air observations and it appears that a secondary Jet streak is now setting up over OH/KY as of the 12Z upper air observations. Is anyone else seeing this jet streak and have any comments on any implications that this may have on the forecast? Thanks!

0Z 9/24 250 mb Upper Air Observations:
https://www.spc.noaa.gov/obswx/maps/250_180924_00.gif
12Z 9/24 250 mb Upper Air Observations:
https://www.spc.noaa.gov/obswx/maps/250_180924_12.gif

The jet streaks you are referring to will have moved far to the east and be gone by the time on Tuesday night/Wednesday when this disturbance or TC comes near Hatteras. But the other, larger jet stream disturbance that is moving into the Rockies now will be approaching the Appalachians by then and if aligned with the 500 mb flow it could help to turn it eastward and out to sea.

A right entrance or left exit has good divergence aloft (which I'm sure you know) but that is more helpful in developing / intensifying non-tropical lows. For TCs an approaching area of divergence aloft from a jet streak entrance or exit will temporarily aid upper divergence in the northwest quadrant of the TC but as it moves closer to overhead of the TC it chokes off upper level outflow. That's why we want a good anticyclone overhead of a TC which stokes outflow in all quadrants. Finally, a strong approaching trough at 500 mb (not 200 or 300mb) can sometimes have it's areea of max vorticity move over the TC and cause rapid strengthening as the TC transitions to a mid-latitude, cold core low. Sandy was the text book example of that.

['CaneFreak]

Thanks!

Hi all,

I had a question. Does it appear to anyone else that Invest 98L may come into the right entrance of the jet streak over the OH Valley and Mid-Atlantic tomorrow? I was just looking at the latest upper air observations and it appears that a secondary Jet streak is now setting up over OH/KY as of the 12Z upper air observations. Is anyone else seeing this jet streak and have any comments on any implications that this may have on the forecast? Thanks!

0Z 9/24 250 mb Upper Air Observations:
https://www.spc.noaa.gov/obswx/maps/250_180924_00.gif
12Z 9/24 250 mb Upper Air Observations:
https://www.spc.noaa.gov/obswx/maps/250_180924_12.gif

The jet streaks you are referring to will have moved far to the east and be gone by the time on Tuesday night/Wednesday when this disturbance or TC comes near Hatteras. But the other, larger jet stream disturbance that is moving into the Rockies now will be approaching the Appalachians by then and if aligned with the 500 mb flow it could help to turn it eastward and out to sea.

A right entrance or left exit has good divergence aloft (which I'm sure you know) but that is more helpful in developing / intensifying non-tropical lows. For TCs an approaching area of divergence aloft from a jet streak entrance or exit will temporarily aid upper divergence in the northwest quadrant of the TC but as it moves closer to overhead of the TC it chokes off upper level outflow. That's why we want a good anticyclone overhead of a TC which stokes outflow in all quadrants. Finally, a strong approaching trough at 500 mb (not 200 or 300mb) can sometimes have it's areea of max vorticity move over the TC and cause rapid strengthening as the TC transitions to a mid-latitude, cold core low. Sandy was the text book example of that.

[OuterBanker]

How interesting. The stratocumulus that pushed southeast offshore here earlier are now being pushed back northwest inland. That is clearing up the skies in eastern VA and northeastern NC. It appears that the environment of 98L has become more dominant than the approaching front from the west. You can also see the dominant high that is pushing it northwest. I’m hoping the front will push it out to sea but I’m not so sure anymore. We should start seeing the outer bands by tomorrow morning here if it develops.

https://www.tropicaltidbits.com/sat/sat ... t=vis-swir

[GCANE]

I am especially watching surface winds over FL.
In general, they are light and out of the east.
If they take a sudden shift from the west, it will tap into the GOM TPW.

[BobHarlem]

This is fairly close out (Wednesday) potential tropical cyclone advisory territory here. They don't have all that much time to do it if it does.