ATL: Ex INVEST 96L - Discussion

[Aric Dunn]

It looks good, but there are no indications of any westerlies at the surface. A 14:30z ASCAT pass confirmed that ex-96L is still an open wave, and there are no surface observations of westerlies. There's a reason why NHC has not mentioned it on their TWO.

This has happened many times where ascat does not pick up on fast moving small systems.

[Aric Dunn]

Well, its headed straight for buoy 42059...so we shall see in fairly short order what going on here

If it does not go north of that bouy it wont really give us anything useful except pressure.

Pressure has fallen currently passed tha average background pressure so we have that at least

[tarheelprogrammer]

This kind of looks like a TD to me. Clear rotation and looks like it is trying its best to make it to a storm, however, shear awaits it soon.

[floridasun78]

This kind of looks like a TD to me. Clear rotation and looks like it is trying its best to make it to a storm, however, shear awaits it soon.

that why nhc not looking at it that much because shear ahead it

[AJC3]

It looks good, but there are no indications of any westerlies at the surface. A 14:30z ASCAT pass confirmed that ex-96L is still an open wave, and there are no surface observations of westerlies. There's a reason why NHC has not mentioned it on their TWO.

This has happened many times where ascat does not pick up on fast moving small systems.

ASCAT doesn't show westerlies with fast-moving systems, small or large, because there usually aren't any ground-relative westerly winds with them. That looks to be the case here - the low cloud elements on the south side of the system are moving toward the N or NNW. A westward motion of 15 knots looks conservative to me....it's probably moving at close to 20 knots.


Edit: granted, I'll give you some low cloud elements on the east side of it are moving a little east of due north. Still this looks like an open wave...something like this...perhaps a wee bit more amplified about its axis, but not to the point closing off on it south side.



Also - is ASCAT METOP-A having some trouble? Last imagery I see is from 30 JUL, even when you select yesterday's date.

[GCANE]

Very intense lightning now.

[floridasun78]

not sure my eye playing game but look like take more circle shape on afternoon sat pic

[AJC3]

not sure my eye playing game but look like take more circle shape on afternoon sat pic

Two things about looking at visible imagery, especially a time lapse of a fast-moving system such as this...

A. The "circular shape" you're seeing is in the mid and high level debris clouds, formed by anticyclonic flow aloft.

B. This is a really important one that I've reiterated on here over and over again. When you look at a time lapse, your eyes are following along with the wave. What this actually does is to create a visual storm relative rotation that is either exaggerated or non-existent at the surface. To get a better ground-relative sense of low cloud motion, you need to: (1) Zoom well in on the system, (2) Fix your eyes on a single point and focus on the motion of cloud elements relative to that point, and finally (3) Focus only on the low cloud elements - not any debris clouds. Look at the motion of the open-cell cumulus (the smaller white 'dots' on the imagery) as well as thunderstorm outflow boundaries. Both of these features exist at around 1-1.5KM (3-5KFT) or so.

Fast moving systems are no doubt tricky to diagnose whether or not they are closed at the surface or low cloud level. While scatterometer (ASCAT) data does have its limitations, in absence of surface observational data over open ocean areas, it gives you a much better indication of what surface/low level streamlines look like than does human visual estimation.

[Aric Dunn]

not sure my eye playing game but look like take more circle shape on afternoon sat pic

Two things about looking at visible imagery, especially a time lapse of a fast-moving system such as this...

A. The "circular shape" you're seeing is in the mid and high level debris clouds, formed by anticyclonic flow aloft.

B. This is a really important one that I've reiterated on here over and over again. When you look at a time lapse, your eyes are following along with the wave. What this actually does is to create a visual storm relative rotation that is either exaggerated or non-existent at the surface. To get a better ground-relative sense of low cloud motion, you need to: (1) Zoom well in on the system, (2) Fix your eyes on a single point and focus on the motion of cloud elements relative to that point, and finally (3) Focus only on the low cloud elements - not any debris clouds. Look at the motion of the open-cell cumulus (the smaller white 'dots' on the imagery) as well as thunderstorm outflow boundaries. Both of these features exist at around 1-1.5KM (3-5KFT) or so.

Fast moving systems are no doubt tricky to diagnose whether or not they are closed at the surface or low cloud level. While scatterometer (ASCAT) data does have its limitations, in absence of surface observational data over open ocean areas, it gives you a much better indication of what surface/low level streamlines look like than does human visual estimation.

Yeppers.. learned that from you like 15 years ago or something lol

[Aric Dunn]

Funny thing .. if this had formed earlier the models would have been pretty far off. the ridging was quite a bit stronger and built/moved farther west.

[Frank P]

Satellite loops on this system are interesting to watch... best its ever looked IMO... probably go poof right after I post this... still hauling butt but does have a nice overall tropical cloud presentation... wonder if the NHC will resurrect it tomorrow if it maintains this consistency, currently not getting any respect from anyone yet... make note, in the unlikely event it holds up what it has and reaches the GOM then I recon things could be a little more interesting.. its all we have to track at the moment..

[TheStormExpert]

How is this at least not getting a mention by the NHC!?

This is the best 96L has EVER looked!

[Aric Dunn]

Well it tried really hard..

[GCANE]

Well it tried really hard..

It went all day long sparked by that big tower this morning.

Still has a lot to work with.

I am waiting to see what happens in the morning.

[floridasun78]

if not thing by now i think time to look next invest few week thing not going it way

[Aric Dunn]

Well it tried really hard..

It went all day long sparked by that big tower this morning.

Still has a lot to work with.

I am waiting to see what happens in the morning.

I wont write it off I know better.. but if the convection collapsed almost certainly is open

The other thing is the low level circ and mid level are clearly not stacked at the moment. though the mid level has still about 24 hours till it runs into the shear. the northern low level circ has about 12 hours.

[wxman57]

ASCAT hit today says trof axis at the surface. There is no LLC.

[Hurricane Jed]

There is too much going against it

[SouthFloridawx]

I wasn't expecting anything, so it's nice to just have something to watch.

Sent from my SM-G930P using Tapatalk

[Monsoonjr99]

Seems like convection has waned. Nice mid-level swirl, but this is moving too fast and will soon hit shear. The NHC removed this from the TWO for a reason. Conditions currently are just unfavorable for development. Time to wait for the next disturbance...