ATL: SAM - Remnants - Discussion

[Teban54]

To my naked eye the system seems to be consolidating between 10N and 11N, yet most models have it forming south of 10N. Is there an expected WSW motion in the short term, or are the models just initializing it wrong?

[storminabox]

It’ll really throw the models for a loop if 98L consolidates way quicker than forecast and further north than expected. The model consensus doesn’t show a TS until Friday, and the disturbance takes a SW dip during the next 24-36 hours before coming back north.

The way I imagine it is like a Douglas 2020-like path except in the Atlantic MDR.

Good comparison!

[USTropics]

To my naked eye the system seems to be consolidating between 10N and 11N, yet most models have it forming south of 10N. Is there an expected WSW motion in the short term, or are the models just initializing it wrong?

The system is a bit decoupled at the present moment. You can see in the 00z GFS analysis sounding (particularly the hodograph) that there is currently 20-25kt of shear, which has displaced the mid-upper level circulation to the north:


Models are in agreement that shear will begin to decrease in 36-48 hours, with shear vector direction also becoming more uniform from east to west:


As of the last visible imagery from yesterday evening, the low-level flow was still quite elongated from east to west. There was evident banding (outlined in pink), but lacking any strong evidence of southeasterly flow in the western quadrant to close off a definitive LLC:


Since that time though, as we can see in the 850mb CIMSS vorticity product, consolidation of the low-levels has occurred just south of 10N:


Upper-level vorticity still remains a bit disorganized and to the north (the convection associated with the mid-upper levels gave the appearance the center was quite a bit more north):

[aspen]

Wow this looks fantastic, and seems to be consolidating at around 11N. It doesn’t seem to be decoupled based on current imagery. This rapid genesis is really going to impact model tracks unless the system moves further south.

[kevin]

Looks quite healthy to me, like aspen said I wouldn't be surprised if this forms earlier than most models are saying right now.

[Chemmers]

Looking impressive this morning, think we will see development sooner rather than later

[aspen]

Strange that 98L seems to be consolidating at 11N, but the most recent CIMSS vorticity map update still shows the center of vorticity at 8-9N. Either 98L will adjust further south in the next 24 hours or so, or the vort will relocate further north.

[Iceresistance]

4 AM ASCAT

[aspen]

4 AM ASCAT

https://s9.gifyu.com/images/ascat_98L_barb_202109212302.png

https://s9.gifyu.com/images/ascat_98L_speed_202109212302.png

That pass is from 23z last night, so nearly 12 hours old. We’ll need something far more recent to determine if 98L is about to become a TC closer to 11N.

[KirbyDude25]

4 AM ASCAT

https://s9.gifyu.com/images/ascat_98L_barb_202109212302.png

https://s9.gifyu.com/images/ascat_98L_speed_202109212302.png

That pass is from 23z last night, so nearly 12 hours old. We’ll need something far more recent to determine if 98L is about to become a TC closer to 11N.

I looked at the 10z ASCAT that's up now, and it seems like it missed 98L (that or I fat-fingered the viewing window)

[Blown Away]

[tolakram]

These angle corrected floaters can be deceiving.

Uncorrected: https://weather.cod.edu/satrad/?parms=meso-meso1-natcolor-12-1-100-1&checked=map&colorbar=undefined

Center may be on the SE side of the convection.

[Stormybajan]

https://i.imgur.com/pchowd2.gif

Convection did trick me last night into thinking it was forming more to the north around 11-12N,...however based on this visual it seems like its actually on the SE section of the system down to around 10N where most of the vorticity is. Looks can be deceiving I guess.

[abajan]

Showers and thunderstorms continue to become better organized in
association with a tropical wave located several hundred miles
southwest of the Cabo Verde Islands. Environmental conditions are
expected to remain conducive for additional development, and a
tropical depression is expected to form within a day or two while
the system moves westward at 10 to 15 mph across the eastern and
central tropical Atlantic Ocean. Additional information on this
system, including gale warnings, can be found in High Seas Forecasts
issued by the National Weather Service.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

[abajan]

Are they expecting its forward speed to decelerate?
Compare the position of the western edge of the "cone" (for want of a better term) in the previous TWO versus the latest one:

[JRD]

Seeing evidence of a closed circulation in both Windy and Ventusky (most apparent in the latter). Windy shows that the southern portion of the circulation is quite slow.

[aspen]

Are they expecting its forward speed to decelerate?
Compare the position of the western edge of the "cone" (for want of a better term) in the previous TWO versus the latest one:

https://i.imgur.com/hwfV9oN.png

https://i.imgur.com/lBIbpGe.png

I think they shorten the cone when it’s more likely to develop in the short term. The edge of the cone is probably the latest point it will develop by.

[Blown Away]

Are they expecting its forward speed to decelerate?
Compare the position of the western edge of the "cone" (for want of a better term) in the previous TWO versus the latest one:

https://i.imgur.com/hwfV9oN.png

https://i.imgur.com/lBIbpGe.png

I think so, models seem to be slowing 98L's forward motion which may give more opportunity to recurve this time of year.

[MJGarrison]

Seeing evidence of a closed circulation in both Windy and Ventusky (most apparent in the latter). Windy shows that the southern portion of the circulation is quite slow.

Which model do you have selected in each? I think Windy has the Euro, right, which I assume is 0z from last night? Is Ventusky on the GFS?


Sent from my iPad using Tapatalk

[cycloneye]

AL, 98, 2021092212, , BEST, 0, 99N, 315W, 30, 1009