2021 Tropical Waves Thread

[PTrackerLA]

*rubs eyes

[tolakram]

12Z Euro, in late June?


It's been a long long time, and a lot of upgrades, since Hurricane Dean, but I remember the Euro had issues even seeing it down here. Will be a very interesting few days.

[Category5Kaiju]

*rubs eyes

https://i.imgur.com/LWpU3zZ.png

What the...is this wave trying to join Dennis and Emily's elite July major club?

[aspen]

*rubs eyes

https://i.imgur.com/LWpU3zZ.png

What is this, a late August ensemble run?

Most of the high intensities are from way outside the even marginally reliable time range, but some members get to hurricane intensity while in the MDR, presumably within the next 7 days. If the wave starts to get its act together quickly, those scenarios might be possible. Also, there seems to be decent support for a subtropical system, which I recall has appeared in other ensemble runs.

[cycloneye]

A strong tropical wave is expected to emerge off the coast of
Africa overnight and on Thursday. Some development of this system
is possible late this week and into early next week while it moves
westward to west-northwestward at about 15 mph across the tropical
eastern and central Atlantic Ocean, where ocean temperatures are
only marginally conducive for tropical cyclone formation.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...30 percent.

[aspen]

A strong tropical wave is expected to emerge off the coast of
Africa overnight and on Thursday. Some development of this system
is possible late this week and into early next week while it moves
westward to west-northwestward at about 15 mph across the tropical
eastern and central Atlantic Ocean, where ocean temperatures are
only marginally conducive for tropical cyclone formation.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...30 percent.

https://i.imgur.com/5jQQGjL.jpg

What even are the SSTs in the southern MDR? It’s hard to tell because the Coral Reef map is not sensitive to SAL, while the maps on Tropical Tidbits are.

[Kingarabian]

A strong tropical wave is expected to emerge off the coast of
Africa overnight and on Thursday. Some development of this system
is possible late this week and into early next week while it moves
westward to west-northwestward at about 15 mph across the tropical
eastern and central Atlantic Ocean, where ocean temperatures are
only marginally conducive for tropical cyclone formation.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...30 percent.

https://i.imgur.com/5jQQGjL.jpg

What even are the SSTs in the southern MDR? It’s hard to tell because the Coral Reef map is not sensitive to SAL, while the maps on Tropical Tidbits are.

Reynolds method is probably your best bet for accurate SST's since it's what NOAA likely uses.
https://www.nhc.noaa.gov/sst/

[Category5Kaiju]

A strong tropical wave is expected to emerge off the coast of
Africa overnight and on Thursday. Some development of this system
is possible late this week and into early next week while it moves
westward to west-northwestward at about 15 mph across the tropical
eastern and central Atlantic Ocean, where ocean temperatures are
only marginally conducive for tropical cyclone formation.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...30 percent.

https://i.imgur.com/5jQQGjL.jpg

What even are the SSTs in the southern MDR? It’s hard to tell because the Coral Reef map is not sensitive to SAL, while the maps on Tropical Tidbits are.

The skin temperatures are roughly 27-28 degrees C, with the areas south of that nearly 29. So pretty warm and definitely TC-supportive.

[aspen]

A strong tropical wave is expected to emerge off the coast of
Africa overnight and on Thursday. Some development of this system
is possible late this week and into early next week while it moves
westward to west-northwestward at about 15 mph across the tropical
eastern and central Atlantic Ocean, where ocean temperatures are
only marginally conducive for tropical cyclone formation.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...30 percent.

https://i.imgur.com/5jQQGjL.jpg

What even are the SSTs in the southern MDR? It’s hard to tell because the Coral Reef map is not sensitive to SAL, while the maps on Tropical Tidbits are.

Reynolds method is probably your best best for accurate SST's since it's what NOAA likely uses.
https://www.nhc.noaa.gov/sst/

So judging from those maps, SSTs aren’t great but they’re…acceptable for TC development. The wave will need to stay at or below 10N in order to remain in SSTs of no less than 27C, and >28C waters at ~10N don’t exist until it gets to roughly 50W.

[Ubuntwo]

Festering

[Kingarabian]

18z Euro less bullish on this wave but still eventually closes it off and deepens it to a TD/weak TS.

[Aric Dunn]

Loop of the well defined LLC becoming exposed again.. but moving in the wrong direction.... Steering would suggest a wsw to West motion... not sure where the models are getting wnw/nw.. but..

https://rammb-slider.cira.colostate.edu ... aw_width=6

[USTropics]

This has been one of those cases where the models have underestimated short-term development, you can see it in the GFS trend from the past 4 runs with a correction to the south:



Current low-level vort analysis:


Why is this important? This his allowed the AEW to moisten the environment to the north, instead of becoming washed out and moving directly NW into the dry mid-level air mass:


While there is still shear present, the more southern location has also escaped the severe zonal shear to the north:

[Aric Dunn]

This has been one of those cases where the models have underestimated short-term development, you can see it in the GFS trend from the past 4 runs with a correction to the south:

https://s6.gifyu.com/images/gfs_z850_vort_atl_fh6_trend.gif

Current low-level vort analysis:
https://s6.gifyu.com/images/wg8vor5.gif

Why is this important? This his allowed the AEW to moisten the environment to the north, instead of becoming washed out and moving directly NW into the dry mid-level air mass:
https://s6.gifyu.com/images/gfs_midRH_eatl_2.png

While there is still shear present, the more southern location has also escaped the severe zonal shear to the north:
https://i.imgur.com/qTlP6Pz.png

Yep.

the lack of any SCAT data for the last 36 hours has made this more of an issue. the models are barely picking up anything.

and clearly this could easily be a TD..

[aspen]

So close.
https://mobile.twitter.com/TropicalTidb ... gr%5Etweet

[tolakram]

saved loop

[Aric Dunn]

saved loop
https://i.imgur.com/yhqfx3v.gif

Yeah in this loop you can see the llc moving w/wsw..

the background flow is very steadily east to west





Current low to mid level steering give credence to the noticeable wsw motion.







All of this may keep it just south of the shear axis .. for which it is already right on the edge.

[Aric Dunn]

HY-2B Scat just came in.. decent for light to moderate convection and clear air. It has some issues with heavy convection but in this case things look pretty reliable.

clear cut case here. Should be a TD

[Blinhart]

So this is the system that they are giving 10% chance to right now????

From what I'm looking at that you guys are posting, I would of thought it would of had a higher percentage. This is a very robust wave for this early.

[Blinhart]

Was I in a coma for a couple months, this looks like something in August not June, what will we be looking at in August-October???