ATL: NANA - Remnants - Discussion

[NDG]

There was storm relative circulation yesterday, but I'm surprised the ASCAT picked up west winds.
Would be a depression if it were headed into favorable conditions.

So what are the unfavorable conditions that you see?

[Aric Dunn]

There was storm relative circulation yesterday, but I'm surprised the ASCAT picked up west winds.
Would be a depression if it were headed into favorable conditions.

There is nothing but light shear and an upper high over it for the entire trip across the carrib. per the GFS anyway.

and shear maps have been trending the upper low over western cariib to be weaker and dying.

[Hypercane_Kyle]

I'm honestly baffled as to why none of the global models show development. Low shear, warm SSTs, all point to what should be at least some development in the western Caribbean at least.

[shiny-pebble]

We have to see if the convection is able to sustain at least somewhat. Because we saw this look with pre-Marco but then it would poof. But it does look pretty good right now and it has a decent environment. Should get more favorable later on.

Sent from my SM-G970U using Tapatalk

[MarioProtVI]

In no way am I trying to wishcast this thing, but I’m getting eerie Felix vibes from 99L...similar time, favourable conditions ahead of it and almost track wise too. Also something to note is models seemed to struggle with Felix too. Let’s hope to god this doesn’t try to rapidly spin up to a C5 which would be disastrous, especially in 2020!

[CyclonicFury]

I'm honestly baffled as to why none of the global models show development. Low shear, warm SSTs, all point to what should be at least some development in the western Caribbean at least.

The big question will be if this can develop soon and gain some latitude before central America. Environmental conditions in the Caribbean have been quite favorable so far this season, we just haven't had a well developed system take advantage yet.

[drezee]

Special Tropical Weather Outlook issued to update the discussion on
the system over the eastern Caribbean Sea in the first paragraph.

UPDATED: Showers and thunderstorms associated with a tropical wave
over the eastern Caribbean Sea are beginning to show signs of
organization. Recent satellite-derived surface winds also indicated
that a broad low pressure system has formed in association with the
wave. Additional development of this disturbance is expected over
the next few days, and a tropical depression could form during the
next couple of days while the system moves moves westward at about
15 mph across the Caribbean Sea. Interests in Jamaica, Honduras,
Belize, Guatemala and Yucatan should monitor the progress of this
disturbance.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...60 percent.

[aspen]

In no way am I trying to wishcast this thing, but I’m getting eerie Felix vibes from 99L...similar time, favourable conditions ahead of it and almost track wise too. Also something to note is models seemed to struggle with Felix too. Let’s hope to god this doesn’t try to rapidly spin up to a C5 which would be disastrous, especially in 2020!

The big difference between 99L and Felix, and the main limiting factor on 99L, is time. Felix had five days between forming just east of the Lesser Antilles and landfall in Central America, while 99L hasn’t developed yet and only has four days until landfall, unless it does the opposite of Felix and tries gaining latitude. Felix also deepened ridiculously fast — 3.4 mbar/hr, even faster than this year’s Cyclone Amphan (~3 mbar/hr). RI of that scale within the next 120 hours seems highly unlikely.

[NDG]

Special Tropical Weather Outlook issued to update the discussion on
the system over the eastern Caribbean Sea in the first paragraph.

UPDATED: Showers and thunderstorms associated with a tropical wave
over the eastern Caribbean Sea are beginning to show signs of
organization. Recent satellite-derived surface winds also indicated
that a broad low pressure system has formed in association with the
wave. Additional development of this disturbance is expected over
the next few days, and a tropical depression could form during the
next couple of days while the system moves moves westward at about
15 mph across the Caribbean Sea. Interests in Jamaica, Honduras,
Belize, Guatemala and Yucatan should monitor the progress of this
disturbance.
* Formation chance through 48 hours...medium...50 percent.
* Formation chance through 5 days...medium...60 percent.

There you go, nowcasting and throwing out the GFS and Euro operational runs out the window which still show no development despite good environment ahead of it over the next 3-4 days before moving into C.A.

[Aric Dunn]

Suppose I am not surprised.

lets add this to the list of poopy model.. except the ICON which has been showing it for a week now

[CyclonicFury]

Remember the ECMWF didn't develop Marco at all before it formed, and it became a brief hurricane.

[underthwx]

Looks like it's getting healthier..growing in size...I don't have a clue where it's goin...but the way this season has gone so far..it's gotta be watched...

[aspen]

Is there some dry air in the Caribbean that is responsible for the models weakening or not developing 99L?

[tailgater]

Well we are just past D max, let’s see if the convection wanes over the next 8 hrs.

[Aric Dunn]

The overall expansion of the convection will assist with latent heat release and convergence. convection is still a little sporadic but looks like a solid MLC is starting to take shape which should help concentrate future convective bursts.

[underthwx]

Is there some dry air in the Caribbean that is responsible for the models weakening or not developing 99L?

I am wondering the same thing...and also...99L seems to be moving fairly quickly...but yet it appears to be getting it's act together fairly quickly?

[gatorcane]

Is there some dry air in the Caribbean that is responsible for the models weakening or not developing 99L?

I am wondering the same thing...and also...99L seems to be moving fairly quickly...but yet it appears to be getting it's act together fairly quickly?

I posted some model graphics in the models threads that may explain it. But that said, I do think some development is possible once it reaches the Western Caribbean.

[Nimbus]

Suppose I am not surprised.

lets add this to the list of poopy model.. except the ICON which has been showing it for a week now

GFS runs the 1016 isobar all the way west into NOLA at 72 hours then starts shifting the ridge back East.
Its going to be a depression but where would you run the track?
Puerto Rico received a nasty mesovortex that wasn't forecast from the south and any track going north of the Mexican border would be difficult to call with the coastline angles and potentially receding ridge.

[tropicwatch]

Special TWO out.
A broad area of low pressure has formed with Invest 99L. Development chances are now at 60%. Interests in Jamaica, Honduras,
Belize, Guatemala and Yucatan should monitor the progress of this
disturbance.

[ColdMiser123]

Well we are just past D max, let’s see if the convection wanes over the next 8 hrs.
https://i.imgur.com/9ITCnFZ.png

Diurnal maximum happens at sunrise since this is when thunderstorm activity is maximized due to a strong temperature decrease with height. When the sun rises, the middle and upper troposphere warms, and reduces this temperature decrease with height. Temperatures close to the surface do not change very much because of the ocean surface temperatures being relatively constant throughout the day.

So we are actually pretty close to diurnal minimum, since we are close to the middle of the day.