ATL: TROPICAL DEPRESSION ALEX - DISCUSSION

[tolakram]

It's interesting they downgraded the chance. Here's what my amateur eyes see.

Loop: http://wwwghcc.msfc.nasa.gov/cgi-bin/ge ... mframes=12



Key will be if convection dies out again tonight as most of the southern inflow appears to be outflow boundaries from storms near the SA coast.

[Aquawind]

What's up with the wave near 35W? Typo or is it going in reverse? lol

Pretty Wavey our there..and it still JUNE..

[I-wall]

When is the upper level anti-cyclone supposed to develop over 93L?

There is is.

Thank you for that. I assume the tan colored lines are showing the pressure differences? If so, it looks like the high is off to the west of 93L. Could this impart some shear onto 93L?

[cycloneye]

tolakram,that is why it has to go away from the South America influence to have a better chance to develop.

[KWT]

I'm really not sure why they have downed the risk right the way to 20%, I can only assume they believe the highly divergent conditions which is allowing convection to occur where it is will not support the convection for much longer and the position of the upper high isn't condusive enough just yet as its bringing in weak southerly airflow aloft.

That being said the main zone for development is still to the west, I'd think it has a far bigger chance of developing in the W.CAribbean and the Gulf.

[thetruesms]

Thank you for that. I assume the tan colored lines are showing the pressure differences? If so, it looks like the high is off to the west of 93L. Could this impart some shear onto 93L?

The tan lines are actually streamlines, but since air flow is a function of pressure gradients, you can kind of use it as a proxy. But yes, the upper high is now to the west of 93L - I already forget who, but it was mentioned in a post earlier today that it looked like it was seeing some shear, and it's become even more apparent since then.

edit - it was Sanibel, on a check back.

[Brent]

I'm really not sure why they have downed the risk right the way to 20%, I can only assume they believe the highly divergent conditions which is allowing convection to occur where it is will not support the convection for much longer and the position of the upper high isn't condusive enough just yet as its bringing in weak southerly airflow aloft.

That being said the main zone for development is still to the west, I'd think it has a far bigger chance of developing in the W.CAribbean and the Gulf.

Yeah, I'm very surprised they went down to 20%, but I guess the better chance was always when it got further west.

[jasons2k]

You have to remember the 20% is for the next 48 hours.

That's probably about right. IMO chances for development after 48 hours increase substantially. I still think we will see Alex by the end of the week and I see no reason to change that thinking.

Patience, patience, patience is the word for the day. Even the 'bullish' forecasts I have seen with an eventual hurricane in the Gulf don't expect much out of this until it gets past 75 or 80W.

[I-wall]

low pressure forecasted to form south of Jamaica

Makes sense since we're starting to see stronger rotation. When is the low forecasted to form?

[KWT]

Looking at the AVN imagery it just confirms its the shear that is helping to create the convection, nice outflow channel provided by that jet. I think I understand better why the NHC dropped as low as they did, the wave feature is outrunning that convection and the MLC that is with this convection is going to struggle to develop any further than that.

The ECM once again develops the southern portion in the W.Caribbean and hits the Yucatan, looks a little too far south though...

[hurricaneCW]

Shear seems kind of high in the Atlantic right now even for late June. Plus since we are right near La Nina conditions, I'd expect lower than normal shear levels. I wonder what the first week of July will be like in terms of favorable conditions..

[wxman57]

Shear seems kind of high in the Atlantic right now even for late June. Plus since we are right near La Nina conditions, I'd expect lower than normal shear levels. I wonder what the first week of July will be like in terms of favorable conditions..

Here's a map of the current shear anomaly across the basin. Shear is about 10kts below normal across the Caribbean and Gulf:


Caribbean shear compared to normal:

[HURAKAN]

Loop - http://www.ssd.noaa.gov/goes/flt/t1/flash-rgb.html

Albeit slowly but it seems to be getting better organized

[Blown Away]

http://www.ssd.noaa.gov/goes/east/tatl/loop-vis.html
IMO, looks like the mid level circulation is just S of Cabo Rojo, DR and moving towards Haiti?

[cycloneye]

Blown Away, to clarify,South of Barahona, DR. Cabo Rojo is a town in the SW corner of Puerto Rico.

[KWT]

I think there probably is a MLC with that convection, the problem is they are blowing up just south of the jet axis, which means the wave will probably carry on westwards and leave this convective mass behind, if the jet shifts, this convection will soon decay like the northern area did a few hours ago. Nice little curve with it though thats true.

[hurricaneCW]

Oh I guess since the normal June values are still quite high, it just seems that way. By the way what is the average shear a month from now and August for the Atlantic. Do you have maps for that?

[tolakram]

http://rammb.cira.colostate.edu/product ... 211315.GIF

Looking at that loop, which is SW of the apparent MLC, it appears an LLC is developing. Not very many frames to judge, so it could very well be an illusion, but convection seems to be starting to fire around this area.

[HURAKAN]

Latest

[Frank2]

Turning visible near 16.8N 71.5W:

http://www.ssd.noaa.gov/goes/flt/t1/flash-vis.html