ATL: ISAAC - Post-Tropical - Discussion

[SFLcane]

Latest IR loop.

Starting to move pretty fast ... I can't help but wonder if the models forecasting a weak system are onto something.

Where have i heard that before? Indeed though the trend towards a weaker storm continues.

[Cyclenall]

Here's one reason the COC is spinning up so quickly. The MLAEJ (Mid-Level African Easterly Jet) is quite strong and well established right now. The first image shows it's steady westward flow at 600mb (in METERS/SEC). This is very good for carrying and sustaining easterly waves over Africa and then westward into the Atlantic off of Africa. But much more important is how differently it is behaving compared to normal, i.e. the anomalies with it. Note the second image, which is the analysis at 600mb of its variation from normal over the last week, i.e. the anomalies in its strength and direction. Note how it is a little faster than normal right where 94L is and most importantly, note that the wind direction points to the east at 10 degrees, which means that there is a weakness in the westerly component at lower latitudes. What does this all mean? That between about 10 and 15 degrees there is horizontal shear which encourages a twist in the atmosphere. This is allowing a rapid spin-up at mid levels. Combined with such warm SSTs and low vertical wind shear, this one could spin up very quickly.

*Images Cut*

I've never heard of this before, all that was brand new to me and sounded like it came from a met.

Well Aric,here is a pass made around 7:40 PM EDT,but it missed almost the entire circulation.

That sucks.

[jinftl]

Impressive looking until you consider the estimated center is not in that ball of convection from 15N to 17N. Unless it is reforming even further north or the MLC and LLCC are decoupling due to the fast motion west or shear?

[floridasun78]

Latest IR loop.

Starting to move pretty fast ... I can't help but wonder if the models forecasting a weak system are onto something.

http://img843.imageshack.us/img843/9053 ... imated.gif

Where have i heard that before? Indeed though the trend towards a weaker storm continues.

going like td7?

[TropicalAnalystwx13]

The global models show intensification of the storm, that's all that matters. Leave the rest to the hurricane models.

[tolakram]

Another loop, short wave IR, though not a very good shot. LLC should be somewhere due west of the previous position, denoted with I.

[jinftl]

I'm leaving it to the NHC. They have a slow and steady approach to developing systems like this for a reason. Some folks are no doubt wondering what happened to the 'it' storm they saw on some model runs before, the one they have been waiting for this hyper-active yet dull season. Keep this in mind, 94L has never been more than an invest so the disappointment is in losing the model run showing the Cat 3 or 4 moving over every city island and then touching every city on the east coast. Some model will flip back to a more exciting outcome 5 times before Monday - the key is to stick with the model run you like, not the current one!.

The global models show intensification of the storm, that's all that matters. Leave the rest to the hurricane models.

[rainstorm]

maybe 2012 just isnt going to produce anything except north of 35 and in the BOC. ive been reading how conditions were so much better for 94L, but it seems nothing much has changed.

[ozonepete]

Here's one reason the COC is spinning up so quickly. The MLAEJ (Mid-Level African Easterly Jet) is quite strong and well established right now. The first image shows it's steady westward flow at 600mb (in METERS/SEC). This is very good for carrying and sustaining easterly waves over Africa and then westward into the Atlantic off of Africa. But much more important is how differently it is behaving compared to normal, i.e. the anomalies with it. Note the second image, which is the analysis at 600mb of its variation from normal over the last week, i.e. the anomalies in its strength and direction. Note how it is a little faster than normal right where 94L is and most importantly, note that the wind direction points to the east at 10 degrees, which means that there is a weakness in the westerly component at lower latitudes. What does this all mean? That between about 10 and 15 degrees there is horizontal shear which encourages a twist in the atmosphere. This is allowing a rapid spin-up at mid levels. Combined with such warm SSTs and low vertical wind shear, this one could spin up very quickly.

*Images Cut*

I've never heard of this before, all that was brand new to me and sounded like it came from a met.

I am a met. I just haven't asked for the designation here yet but will pretty soon.

[rainstorm]

Here's one reason the COC is spinning up so quickly. The MLAEJ (Mid-Level African Easterly Jet) is quite strong and well established right now. The first image shows it's steady westward flow at 600mb (in METERS/SEC). This is very good for carrying and sustaining easterly waves over Africa and then westward into the Atlantic off of Africa. But much more important is how differently it is behaving compared to normal, i.e. the anomalies with it. Note the second image, which is the analysis at 600mb of its variation from normal over the last week, i.e. the anomalies in its strength and direction. Note how it is a little faster than normal right where 94L is and most importantly, note that the wind direction points to the east at 10 degrees, which means that there is a weakness in the westerly component at lower latitudes. What does this all mean? That between about 10 and 15 degrees there is horizontal shear which encourages a twist in the atmosphere. This is allowing a rapid spin-up at mid levels. Combined with such warm SSTs and low vertical wind shear, this one could spin up very quickly.

*Images Cut*

I've never heard of this before, all that was brand new to me and sounded like it came from a met.

I am a met. I just haven't asked for the designation here yet but will pretty soon.

you still think it will spin up quickly?

[Dean4Storms]

I think what we have here is a fujiwara effect of two vorts....

Note the 12z ECMWF..........


http://raleighwx.americanwx.com/models/ ... _loop.html

[AJC3]

Well Aric,here is a pass made around 7:40 PM EDT,but it missed almost the entire circulation.

Based on that image, i'd raise the PoF (Probability of Formation) to 90%. You can see SWrly winds on the edge of that pass, which may be a little less accurate just due to the data being on the edge. This appears to be a depression now on satellite and microwave, but with no confirmation... the call from NHC is good.

The question, yet again, is given the fast forward speed, are there any ground-relative NW winds on the forward flank of the wave axis. If so, they're light and confined to a really small area. Without a good ASCAT pass (did I mention lately how much I miss QS? LOL), there's just no way to know for sure right now.

[psyclone]

Despite the recent model trend with regard to strength, i wouldn't be surprised if 94L eventually huffed and puffed its way to a significant (possibly major) hurricane. it just has that look of an eventual significant storm, particularly with the curved banding effort in the southern semi-circle. And it has the calendar on its side too. MDR whoppers love the latter third of August and the first two thirds of September. Needless to say I'm watching with interest.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[ozonepete]

you still think it will spin up quickly?

It already clearly is. I don't know who could look at that circulation and not think so.

[ozonepete]

Well Aric,here is a pass made around 7:40 PM EDT,but it missed almost the entire circulation.

Based on that image, i'd raise the PoF (Probability of Formation) to 90%. You can see SWrly winds on the edge of that pass, which may be a little less accurate just due to the data being on the edge. This appears to be a depression now on satellite and microwave, but with no confirmation... the call from NHC is good.

The question, yet again, is given the fast forward speed, are there any ground-relative NW winds on the forward flank of the wave axis. If so, they're light and confined to a really small area. Without a good ASCAT pass (did I mention lately how much I miss QS? LOL), there's just no way to know for sure right now.

Ha Ha. Boy do I miss QuikScat.

[Hurricaneman]

If you look carefully at the animation of 94L, it looks to me like it the area around 15N sucked the LLCC into it, if so what implication will that have in strengthening it

Personal Forecast Disclaimer:
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[floridasun78]

alot us do i bet nhc do too i hear one could go up 2014

[MississippiWx]

It's really not surprising that the models have eased up on intensity. The Eastern part of the MDR is not and has not been favorable for development this season due to an abundance of dry air. The dry air is not as intense currently as it was when TD7 formed (struggled) and that is why 94L is looking more healthy. However, it is just not conducive enough for fast strengthening. As 94L gets closer to the islands, it will have a better chance of strengthening at a faster rate. One thing I noticed in the 18z run of the SHIPS is that shear picks up dramatically towards the end of the run. It could be seeing an increase in shear due to the semi-permanent TUTT axis NE of the island chain. That is one thing to consider.

El Nino years are not very favorable for fast strengthening storms in the Eastern Atlantic. Conditions are typically much more favorable north of 20N and west of 55W. This shouldn't be a huge year in the MDR. Further north has been the trend and it should stay that way.

Personal Forecast Disclaimer:
The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS

[RL3AO]

There is a band of strong SW shear near 50W that is streaming NE between the ULL and ridge.

Now I think the TUTT is supposed to weaken over the next day or two so that shear will probably weaken some.

[floridasun78]

wow some say going get weaker other models say going get stronger we should know by wed how system look and what models was right