ATL : INVEST 90L - DISCUSSION

[Blown Away]

I find it interesting the NHC has not dropped the percentage at all and has maintained 20 percent throughout. This leads me to believe they think this has a good shot

FYI, we were doing some calculations yesterday on probability of development of tropical waves in August and September. Since we've been counting the waves since about 2004, we have records of how many moved off the coast of Africa during each month and of how many of them developed. On average, any wave in August has a 20-30% chance of development. Chances go up to 30-40% in September. So, statistically, a 20% chance of development would be below average for August.

Really, these estimates are little more than an educated guess by the forecaster based upon what he/she is presently observing in terms of organization. One could certainly argue that the current state of the wave would indicate about zero chance of development within 48 hrs, but possibly 30-40% in the very long term (in 6-8 days) when it reaches the central to western Caribbean Sea. That would be just slightly higher than average for August.

So the only chance you give this wave to develop is in the Western Caribbean?

[CourierPR]

I just read a very interesting and detailed analysis regarding possible cyclogenesis in this area on Crown Weather Services. All I can say is be patient my friends.

[Blown Away]

I just read a very interesting and detailed analysis regarding possible cyclogenesis in this area on Crown Weather Services. All I can say is be patient my friends.

Yes it was good info: http://www.crownweather.com

The Eastern Atlantic:
First area to discuss is a pretty large area of showers and thunderstorms over the eastern Atlantic. This large system is a combination of a tropical wave located near the Cape Verde Islands and a trough of low pressure (which is/was Invest 90L) located about 750 miles southwest of the Cape Verde Islands. It looks like to me that the tropical wave near the Cape Verde Islands will likely become the more dominant system as environmental conditions are more favorable in this area and there is more moisture to work with. Looking at the forecast environmental conditions over the next few days, it appears that conditions should remain favorable for development in this area over the next few days. With that said, development will be quite slow to occur. The reason why is that if we get a low pressure system forming in this area, it will need to break off and sustain itself away from the Inter-Tropical Convergence Zone. In addition, the disturbance near the Cape Verde Islands may actually combine with whatever is left of Invest 90L. It seems very likely that either of these systems (Invest 90L or the Cape Verde system) will be classified as a tropical depression this weekend into early next week and I think the earliest that this may happen is perhaps Tuesday or Wednesday.

The model guidance has been very inconsistent on whether this develops or not. The latest NOGAPS model forecast is very aggressive and forecasts a hurricane moving through the Leeward Islands headed for Puerto Rico next Saturday. The other model guidance really does not forecast development from this system. In fact, there is no in between in the model guidance, they’re either forecasting a tropical wave that never develops or a full-fledged hurricane. What this may mean is that environmental conditions will be favorable for development, but it is unsure whether this system consolidates into one main system. I strongly suspect that you will see the model guidance continue to be inconsistent on development over at least the next few days.

So, let’s throw out the exact model details and look at the upper level conditions and patterns: As I have already mentioned, I don’t think you will see classification of a tropical depression from this system until Tuesday or Wednesday. After that, if this develops, I think the chances are pretty high that it would strengthen and track westward. I really do not think that this system will recurve out into the open Atlantic; therefore this could be a threat to land down the road. The reason why I don’t think this system will curve out into the open Atlantic is that with the Madden Julian Oscillation returning to a more favorable phase very shortly; this would favor a ridge of high pressure to be dominant over the eastern United States. It should be noted that while the model guidance do not agree on the specifics of this system (whether it develops or not), they do agree that a ridge of high pressure will be dominant to the north of this system for at least the next week. This leads me to strongly believe that the northeastern Caribbean Islands need to monitor this system very closely since this will be on your doorstep in about 5 to 7 days. After that, the pattern would favor a west-northwest course during the week of August 8th and potentially track either through the Bahamas and potentially towards the United States. Bottom line is that this system should be watched over the next several days to see if it develops or not.

Right now, I give this entire system a very low chance of developing into a tropical depression through Monday and a moderate chance of developing sometime between Tuesday and Thursday with this system in whatever form it is in potentially affecting the northeastern Caribbean between Thursday and next Saturday. Any threat to the US coastline is at least 10 to 12 days away, so for now we will keep a very close eye on it for a possible long range threat. I just noticed that the 0600 UTC GFS model is back on board with developing this system into a tropical cyclone around Wednesday; however, it is faster with the overall track and affects the Lesser Antilles on Wednesday night or Thursday morning and then Puerto Rico on Thursday night. After that, the GFS model forecasts a possible impact from eastern Florida on August 11th to South and North Carolina from August 13th to August 15th. Again, I want to strongly emphasize that you should not look at the details of the model, in terms of storm tracks, just that the model is seeing a favorable environment for development.

[wxman57]

So the only chance you give this wave to develop is in the Western Caribbean?

I think that's when its best chance of development will come - central to western Caribbean. I don't think it'll track north of the Caribbean as a tropical wave. And that means I can head out on my bike for a long ride this morning and not worry about any phone calls from work.

[bajan]

So what is the deal?? Is 90L really as far east as they are saying or is the activity now re-energising on the area further west that they were focusing on at first??

[cycloneye]

Here is a visible image loop where 90L was located. The wave still is not seen there. You can go to the thread for the wave at Talking Tropics forum to make comments about that system until a new invest is up.

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

[Countrygirl911]

Has 90L completely dissapeared becasue it is not on the map at teh top of the page soory been away for a little while need to catch up on the reading

[sunnyday]

Re the discussion by Crown Weather, the writer mentioned 12/13 storms between Aug. and Oct. That is far short of the 19/20 predicted earlier this year. I have been wondering when someone would lower the prediction for the extreme number of storms. It's been pretty dull so far. I wonder if it won't stay that way for the most part.

[Sanibel]

No central vortex yet. No vortex, no system.

[Brent]

next invest please....

Colin please! It gets tiring to track invests!!!

This.

[cycloneye]

FYI, the discussions are going on at the Wave SSW of CV thread at Talking Tropics including the posting of the 12z package of models. 90L may be reactivated or new invest 91L is up so stay tuned.

[HURAKAN]

Patience, patience, and more patience. Sometimes it can be worse than watching grass grow!!!

[Gustywind]

Patience, patience, and more patience. Sometimes it can be worse than watching grass grow!!!

[JTD]

The Atlantic just doesn't have it's mojo this year....Shocked at what has occurred with this invest. The favorable dynamics just aren't there yet and I'd like to see some evidence that the ATL has it's mojo within the next 10 days or.....

[Brent]

The Atlantic just doesn't have it's mojo this year....Shocked at what has occurred with this invest. The favorable dynamics just aren't there yet and I'd like to see some evidence that the ATL has it's mojo within the next 10 days or.....

I should mention, the models didn't form this til the wave behind it joined up. Well it's happened and it looks really good(much better than it has in 2 days) Probably be 91L soon and the models are latching onto it still. 90L may be dead, but the storm isn't... Check out the tropics board.

GFS goes insane in the long term and shows 3 storms by the 15th.

[lester]

The Atlantic just doesn't have it's mojo this year....Shocked at what has occurred with this invest. The favorable dynamics just aren't there yet and I'd like to see some evidence that the ATL has it's mojo within the next 10 days or.....

Patience, young grasshopper. The storm is slowly starting to form

[KWT]

Probably a short window for development is opening up now before for whatever reason conditions aloft according to the models start to prevent anything from occuring.

By the way, just what are the NHC going to, reactivate 90L when the time comes or bring up 91L...gosh not a clue!

[minter45]

We have Code orange.

[AdamFirst]

The Atlantic just doesn't have it's mojo this year

Are you kidding? It's still July.

[TwisterFanatic]

Lol they drop the invest and give it a code orange.