ATL: LESLIE - Post-Tropical - Discussion

[Aric Dunn]

They may go right to TS at 11 or at 2. there are already some indications of curved bands developing

[LarryWx]

Hmm thats quite a brave call Wxman57, especially when all models have already been too far north in the short term, and given this one is still tracking near due west and winds to the NW still look pretty strongly to the west.

Center looks like its trying to tuck into the convection at the moment.

I disagree. I don't think that saying 80-90% chance for recurve north of the LA's is brave at all when considering both the many model runs in a row that have shown just that (with no strong high holding it down) as well as El Nino climo. During the 33 El Nino seasons since 1900, 19 storms formed in the MDR east of 50W. Out of these, only 5 of 19 (26%) crossed the Lesser Antilles. So, without model support, betting on a hit in the L.A.'s is what would be quite brave.

Based on a combo of these models (with no strong high to hold it down) and El Nino climo, I'm going with only a 5% chance of a U.S. hit since it has already become a TD so far east. IF that 5% were to occur, I'd go with New England.

El Nino seasons: 19 CV storms formed in August during 33 seasons since 1900. Out of these 19, only 3 later hit the U.S. (1900's Galveston storm, 1930's storm #2, and 2004's Frances), which equates to a mere 16% U.S. hit rate during Ninos for Aug. formations. Since 1960, there have been 0.8 CV formations/August (14 in 17 Aug.'s) and a mere 7% U.S. hit rate (1 of 14).

*My def. of a CV a storm: a storm that first becomes a TD east of 50W and south of 20N.

Its not a el nino season.

I respectfully disagree. Why do you say not an El Nino? Nino 3.4 has been at a +0.5+ anomaly for six weeks in a row and models are pretty much all in agreement that this will hold (other than the chance that a week or two temporarily fall below +0.5) through the fall. Based on this, I firmly believe that we are now in a weak El Nino. The problem is that based on the ONI, the official retrospective declaration by NOAA has to wait a number of months. However, its effects on the tropics obviously don't wait for the official retrospective declaration and it would almost surely be declared retrospectively to include the present time.

[Aric Dunn]

I disagree. I don't think that saying 80-90% chance for recurve north of the LA's is brave at all when considering both the many model runs in a row that have shown just that (with no strong high holding it down) as well as El Nino climo. During the 33 El Nino seasons since 1900, 19 storms formed in the MDR east of 50W. Out of these, only 5 of 19 (26%) crossed the Lesser Antilles. So, without model support, betting on a hit in the L.A.'s is what would be quite brave.

Based on a combo of these models (with no strong high to hold it down) and El Nino climo, I'm going with only a 5% chance of a U.S. hit since it has already become a TD so far east. IF that 5% were to occur, I'd go with New England.

El Nino seasons: 19 CV storms formed in August during 33 seasons since 1900. Out of these 19, only 3 later hit the U.S. (1900's Galveston storm, 1930's storm #2, and 2004's Frances), which equates to a mere 16% U.S. hit rate during Ninos for Aug. formations. Since 1960, there have been 0.8 CV formations/August (14 in 17 Aug.'s) and a mere 7% U.S. hit rate (1 of 14).

*My def. of a CV a storm: a storm that first becomes a TD east of 50W and south of 20N.

Its not a el nino season.

Why do you say that? Nino 3.4 has been at a +0.5+ anomaly for six weeks in a row and models are pretty much all in agreement that this will hold (other than the chance that a week or two temporarily fall below +0.5) through the fall. Based on this, I firmly believe that we are now in a weak El Nino. The problem is that based on the ONI, the official retrospective declaration by NOAA has to wait a number of months. However, its effects on the tropics obviously don't wait for the official retrospective declaration and it would almost surely be declared retrospectively to include the present time.

even if it does develop officially. the change in the global/ atlantic weather pattern does not immediately change it takes typically around 6 months to see the effect. so this season will go as neutral.

so leslie to be just as the past few systems have not had typical el nino conditions. we shall see what she does

[cpdaman]

i unbiasedly agree with aric .....with the -PDA , the global wx circulations have had a LA NINA look for a while and maybe more neutral soon, but no we will likely have a weak el nino this winter, but the nino pattern isn't really any where to be seen IMO.


with that said or not, i am getting somewhat concerned that this thing seems to be on a 265 heading and actually lost a tiny bit of latitude today.

if this bury's itself near 14 N and the E coast trough is flatter near 65 W on sunday , could it may be waiting on trough numba 2?

[HurrMark]

This is my opinion, and my opinion only...please don't take this as an official forecast.

I don't see this threatening any land except maybe Bermuda and Newfoundland. The ridge will be too weak for it to maintain a westerly track, and the east coast trough, which has essentially been semi-permanent the last four seasons, will keep this far offshore.

And I will go out on a limb here, but with El Nino probably starting to make an impact in the next few weeks over the Atlantic, I personally think that Isaac may be the last major threat to the U. S. this year.

[KWT]

I think its pretty obvious that the Atlantic is still more or less in a neutral mode, and I always think when you get one long tracker (Issac, Ernesto was another I suppose) then you have a higher chance of it happening again. The shear pattern has been closer to El Nino though which is why we've seen alot of weak storms for the numbers we've had.

The models have been either too slow or too far south, the GFS has been closest thus far but even that will start to be out soon if it doesn't start gaining latitude.

Anyway, I'm not saying it'll be a threat to the US...but I think its a little far south to rule out a threat to NE Caribbean, especially when nearly every system has been forecasted too far north by the models this year...and indeed thats been sometihng of a trend in the last few years (Earl, etc)

[ozonepete]

I disagree. I don't think that saying 80-90% chance for recurve north of the LA's is brave at all when considering both the many model runs in a row that have shown just that (with no strong high holding it down) as well as El Nino climo.

Its not a el nino season.

Correct. It's ENSO neutral. Also, most importantly, the CPC has specifically said that the current atmospheric conditions over the EASTPAC and ATLANTIC are NOT representative of El Nino. Here's a direct quote from their last update:
Although sub-surface and surface temperatures were above average, many aspects of the tropical atmosphere were inconsistent with El Niño conditions. Upper-level and low-level trade winds were near average along the equator, while tropical convection remained enhanced over Indonesia (Fig. 5). However, convection increased near and just west of the International Date Line, which may eventually reflect a progression towards El Niño. The lack of a clear atmospheric response to the positive oceanic anomalies indicates ongoing ENSO-neutral conditions.

[KWT]

I agree with Aric, this may well be a TS already, there is some real signs of curving and bands are already starting to show. I suspect we'll have Leslie today.

[LarryWx]

Its not a el nino season.

Why do you say that? Nino 3.4 has been at a +0.5+ anomaly for six weeks in a row and models are pretty much all in agreement that this will hold (other than the chance that a week or two temporarily fall below +0.5) through the fall. Based on this, I firmly believe that we are now in a weak El Nino. The problem is that based on the ONI, the official retrospective declaration by NOAA has to wait a number of months. However, its effects on the tropics obviously don't wait for the official retrospective declaration and it would almost surely be declared retrospectively to include the present time.

even if it does develop officially. the change in the global/ atlantic weather pattern does not immediately change it takes typically around 6 months to see the effect. so this season will go as neutral.

so leslie to be just as the past few systems have not had typical el nino conditions. we shall see what she does

The key is that the seasons upon which I base the stats are based on the official ONI classifications back to 1950 as well as the equivalent
for 1900-1949 based on looking at monhly Nino 3.4 anomalies. If I were to assume a six month lag, then virtually none of those 33 seasons would count as Nino's.
Regardless, I don't agree about your idea of a six month lag and don't see why this season would go as neutral. I have actually found a couple of months' lag on avg. between the -SOI and rising Nino 3.4 SST's. I do believe that once the SOI goes consistently negative that weather patterns start to reflect an El Nino pattern. By the way, I have read that shear isn't the only main effect of Nino's on the tropics. More than average amounts of SAL may very well be another byproduct.
I admit that it is a weak El Nino, which means less effects than a strong one.

[HurrMark]

We have an El Nino...not officially, but by definition, this is a weak El Nino. It is not 1997 level, but it is strong enough that it will likely have some effects. The teleconnections take time to transport across the globe, so that is why things don't look so out of whack right now. But things can change dramatically in a few weeks.

[Ntxw]

Okay guys lets stay on topic, there's a whole thread on ENSO and one can look at all the countless data to decide for themselves.

Can anyone post storms that have formed for the general area 98L/leslie did/will and tracks?

[ozonepete]

The key is that the seasons upon which I base the stats are based on the official ONI classifications back to 1950 as well as the equivalent
for 1900-1949 based on looking at monhly Nino 3.4 anomalies. If I were to assume a six month lag, then virtually none of those 33 seasons would count as Nino's.
Regardless, I don't agree about your idea of a six month lag and don't see why this season would go as neutral. By the way, I have read that shear isn't the only main effect of Nino's on the tropics. More than average amounts of SAL may very well be another byproduct.
I admit that it is a weak El Nino, which means less effects than a strong one.

You can't "admit it's a weak El Nino" when the CPC says it ISN'T one. They aren't saying it might be one; they are saying it ISN'T one, so you should add a disclaimer. Many people on here are stating that it's an El Nino which is confusing and misleading many posters here into thinking it is when the CPC and all of the scientists there and the NHC, etc, are saying it is not.
Also, did you see the quote I posted from the CPC? I watch the upper atmosphere every day to see if it's responding and check the CPC updates for atmospheric changes in response to El Nino. None of the shear, etc. that you say is a result of El nino are being observed.

[cpdaman]

for craps and giggles could you larry run for enso neutral conditions

i value your opinion and your posts pretty highly on here and where ever you post, i was just wanting to see if the numbers changed dramatically for enso neutral conditions, and it that it is worth looking at since we are barely into the weak nino territory and the CPC noted that enso conditions are currently not nino like, if you don't mind i would just like to see if there is a sign change in percentages, thank you

[cycloneye]

Ok folks, let's return to the topic of this thread.We have the ENSO thread at Talking Tropics forum where those good discussions can go on.


No plans to send recon tells me that they dont think is a threat to islands.

WEATHER RECONNAISSANCE FLIGHTS
CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.
1000 AM EDT THU AUGUST 3O 2012
SUBJECT: TROPICAL CYCLONE PLAN OF THE DAY (TCPOD)
VALID 31/1100Z AUGUST TO 01/1100Z SEPTEMBER 2012
TCPOD NUMBER.....12-103

I. ATLANTIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

[Aric Dunn]

looking at sat. there definitely appears to be some banding feature developing and also appears to have a slight very slight south of west motion the last few hours. I think the riding between kirk and so to be leslie might be nosing farther west as kirk lifts out. could be getting pumped up a litle or squeezed between the two. All I can say is the models had this turning or moving nw every run from the initialized position and it has maintained this westerly course. think the ridge is stronger than the models are showing.

[cpdaman]

Can anyone post storms that have formed for the general area 98L/leslie did/will and tracks?

[beoumont]

I disagree. I don't think that saying 80-90% chance for recurve north of the LA's is brave at all when considering both the many model runs in a row that have shown just that (with no strong high holding it down) as well as El Nino climo.

Its not a el nino season.

Correct. It's ENSO neutral. Also, most importantly, the CPC has specifically said that the current atmospheric conditions over the EASTPAC and ATLANTIC are NOT representative of El Nino. Here's a direct quote from their last update:
Although sub-surface and surface temperatures were above average, many aspects of the tropical atmosphere were inconsistent with El Niño conditions. Upper-level and low-level trade winds were near average along the equator, while tropical convection remained enhanced over Indonesia (Fig. 5). However, convection increased near and just west of the International Date Line, which may eventually reflect a progression towards El Niño. The lack of a clear atmospheric response to the positive oceanic anomalies indicates ongoing ENSO-neutral conditions.

Ditto.

And, going along with the ground truth that el-nino atmospheric conditions have yet to set in, all those long-term soothsayers that "predicted" that this season would feature only "close in" development, with no Cape Verde systems, have done anything but verify. We have had one Cape Verde development after the other.

[HurrMark]

2006 was a weak El Nino (anomalies never exceeded +1C), but we had a whopping one storm after September 12.

[cycloneye]

ENSO discussions at Talking Tropics forum thread

viewtopic.php?f=31&t=92137&p=2271920#p2271920

[KWT]

looking at sat. there definitely appears to be some banding feature developing and also appears to have a slight very slight south of west motion the last few hours. I think the riding between kirk and so to be leslie might be nosing farther west as kirk lifts out. could be getting pumped up a litle or squeezed between the two. All I can say is the models had this turning or moving nw every run from the initialized position and it has maintained this westerly course. think the ridge is stronger than the models are showing.

Yeah this system has tucked into the convection, its certainly not gained any latitude recently, as you say maybe on something like 265 for the very short term.

The westerly motion of the lower-mid motion extends at the moment till around 47-48W and seems to be pushing west still, so unless this really bombs I don't think its going to be lifting off from this 265-280 type track for the next 12hrs.