ENSO Updates (2007 thru 2023)

[Ntxw]

It's becoming more evident, for July, that the background state will move to look more like an El Nino episode. CFSv2 showed this as others posted, OP guidance is moving that way. Tropical forcing will center near the dateline and progress eastward. For the past few months it has been focused over Indonesia which is more favored for La Nina.



Seasonal OLR depicts pretty well the Indonesian convection (also favors Africa) for the past few months

[tarheelprogrammer]

It's becoming more evident, for July, that the background state will move to look more like an El Nino episode. CFSv2 showed this as others posted, OP guidance is moving that way. Tropical forcing will center near the dateline and progress eastward. For the past few months it has been focused over Indonesia which is more favored for La Nina.

A negative for the Atlantic correct?

[Ntxw]

A negative for the Atlantic correct?

If the forecasts are correct, there could be more episodes of mid level dry air with that kind of spatial pattern. CPAC and WPAC activity would likely pick up.

[TheStormExpert]

It's becoming more evident, for July, that the background state will move to look more like an El Nino episode. CFSv2 showed this as others posted, OP guidance is moving that way. Tropical forcing will center near the dateline and progress eastward. For the past few months it has been focused over Indonesia which is more favored for La Nina.



Seasonal OLR depicts pretty well the Indonesian convection (also favors Africa) for the past few months

Wouldn't that green area eventually migrate east into the Atlantic basin as time progresses? I don't quite understand the map.

[RL3AO]

A negative for the Atlantic correct?

If the forecasts are correct, there could be more episodes of mid level dry air with that kind of spatial pattern. CPAC and WPAC activity would likely pick up.

I will note some unpublished research I've seen that shows the CFS under forecasts convection over the Maritime Continent during NH summer and over forecasts convection in the central/east Pacific.

[Ntxw]

Wouldn't that green area eventually migrate east into the Atlantic basin as time progresses? I don't quite understand the map.

It is a much broader, overall background state and it tends to traverse the tropics from the Indian Ocean through the Pacific. It doesn't really go to the Atlantic as the walker cell is often ENSO driven. The favorable area for the Atlantic is when convection persists over Indonesia and the Maritime continent. That spatial pattern reflects a more Nina-like background state and can help boost African convection and the MDR with rising air as we have seen the past 12+ months. But that pattern will be changing.

[Ntxw]

A negative for the Atlantic correct?

If the forecasts are correct, there could be more episodes of mid level dry air with that kind of spatial pattern. CPAC and WPAC activity would likely pick up.

I will note some unpublished research I've seen that shows the CFS under forecasts convection over the Maritime Continent during NH summer and over forecasts convection in the central/east Pacific.

It will be reflective of how the ENSO regions behave. The 28C surface temps (necessary for persistent tropical convection) has made its way slowly to 140W. This will likely be key whether or not the walker cell moves with the weak ENSO event

[TheStormExpert]

Wouldn't that green area eventually migrate east into the Atlantic basin as time progresses? I don't quite understand the map.

It is a much broader, overall background state and it tends to traverse the tropics from the Indian Ocean through the Pacific. It doesn't really go to the Atlantic as the walker cell is often ENSO driven. The favorable area for the Atlantic is when convection persists over Indonesia and the Maritime continent. That spatial pattern reflects a more Nina-like background state and can help boost African convection and the MDR with rising air as we have seen the past 12+ months. But that pattern will be changing.

What will this all mean for the remainder of the Atlantic hurricane season ?

[Kingarabian]

Here are my averages for today and the next 3 days:

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June 29: Tahiti: 1013.75,   Darwin: 1013.50, Daily value: -6 to -8
June 30: Tahiti: 1013.25,   Darwin: 1013.75, Daily value: -10 to -12
July 01:  Tahiti:  1012.00,  Darwin: 1013.00, Daily value:  -15
July 02:  Tahiti:  1013.00,  Darwin: 1013.75, Daily value:  -13


My daily values may be slightly off since I'm just eyeballing longpaddock's previous estimates and applying them here.

Now looking ahead past this weekend, Tuesday to Thursday look really positive according to the GFS. Could see +10's to +25's. Then by next week Friday and through the weekend it'll flip negative again, and we could also see -10's to -25's. GFS is showing long spells of 1016's sitting over Darwin late next week. However this is a long way out, and models show little skill this far out.

Edit: In the beginning of June, I recall the EPS weeklies showing a week in July with positive daily values before they tanked again. Looks like it'll be this upcoming week.

In regards to the SOI, my forecast for June 30 for did not verify since pressures at Darwin came in lower.

But for June 1, My forecast was 1012mb @ Tahiti, and Tahiti airport average did in fact came in @ around 1012mb (29.88inhg). But LongPaddock had a much higher pressure of 1012.76 mb @ Tahiti... I wonder what their methodology to determine the pressures are. Oh well. I was thinking with my numbers that we would see June come in @ -10.50 or lower.

Edit: LongPaddock's June average was -9.45, but the BOM came in lower @ -10.40. Interesting.

[Ntxw]

What will this all mean for the remainder of the Atlantic hurricane season ?

I wouldn't put too much worry about it putting a lid on the Atlantic quite yet. It's still relatively short term in the grand scheme and it just means for a few weeks the atmosphere will work against things trying to form and that the 2-3 months of 0.5C readings are reflecting some. It also coincides with typical lull that happens in July anyway for the Atlantic. Should the spatial pattern continue into August with the ENSO event persisting then its worth re-evaluating.

We've seen 0.5C readings for many months now, completely disregarding that ENSO won't play any kind of a role because it's not an "official Nino" is fool's gold. It is still enough for a weak event, we've been walking that fine line for awhile now.

[TheStormExpert]

Also what exactly is the Walker Cell?

[RL3AO]

Also what exactly is the Walker Cell?

It is a zonal (west to east) atmospheric circulation that sets up in response to deep tropical convection. The location of sustained convection shifts where the rising air is, which in turn shifts where the sinking air is. It's the primary reason that the Atlantic is unfavorable during El Nino and favorable during La Nina.

[Kingarabian]

Also what exactly is the Walker Cell?

The Walker Cell is essentially a circulation of rising and sinking air. The places where you have predominately warm waters is where the rising air part of the cell sets up, and this is very important for TC genesis. This is why the Pacific sees such an uptick in activity during an El-Nino. However, whatever goes up must come down, and that's the sinking part of the cell. So when you have an El Nino event (which occurs in the Pacific), air usually rises in the Pacific (CPAC->EPAC) and sinks in the GOM->Caribbean.

And this is why a lot of people are bringing up the term Modoki this season. If the El-Nino is central pacific based or the water is warmer @ Nino 4 and Nino 3.4, the Walker cell sets up further west and the sinking air lands in the far Eastern Pacific vs the GOM and the Caribbean.

[Kingarabian]

However in a Modoki event, Nino 1+2 is substantially cooler than what it is now. Nino 1+2 is actually quite warm at the current moment, but check the GOM where we see cool anomalies. Could it be that the sinking air is landing in the GOM vs the eastern EPAC?

[cycloneye]

However in a Modoki event, Nino 1+2 is substantially cooler than what it is now. Nino 1+2 is actually quite warm at the current moment, but check the GOM where we see cool anomalies. Could it be that the sinking air is landing in the GOM vs the eastern EPAC?

Part of that cooling is related to Cindy.

[Kingarabian]

However in a Modoki event, Nino 1+2 is substantially cooler than what it is now. Nino 1+2 is actually quite warm at the current moment, but check the GOM where we see cool anomalies. Could it be that the sinking air is landing in the GOM vs the eastern EPAC?

[img]http://i.imgur.com/obwSAOI.gif[/mg]

Part of that cooling is related to Cindy.

It's been cool since the past 3 months if you look at the NESDIS SST's http://www.ospo.noaa.gov/Products/ocean/sst/anomaly/

And Cindy has been gone for more than 2 weeks now, so they should've recovered.

[TheStormExpert]

SST's in the GoM are already in the mid-upper 80's so I don't know what all the fuss about slightly cooler than average anomalies is.

[Kingarabian]

:uarrow: SST's in the GoM are already in the mid-upper 80's so I don't know what all the fuss about slightly cooler than average anomalies is.

The GOM SST's are almost always sufficient enough to support the strongest of hurricanes. However, what the above map is showing is that the GOM this year is anomalously cooler than the 30 year average. So something IS going on there.

[TheStormExpert]

:uarrow: SST's in the GoM are already in the mid-upper 80's so I don't know what all the fuss about slightly cooler than average anomalies is.

The GOM SST's are almost always sufficient enough to support the strongest of hurricanes. However, what the above map is showing is that the GOM this year is anomalously cooler than the 30 year average. So something IS going on there.

Yeah but I'd think something like that in that particular sub-basin wouldn't be enough to cause any side effects.

[RL3AO]

However in a Modoki event, Nino 1+2 is substantially cooler than what it is now. Nino 1+2 is actually quite warm at the current moment, but check the GOM where we see cool anomalies. Could it be that the sinking air is landing in the GOM vs the eastern EPAC?

Anomalous sinking air would lead to above average SSTs, not below average.