GaWx

Well, well, well…if it isn’t the GFS up to its old tricks again. The 18Z GFS literally gives Tahiti on 5/13 a record low May SLP due to a nearby tiny surface low that gets as low as 1002 mb, highly unusual for May as it’s ~12 mb/0.36” BN. This results in ~1004.5 mb Tahiti pressure on 5/13. How low is this vs May history back to 1992? Well, the record low is 1004.7 (5/10/2002, during another incoming Nino). Second lowest? 1006.1 (5/31/1997, another incoming El Niño). Other very low SLPs there in May were also during incoming El Niño periods: 1007.5 on 5/9/2015 and 1007.8 on 5/19/2009. Will the record low May Tahiti SLP verify? Very highly doubtful considering that only the 18Z GFS had it that low with a tiny low almost right on top of Tahiti whereas other models had no low: 18Z GFS: 1002 low very near Tahiti But other recent GFS runs have also had a tiny low nearby though not as close. The brand new 0Z has the low but it’s not as close nor as strong (1005 instead of 1002). So, its lowest 24 hour averaged Tahiti pressure is only down to 1009 mb (on 5/12). I thought it was a good idea to post this because this could cause a couple of very strong -SOIs 5/12-13. Even just down to 1009 at Tahiti like the 0Z GFS has would mean a -35ish 5/12 SOI with near avg Darwin SLPs. This reminds me to mention that while Tahiti SLPs have been BN to MBN for most of the last 30 days (common with incoming Nino), there still have been no high pressures at Darwin, which have largely been NN. This is near the opposite of how April of 1997 went. It had 17 days of Darwin SLP of 1012+ vs only one day of that in April of 2026! There are few, if any, 1012+ in sight as of now other than possibly today, which may end up just above 1012 at Darwin.

Lots of power outages in Boulder and Denver areas from the very heavy wet snow. Is this going to end up a May record breaker for Boulder? This is from Boulder:

I had another enjoyable evening walk due to still pretty comfy dewpoints for early May. Third nice day in a row!

They’re not mentioning that the Euro has had a warm bias though it’s lowest for an actual Nino (few ticks on average with a couple almost perfect). May run has almost never verified too cool. They’re probably not aware of this bias. You won’t be less you study the verifications going back aways like I did. Of course even a warm bias doesn’t mean it will definitely verify colder.

1982-3 was east based and was an amazing winter snow wise in much of the SE US (E AL to NE NC)!

Also, note that like the CFS that the Euro has the Nino being pretty east based. Taking a few tenths off of this Euro prog due to its warm bias and then cooling it ~0.5 to roughly estimate RONI likely yields something pretty similar to the +2.5 C peak RONI (+2.7C peak month) of the most recent CFS runs, which would be near a record warm RONI (back to 1950) and would be a 1982-3 redux.

Also, note that climo used for TT’s CFS is 1984-2009, which is cooler than 1991-2020. If these CFS happen to verify, they’d make much more sense vs history of strong El Niño with their coolest anomalies in the S US vs the coolest anomalies on Cansips being in the N US, which is extremely out of sync with strong Nino climo. Also, the CFS has had and continues to have a stronger and more E based Nino vs a not quite as strong C to W based Nino on the Cansips runs: CFS: pretty E based and very strong Cansips: much more C to W based and not quite as strong

The slight lowering from March does though jibe with the slight downward trend of these WCS dailies:

The April and FMA relative and non-relative have just been released and they suggest the most recently calculated differential is ~0.6C: 1. FMA: ONI +0.11 RONI -0.48 0.59 diff vs 0.56 diff. JFM 2. April alone: ONI +0.36 RONI -0.24 0.60 diff. vs 0.55 in March

My leaning of the weekly relative 3.4 going up from +0.2 in last week’s release to +0.4 in today’s turned out to be what happened for its 4th rise in a row. Nino 1+2 cooled again (by 0.2) to +0.7. Nino 3, like Nino 3.4, rose for the 4th week in a row to +0.5. Nino 4 was unchanged at +0.5. So far, it’s not behaving as if it is headed to strongly E based this autumn. Cansips has been suggesting central to W based with E (1+2 to 3) not as warm as C to W (3.4 to 4), but we’ll see as there’s a long way to go: Date (avg for wk centered on)………………....1+2………..3………..3.4………..4 01APR2026 0.8 -0.3 -0.3 0.2 08APR2026 1.1 -0.1 -0.2 0.3 15APR2026 1.2 0.2 0.1 0.6 22APR2026 0.9 0.3 0.2 0.5 29APR2026 0.7 0.5 0.4 0.5 ——————- The latest SSTa charts suggest a pause, which is long overdue, MAY finally be occurring temporarily:

There was a historic very heavy snowstorm in the SE US on 3/24/1983. ATL got 7.9” of very wet snow, their heaviest snowstorm since Jan of 1940. That even gave Savannah a trace of sleet! ATL also had its snowiest winter (10.3”) since 1939-40 (another El Niño by the way).

But this CFS run is still showing a RONI-ONI gap of 0.5C (+2.5 vs +3.0). That narrowing is <0.1 vs the JFM gap of 0.56.

Officially I see only 0.05” at RDU for May 1-2: https://kamala.cod.edu/nc/latest.cdus42.RDU.KRAH.html Also, I see only 0.63” at FAY vs 0.91” on the map: https://kamala.cod.edu/nc/latest.cdus42.FAY.KRAH.html It’s as if they put in the wrong map. Maybe that was a forecast map?? But it has GSO right with nothing. Here’s a link to the last 7 days rainfall, which shows 0.44” at RDU, 0.77” at FAY, and 0.16” at GSO: https://kamala.cod.edu/offs/KRAH/2605031100.sxus52.html

Thanks, snowman. Indeed, it’s forecasting a 1982-3 redux as of now. The corresponding latest CFSv2 ONI forecast is at +3.0C, which is maintaining the recent ~0.5C difference between ONI and RONI:

There’s a May 2026 obs thread here: