GaWx

Per this, Nino 3.4 wasn't focused on until 1997: "Niño 3 (5N-5S, 150W-90W): This region was once the primary focus for monitoring and predicting El Niño, but researchers later learned that the key region for coupled ocean-atmosphere interactions for ENSO lies further west (Trenberth, 1997). Hence, the Niño 3.4 and ONI became favored for defining El Niño and La Niña events." https://climatedataguide.ucar.edu/climate-data/nino-sst-indices-nino-12-3-34-4-oni-and-tni

This is close to the most impressive looking cat 1 I can recall ever seeing. All 12Z trop models, which had it at cat 1 as of 18z, strengthen it to well into cat 2 (90-95 knts) as we head into tonight with a peak near DMAX/6Z. The NHC otoh has it weakening back to 60 knots at 6Z: "Today's strengthening was the result of the storm passing over the warmer waters of the Gulf Stream, however it will move north of those warmer waters later this evening, and Don has likely peaked in intensity. Weakening should begin overnight, with a faster rate of weakening expected Sunday through Monday as Don moves over even colder waters and the vertical wind shear increases. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 40.1N 50.0W 65 KT 75 MPH 12H 23/0600Z 42.0N 49.6W 60 KT 70 MPH 24H 23/1800Z 44.5N 47.6W 50 KT 60 MPH 36H 24/0600Z 46.4N 44.5W 40 KT 45 MPH...POST-TROPICAL 48H 24/1800Z 47.7N 40.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 25/0600Z...DISSIPATED $$ Forecaster Brown"

Don's a cane officially!

Not only that, but the 12Z models don't have Don reach peak strength for still another 12 hours (DMAX): -HWRF has it drop from 995 mb at 18Z to 988 mb at 6Z along with an increase from 70 knots at 18Z to 95 knot winds tonight -HMON rises from 80 to 90 knots -HAFS A rises from 65 to 95 knts -HAFS B rises from 70 to 95 knots So, the 4 Hurr models already have him cat 1 and strengthen him to strong cat 2!

1. Ooops, I misinterpreted that since they're in S Hem although them saying summer of 2024 instead of summer of 2023-4 threw me off, too. Thanks for pointing that out. 2. I looked at the report to better decipher what they're saying: https://cdn.www.gob.pe/uploads/document/file/4887650/Informe Tecnico ENFEN 20 JULIO 2023.pdf?v=1689981215 I looked at tables 8 and 10 along with figure 41. They have in table 8 moderate as being most likely by a good margin Sept-Dec with 65-61% chances with weak at only 10-21%. So, they're saying the best chance by a good margin is for Sept-Dec to have a moderate peak. But then table 10 shows weak favored over moderate for DJFM averaged out 43% to 38%. So, I'd say we're both right. They are calling for a moderate peak most likely for fall/early winter peak. But after that period when looking at the average for DJFM, alone, they're saying there's a slightly higher chance (43% vs 38%) for it to weaken to weak rather than maintain moderate. So, they are going against the model consensus in saying a moderate rather than strong+ peak. That's significant. And they're calling for a rapid enough weakening starting by Jan to allow DJFM to have a slightly better chance to average only weak.

They're saying that weak (43%) is more likely than moderate (38%) "by summer of 2024". That's after weakening from its fall/winter max, which would be moderate+.

I just checked all 4 6Z hurricane models. All strengthen to a peak near 6Z tomorrow/DMAX. All 4 have minimal H force winds somewhere between 0Z and 6Z.

Thank you! Thus is great info. So, the nearby pavement is why highs are hotter than Key West. That along with SSTs in the low 90s is allowing upper 90s highs. But what I'm trying to decipher is whether or not we have an apples to apples comparison to past Marathon records. How far back has there been similar pavement closeby? I don't think the article is real clear on that.

The heat and humidity has been awful all week here with mid to upper 90s highs and DPs averaging in the low 70s. All of my walking for the last month+ has been on the treadmill in AC. That's not unusual for most of the summer. I miss my summer trips to the beautiful and so comfortable CO Rockies! Maybe I'll go back there again at some point.

Thanks. I forgot to mention that it has been VERY dry in the FL Keys and surrounding areas. That lack of rainfall/above average sunshine has played a part in the hot waters there, especially the shallow ones, as it typically does in other areas in the summer. In my daily looks at the Johnson Key buoy, I see this with SSTs cooler on the few showery days.

Don a bit stronger and now forecasted to reach 55 knots: SUMMARY OF 500 PM AST...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...36.6N 47.5W ABOUT 755 MI...1215 KM SSE OF CAPE RACE NEWFOUNDLAND MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES ------------ FORECAST POSITIONS AND MAX WINDS INIT 21/2100Z 36.6N 47.5W 50 KT 60 MPH 12H 22/0600Z 37.9N 48.9W 55 KT 65 MPH 24H 22/1800Z 40.0N 50.2W 55 KT 65 MPH 36H 23/0600Z 42.4N 50.0W 50 KT 60 MPH 48H 23/1800Z 44.6N 48.6W 40 KT 45 MPH...POST-TROPICAL 60H 24/0600Z 47.1N 45.1W 35 KT 40 MPH...POST-TROPICAL 72H 24/1800Z 48.7N 41.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 25/1800Z...DISSIPATED $$ Forecaster Brown Edit: The 12Z models including hurricane models and Euro ens don't have Don peaking til near DMAX early Sun AM. But this NHC forecast has him peaking before that and then weakening early Sun AM.

05L DON 230721 1800 36.2N 47.0W ATL 50 998 This drop of 4 mb from 1002 to 998 is the first change in the pressure by the NHC since way back at 11PM EDT Wednesday night. It had been stuck at 1002 mb for 36 hours. Edit: He is approaching his own wake and will be crossing it tonight. I wonder if reduced SSTs from that will lead to weakening through tonight. Also, DMIN is approaching. Opinions?

All four of the new hurricane model runs (12Z) now strengthen Don through DMAX of early Sunday morning. That's a full 36 hours from now. They're all stronger than recent runs and the HMON is the strongest run yet for it as of that time.

To show how unprecedented in the records is the heat this month at Marathon in the FL Keys (records back to 1950), the largest # of days with highs of 96+ for the entire YEAR before 2023 was 11 in 1987, followed by 9 in 2019 and 8 in 2022. There have been 15 straight days counting today with highs of 96+ and 16 total days this month! That's truly amazing for a location surrounded by ocean. Prior to this month, the warmest month on record was 88.0 set in June of 2019. July of 2023 is at 90.0 MTD! Should that hold up, a two degree margin over the prior record for a station surrounded by water would be quite notable. Assuming there haven't been any recent changes in or location of the sensors at Marathon Airport, July of 2023 there will be considered astounding. I'm not aware of any. The 90.0 MTD air temp there is very believable when considering SSTs in and near the Keys averaging in the low 90s MTD. If they were, say, instead in the upper 80s, I might have questioned the Marathon sensors as the average air temp is often 1-2 F cooler than the average nearby SST. Besides the background support from AGW, what else is causing this extreme marine heatwave? Any ideas? What is causing SST averages in the area to be stuck in the lower 90s for the entire month? Some of the very shallow waters such as at Johnson Key buoy to the north in FL Bay even had 5+ days of upper 90s SST highs last week! (That location has water that is only ~5 feet deep though. So, it routinely has daily ranges of 8+ degrees. So, even when it had SST highs of 97+, it had SST lows of upper 80s/near 90 and daily averages near 93.) Is the Tonga volcano that put a lot of water vapor in the air an additional factor there and worldwide?

I don't at all believe that Don is still only at 45 knots.This will likely be strengthened during post storm reviews.

1. The 12Z GEFS is by a good margin the most active GEFS with this in the last two days of runs with ~3 H. 2. ASCAT/visible imagery suggests a LLC near 11N, 39W, but the NHC is focusing on an area near 11N, 30W: https://www.nhc.noaa.gov/gtwo.php?basin=atlc&fdays=7

The inferior CFS today suddenly has the MJO only getting to the circle (i.e., amplitude of 1.0) on top as opposed to above it, including in your post from Monday. Just yesterday and every day for the last 10+ days it also had it well into phases 5 and 6. Earlier this month, it had an amplitude as high as the low 2 range! Today's CFS MJO: To compare, here's 7/11/23 CFS:

This climate.gov list is strictly based on DJF ONI as opposed to peak ONI. That's why 1965-6, which peaked way up at 2.0 in SON and OND, is classified as only moderate in it. That's likely why 2009-10, which peaked at 1.6 in NDJ (D was 1.74 and J was 1.51) counted as only moderate. 2002-3, which peaked well into moderate (1.3) in OND (D was 1.31), and 1987-8 are counted as only weak here for a similar reason. Also, this apparently was done before 2018-9 since it isn't on it though the link has 7/2021 in it. The list we're discussing: https://www.climate.gov/sites/default/files/2021-07/ENSO_winters_ElNino_temp_1240.jpg ONI: https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php

The Euro ens keeps going back and forth from fairly inactive to moderately active. The 12Z run is back to 5H, which is what yesterday's 12Z had. Meanwhile, TS Don is now predicted to peak at 50 knots/60 mph during 24-48 hours on the new NHC track due to better organization. That implies a slightly increased chance for it to reach H status.

This is from a reply to me by @bdgwx about this when I asked in April for feedback regarding JB's article regarding his feeling that warmer SSTs and underwater seismic activity could be connected: "2) He doesn't explain where he got the seismic data so I cannot replicate his work. But assuming the data is correct and there are no caveats to it's use (experience tells us that is a big IF coming from JB) that still does not mean seismic activity is THE cause of the warming. Correlation does not guarantee causation. Furthermore, we know the planetary energy imbalance is about +0.8 W/m2. It is generally accepted that geothermal activity releases about 0.1 W/m2 on average. If JB is going to make the extraordinary claim that geothermal activity increased by a factor of 9 (0.9 - 0.1 = 0.8 W/m2) then he needs to present extraordinary evidence. Finally, he will need to explain how warming from bottom up can cause the stratosphere to cool."

However, looking at the NH itself on the CFSR, it is now holding its own as it is actually significantly hotter than it was on July 6th. On that day it was 21.93, which was well under the then record CFSR high of 22.18 set on 8/9/2022. But that 22.18 was subsequently exceeded on 7/16/2023, when the NH hit 22.21. Moreover, it has since risen to 22.42 as of 7/18/2023, nearly 0.5 above 12 days prior! In the meantime, the SH has fallen markedly from the 7/6/2023's 12.62 down to 12.00 as of 7/18/2023. So, the global warmth is in mid July of 2023 more NH than SH driven vs the more SH driven record warmth of early July of 2023.

You're correct about early this month per this from the CFSR site: "It is important to note that much of the elevated global mean temperature signal was associated with weather patterns in the Southern Hemisphere that brought warmer-than-usual air over portions of the Antarctic."

CFS/CFSR is a numerical climate/weather modeling framework that ingests surface, radiosonde, and satellite observations to estimate the state of the atmosphere at hourly time resolution onward from 1 January 1979. The horizontal gridcell resolution is 0.5°x0.5° (~ 55km at 45°N). The daily means are calculated from eight 3-hourly CFS timeslices beginning at 0000 UTC. The chart and maps update each day at about 0500 UTC with CFS estimates for the preceding day. Temperature anomalies are in reference to 1979–2000 climatology for each specific day of the year.

After falling from the record global high 17.23C on July 6th back down to 16.94 on July 14th, CFSR has rewarmed to 17.17 on July 18th. It will be interesting to see whether it rises above 17.23 within the next couple of weeks as normals don't start dropping for another 2 weeks or so. Does anyone have a prediction? https://climatereanalyzer.org/clim/t2_daily/

Marathon, FL, in the Keys has had an amazing 12 days in a row of 96-99F for highs including today! Their highest on record back to 1950 is 99, which was tied this month.