2025 Indicators: SST's, MSLP, Shear, SAL, Steering, Instability (Day 16+ Climate Models)

[WeatherBoy2000]

The OISST data (as Andy tweeted) actually looks somewhat different with Coral Reef Watch when it comes to the "southern MDR" near 10N:

https://i.postimg.cc/6q8GppQn/image.png

https://i.postimg.cc/zXRgmv61/image.png

Don't know what's up with the discrepancy between the two. The Coral Reef watch still shows a slightly above normal mdr while the OISST has had the mdr tank below normal in the past couple days:

https://cyclonicwx.com/data/sst/crw_ssta_graph_atlmdr.png

https://cyclonicwx.com/data/sst/oisst_ssta_graph_atlmdr.png

This is something I looked into a few years ago, and there are primarily three factors in the differences: (1) variability in data input, (2) gridded resolution, and (3) interpolation used to determine missing gridded values/correction algorithms to biases.

Coral Reef Watch (CRW)
Data input - This is derived using primarily SST data from thermal infrared sensors on nine polar-orbiting satellites (also known as the real-time Geo-Polar Blended SST) and all of the in situ data contained within the the International Comprehensive Ocean-Atmosphere Data Set (ICOADS).

Resolution - The CRW product has a 5km resolution (0.05 degree spatial resolution).

Processing/algorithms - Gaps are filled using optimal interpolation, with bias corrections based on the OSTIA (Operational Sea Surface Temperature and Sea Ice Analysis) dataset.

This is also only a nighttime product, from NOAA's methodology section:

The CoralTemp SST provides a measurement of the nighttime ocean temperature at the sea surface, calibrated to 0.2 meters depth. Nighttime-only satellite SST observations are used to reduce the influence of daytime warming caused by solar heating at and near the sea surface and to avoid contamination from solar glare. Furthermore, at night, water temperatures at and near the sea surface are more vertically uniform.

https://coralreefwatch.noaa.gov/product/5km/methodology.php#sst

Optimum Interpolation Sea Surface Temperature (OISST)
Data input - OISST employs optimal interpolation to combine satellite data (primarily AVHRR), in situ measurements (ships, buoys, Argo floats), and proxy SSTs from sea ice concentrations. Essentially, it uses a more comprehensive range of data sources.

Resolution - OISST uses a much coarser resolution at 25km (0.25 degree spatial resolution).

Processing/algorithms - OISST incorporates both daytime and nighttime observations, which can introduce differences due to diurnal warming effects. It uses a broader range of data sources and applies bias corrections relative to buoy data, with monthly adjustments to ship and satellite data.

https://i.imgur.com/vweDfr3.png

TL;DR
OISST’s inclusion of in situ data and broader interpolation techniques may smooth out anomalies over larger areas, while CRW’s higher-resolution, satellite-focused approach captures finer-scale variations. CRW focuses heavily on resolution since the product was designed to examine abrupt SST departures/thermal stresses and coral reef monitoring. OISST is considered a more general-purpose climate data product; its coarser resolution and broader data integration prioritize global consistency over localized precision (like ENSO monitoring).

Official documentation
CRW - https://coastwatch.noaa.gov/cwn/products/noaa-geo-polar-blended-global-sea-surface-temperature-analysis-level-4.html
OISST - https://www.ncei.noaa.gov/products/optimum-interpolation-sst

Thanks for the info. I just found it odd given that up until a few days ago they were similar.

[USTropics]

Don't know what's up with the discrepancy between the two. The Coral Reef watch still shows a slightly above normal mdr while the OISST has had the mdr tank below normal in the past couple days:

https://cyclonicwx.com/data/sst/crw_ssta_graph_atlmdr.png

https://cyclonicwx.com/data/sst/oisst_ssta_graph_atlmdr.png

This is something I looked into a few years ago, and there are primarily three factors in the differences: (1) variability in data input, (2) gridded resolution, and (3) interpolation used to determine missing gridded values/correction algorithms to biases.

Coral Reef Watch (CRW)
Data input - This is derived using primarily SST data from thermal infrared sensors on nine polar-orbiting satellites (also known as the real-time Geo-Polar Blended SST) and all of the in situ data contained within the the International Comprehensive Ocean-Atmosphere Data Set (ICOADS).

Resolution - The CRW product has a 5km resolution (0.05 degree spatial resolution).

Processing/algorithms - Gaps are filled using optimal interpolation, with bias corrections based on the OSTIA (Operational Sea Surface Temperature and Sea Ice Analysis) dataset.

This is also only a nighttime product, from NOAA's methodology section:

The CoralTemp SST provides a measurement of the nighttime ocean temperature at the sea surface, calibrated to 0.2 meters depth. Nighttime-only satellite SST observations are used to reduce the influence of daytime warming caused by solar heating at and near the sea surface and to avoid contamination from solar glare. Furthermore, at night, water temperatures at and near the sea surface are more vertically uniform.

https://coralreefwatch.noaa.gov/product/5km/methodology.php#sst

Optimum Interpolation Sea Surface Temperature (OISST)
Data input - OISST employs optimal interpolation to combine satellite data (primarily AVHRR), in situ measurements (ships, buoys, Argo floats), and proxy SSTs from sea ice concentrations. Essentially, it uses a more comprehensive range of data sources.

Resolution - OISST uses a much coarser resolution at 25km (0.25 degree spatial resolution).

Processing/algorithms - OISST incorporates both daytime and nighttime observations, which can introduce differences due to diurnal warming effects. It uses a broader range of data sources and applies bias corrections relative to buoy data, with monthly adjustments to ship and satellite data.

https://i.imgur.com/vweDfr3.png

TL;DR
OISST’s inclusion of in situ data and broader interpolation techniques may smooth out anomalies over larger areas, while CRW’s higher-resolution, satellite-focused approach captures finer-scale variations. CRW focuses heavily on resolution since the product was designed to examine abrupt SST departures/thermal stresses and coral reef monitoring. OISST is considered a more general-purpose climate data product; its coarser resolution and broader data integration prioritize global consistency over localized precision (like ENSO monitoring).

Official documentation
CRW - https://coastwatch.noaa.gov/cwn/products/noaa-geo-polar-blended-global-sea-surface-temperature-analysis-level-4.html
OISST - https://www.ncei.noaa.gov/products/optimum-interpolation-sst

Thanks for the info. I just found it odd given that up until a few days ago they were similar.

Yea I would say there is probably some localized resolution issues that the OISST 'smooths' out and it runs just slightly cooler than the CRW product (particularly along those areas in the southern MDR like you stated earlier). If you look at raw SSTs for eastern Atlantic, they are about ~0.2 degrees STD difference.




I've been working with COWVR-TEMPEST data the past few months and can state there are definitely contamination issues with heavy precip/SAL in these high-res polar orbiting instruments. I don't believe that is the case here, but when we do get an active ITCZ/WAM or significant dust/SAL outbreak, I would lean more towards the in situ data from OISST. Essentially, if the satellite data is flagged as rain/SAL contaminated, it's ignored (and CRW defaults to ICOADS data, which is not nearly as good as the in situ data for OISST). Otherwise, I think the resolution on the CRW product will give a more accurate measurement for localized areas.

[TomballEd]

I saw a Facebook post, going off (I think Euro) there should be an 850 mb wind anomaly that should warm the MDR back up, which would mean things would be generally favorable for an active ASO heart of the season but I'll believe weaker/reversed trades when I see it although CFS and CanSIPS surface pressure anomalies would seem to support Euro longer range ensembles.

I have to ask my wife for permission to pay for Giphy. My free trial has expired.

[WeatherBoy2000]

I saw a Facebook post, going off (I think Euro) there should be an 850 mb wind anomaly that should warm the MDR back up, which would mean things would be generally favorable for an active ASO heart of the season but I'll believe weaker/reversed trades when I see it although CFS and CanSIPS surface pressure anomalies would seem to support Euro longer range ensembles.

I have to ask my wife for permission to pay for Giphy. My free trial has expired.

Looks like around the turn of the month might be when things start to warm up.

[mixedDanilo.E]

I think Andy Hazelton might have mentioned it but this year we have a pretty similar look currently to 2003 in the Atlantic:


Eventually, in 2003 lots of the subtropics warmth made it's way into the MDR by the peak, and this is the look we ended up with by August:



The models showing trades weakening as we head into July means that the MDR might have a chance to warm up significantly soon and if it persists throughout the whole month, I wouldn't be shocked if we end up with a look more like 03 in August. Mind you, 2003 as whole ended up producing 176 ACE points, which does count as hyperactive. Not saying that will happen for this year, but it is interesting that we do look similar to a year like 03 where it did end up happening. That'll be very reliant on the peak season though, which in 03 we had storms like Fabian and Isabel which helped rack up the ACE as they were very long tracked storms. For that we'll have to rely on perfect MJO timing for the peak, which we certainly had a lack of last year.

[DorkyMcDorkface]

I think Andy Hazelton might have mentioned it but this year we have a pretty similar look currently to 2003 in the Atlantic:
https://coralreefwatch.noaa.gov/data/5km/v3.1_op/image/daily/ssta/png/2003/06/ct5km_ssta_v3.1_global_20030619.png https://coralreefwatch.noaa.gov/data/5km/v3.1_op/image/daily/ssta/png/2025/06/ct5km_ssta_v3.1_global_20250619.png

Eventually, in 2003 lots of the subtropics warmth made it's way into the MDR by the peak, and this is the look we ended up with by August:

https://coralreefwatch.noaa.gov/data/5km/v3.1_op/image/daily/ssta/png/2003/08/ct5km_ssta_v3.1_global_20030819.png

The models showing trades weakening as we head into July means that the MDR might have a chance to warm up significantly soon and if it persists throughout the whole month, I wouldn't be shocked if we end up with a look more like 03 in August. Mind you, 2003 as whole ended up producing 176 ACE points, which does count as hyperactive. Not saying that will happen for this year, but it is interesting that we do look similar to a year like 03 where it did end up happening. That'll be very reliant on the peak season though, which in 03 we had storms like Fabian and Isabel which helped rack up the ACE as they were very long tracked storms. For that we'll have to rely on perfect MJO timing for the peak, which we certainly had a lack of last year.

Neutral ENSO and warm stripe in the subtropics with middling MDR definitely is reminiscent of 2003. I suppose it's one of the more upper echelon analogs given it was a hyperactive year as you mentioned, but that look isn't far off from what we have now yeah, and as you mentioned if the trades relax significantly as modeled there's a good chance a more classic +AMO pattern (EOF1 anyway) could resurface with that subtropical warmth migrating southward.

[gatorcane]

My thinking is that we will see an active, above normal season. While the SST configuration with above normal SSTs appear to be in the subtropical Atlantic this year, which could induce some subsidence and less favorable conditions across the MDR east of the Lesser Antilles, I expect tropical waves to develop potentially further west where there should be favorable conditions across the Caribbean and Gulf with above normal SSTs there. SSTs across the EPAC are below normal and looks very likely we could be in a La Nina configuration come peak Atlantic hurricane months which should favor activity across the Gulf and Caribbean. The other thing to point out here is that we are two years after El Nino end and we have seen where it is this second year where the Atlantic can be very active. Overall, indicators to me suggest an active season especially late Aug through October.

[WeatherBoy2000]

My thinking is that we will see an active, above normal season. While the SST configuration with above normal SSTs appear to be in the subtropical Atlantic this year, which could induce some subsidence and less favorable conditions across the MDR east of the Lesser Antilles, I expect tropical waves to develop potentially further west where there should be favorable conditions across the Caribbean and Gulf with above normal SSTs there. SSTs across the EPAC are below normal and looks very likely we could be in a La Nina configuration come peak Atlantic hurricane months which should favor activity across the Gulf and Caribbean. The other thing to point out here is that we are two years after El Nino end and we have seen where it is this second year where the Atlantic can be very active. Overall, indicators to me suggest an active season especially late Aug through October.

Yeah despite the record-breaking activity in the epac now, climate modelling seems to be more in the Atlantic's court later down the road. They're leaning more in the -enso/la nina direction by the fall, and there are indications of a more favorable mdr warming pattern come July. As already mentioned, there's little correlation between early season activity (or a lack there of) and activity overall.

[Category5Kaiju]

Merely several days ago, the idea of June going stormless in the Atlantic seemed very real. I mean, even I believed that. And then popped up the first named storm of the season.

A cautionary tale that things in the tropics can change abruptly and that sometimes models don’t see a potential for a named storm until close range. Especially if it’s a shorty.

[chaser1]

Merely several days ago, the idea of June going stormless in the Atlantic seemed very real. I mean, even I believed that. And then popped up the first named storm of the season.

A cautionary tale that things in the tropics can change abruptly and that sometimes models don’t see a potential for a named storm until close range. Especially if it’s a shorty.

All of the above is very true; Heck, we could end up with one or two more named storms before July 1st if classification standards have truly "de-volve" to include:
Nominally supportive ASCAT data, no supported ship report or recon data, 6 - 12 hours of system center co-located sustained convective bursting and banding continuity, incorporating model composite reflectivity interpretation for actual surface condition verification, and overall consensus that a warm core Tropical Storm is technically defined by forming over at least 22C SST and having sustained winds near the center to reach a minimum of "30 - 35 knots" (not 39 mph).

It really is about time that updated meteorology docs/books be published to more accurately define & represent definition benchmarks. At a minimum, the standards used to define a named tropical storm should be no different regardless of whether a tropical disturbance were in the GOM, far N. Atlantic, or the far Eastern MDR. There have been more instances than I could possibly remember where an equally or more impressive disturbance in the E. MDR with better supporting ASCAT data, remained unclassified due to "no immediate risk to land or shipping interests" and/or unanimous agreement on near term condition volatility (upper wind shear, dry air intrusion, or significant decrease in SST along the immediate path).
(This edit to clearly point out that my post above is meant in NO way as bashing NHC or any forecaster, but to soley point out the need for continuity in science, nomenclature, classification & definition).

[TomballEd]

Just peeking at the Weathernerd 10 day ECENS for the EPac and the WPac, excluding short lived systems forming well N of the tropics that barely reach gale force, the Atlantic stays dead for a while. Waiting to see if weak trade winds/WWB will warm the MDR back up in time for ASO primetime. The Euro ensembles for the WPAC suggests that will provide a substitute for a slow Atlantic. A lot of majors in the general vicinity of Hong Kong.

[DorkyMcDorkface]

The CFS is actually looking like it's trending towards more of a favorable pattern for July in recent runs, with less widespread sinking in the Atlantic, a weaker MC standing wave and more -VP over Africa.

[chaser1]

Just my opinion but your perspective of "Less widespread sinking" throughout the Atlantic during July based on the latest CFS seems....... quite the generous relative comparison to the prior forecast.

[weeniepatrol]

Disgusting. Say goodbye to SSMIS.

[DorkyMcDorkface]

Just my opinion but your perspective of "Less widespread sinking" throughout the Atlantic during July based on the latest CFS seems....... quite the generous relative comparison to the prior forecast.

Perhaps I was being hyperbolic with my terminology but my main focus really was on Africa and the eastern Atlantic, because that is where a -VP standing wave is most optimal. Outside of CAG season (which we are on the verge of exiting) you don't want persistent anomalous rising in the western part of the basin if you are looking for Atlantic activity since that's more likely to favor the EPAC.

[cycloneye]

That is a very strong dry signal for the next few weeks.

 https://x.com/BenNollWeather/status/1938233285965979666

[OURAGAN]

Yes

[OURAGAN]

Below average rainfall is predicted for caribbean and the Atlantic MDR the next two weeks

[chaser1]

Just my opinion but your perspective of "Less widespread sinking" throughout the Atlantic during July based on the latest CFS seems....... quite the generous relative comparison to the prior forecast.

Perhaps I was being hyperbolic with my terminology but my main focus really was on Africa and the eastern Atlantic, because that is where a -VP standing wave is most optimal. Outside of CAG season (which we are on the verge of exiting) you don't want persistent anomalous rising in the western part of the basin if you are looking for Atlantic activity since that's more likely to favor the EPAC.

Valid point and to what extent we continue to see continued westward expansion of that wave further into the basin, should go a long way toward suggesting the Atlantic MDR may be soon waking up (which I do get was your point to begin with )
For now though I think this progression will be a slow one.

[cycloneye]

Not good if you want to see tropical activity.

 https://x.com/wxjerdman/status/1938546547869765947