2024 Indicators: SST's, MSLP, Shear, SAL, Steering, Instability (Day 16+ Climate Models)

[psyclone]

The relative calm we're experiencing really torches peak season for western areas (like the western gulf) but for areas farther east a late start is of little help. Peak season for Fl is latter Sept through October. For Texas the sedate conditions are really mitigating risk...out east...not so much..at least not yet. So if we think of peak season being late August through Early October...each day is about 2%. 4% good...but I still have nagging concerns about the remaining 96%...Nevertheless...each 12 hour segment is 1% through the hourglass and reflective of a small victory..

[cycloneye]

Interesting post on X from Dr Kim Wood. That last message was the most interesting one.

 https://x.com/DrKimWood/status/1826323775979413778




 https://x.com/DrKimWood/status/1826324331867374015




 https://x.com/DrKimWood/status/1826325665597325820

Dry, dusty air from the Sahara can be tracked in multiple ways. Here's a perspective from Band 10, lower-level water vapor, on GOES-16 comparing August 2020 (left) and August 2024 (right).

Higher values imply warmer and/or drier air, which can inhibit tropical activity.

These Hovmöller diagrams show evolution over time and space. Y-axis is time, with older on top and newer at the bottom. X-axis is longitude from west (left) to east (right).

Diagonal slopes from older/east to newer/west show westward-moving phenomena like African easterly waves.

Now that we've constructed this perspective, and since anomalies are calculated the same way in both plots (relative to 2017-2024), we can see that drier air in 2020 was of similar magnitude to drier air currently in place in 2024.

[SconnieCane]

Atlantic tropical watchers in August 2024 (can't get Youtube tags to work):

https://www.youtube.com/watch?v=9WatQeG5fMU

[IcyTundra]

The relative calm we're experiencing really torches peak season for western areas (like the western gulf) but for areas farther east a late start is of little help. Peak season for Fl is latter Sept through October. For Texas the sedate conditions are really mitigating risk...out east...not so much..at least not yet. So if we think of peak season being late August through Early October...each day is about 2%. 4% good...but I still have nagging concerns about the remaining 96%...Nevertheless...each 12 hour segment is 1% through the hourglass and reflective of a small victory..

Like you said here in the western gulf we are usually in the clear after September. It is rare for a TC to impact us in October so I am enjoying this quiet period right now but I still have another 5 and a half weeks to get through until I will feel much better.

[Steve]

IMO, the problem has been the seasonal forecasts from April and May from CSU, TSR, NOAA and other private firms that where bullish will numbers over 20 and some added words like hell (JB), explosive (Accuweather) etc that penetrated in the public and was in the news on TV, internet and newspapers and that has sticked until now and will continue to dominate the conversation as long the quiet period continues. But there is the other side about this and is, if we just got 4 more cat 3 or higher intensity TC's, ACE wise we could verify hyperactive ACE at the 165 threshold, with only 9 more named storms. Looking more and more quality over quantity.

The other problem is that in addition to the extreme forecasts they mostly all said that their forecasts were of above-average confidence.

This is for sure at least many of them. So it’s probably going to be a rocky rest of the season. If the extreme forecasts bust (talking more ACE than actual number), **** will be figured out in the future by research mets. As of now most are speculating, conjecturing or offering possible clues as to the current lull.

[Hammy]

Saw this in 1998 and 1999 (notable for being the first two seasons after 1997 that I closely tracked, but was also wondering if August-free years would be the norm given the late starts) a week or so before activity took off, that huge tail of moisture. Unless we're missing some large scale yet-to-be-known atmospheric or oceanic factor like in 2007 or 2013, the waves are going to start pulling this moisture into them as they come off--Bonnie in 1998 formed from an almost cloud-free tropical wave after pulling it in.

[Category5Kaiju]

https://i.imgur.com/rMw5Fbn.png

Saw this in 1998 and 1999 (notable for being the first two seasons after 1997 that I closely tracked, but was also wondering if August-free years would be the norm given the late starts) a week or so before activity took off, that huge tail of moisture. Unless we're missing some large scale yet-to-be-known atmospheric or oceanic factor like in 2007 or 2013, the waves are going to start pulling this moisture into them as they come off--Bonnie in 1998 formed from an almost cloud-free tropical wave after pulling it in.

Interesting you bring up 1998 and 1999; those years were very quality over quantity years, with the bulk of their Cape Verde activity starting in September. Between Georges, Mitch, Floyd, and Lenny, some pretty strong storms too, extending into October/November.

[Teban54]

Reminder: Models showed a storm-free August 2019 five days before Dorian formed.

 https://x.com/AndyHazelton/status/1826353695048827170

[aspen]

Reminder: Models showed a storm-free August 2019 five days before Dorian formed.

 https://x.com/AndyHazelton/status/1826353695048827170

Ryan brings up something interesting in the comments: the strong circulations of the tropical waves exiting over the cool Canary Current may be enhancing the SAL issues in the area, further snuffing out these northerly-tracking waves.

[caneseddy]

One thing I will say..it may be quiet right now but for us here in SE Florida September is when the action begins. SE Florida rarely gets August impacts, other than Andrew and the 1949 Delray Beach Hurricane..all the big ones have been from September onwards so we will see what this month brings.

[Hammy]

I created a thread (The post is exceptionally long) but I'll post the final numbers here, the comparison years that I used that have progressed largely the same up to this point, factoring if the rest of the season goes as those years did, we would end up at:

2000: 15/8/3 and 107 ACE.
2006: 9/6/3 and 118 ACE (note: this is only through September 30)
2022: 15/10/3 and 146 ACE
2001: 16/12/5 and 151 ACE
2018: 15/8/3 and 167 ACE
2016: 14/7/5 and 181 ACE
2003: 16/7/3 and 212 ACE
2017: 14/9/6 and 240 ACE

2006 was included as we were not in an El Nino originally and as it progressed to that, led to the forecast bust (this year is not going in that direction so using September-only still works as Oct-Nov would add even more this year)

[SteveM]

Reminder: Models showed a storm-free August 2019 five days before Dorian formed.

 https://x.com/AndyHazelton/status/1826353695048827170

A fair point, although it is worth noting that most of the time models show a storm-free 5 days, there are no storms. We can't be sure but let's see.

[Woofde]

Reminder: Models showed a storm-free August 2019 five days before Dorian formed.

 https://x.com/AndyHazelton/status/1826353695048827170

Ryan brings up something interesting in the comments: the strong circulations of the tropical waves exiting over the cool Canary Current may be enhancing the SAL issues in the area, further snuffing out these northerly-tracking waves.

Its certainly not a fun time for a wave that's for sure. Does the monsoon trough being further North work to moisten that area and as such reduce dust later in the season, or is it a largely futile effort due to the geography of that part of Africa?

[LarryWx]

Euro weeklies mean ACE forecast update vs norm last 7 days (newest far right, which is 0Z of Wed):

8/26-9/1: 60%/50%/50%/50%/30%/20%/20%; Norm 14
9/2-8: 110%/120%/100%/110%/70%/70%/60%; norm 15
9/9-15: 80%/90%/80%/100%/80%/90%/80%; norm 16
9/16-22: 90%/80%: norm 13

So, in today’s Euro Weeklies update regarding these 4 weeks, the progged ACE mean is 35, which is a drop vs yesterday’s 40 and is significantly below the 1991-2020 avg of 58. Nearly 3/4 of this deficit is due to weeks 1-2.
Thoughts?

https://charts.ecmwf.int/products/mofc_ ... 2409020000

[toad strangler]

Euro weeklies mean ACE forecast update vs norm last 7 days (newest far right, which is 0Z of Wed):

8/26-9/1: 60%/50%/50%/50%/30%/20%/20%; Norm 14
9/2-8: 110%/120%/100%/110%/70%/70%/60%; norm 15
9/9-15: 80%/90%/80%/100%/80%/90%/80%; norm 16
9/16-22: 90%/80%: norm 13

So, in today’s Euro Weeklies update regarding these 4 weeks, the progged ACE mean is 35, which is a drop vs yesterday’s 40 and is significantly below the 1991-2020 avg of 58. Nearly 3/4 of this deficit is due to weeks 1-2.
Thoughts?

https://charts.ecmwf.int/products/mofc_ ... 2409020000

Wake me up when its ZERO

[WeatherBoy2000]

 https://x.com/rushtropicalwx/status/1826311473292845566

[Spacecoast]

Euro weeklies mean ACE forecast update vs norm last 7 days (newest far right, which is 0Z of Wed):

8/26-9/1: 60%/50%/50%/50%/30%/20%/20%; Norm 14
9/2-8: 110%/120%/100%/110%/70%/70%/60%; norm 15
9/9-15: 80%/90%/80%/100%/80%/90%/80%; norm 16
9/16-22: 90%/80%: norm 13

So, in today’s Euro Weeklies update regarding these 4 weeks, the progged ACE mean is 35, which is a drop vs yesterday’s 40 and is significantly below the 1991-2020 avg of 58. Nearly 3/4 of this deficit is due to weeks 1-2.
Thoughts?

https://charts.ecmwf.int/products/mofc_ ... 2409020000

I'll go out on a limb.
It's possible that the models may be correctly forecasting the next two weeks below normal activity. The recent 2 week CSU forecast had a 80% chance of less than 22 ACE for the same period. They use tercile ranges instead of normal 14 ACE, but still had a higher probability of below normal ACE (25%), than above normal ACE (20%).

What's surprising is that ACE forecast remains below the 20 year climate mean (which includes both active, and 'inactive' years) through weeks 3-4. I have noticed that the extended range anomaly forecast seems to also show below normal activity through most of Sept.

Of course, it's possible the models are wrong.....

[MarioProtVI]

Euro weeklies mean ACE forecast update vs norm last 7 days (newest far right, which is 0Z of Wed):

8/26-9/1: 60%/50%/50%/50%/30%/20%/20%; Norm 14
9/2-8: 110%/120%/100%/110%/70%/70%/60%; norm 15
9/9-15: 80%/90%/80%/100%/80%/90%/80%; norm 16
9/16-22: 90%/80%: norm 13

So, in today’s Euro Weeklies update regarding these 4 weeks, the progged ACE mean is 35, which is a drop vs yesterday’s 40 and is significantly below the 1991-2020 avg of 58. Nearly 3/4 of this deficit is due to weeks 1-2.
Thoughts?

https://charts.ecmwf.int/products/mofc_ ... 2409020000

I'll go out on a limb.
It's possible that the models may be correctly forecasting the next two weeks below normal activity. The recent 2 week CSU forecast had a 80% chance of less than 22 ACE for the same period. They use tercile ranges instead of normal 14 ACE, but still had a higher probability of below normal ACE (25%), than above normal ACE (20%).

What's surprising is that ACE forecast remains below the 20 year climate mean (which includes both active, and 'inactive' years) through weeks 3-4. I have noticed that the extended range anomaly forecast seems to also show below normal activity through most of Sept.

Of course, it's possible the models are wrong.....

CFS shows the opposite of this sentiment with at least 5-6 MDR storms through September 15..

[Spacecoast]

CFS shows the opposite of this sentiment with at least 5-6 MDR storms through September 15..

Yes, indeed. A completely different picture...


It looks like mainly TD's / TS's, enseble members (out of 40) with one or two strengthening Cat1 near upper latitudes. It's hard to tell how many members show development.
I must admit that I am not familiar with CFSv2.
I found this from the latest run. It seems to forecast 3.7/3.8 storms over the next 30 days, unless I am misinterpreting:

Storm Count Forecast

RAW NUMBERS

PERIOD START END ATL ENP WNP NI SI AUS SP
-----------------------------------------------------------
Week 1 20240821 20240827 0.6 2.2 0.3 1.4 0.0 0.0 0.0
Week 2 20240828 20240903 1.2 3.1 0.4 1.1 0.1 0.0 0.0
Week 3 20240904 20240910 1.9 3.0 0.4 0.4 0.2 0.2 0.1
Week 4 20240911 20240917 2.5 3.0 1.1 0.9 0.3 0.1 0.1
Week 5 20240918 20240924 1.4 1.2 0.9 0.9 0.2 0.0 0.0
Week 6 20240925 20241001 0.0 0.0 0.0 0.0 0.0 0.0 0.0

30 Day 20240821 20240919 3.8 6.1 1.9 2.5 0.3 0.2 0.1


BIAS CORRECTED

PERIOD START END ATL ENP WNP NI SI AUS SP
-----------------------------------------------------------
Week 1 20240821 20240827 0.2 2.0 0.4 1.0 0.0 0.0 0.0
Week 2 20240828 20240903 1.1 2.3 0.5 0.5 0.0 0.0 0.0
Week 3 20240904 20240910 1.4 1.7 0.3 0.0 0.0 0.1 0.0
Week 4 20240911 20240917 2.0 2.3 0.9 0.0 0.0 0.0 0.0
Week 5 20240918 20240924 1.2 0.9 0.7 0.0 0.0 0.0 0.0
Week 6 20240925 20241001 0.0 0.0 0.0 0.0 0.0 0.0 0.0

30 Day 20240821 20240919 3.7 5.7 2.4 0.2 0.0 0.0 0.0

[aspen]

CFS shows the opposite of this sentiment with at least 5-6 MDR storms through September 15..

Yes, indeed. A completely different picture...
https://i.ibb.co/18NHd2G/cfsa.jpg

It looks like mainly TD's / TS's, enseble members (out of 40) with one or two strengthening Cat1 near upper latitudes. It's hard to tell how many members show development.
I must admit that I am not familiar with CFSv2.
I found this from the latest run. It seems to forecast 3.7/3.8 storms over the next 30 days, unless I am misinterpreting:

Storm Count Forecast

RAW NUMBERS

PERIOD START END ATL ENP WNP NI SI AUS SP
-----------------------------------------------------------
Week 1 20240821 20240827 0.6 2.2 0.3 1.4 0.0 0.0 0.0
Week 2 20240828 20240903 1.2 3.1 0.4 1.1 0.1 0.0 0.0
Week 3 20240904 20240910 1.9 3.0 0.4 0.4 0.2 0.2 0.1
Week 4 20240911 20240917 2.5 3.0 1.1 0.9 0.3 0.1 0.1
Week 5 20240918 20240924 1.4 1.2 0.9 0.9 0.2 0.0 0.0
Week 6 20240925 20241001 0.0 0.0 0.0 0.0 0.0 0.0 0.0

30 Day 20240821 20240919 3.8 6.1 1.9 2.5 0.3 0.2 0.1


BIAS CORRECTED

PERIOD START END ATL ENP WNP NI SI AUS SP
-----------------------------------------------------------
Week 1 20240821 20240827 0.2 2.0 0.4 1.0 0.0 0.0 0.0
Week 2 20240828 20240903 1.1 2.3 0.5 0.5 0.0 0.0 0.0
Week 3 20240904 20240910 1.4 1.7 0.3 0.0 0.0 0.1 0.0
Week 4 20240911 20240917 2.0 2.3 0.9 0.0 0.0 0.0 0.0
Week 5 20240918 20240924 1.2 0.9 0.7 0.0 0.0 0.0 0.0
Week 6 20240925 20241001 0.0 0.0 0.0 0.0 0.0 0.0 0.0

30 Day 20240821 20240919 3.7 5.7 2.4 0.2 0.0 0.0 0.0

The CFS seems to undershoot intensity, probably because it’s a large-scale, low-res model. Basically if you’re seeing a solid TS on it, it could easily be a hurricane in reality. Like in the top plot where you can see Hurricane Gilma and none of the spaghetti tracks show even a C1.

Those MDR storms in weeks 2-4, if they verify, could easily be long-tracking hurricanes. Perhaps even at least one major. I’m not a fan of how close they get to the East Coast in week 3. While not gospel, the CFS sometimes can be shockingly accurate in its predictions, like with Isaias in 2020.