2025 Atlantic Hurricane Season

[TriPol]

It’s the GFS, so take it with a grain of salt..

https://x.com/lockingitin/status/1952375266569064644?s=61

[GaWx]

 The concern I have that there may actually be something threatening somewhere in the Conus (Gulf or Atlantic coasts) (hopefully not!) as we approach midmonth is increased because the model consensus is suggesting there may be an extended period of the MJO being in or near phase 2 around then.

 Why would a long period in phase 2 be a concern?
 

US MH hits during phase 2 (**either inside or outside the circle**) during July-Sep since 1975:

-Ida (2021)

-Harvey (2017)

-Irma (2017)

-Ivan (2004)

-Bret (1999)

-Emily (1993)

-Hugo (1989)

-Frederic (1979)

-Eloise (1975)

 That’s 9 of 23 (39%) of Jul-Sep Conus MH hits during 1975-2024 having occurred just during phase 2, alone! The 39% is more than double the ~17% of days in phase 2, meaning a significant/non-random signal for increased danger.

Latest MJO forecasts: 

GEFS suggests long period in phase 2 (it’s mainly inside circle phase 2, which unfortunately is almost equally as high risk as outside):

EPS is similar

 

Maybe that’s why avg Jul-Sep precip is heaviest during phase 2 (this is for both inside and outside circle):

[Stormchaserchuck1]

Usually 60N/20N is a big marker.. storms that pass NE of it steer out to sea >90% of the time. If they go SE of it, it's closer to 50/50.  Obviously early in the year the steering currents are more east to west. 

[WxWatcher007]

28 minutes ago, GaWx said:

 The concern I have that there may actually be something threatening somewhere in the Conus (Gulf or Atlantic coasts) (hopefully not!) as we approach midmonth is increased because the model consensus is suggesting there may be an extended period of the MJO being in or near phase 2 around then.

 Why would a long period in phase 2 be a concern?
 

US MH hits during phase 2 (**either inside or outside the circle**) during July-Sep since 1975:

-Ida (2021)

-Harvey (2017)

-Irma (2017)

-Ivan (2004)

-Bret (1999)

-Emily (1993)

-Hugo (1989)

-Frederic (1979)

-Eloise (1975)

 That’s 9 of 23 (39%) of Jul-Sep Conus MH hits during 1975-2024 having occurred just during phase 2, alone! The 39% is more than double the ~17% of days in phase 2, meaning a significant/non-random signal for increased danger.

Latest MJO forecasts: 

GEFS suggests long period in phase 2 (its mainly inside circle phase 2, which unfortunately is almost equally as high risk as outside):

EPS is similar

 

Maybe that’s why avg Jul-Sep precip is heaviest during phase 2 (this is for both inside and outside circle):

This is really good stuff, thanks for posting. I agree, and I think the current orange is a candidate, GFS depictions notwithstanding. Notice how the Euro takes the follow up wave and makes that a Caribbean cruiser at 00z. The steering pattern is there. You may actually want the current lemon to get further north to weaken the ridge but not sure that’ll happen.

[cbmclean]

1 hour ago, GaWx said:

 That’s 9 of 23 (39%) of Jul-Sep Conus MH hits during 1975-2024 having occurred just during phase 2, alone! The 39% is more than double the ~17% of days in phase 2, meaning a significant/non-random signal for increased danger.
 

Where did you find data about things like a day-by-day count of days by MJO phase?

[BarryStantonGBP]

1 hour ago, WxWatcher007 said:

This is really good stuff, thanks for posting. I agree, and I think the current orange is a candidate, GFS depictions notwithstanding. Notice how the Euro takes the follow up wave and makes that a Caribbean cruiser at 00z. The steering pattern is there. You may actually want the current lemon to get further north to weaken the ridge but not sure that’ll happen.

Have you seen the latest GFS model with a gulf track 

bombed out 

[WxWatcher007]

Models will probably be all over the place for a while

[Normandy Ho]

models are consistent with this being a threat though.  Seems like too much ridging for it to escape OTS

[WxWatcher007]

18 minutes ago, Normandy Ho said:

models are consistent with this being a threat though.  Seems like too much ridging for it to escape OTS

Agree with this mostly—models are definitely consistent in showing this is worth watching and the steering pattern looks ripe, I just meant the final outcome is uncertain. 

[GaWx]

54 minutes ago, cbmclean said:

Where did you find data about things like a day-by-day count of days by MJO phase?

 From the maps available at the link below, I looked at the 50 Jul-Aug-Sep maps for each season 1975-2024 and counted the days. It took ~2 hours to count it accurately, but it was well worth the time so I could figure out how statistically significant the 39% of MH hitting during phase 2 really is.
 

 There are 4,508 days Jul-Sep 1975-2024 excluding 1978, which for some reason is blank. I counted 749 of those 4,508 days (16.6%) to be when it was in phase 2 (outside or inside circle). I rounded that up to 17%. The 16.6% is exactly 1 in 6 days rather than 1 in 8 days. That’s because there’s been somewhat of a tendency for the MJO to be longer in phase 2 in July-Sept vs the average of the other 7 phases for whatever reason. But even so, 1/6 is nowhere close to 39% as it is  only 43% of it. Thus, I consider this to be a pretty strong signal for phase 2

http://www.bom.gov.au/climate/mjo/#tabs=Monitoring

[A-L-E-K]

cat 5 into miami or bust

[TriPol]

In the last 8 hours, the GFS has given us Hurricane Hugo wrecking South Carolina, Andrew bulldozing South Florida, and now it’s serving up Katrina like it’s a greatest hits album from Mother Nature’s rage collection

[BarryStantonGBP]

9 minutes ago, TriPol said:

In the last 8 hours, the GFS has given us Hurricane Hugo wrecking South Carolina, Andrew bulldozing South Florida, and now it’s serving up Katrina like it’s a greatest hits album from Mother Nature’s rage collection

How many NS?

[BarryStantonGBP]

quoted from another board

Quote

I can't easily post Google's DeepMind AI run for 12z that just came out a bit ago because it's a a series of images, but I think everyone should look at it! (It's called Weather Lab: Cyclones, and yes, you have to log in to see it I believe) It features a parade of activity over the next 2 weeks, even more than previous runs. It shows 1) 95L (Dexter) 2) the Orange area in the ATL "Erin", 3) the area near the east coast behind 95L "Fernand", 4) The eastern Gulf "Gabrielle", 5) and 6) Two more MDR systems behind the Orange, "Humberto and Imelda" and 7) an Eastern Caribbean possible storm "Jerry" that moves west.

All in the next 14 days. Either it's going to take a huge L or it's seeing a gigantic awakening that's about to rock the basin.

 

Quote

Globals and newer AI models (like the above mentioned DeepMind model) are showing a strong signal for a potential large and powerful cyclone well west of the Hebert Box around D10-12. (Seems to be "Humberto" according to DeepMind)

Euro drops it to 920s near the Bahamas, GFS had it in the 930s off the coast of GA/FL and the Deep Mind models have an averaged intensity of Cat 3 near Florida.

 

[Newman]

Echoing what Andy said on twitter here, this has been my thinking with any tropical system development in the MDR this month:

https://x.com/AndyHazelton/status/1952439813619003854

 

We've had round after round of SAL outbreaks across the Atlantic the past month or two. It looks to relax a bit in this favorable stretch approaching, but I won't believe any model until we see a potent AEW with persistent convection. Also, beyond just a wave developing into a TC, I think the real key in the modeling is how they handle the weak ULL in the north Atlantic and if that allows for a weakness for a TC to slip north.

Current SAL situation:

 

12z GFS with the tropical wave and some lessening of the dry upper air regime.