NATL: MELISSA - Models

[USTropics]

12z HAFS-A coming in (I'm a HAFS-A hugger for Melissa ), it actually increases pressure some until about 8PM ET tonight (relative to what the run started at):
https://i.imgur.com/2MItvl1.png

A new RI period begins shortly after that, with a drop to 931mb in 12 hours (8AM ET):
https://i.imgur.com/zDtdlx6.png

Now that’s been a few hours since you made this post, and now that Melissa has resumed intensification, do you have any ideas as to what particular reason for the hafs’ leveling off and resuming of intensification? Do you think it was able to accurately see the dry air intrusion we observed, and do you think it could be due to the storm’s western inflow channel being blocked from moist inflow by Jamaica to the north? Is the resuming of intensification due to that channel no longer being blocked now that the storm has moved sufficiently westward?
Hope that wasn’t too many questions

The short answer is, good luck figuring out the physics of a category 4 hurricane I'll give my opinion on some of your questions:

From 15z (11AM ET) to 18z (2PM ET) it did have a drop in pressure, but then an increase thereafter. A good comparison case is the HAFS-B, which had a smooth decrease in pressure throughout the day (which verified). The main difference here is in initialization, where HAFS-A did not have quite the compact core that HAFS-B did:



If we look at projected IR-simulations for both models 3 hours later, that gives the most clues about the outflow restriction (and core representation) and some of that inflow restriction like you were stating (overdone by the HAFS-A at this timestep):



From actual satellite imagery, we can see which one verified better:



With that said, it was a very brief oscillation on the HAFS-A, and by 8PM tonight it was showing a rapid intensification period again.

[BobHarlem]

18z Hurricane models, all but the HWRF landfall's as a cat 5.
HAFS-A

HAFS-B

HWRF

HMON

[WaveBreaking]

06Z HAFS models are still showing ~154kt landfalls over W Jamaica.

HWRF is at the same location at 124kts.

HMON is at the same location at 141kts.

[Teban54]

06Z HAFS models are still showing ~154kt landfalls over W Jamaica.

HWRF is at the same location at 124kts.

HMON is at the same location at 141kts.

The fact that earlier HAFS-A and HAFS-B runs "only" showed ~130 kt for right now (when Melissa got to 145 kt in reality), yet still had an even stronger landfall, is a bit scary.

On the other hand, IIRC it's not uncommon for the intensities and timings of 1st and 2nd peaks on hurricane models to be "flipped". When Milton formed, the hurricane models generally forecasted its second peak to be stronger than the first. That didn't verify: the actual intensities were 895/155 for the first peak, 902/145 for the second.

[Kazmit]

One of the worst GFS performances I’ve ever seen for an Atlantic hurricane. Got absolutely nothing right in any aspect, besides sniffing out its development in the first place. It’s gonna need some major upgrades for next season if it wants to be taken seriously.

[Kazmit]

The 12z HAFS-A shows an insane 195mph peak this afternoon. This would be on par with Haiyan and surpass Allen to be the strongest Atlantic hurricane on record by wind speed.

[Teban54]

The 12z HAFS-A shows an insane 195mph peak this afternoon. This would be on par with Haiyan and surpass Allen to be the strongest Atlantic hurricane on record by wind speed.

Insane intensities from these 12z runs:

• 12z HAFS-A, valid in 3 hrs (15z,11am EDT): 903.5 mb | 171.0 kt
• 12z HAFS-A, valid in 6 hrs (18z, 2pm EDT): 900.3 mb | 169.2 kt
• 12z HAFS-B, valid in 6 hrs (18z, 2pm EDT): 892.4 mb | 166.9 kt
• 12z HMON, valid in 6 hrs (18z, 2pm EDT): 896.9 mb | 159.7 kt

Fortunately, given that a lot of these times have either already passed or will come up very soon, it's fair to say that they won't verify exactly as shown. But still...

HAFS-A and B also continue to show a second round of intensification prior to landfall, after briefly weakening to Cat 4 before then. HAFS-A even shows 162 kt at landfall.

[USTropics]

12z HAFS-A coming in (I'm a HAFS-A hugger for Melissa ), it actually increases pressure some until about 8PM ET tonight (relative to what the run started at):
https://i.imgur.com/2MItvl1.png

A new RI period begins shortly after that, with a drop to 931mb in 12 hours (8AM ET):
https://i.imgur.com/zDtdlx6.png

Now that’s been a few hours since you made this post, and now that Melissa has resumed intensification, do you have any ideas as to what particular reason for the hafs’ leveling off and resuming of intensification? Do you think it was able to accurately see the dry air intrusion we observed, and do you think it could be due to the storm’s western inflow channel being blocked from moist inflow by Jamaica to the north? Is the resuming of intensification due to that channel no longer being blocked now that the storm has moved sufficiently westward?
Hope that wasn’t too many questions

The short answer is, good luck figuring out the physics of a category 4 hurricane I'll give my opinion on some of your questions:

From 15z (11AM ET) to 18z (2PM ET) it did have a drop in pressure, but then an increase thereafter. A good comparison case is the HAFS-B, which had a smooth decrease in pressure throughout the day (which verified). The main difference here is in initialization, where HAFS-A did not have quite the compact core that HAFS-B did:
https://i.imgur.com/YDXfAA7.png
https://i.imgur.com/GygG8N3.png

If we look at projected IR-simulations for both models 3 hours later, that gives the most clues about the outflow restriction (and core representation) and some of that inflow restriction like you were stating (overdone by the HAFS-A at this timestep):
https://i.imgur.com/0J0yvW7.png
https://i.imgur.com/pwVJYlr.png

From actual satellite imagery, we can see which one verified better:
https://i.imgur.com/59jqVDh.png


With that said, it was a very brief oscillation on the HAFS-A, and by 8PM tonight it was showing a rapid intensification period again.

I wanted to follow up on this, we moved our usual Friday weather discussion at FSU to Monday (for obvious reasons) so we were able to discuss the pause in intensification that Melissa exhibited yesterday. One of our graduate students deals specifically with this (shoutout to Connor Stoll) and he shared some good insight. If we look at along-shear RH from yesterday during the time period of the intensity level-off, notice this western infringement of drier air (due in part to that undercutting shear). This was the main culprit:



I'll do every 12 hour timesteps to current time, but we can see how this slowly abated throughout the day and into today:






You can find these products here - https://storm.aoml.noaa.gov/viewer/ (under TC Structure -> RH Along Shear).

[cheezyWXguy]

Now that’s been a few hours since you made this post, and now that Melissa has resumed intensification, do you have any ideas as to what particular reason for the hafs’ leveling off and resuming of intensification? Do you think it was able to accurately see the dry air intrusion we observed, and do you think it could be due to the storm’s western inflow channel being blocked from moist inflow by Jamaica to the north? Is the resuming of intensification due to that channel no longer being blocked now that the storm has moved sufficiently westward?
Hope that wasn’t too many questions

The short answer is, good luck figuring out the physics of a category 4 hurricane I'll give my opinion on some of your questions:

From 15z (11AM ET) to 18z (2PM ET) it did have a drop in pressure, but then an increase thereafter. A good comparison case is the HAFS-B, which had a smooth decrease in pressure throughout the day (which verified). The main difference here is in initialization, where HAFS-A did not have quite the compact core that HAFS-B did:
https://i.imgur.com/YDXfAA7.png
https://i.imgur.com/GygG8N3.png

If we look at projected IR-simulations for both models 3 hours later, that gives the most clues about the outflow restriction (and core representation) and some of that inflow restriction like you were stating (overdone by the HAFS-A at this timestep):
https://i.imgur.com/0J0yvW7.png
https://i.imgur.com/pwVJYlr.png

From actual satellite imagery, we can see which one verified better:
https://i.imgur.com/59jqVDh.png


With that said, it was a very brief oscillation on the HAFS-A, and by 8PM tonight it was showing a rapid intensification period again.

I wanted to follow up on this, we moved our usual Friday weather discussion at FSU to Monday (for obvious reasons) so we were able to discuss the pause in intensification that Melissa exhibited yesterday. One of our graduate students deals specifically with this (shoutout to Connor Stoll) and he shared some good insight. If we look at along-shear RH from yesterday during the time period of the intensity level-off, notice this western infringement of drier air (due in part to that undercutting shear). This was the main culprit:

https://i.imgur.com/u4qudoU.gif

I'll do every 12 hour timesteps to current time, but we can see how this slowly abated throughout the day and into today:
https://i.imgur.com/7IyToeo.gif

https://i.imgur.com/Tq0fB8L.gif

https://i.imgur.com/Oh6UoST.gif

You can find these products here - https://storm.aoml.noaa.gov/viewer/ (under TC Structure -> RH Along Shear).

Thanks for the double reply! A lot of interesting information here.

[Hurricane2022]

 https://x.com/HurricaneAddict/status/1982947998528123081

[Teban54]

 https://x.com/HurricaneAddict/status/1982947998528123081

18z HAFS-A:

• Peak: 03z (11pm EDT), 895.5 mb | 176.6 kt
• Landfall: 15z (11am EDT), 905.3 mb | 162.3 kt

18z HAFS-B:

• Min pressure: 06z (2am EDT), 898.2 mb | 133.1 kt
• Max wind speed & just before landfall: 12z (8am EDT), 907.5 mb | 154.8 kt

[Kazmit]

 https://x.com/HurricaneAddict/status/1982947998528123081

18z HAFS-A:

• Peak: 03z (11pm EDT), 895.5 mb | 176.6 kt
• Landfall: 15z (11am EDT), 905.3 mb | 162.3 kt

18z HAFS-B:

• Min pressure: 06z (2am EDT), 898.2 mb | 133.1 kt
• Max wind speed & just before landfall: 12z (8am EDT), 907.5 mb | 154.8 kt

HAFS-A with a 200 mph peak.

[Kazmit]

Both HAFS models also reintensify Melissa back to major hurricane strength en route to Bermuda. Maybe some baroclinic enhancement from the trough?

[Pelicane]

This is the strongest depiction I've seen the HAFS model spit out for a storm. Obviously very overcooked, but in model land this is a record-breaking 220 mph storm currently. Does eventually landfall around the current intensity, but just thought I'd share because of how absurd it is.

[jlauderdal]

This is the strongest depiction I've seen the HAFS model spit out for a storm. Obviously very overcooked, but in model land this is a record-breaking 220 mph storm currently. Does eventually landfall around the current intensity, but just thought I'd share because of how absurd it is.

https://i.imgur.com/y5LgxEJ.png

Not too overdone in the final analysis.

[cycloneye]

By far HAFS-A wins the crown as the best one that predicted the final intensity peak. This was 6 days ago when Melissa was still a tropical storm.

[tomatkins]

12Z hurricane models are out. ALl of the initated too far east (land fall to the east of Black River) so they will likely have more time over land than the actual outcome. All landfall around Chivrico (west of Santiago de Cuba) sometime around 6-9Z tomorrow.

HWRF - landfall at 927 mb, 123 kt
HMON - landfall at 958 mb, 96 kt
HAFS-A - landfall at 935 mb, 112 kt
HAFS-B - landfall at 953 mb, 93 kt.

None of the models show any singificant strengthening post-Jamaica. All emerge from Cuba in the 950-970 range before striking the relatively unpopular southern Bahamas and then scooting west of Bermuda and out to sea.

CMC still has a Newfoundland strike for the post-tropical remnants, while ICON and GFS turn east south of Newfoundland.

[MEANINGLESS_NUMBERS]

HWRF showing Cat 4 landfall in Bermuda:



This would be the strongest landfall in living memory.

[GCANE]

 https://x.com/AndyHazelton/status/1983265734508925111

[Beef Stew]

Melissa will go down as a massive win for the HAFS A/B, and especially Google DeepMind (...not to mention a huge L for the GFS). Yes, you could argue that the HAFS models have tended to have a desire to blow most storms up in the few years since they've been introduced (showing more intense peaks for storms like Helene, Lee, etc. than actually occurred), but ultimately the difference we've seen in the accuracy of intensity forecasts and modeled RI has been really significant from even the late 2010's. While intensity is still hard to predict, the strides we've made in recent years really stand out to me.