NATL: MELISSA - Aftermath - Discussion

[cycloneye]

From the 11 AM discussion:

The peak flight level winds at 700 mb were up to 68 kt.
Using a standard 0.9 adjustment factor to surface winds yields an
intensity of 60 kt, but Melissa could become a hurricane at any
time, as other satellite intensity estimates already support a
higher value.

[BobHarlem]

Discussion on intensity:

it appears likely that a period of rapid intensification
will occur as the storm moves slowly over very warm ocean waters
(30-31C sea-surface temperatures) which is also over the highest
oceanic heat content in the entire Atlantic basin, which will limit
initial ocean upwelling under the slow moving storm. Similar to the
previous cycles, roughly 40/50 Google DeepMind ensemble members show
Melissa becoming a Category 5. While I am not ready to forecast that
intensity yet given the track uncertainty, that remains a
possibility

[ronjon]

NHC is projecting a high end CAT 4 at 150 mph winds for the Jamaican landfall. Only 5 mph lower than a CAT 5. And really what's the practical difference at those high winds. Like a large tornado hitting the island.

[ChrisH-UK]

This is the Optical Depth product from GOES-19 with a 1 hout loop of the meso sector. In the las few frames you can see a change in the clouds from bubbling randomly to been organised into Melissa's rotation.

GOES-19 Red Band + Optical Depth

[Travorum]

My guess on the steady pressure is dry air entrainment disrupting development of the NE eyewall. Based on the last VDM reporting a closed eyewall and the convection wrapping up that way it should be worked out pretty quickly.



Edit: also cyan ring in the 37ghz scan.

[Hurricane2022]

We should see a small and beautiful eye opening later tonight.

[Hypercane_Kyle]

I'm surprised they didn't pull the trigger on hurricane, regardless should be one by 2pm.

[cheezyWXguy]

My guess on the steady pressure is dry air entrainment disrupting development of the NE eyewall. Based on the last VDM reporting a closed eyewall and the convection wrapping up that way it should be worked out pretty quickly.

https://i.imgur.com/VGzbyay.jpeg

https://i.imgur.com/rW54EOk.png

Edit: also cyan ring in the 37ghz scan.

Yeah I think that dry air entrainment led to the development of that prominent band on the eastern side which is competing for energy. Seems to be starting to lose influence now though as new cells pop up in that dry slot on the SE side

[cycloneye]

The inteprid Josh once again will go to chase a biggie, this time in Jamaica.

 https://x.com/iCyclone/status/1982103189685244193

[USTropics]

My guess on the steady pressure is dry air entrainment disrupting development of the NE eyewall. Based on the last VDM reporting a closed eyewall and the convection wrapping up that way it should be worked out pretty quickly.

https://i.imgur.com/VGzbyay.jpeg

https://i.imgur.com/rW54EOk.png

Edit: also cyan ring in the 37ghz scan.

I'm impressed with the HAFS-A grasp on the evolution of Melissa over the past few days. It was one of the few models that captured the eastern reformation yesterday morning:


It's pretty much nailed the slight dry slot like you alluded to here:


The model had a large upgrade over the summer to 2.0, some of the highlights:

• Improved Model Initialization: Enhanced vortex cycling and data assimilation techniques to better incorporate real-time observations, reducing initialization errors in the storm's core structure.
• Upgraded Model Physics: Refinements to physical parameterizations for cloud microphysics, boundary layer processes, and eyewall dynamics, leading to more realistic simulations of storm evolution.
• Higher-Resolution Nesting: The moving nest now supports finer grid resolutions (down to ~1-3 km in the inner domain), improving depiction of small-scale features like rainbands and tornado genesis.

You can play around with some of the new experimental stuff here as well - https://storm.aoml.noaa.gov/viewer/

[BobHarlem]

Jamaica radar since the eye was visible on both sides on it.

[IsabelaWeather]

NHC is projecting a high end CAT 4 at 150 mph winds for the Jamaican landfall. Only 5 mph lower than a CAT 5. And really what's the practical difference at those high winds. Like a large tornado hitting the island.

Technically its 6mph shy, but in reality its 10 mph shy.

[ScottNAtlanta]

Jamaica radar since the eye was visible on both sides on it.
https://i.postimg.cc/fbfhkfVp/Jamaica-Radar-Melissa-7.gif

Looks like the rain is already falling and they have days before landfall. They are going to get catastrophic amounts of rain in Jamaica.

[cheezyWXguy]

Huge burst in the northern eyewall. Let’s see how far it wraps around.

[mrbagyo]

explosive burst of convection on the NorthEast Quadrant.

[chaser1]

Whether it is just "a hair" faster, I tend to perceive a slightly more westerly motion then during last night & this a.m. I would not be one bit surprised to see a bit greater westward track than forecasted. As mentioned in the discussion, the increased vertical improvement would suggest greater influence by the minimal ridging that extends eastward to just north of the storms Longitude. The orientation of that ridge would imply to me that a 4-5 knot motion would not be that unreasonable. Realizing of course that all guidance is well honed in to a Jamaica landfall, I still think a landfall toward the very Western tip of Jamaica is plausible. There would need be a solid 6+ hours of such motion for models to slightly shift though.

[chaser1]

https://s12.gifyu.com/images/b3n2T.gif
explosive burst of convection on the NorthEast Quadrant.

Far far improved overall structure!

[Hurricane2022]

 https://x.com/MikeFischerWx/status/1982118595036336375

[GCANE]

Had a number of eddies around this since last night from the boundary layer to 500mb.
Looks like they are dissipating.

[GCANE]

Massive, high-helicity tower firing off on the NE eyewall.
That should nail it,

https://rammb-data.cira.colostate.edu/t ... 251610.gif