ATL: EARL - Models

[drezee]

 https://twitter.com/andretrotter/status/1566681908905275392

[aspen]

All three hurricane models turn Earl into a major and have it start to structurally improve sometime on Wednesday, but they have quite different outcomes.

The HWRF is a little slower to show Earl with a complete eyewall, but in terms of forward speed, it’s the fastest of the three and has Earl at 38N on Saturday morning. A fast recurve isn’t guaranteed because some of the models or ensemble members are showing the possibility of a stall or Felix ‘95/Jose ‘17 loop. The HWRF gets this into the 940s.

The HMON is a little slower than the HWRF and maybe gets a complete eyewall slightly faster, but the difference is that it keeps starting an EWRC as Earl passes by Bermuda. It also gets into the low 940s, but if that EWRC were to verify, Earl would probably be weaker.

The HAFS is the quickest to show Earl with a complete eyewall, and then goes nuts and turns this into a 145kt/920mb Cat 5…at over 30N. Technically not impossible because the SSTs can support a Cat 5 MPI, but highly unlikely.

Both the HWRF and HMON seem to have shifted a little west from their runs at this point yesterday. Bermuda gets impacted by Earl’s western rain bands and might be receiving TS force winds on both runs.

[Cuda]

https://twitter.com/andretrotter/status/1566681908905275392?t=JoIR7LPapgSPuKXqygP1bg

Could someone break this down for me a bit more? I'm trying to learn how to read/understand these maps, the lows/highs and how they affect track.

It looks like to me the Bermuda high is very far north/west. Would that mean that it would have very little impact in terms of steering on Danielle since it is so far removed from that area? How does that midwest feature that is circled affect things?

[tolakram]

6Z Euro

[tolakram]

https://twitter.com/andretrotter/status/1566681908905275392?t=JoIR7LPapgSPuKXqygP1bg

Could someone break this down for me a bit more? I'm trying to learn how to read/understand these maps, the lows/highs and how they affect track.

It looks like to me the Bermuda high is very far north/west. Would that mean that it would have very little impact in terms of steering on Danielle since it is so far removed from that area? How does that midwest feature that is circled affect things?

Storms are driven by upper level wind flow. The stronger the storm the higher the level. 850MB is right above the surface, or low level flow. Waves track with lower level flow. 500MB is generally a good level for most tropical storms and hurricanes since flow up at 500MB and higher is usually, but not always, similar. The flow around a low pressure system is counter clockwise, so in that upper level low over Wisconsin exerts some influence over Earl IF it's actually in that position AND it's strong enough AND no other feature is strong enough to override it.

A strong high pressure system, clockwise flow, drives storms west but it also depends on the tilt, position, and strength. Most importantly these are model predictions and the further one gets from NOW the less accurate every model gets.

That's amateur analysis, it's dramatically more complex than that and quickly goes above my ability to understand it, other than the basics.

You can go to this page on CIMSS to see current steering winds. https://tropic.ssec.wisc.edu/real-time/dlmmain.php?&basin=atlantic&sat=wg8&prod=dlm1&zoom=&time=

Edit: Adding a suggestion from AJC3

Storms are driven by mean layer wind flow. The stronger the storm the deeper the steering layer.

The reason I wanted to point this out is that no matter how strong a TC is, there is always going to be some contribution to the steering flow from the low to mid level (i.e. 850-700MB) wind flow.

[Cuda]

Thank you. That gives me a lot of good additional info to learn about.

[aspen]

The hurricane models are in good agreement that Earl will start to improve tomorrow, with more of a proper eyewall forming. The eye then pops out midday Thursday or later that afternoon, and RI commences before ending early Saturday as it starts to undergo post-tropical transition. It won’t be a super high ACE major, but it could get up to 15-20 ACE and potentially reach Category 4 status.

[tolakram]

Thank you. That gives me a lot of good additional info to learn about.

On of our pro-mets had something to add to my description:

from: AJC3

Hey Mark...wanted to let you know of a minor correction to your post, so that you can tweak it as you see fit.

This...
Storms are driven by upper level wind flow. The stronger the storm the higher the level.

Would be better written as...
Storms are driven by mean layer wind flow. The stronger the storm the deeper the steering layer.

The reason I wanted to point this out is that no matter how strong a TC is, there is always going to be some contribution to the steering flow from the low to mid level (i.e. 850-700MB) wind flow.

I'm going to add that bit to my original reply.

[cycloneye]

 https://twitter.com/pppapin/status/1567683372431937539

[cycloneye]

 https://twitter.com/AndyHazelton/status/1568377298105290752