ATL: FIONA - Models

[Category5Kaiju]

Genuinely curious, but I keep hearing about Puerto Rico, the Dominican Republic, and Bermuda, but how safe are the Turks and Cacos?

[pgoss11]

Euro still has some ensembles going pretty far west, Gfs has none.

Those far western solutions must be if Fiona just stays disorganized or weakens to the point it gets caught up in the westerlies. Doesn’t seem like that’s a possibility at the moment but time will tell.

[bjackrian]

I'm curious how people think the lack of some upstream radiosonde data is affecting the models for Fiona. I believe that all 12 US sites that launch balloons using helium are still not launching (and haven't been since late July) due to a helium shortage. While it's only about 10% of the sites, it still seems like a loss of data that may affect modelling?

From local media here in Denver: https://www.foxweather.com/weather-news ... ons-helium

Out of 122 NWS offices across the nation, 92 of those offices launch weather balloons. NWS Boulder is one of 12 offices that rely on helium to send their balloons floating high into the atmosphere.

"The main plant has gone offline, and that's down in Texas," Stark said. "So that is why it's impacting not only us but other locations."

The other locations that rely on helium include Albany and Upton in New York, Caribou, Maine; Wallops Island, Virginia; Greensboro, North Carolina; Charleston, South Carolina; Key West and Tallahassee in Florida, Salt Lake City, Utah; Las Vegas, Nevada; and Tucson, Arizona.

[somethingfunny]

12z Euro ensembles... ~ 6-7 weaker members (12-14%) drift westward after going over central DR...

Ope, this might be a problem for Canada then eh?

[Emmett_Brown]

A bit of a W shift in the 18Z GFS. Not enough to allow it to miss PR, but this run passes a little more W of Bermuda (but still impacting them)

[tolakram]

18Z models

[Iceresistance]

Here's the dry air on HWRF killing off its western bands, and almost getting into the core through the west. The location matches perfectly on the water vapour I posted as well.

https://i.imgur.com/X7a12F9.png

I'm impressed that the model predicted it almost perfectly.

Not doing well beyond 6h though, 00z run had it 982mb by now and much tighter.

Pressure? Poor. C-

Dry Air intrusion? Perfect. A+

(Btw, I've posted it in the models section since we were basically talking about that HWRF model.)

[skyline385]

0Z runs going to be interesting

 https://twitter.com/EricBlake12/status/1571313191698763776

[LarryWx]

The 18Z EPS 144 has fewer left outliers (almost none that would threaten the CONUS) vs the 12Z EPS 150.

[KirbyDude25]

Well, looks like the 18Z HAFS-0.3 has gone completely off the rails. Has Fiona reaching Puerto Rico as an 80-knot hurricane at hour 24, with it peaking (so far, it's not completely loaded) at 918mb/139kt at hour 102

The other 18Z models look mostly like they have earlier today, forecasting a PR landfall at around 60kt/990mb and a peak around 950mb, so I'm not sure what HAFS is seeing here

[tolakram]

18Z HWRF for what it's worth.

[skyline385]

Well, looks like the 18Z HAFS-0.3 has gone completely off the rails. Has Fiona reaching Puerto Rico as an 80-knot hurricane at hour 24, with it peaking (so far, it's not completely loaded) at 918mb/139kt at hour 102

The other 18Z models look mostly like they have earlier today, forecasting a PR landfall at around 60kt/990mb and a peak around 950mb, so I'm not sure what HAFS is seeing here

You were looking at the HAFS-S (S is for secondary) which is basically the HWRF on steroids. HAFS-A has done relatively better so far this season but in the end both are experimental models and have been all over the place.

[tolakram]

Intensity errors so far



source: https://www.atmos.albany.edu/facstaff/tang/tcguidance/

[tolakram]

Euro now stays just south of PR


GFS similar

[tolakram]

HWRF 6Z still running. Now the short term intensity looks realistic.

[tolakram]

6Z Euro still sees this staying south of PR


Center crossing or not there will be a lot of rain, probably more than if it crossed over.

[aspen]

All three hurricane models show Fiona starting an EWRC between Wednesday afternoon and very early Thursday morning. The HAFS starts the EWRC earlier, probably due to it showing a smaller initial core and higher intensity (135-140 kt and 923mb) by Wednesday afternoon compared to the HWRF and HMON (940s to upper 930s). The HMON has the largest secondary eyewall of the three models, around the size of Larry’s outer eyewalls during its endless EWRC phase.

[tolakram]

12Z GFS

[ThetaE]

I have to say I'm pretty suspicious about how little models weaken Fiona as it skirts PR and DR. Maybe a neutral intensity or slight drop in pressure is possible if environmental conditions improve at the same time, but my intuition says that's not likely.

In my observation, close calls and brief (but mountain-y) island landfalls often seem innocuous at first, only for structural damage to appear 12-24 hours later. We've arguably already seen this with Fiona-- it seemed to be intensifying and fighting off shear during and immediately after crossing Guadeloupe, but the next morning the pressure had risen, the wind field was broad, and there were multiple centers.

[Iceresistance]

 https://twitter.com/RyanMaue/status/1571545046746275840