2021 Global Model Runs Discussion (Out thru day 16)

[Big O]

Interesting discussion from the BRO office of the NWS regarding ridge and possible tropical system:

LONG TERM (Tuesday Night through Sunday): A somewhat unsettled
pattern develops in the long term, bringing rain chances each day.
The mid level ridge over Texas and the Southern Plains will begin to
lift north and break down as an inverted mid level shortwave trough
approaches Florida and the Southeast from the Atlantic and a mid
level trough penetrates a little further south over the Pacific
Northwest. A series of perturbations in the mid level flow will
rotate around the base of the lifting ridge mid to late week and
provide enough upper level support over Deep South Texas to enhance
diurnal convective processes...and with PWATs increasing to near 2
inches for most of the latter part of the week, plenty of moisture
will be available.

This weekend and beyond gets interesting...mostly due to the
possibility that a tropical cyclone will develop in the western
Caribbean Sea late this week and then move into the southwestern
Gulf of Mexico late this weekend. The NHC has included this feature
in the 5 Day Tropical Weather Outlook and given it a 20% chance of
development in the next 5 days. The potential development of this
feature will impact this weekend`s forecast, and with the
uncertainty in place, forecast confidence (particularly for the
PoPs) Friday and beyond is low to moderate.

With the 00Z runs, the GFS is noticeably wetter than the ECM Friday
and beyond. However, it`s worth noting that they show another surge
in PWATs Sunday Night into Monday as the potential tropical system
moves across the southwestern Gulf of Mexico...hinting at the
possibility of heavy rain early next week.

[SoupBone]

06z GFS keeps the 2 WCar storms I mentioned earlier. First one still into Mexico (forms at +108, landfall at +186) with 985 mbar. Second one into East Texas this time (forms at +198, landfall at +330) with 955 mbar.

Yeah so what stinks about this is if you like the GFS, you're spared in Texas from this first system but impacted by the second one.

Luckily, the second hit is 2 weeks out, but it's at least been consistent with something developing in that timeframe.

[SFLcane]

What a joke the CFS weekly forecast has become, even at its 1-2 week short range.

https://i.imgur.com/P14ccM1.png
https://i.imgur.com/Lye8U8p.png

That week 1 forecast looks fine. You'll have shear like that thanks to the CAG/TC near Mexico. Not sure about week 2 though

[cheezyWXguy]

Not sure how well it’s performed in the past, but the 0z Canadian ensemble is an all-out assault on the Texas coast with the upcoming system. It looks like the majority of its members are showing development with the northeastern lobe.

[Ubuntwo]

They are not underestimating ridging, but intensifying storms too quickly, hence W corrections.

Grace tracked southwest of modeling in spite of outperforming almost all guidance. This is anecdotal but it does seem like models have underestimated ridging more often over the past few years, a pretty drastic shift from the early 2010s especially.

[aspen]

If the 00z CMC verifies, we could see Ida and Julian by Friday/Saturday. A track like this for Julian would likely make it a hurricane or even a major, with less time spent over the Yucatan than the GFS and 42 hours over 30-31C SSTs. It also shows the precursor wave to what becomes Kate on the Euro/EPS, but doesn't develop it.

[Iceresistance]

0z Models

Western Caribbean to BoC/GoM System

0z GFS first hints it in the Western Caribbean Saturday as a ~1000 MB Tropical Storm, makes landfall over the Yucatán by Sunday, & restrengthens into a stronger system (989 MB) by the time it makes landfall in Mexico Next Monday
The 0z Euro is similar, but is Weaker & little later . . . (~995 MB & makes landfall late Monday)
0z CMC is similar to the GFS in Strength, similar to the Euro in timing, but is farther north, & makes landfall in Northern Mexico with it's rainbands spreading into Southern & South-Central Texas
0z ICON is into the Central Gulf & Louisiana Landfall as a ~980 MB Hurricane

Central Atlantic System

0z GFS Develops this on Friday, & the system may become a hurricane before becoming Post-Tropical & gets caught up into a Trough
0z ICON is in the Central Atlantic as a Weaker System
0z CMC Develops this on Thursday, Drifts slowly until at least Saturday/Sunday when it becomes a Hurricane & becomes post-tropical as it gets caught up by a incoming trough
0z Euro does not develop this at all

The posts in this forum are NOT official forecasts and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or STORM2K. For official information, please refer to products from the NHC and NWS.

[ColdMiser123]

The potential western GOM system has at least three pretty notable uncertainty factors still.

1) Where the gyre eventually ends up consolidating. If it consolidates farther northeast near the region where curvature vorticity is maximized, this could lead to Texas being a landfall location. If it consolidates farther west, Mexico would likely see another landfall.

2) The erosion of the ridge over Texas. Depending on how strong the western trough becomes could determine if a WNW motion becomes more NW or NNW, some EPS members are highlighting this possibility.

3) The interaction with another low-level disturbance progressing across the western Caribbean. The CMC causes interaction with this disturbance, which pulls the potential western GOM system farther north.

Bears watching since we are still far out from the eventual landfall location, should a storm develop.

[AutoPenalti]

If the CMC verifies, I would assume Kate would move in to that same weakness as future Ida.

[CyclonicFury]

00z EPS continues to show a strong signal for the first legit Cape Verde hurricane in the 9-15 day timeframe. However, like I've stressed before, 1) models often whiff on genesis before waves exit Africa and 2) I wouldn't put too much stock into the universal recurve agreement yet.

[aspen]

If the CMC verifies, I would assume Kate would move in to that same weakness as future Ida.

It depends on how much of a weakness remains when Ida exits the scene. By the time the precursor to Kate emerges into the eastern MDR, Ida will be rapidly moving into the northern latitude and undergoing post-tropical transition, or it might already have become post-tropical.

[SoupBone]

So the 12Z GFS has the WCAB system way further south into Mexico. What worries me is that you see the ridge breakdown and then build back in. Any change in that, and Texas would obviously be in play. It's also slowed the system down a bit by a few days as well.

[Hypercane_Kyle]

GFS is being inconsistent with EPAC development. That'll have an impact on what forms in the Caribbean.

[jaguars_22]

The GFS is sticking to its guns of the high being strong. I believe it hits the same area that was hit by grace… which is not good. I don’t see a Texas worry until maybe the next storm but it has been dry here in central Texas coast thanks to this strong high. It should remain over us

[aspen]

12z CMC is nuts through 240 hours. It shows:
—Hurricane Ida in the subtropics forming in three days
—TS/Hurricane Julian in the SW Caribbean and Gulf starting this weekend
—The August 30/31st wave becoming TS Kate
—A wave behind Kate developing into what would be TS Larry
—The second WCar system developing at the very end of the 240hr time frame, soon to become TS/Hurricane Mindy

[SoupBone]

The GEFS wants some Tex/Mex to Corpus Christi action on the 31st with some members still pointing to Northern Mexico.

[Teban54]

06z GFS keeps the 2 WCar storms I mentioned earlier. First one still into Mexico (forms at +108, landfall at +186) with 985 mbar. Second one into East Texas this time (forms at +198, landfall at +330) with 955 mbar.

The second WCar system is much weaker on the 12z run. I'm not even sure if that's a tropical cyclone at landfall. Brings it to SE Louisiana.

[Blown Away]

12z GFS flipped the "On Switch" for the Atlantic Basin... Wow

[Teban54]

12z CMC is nuts through 240 hours. It shows:
—Hurricane Ida in the subtropics forming in three days
—TS/Hurricane Julian in the SW Caribbean and Gulf starting this weekend
—The August 30/31st wave becoming TS Kate
—A wave behind Kate developing into what would be TS Larry
—The second WCar system developing at the very end of the 240hr time frame, soon to become TS/Hurricane Mindy

Is that some Fujiwhara with Julian and Nora across Mexico on the CMC? Crazy if that verifies.

[SFLcane]

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

12z GFS flipped the "On Switch" for the Atlantic Basin... Wow

It’s getting ride of the tutt slowly it seems and has the wave the eps is going nuts over just north of Puerto Rico.