2025 Global Model Runs Discussion (Out thru day 16)

[revjohn]

We have seen the GFS do this with a CAG, June system year after year. The first system moves to EPAC, but the gyre on the NE side is the one to watch after.

Absolutely agree — textbook June CAG evolution here. EPAC side already showing the consolidation, but the NE side is the one aligning with the improving MJO phase + low shear forecast window. Ridge looks solid too. If anything, I think the ensembles are behaving exactly like they should in this setup — gradual tightening once the NE lobe starts organizing. Still liking that ~7–9 window for possible genesis.

[cycloneye]

CPC hazards has close to Yucatán / BOC for week 2 and only BOC for week 3. And the EPAC very active the next 3 weeks.

[revjohn]

Been a longtime member of Storm2K, though due to work constraints I haven’t posted much over the years. Now that I’m retired and have more time, I wanted to start contributing more.
What I’m sharing here is a simple framework I use to think through tropical development (varies by storm) — basically a checklist of the key fields and signals I track. Hopefully it’s helpful to others as we head into the season. I call it the "Golden Synoptic"

Key Framework for Tracking TC Development — Fields, Sequence, Indicators

A lot of us on here follow the model runs closely (ECMWF, GEFS, CMC, etc.) — but sometimes it helps to take a step back and look at the core environmental setup that drives the model trends.
This is a basic framework I’ve found useful (especially for current Gulf setups) — it’s essentially the thought process some forecasters use, though not called this formally.

CORE FIELDS TO WATCH "Golden Core"

These are the key drivers of whether a tropical system will form, strengthen, and where it will go:

• 500 mb heights → Steering
• 200–850 mb wind shear → Development window
• SST / Ocean heat content → Fuel
• 850 mb vorticity → Spin / seeding
• MJO phase → Timing window

SEQUENCE OF WHEN TO FOCUS ON EACH "Golden Sequence"

This is roughly how I prioritize these fields as a system evolves:

Day -7 to -5 (environment stage-setting):
• MJO phase
• 500 mb steering pattern
• SST/OHC in potential track region

Day -5 to -3 (watch for broad consolidation):
• 850 mb vorticity broadening or focusing
• Shear forecast trends
• MJO phase continuing?

Day -3 to -1 (tightening window / model convergence period):
• 850 mb vorticity focusing into a lobe
• Shear dropping / bubble forming
• 500 mb ridge steady or changing?
• Ensemble spread tightening

Day 0 (genesis onset):
• Vorticity center stacking vertically
• Low-shear bubble over the low
• Deep moisture plume in place

Post-genesis → landfall:
• 500 mb ridge evolution (track shifts?)
• Shear changes (intensity modulator)
• SST/OHC in path
• Core alignment (strengthening potential)

KEY “TELLS” THAT A SYSTEM IS ABOUT TO TIGHTEN "Golden Indicators"

These are the things I’ve noticed tend to precede a jump in model consensus and NHC confidence:

• 850 mb vorticity shifts from broad to focused max
• Vortex stacking: 850 → 700 → 500 mb aligning
• Shear bubble <10 kt forms near center
• Persistent convection anchors over low
• Ensemble spread contracts sharply
• Observed surface pressures start falling
• Upper divergence increases → healthy outflow



If you watch this core set of fields, in this sequence, you’ll often be ahead of deterministic runs — and you’ll understand why the models are trending one way or another.

Not claiming to reinvent the wheel — this is essentially the mental process that many experienced mets follow, just written out clearly for anyone who wants to use it.

Hope it helps — looking forward to contributing more this season.

[Stratton23]

GFS may be getting some weight according to the tropical hazards outlook, interesting to note that noaas 8-14 day precipitation outlook favors the highest odds of above normal rainfall along the texas coast line, interesting how that kind of lines up with the chance for development in the BOC on the hazards tropical outlook from the 11-17th ish

[revjohn]

GFS may be getting some weight according to the tropical hazards outlook, interesting to note that noaas 8-14 day precipitation outlook favors the highest odds of above normal rainfall along the texas coast line, interesting how that kind of lines up with the chance for development in the BOC on the hazards tropical outlook from the 11-17th ish

Yep. That timing window really is starting to look interesting with how those pieces are coming together. Definitely one to keep watching — next several runs should tell us a lot.

[WeatherBoy2000]

GFS may be getting some weight according to the tropical hazards outlook, interesting to note that noaas 8-14 day precipitation outlook favors the highest odds of above normal rainfall along the texas coast line, interesting how that kind of lines up with the chance for development in the BOC on the hazards tropical outlook from the 11-17th ish

Yep. That timing window really is starting to look interesting with how those pieces are coming together. Definitely one to keep watching — next several runs should tell us a lot.

12z eps is much more bullish in that timeframe/location compared to the 00z run.

[Stratton23]

Even though the GFS did as expected with losing that phantom system, it does show that the CAG may start to get more active as we approach the 12th time frame, seeing alot of energy rotating around on the east pacific and NW caribbean side, thats a CAG look and not some random vorticity spin up

[Stratton23]

Interesting to note on the 00z EPS at days 9-10 (216-240 hours) it has good support for an EPAC system, however the members are getting pulled north into the southern/ western gom at day 10 ish , weakness in the ridge over the western gulf, very interesting to see

[kevin]

06z GFS goes wild with the same CAG as the previous few runs. Once again, it's GFS and the CAG and also long-term, but hey at some point it has to be right... right?

Forms around +264hr. Even though the CAG action already starts +140hr and also spits out another EPAC system around +200hr before the one in the WCar forms.
On its way to slam into Houston as a MH at +384 hr, because of course it does.

[DunedinDave]

GfS is making full use of the term “long term windshield wiper effect.”

[LarryWx]

The Euro Weeklies have again been backing off of a mid-June TCG in the Atlantic basin.

[revjohn]

I wanted to loop back and apply my how I do it framework to what we’re seeing the past couple cycles:

Current snapshot (as of 6/4 runs):
✔️ MJO pulse continuing to progress favorably into phase supportive of CAG evolution (good alignment window next 7–10 days).
✔️ 850 mb vorticity already broadening EPAC side — NE lobe gradually sharpening in EPS, some GFS members.
✔️ Shear trends: 200–850 mb forecast generally dropping below 15 kt across WCar / BOC by ~day 7–9 → looking favorable, though exact timing vs ridge evolution will be key to monitor next few cycles.
✔️ Ridge holding firm early, with hints of weakness western Gulf day 10+ (EPS).

Model blend thoughts:
• GFS is out front as usual with aggressive vorticity consolidation / fantasy hurricane late run — but underlying CAG signal timing is valid.
• EPS shows increasing support for NE lobe tightening and possible BOC action ~day 9–12 (which lines up nicely with CPC hazards).
• Euro weeklies still somewhat mixed, but not inconsistent — more a question of timing / shear interplay.

Key tells I’m watching next few runs:
1️⃣ Vorticity lobe → does it focus & stack vertically day 7–9?
2️⃣ Low-shear bubble <10 kt → forming over any low center, and does the timing match ridge pattern?
3️⃣ Ensemble spread → contracting next 2–3 cycles?

Bottom line: Still think the ~June 9–17 window remains “open for business” for some form of BOC genesis potential. Too early to call strength or specifics, but the core environmental pieces continue trending toward alignment — pending how shear and ridge evolution sync up.

Looking forward to the next couple model cycles — should tell us a lot about whether we’re heading for a “real” event or just another CAG tease.

[chaser1]

Not for nothing (and likely transient), but there is a small area of convective confluence around 19N & 86W. Same general area where the GFS has been consistantly trying to spin up something. Doubtful it'll be there 12 hours from now but this small feature has an interesting look.

[revjohn]

Not for nothing (and likely transient), but there is a small area of convective confluence around 19N & 86W. Same general area where the GFS has been consistantly trying to spin up something. Doubtful it'll be there 12 hours from now but this small feature has an interesting look.

Nice spot, chaser1. I also see that little convective area near 19N/86W on the satellite this morning — lines up pretty well with where the GFS has been sniffing for a potential spin-up. Probably a short-lived blip, but sometimes these early flare-ups can hint at where the broader CAG might start focusing. Definitely keeping an eye on it.

[Stratton23]

Regardless of any development, that is a very wet 12z Euro run for texas, it looks likely that a ton of moisture from the pacific and the caribbean will get pulled into texas next week courtesy of a weak frontal boundary stalling out as seen on the euro run. Could be in for a very wet week regardless of tropical development or not

[Kingarabian]

12z GFS has something believable out of this CAG but crashes it into CA in 4 days. Not related to that phantom system we've been seeing this past week.

[Stratton23]

While the GFS not surprisingly dropped the phantom storm, it does have a more realistic scenario in the 10-12 day range with the CAG become much more active with convection , competing lobes of energy on the pacific and NW caribbean side associated with the CAG and not some random vort off SA. I think the CAG is likely going to get active when the MJO moves into the atlantic basin in about 7-8 days or so

[cycloneye]

Great message here about the ghost. Read the whole thread.

 https://x.com/burgwx/status/1930438335765393520

[Stratton23]

A couple of interesting things ive noticed in the models, may get a couple more eastern pacific storms in the next 10-12 days or so on the EPS/ GEFS, but their are some interesting players that could pull a developing EPAC system into the western gulf of mexico ( america lol) 1. Looking likely some sort of stalled frontal boundary will be parked across se texas all of next week, that does a couple of things, it provides opportunities for widespread rain but also erodes ridging in the gulf. There is a weakness on the GFS/ Euro in the gulf that could potentially allow for a developing EPAC system to get pulled north into the southern gulf, that kind of happens on the 12z GFS. 2. How long does the weakness linger? Does look like the ridge tries to build back in after that. All in all things still do have my interest for some mischief in the gulf, at the very least models show a ton of moisture from the pacific getting pulled into texas

[Stratton23]

GFS has been showing a weakness in the ridge over the gulf late next week thats allowing for energy from the pacific crossing into the BOC in the 9-10 day period, 6z run was corpus, 12z run us northern mexico , but its shown some sort of weak- broad low trying to develop, will see if the Euro starts to catch on to this or not, but the energy comes from the pacific side of the CAG, so its not an entirely ridiculous scenario by the gfs this time