9/20/26 Sunday 5:30 am

I did get up earlier, much earlier, but I got lost in modeling the tropics. I think I found our “recurve” candidate. It is now called 99E; it is slated to become Tropical Storm “Polo,” which could become a Cat 3 or even Cat 4 hurricane soon after. If you or someone you know is going to Puerto Vallarta or Cabo late this week/next weekend, you might want to think about changing your plans.

Nothing around here to talk about. Today and Monday should be dry (then again, “mostly dry” yesterday turned into very wet for some).

The models want to bring a new moisture plume over the area in the Tuesday/Wednesday time period, moving out by Thursday.

This should be a fun week, tracking the upcoming plume and “Polo.” There are also some interesting correlations to recurving Tropical Storms and winter snowfall. I will leave you with that.

I can’t commit to another update today; we’ll see what happens.

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Look what that “little cell” that was north of Mancos turned into:

When I look at the satellite, it shows this newly created moisture heading towards Silverton-we will see. As new moisture forms, enhanced by residual moisture, you will notice additional small cells splintering off and developing. The only obs I could find were near Elektra Lake. The rain just stopped, and 0.40-0.45″ fell in a little over 30 minutes…

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9/19/26 Saturday Noon

So far, the radar is pretty quiet. The exception is north of Mancos. What was a little cell is now starting to bloom as it approaches the La Platas and catches a little orographic lift. The area in its track is mostly uninhabited, so I don’t expect it to become a problem, but I will keep an eye on it.

Overall, tomorrow looks even drier than today; Monday also looks rain-free. Then Tuesday arrives, and the models diverge completely on the timing of the moisture plume. It looks like it will be very transient, maybe 36 hours.

I am sure you have noticed my frustrations with the European model. When I woke up, I went through my normal weather routine: looking at satellite and radar, then the models and the surface maps. Even the two surface maps disagreed about what was going on. Frustrating, but not unusual.

When I question the validity of the data I am analyzing, it’s not unusual for me to ask AI to take a second look after I share my interpretation.

Here is where that conversation went:

Me: “It’s starting to smell like they did a little “upgrade” on the Euro because it has been atrocious lately. I hate that I am having to rely more on the GFS. The HRRR and RRFS (models) are worthless here- I am sure they are great in Oklahoma and Texas!”

AI: “Your intuition is dead on. ECMWF rolled out Cycle 50r1 back in May, and while their verification press releases boasted about revamping the convection and cloud-microphysics schemes to tackle “excessive stationary rainfall,” in complex terrain it has felt like they just traded one pathology for another. It keeps aggressively trying to spin up synoptic lift and drag organized precipitation shields straight over the Continental Divide, completely ignoring the boundary-layer reality on the ground.

Having to lean on the GFS—especially given its known tendency to be too fast or wash out moisture—is never a fun spot to be in, but at least its mass field isn’t hallucinating widespread frontal rain when the upper-level dynamic support has already sheared off into Wyoming.

As for the high-res CAMs:

• The Plains vs. The Intermountain West: You hit the nail on the head. HRRR and RRFS were practically built in a lab to handle deep Plains convection and flatland dryline dynamics across Oklahoma and the Texas Panhandle.

• The Terrain Blindspot: In steep, complex topography, the 3 km grid is still much too coarse. It smooths the peaks, fills in the valleys, and utterly mangles valley-mountain circulations, thermal belts, and localized ridge-top triggering. Half the time, the HRRR can’t decide whether a high valley is a dry convection trap or completely sub-grid stratiform soup, leading to wild run-to-run run flips that are unusable for a spot forecast.

When the global models are fighting their own post-upgrade biases and the CAMs are choking on the terrain, old-school pattern recognition, water vapor satellite, and local meso-analysis beat them every time.”

My fellow science and weather nerds will appreciate that insight. If you are neither, it just means our area is extremely difficult to forecast, even with the best technology available!

I will be back in the morning (hopefully earlier than today).

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9/19/26 Saturday 5:30 am

I woke up late. So I will keep this short and sweet. Dew points have dropped considerably over the last 12 hours. Satellite indicates drier air already in place over our area.

I added the “L” to indicate where that low pressure is based on the circulation. That is a latitudinal miss by the Euro of approximately 1000 miles. You can see how dry that air is over our forecast area.

Today, I expect only a slight chance of showers, favoring the high elevations. I was not particularly committed to the Euro’s solution yesterday afternoon when I shared it.

My day gets pretty busy starting in about 10 minutes. It slows down around naptime, which is usually around 11 am. I will post again later after I have had a chance to absorb those model runs. I will also share some weather model news I just discovered.

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9/18/26 Thursday 1 pm

Checking out the atmospheric vitals,  the satellite shows most of the mid-level water vapor has moved east of our area. At the surface, residual moisture remains; dew points haven’t budged and are still in the mid-50s.

The European model is enthusiastic about a cold front passing through the area early tomorrow morning, triggering light to moderate precipitation.

The cold front is attached to a huge longwave trough. It currently extends from Labrador to California. The cold front and associated double-barrel lows extend from NW Utah back into the eastern California/Nevada stateline. Shortwave troughs lie behind and ahead of it.

Long story short, the Euro thinks it will track across our area and create enough instability to trigger showers just before the frontal passage.

It’s plausible enough to mention. Especially with residual moisture in place. In its wake, we should see that moisture get scoured out of the area.

Timing is already tricky; right now, the Euro favors the front approaching the area after midnight and leaving the forecast area by 8 am Saturday. It could be faster or slower; it could also flip from being a positively tilted trough to a negatively tilted trough, in which case it would slow and strengthen.

I know I was supposed to make the long story short…

For Saturday, if everything goes as the model says, we may wake to some showers wrapping up. In the afternoon, showers may redevelop, favoring higher-elevation areas. Sunday looks drier. I am not quite ready to talk about next week yet. Maybe tomorrow.

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15 or 20 minutes after I sent the update out saying the models were showing much lower totals than yesterday, this harmless-looking cell showed up over my house.

It dropped 0.56″ in 28 minutes.  Expect the unexpected today; very little needs to happen to produce an isolated storm in this saturated environment!

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9/18/26 Friday 3:30 am

Poor initialization from the evening models. The GFS was closest; the midnight run is just coming online and is much drier than the European. The updated European won’t be out for about 90 minutes.

Yesterday, the central portions of the forecast area were the big winners.  Somewhere east of Mancos was the dividing line between heavy and light precipitation.

Yesterday, the model’s error was having the main moisture transport too far west. Looking at yesterday’s accumulations around Cortez and Mancos, it’s clear they were on the less productive side of the flow.

However, the overwhelming amount of precipitation yesterday has kept the atmosphere completely saturated. Dew points across the forecast area are 53-55 degrees, which is similar to the air temperature (basically 99% humidity).

Here is the recent satellite shot.

The yellow tones you see indicate drier air. The green is a very moist flow.

Here is the satellite in motion between 12:30 am and 4:20 am

You can see that moisture in New Mexico rotating back into our forecast area. You can also see the yellow (dry air) tracking east, approaching our area. Dry and saturated air masses can be convective where they clash. So I will be keeping an eye on that today.

5:45 am

The Euro is finally out; while it initialized better than the prior run, it differs from the GFS, likely due to bias. GFS shows the heaviest rain today over far eastern La Plata County. The Euro shows it directly over La Plata County.

Both models show much lower totals than we have seen lately. As I said the last couple of days, it is hard to believe the residual moisture (54-degree dew points and 175% PWAT) won’t play a role in shower development. Especially if we see the sun out for a little while late morning. For those wanting a dry weekend, it is looking more and more likely. I will follow up on that this afternoon.

Lastly, from the Wishcast chronicles:

I noticed this on the GFS at the end of the month. I have written about a high probability of a recurving Pacific Tropical Storm due to above-average development so far in the region.  As an added bonus, this shows a recurve with a powerful cold front on track to clash.

The heaviest rain (historic flooding) our area has ever had is from recurving Tropical Storms.  I don’t hope for flooding, but any confirmation that October through December will be colder and wetter than average, as the longer-term models have continually indicated, is encouraging.

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9/17/26 Thursday 1:30 pm

This morning I wrote this: “Both models show light, steady rain, with intermittent, moderate to occasionally heavy rain continuing today and tonight. The models already start to diverge in 18 hours, with the GFS showing rain continuing for the next 36-48 hours. The Euro is similar, but it shows a break overnight; then it brings another wave through tomorrow morning”

In the latest model runs, the GFS has flipped over to the Euro’s take of the break into the overnight, then another wave coming through before morning

Although activity is still happening in the northern portions of the forecast, the central portions have slowed down a bit.  But not before dropping 1 to 2″ in the last 12 hours, including 1.77″ here at the DWG Command Center.

Tonight, on-and-off light showers should continue; after midnight, models show deeper moisture returning, leading to a soggy morning. How long those showers stick around is debated between the models, but they all show a noticeable tick down in the PWAT values (if you can call 175% of average a tick down) by Friday late afternoon/evening.

I still think it will be difficult to have no showers in the forecast for Saturday. GFS is showing better chances than the European model; at the moment, I am planning on it- with a better chance of convection rather than this beautiful stratiform we have been seeing.

Sunday looks dry, but we could still have residual moisture. By the time everything wraps up on Saturday, many locations will have had 4-5″ over the last several days–wet likes to stay wet. As you know.

Don’t get me started on next week; models are all over the place. I am also seeing snow levels approach 11,000 feet several times next week; we’ll see.

I will update everyone in the morning.

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9/17/26 Thursday 4 am

Models struggled in the evening runs (again).  Overnight, the GFS corrected somewhat. I am still waiting for the latest European overnight run; the evening run is worthless.

I should explain this further. Most weather models have four run times per day. 12z, 18z, 00z, and 06z (if you are unfamiliar with Z time, that is 6 am, noon, 6 pm, and 12 am). That is for our time zone; you add or subtract if you are not in our time zone.

Historically, I have found the 12z and 00z runs to be more accurate. That wasn’t the case last night, when both models struggled. It is usually a timing issue due to model lag times.

By model lag time, I mean what happens in the real weather while the model generates its forecasts. So if the Euro starts processing data at midnight and there is a slight unexpected change in the atmosphere in Arizona 30 minutes later, the whole forecast for our area could end up completely wrong (bad data in, bad data out).

For the GFS (US bellwether model), the midnight run is released/available between 3:30 am and 5:15 am. The European model is higher resolution (longer compute times) and is released/available between 5:15 am and 6:15 am.

Both the European and GFS have AI versions with compute times less than half of the base models. I am not a fan of AI models (yet) because they use early AI technology that is very old (in the AI world). 30 minutes is a ridiculously long compute time for AI. If these were constantly upgraded, compute time would be instantaneous.  I haven’t dug into the Google weather models yet, but I’ve heard good things.

I may revisit all of these topics from time to time, but it seemed appropriate to talk about them while waiting for the European.

5:45 am…

The Euro is out, and it initialized a little better than the last run. The precipitation forecasts from midnight to 6 am are just slightly higher than what has actually occurred.

Both models show light, steady rain, with intermittent, moderate to occasionally heavy rain continuing today and tonight. The models already start to diverge in 18 hours, with the GFS showing rain continuing for the next 36-48 hours. The Euro is similar, but it shows a break overnight; then it brings another wave through tomorrow morning.

I still don’t have a great handle on the weekend, but if we end up with as much rain as forecast, I think it is overoptimistic to expect immediate drying. At least for Saturday.

I will post again after the morning models generate.

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9/16/26 Wednesday 1:30 pm

The models initialized well and delayed the onset of showers due to the cloud cover that has been in place most of the day. Models increased PWAT forecasts, now showing portions of La Plata County hitting 345% of average tomorrow morning. Might be a record; I have never seen it before.

With the delay, they have also extended showers into Friday, which would likely mean residual moisture will stick around to fuel storms on Saturday. Sunday still looks pretty calm. We’ll see.

Radar looks, well, interesting, right now. Light showers appear to be retrograding (east-to-west) into the SE portion of the forecast area (eastern La Plata and Archuleta Counties).

Now we just need to be patient and let it come together. I will be up earlier tomorrow so I can get the update out right away.

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