Tuesday Extended Forecasts–Light At The End Of The Tunnel

7/4/23 Tuesday 8:30 am

Happy July 4th! In case anyone is interested Mammoth Mountain ski area in California is still open.

In other news, the Chris Mountain Fire grew by 14 acres yesterday. It is currently at 491 acres as of about midnight. Today, there is another slight chance of mostly high-elevation isolated showers. This should not affect anyone’s plans for the day.

The extended forecast is getting interesting. It does show another 10 to 14 days of mostly dry weather. The Euro extended ensemble forecast is still the driest, and it shows the latest start to the pattern change. It shows the pattern flipping between 7/18-7/21. So I would use that as the worst-case scenario.

Based on what I am seeing in some of the other model runs I am not so sure it will take that long to flip. The other interesting contradiction to the Euro extended ensemble model is, itself.

The European ensemble model is made of 51 model members. There is what is called a “Control” run which is produced from the best-unperturbed data available at the time. The model is then run 50 additional times. Each time, the data fed into the model is slightly changed. The average of the 51 model runs is called the mean. The mean becomes the final forecast.

When I see such a disparity between the European ensembles and the GFS and Canadian ensembles. It throws up a slightly red flag. When I see the ensembles completely disagree with their control run, it concerns me even more. It makes me question the ensemble mean forecast. By concern, I should say it gives me hope that the control run is correct and the mean run is wrong.

That happened several times last year. Not only during the monsoon season, but during our biggest winter storms. The Euro consistently under-forecasted the total precipitation.

Here is what I am referring to.

The European Ensemble Mean total precipitation forecast Ending August 3rd.

Here is the European Control run for the same time period.

Here is the GFS ensemble mean forecast for the same time period.

Just for fun here is the GFS control run.

Here is the Canadian ensemble mean. This only extends to July 30th and I do not have access to the control run.

To summarize, the pattern should change after the 15th, most likely between the 18th and 21st. For those entering the Hard Rock, this is far from a final forecast. Data trends suggest there is a chance that the pattern could flip right as the event begins. The next extended data will be available on Friday.

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