Category: Ensemble Discussion

Permanent link to this article: https://indywx.com/2020/09/14/video-cooler-air-met-with-continued-dry-conditions-latest-on-sally/

Sep 13

Extended Dry Period…

• Filed under AG Report, Client, Ensemble Discussion, Forecast Discussion, Forecast Models, Harvest '20, Heavy Rain, La Nina, Long Range Discussion

• September 13, 2020

IND is now running more than 1.2″ below normal for the month and this is coming off a dry finish to August.

Note the localized, but significant, area of bone dry conditions extending east from eastern IL across central Indiana (while surrounding areas have cashed in on significant rains over the past 30 days):

The upcoming 7-days won’t offer up much relief from the dry conditions as high pressure dominates. Even the mid-to-late week cold front should pass through the region mostly dry.

Most guidance only drops between a trace and 0.10″ of rain on central Indiana over the next (10) days as the dry pattern rolls along. The GFS and European ensemble products highlight the dry regime well:

Ironically, the overall pattern should shift in dramatic fashion as autumn matures and heads into winter. We still expect an about face late autumn as the wet anomalies paint themselves across our region as the southeast turns dry, thanks to the La Nina pattern…

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Sep 11

Long Range Update: Walking Through The Back Half Of September…

• Filed under Client, Ensemble Discussion, Long Range Discussion, MJO, PNA, Unseasonably Cool Weather, Unseasonably Warm

• September 11, 2020

We believe the pattern during the 2nd half of the month will be driven by the MJO and PNA. The MJO is forecast into Phase 6 and 7 by the 18th-24th time frame.

Phase 6 is quite warm, but notice how the chilly air begins to push during Phase 7.

Neither phase is overly wet, but there’s hope compared to how dry it’s been over the past 2-3 weeks.

Interestingly enough, after a “neutral” phase with the PNA, both the GFS and European ensemble products predict a strong positive shift just after the 20th. This suggests to me that the week starting around that point should feature more widespread and stronger chill, compared to normal.

Let’s look at the latest model guidance, starting with the European ensemble:

Week 1 is still warmer than normal across our region, but notice the strong cooling by Week 2 (Sept. 18th-25th time frame).

The GFS ensemble is similar during the Week 1 and Week 2 time frame.

Given that strong PNA by late month, it wouldn’t surprise me to see these anomalies grow cooler as time gets closer during that Week 2 period.

Overall, the pattern continues to look dry, although there should be a better shot of rain/ storms as the cold front moves into the region that will ultimately deliver the much cooler air late month.

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Permanent link to this article: https://indywx.com/2020/09/11/long-range-update-walking-through-the-back-half-of-september/

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