Thread by @davidhelms570

1. Soil Moisture Update: 15 May 2023, a #NAFOWeather🧵
I'm "officially" declaring #MudSeason over based on limited rainfall since May 1st & marginal rain forecast in the next 2 weeks. Soil is dry enough to support most vehicles across most of the LoC.

https://twitter.com/davidhelms570/status/1655566818159861760?s=20

2. Recent Rainfall (past 2 weeks): Donetsk and Luhansk received about 5-15 mm rain of on May 8-9, otherwise, a dry 2 weeks.

3. Soil Moisture Change (past 2 weeks): There has been a general soil drying trend from 30 April to 14 May with least moisture in the south and greatest soil moisture in Donetsk.

4. Soil Moisture Change (past 2 weeks): Looking at a 14 day time-series for regional soil moisture using the NASA FLDAS model, the overall trend is evident with May 8-9 rainfall delaying drying trend for 4-5 days.

5. Predicted Rainfall (15-22 May 2023): Predicted rainfall is meager near the Line of Conflict, only about 0-5 mm; the LoC normally receives about 10 mm rain per week.

6. Predicted Evapotranspiration (ET) (15-22 May 2023): Soil in the LoC is losing about 2.5-3.5 mm moisture per day from ET caused by increasing temperatures, more sun, higher winds, and low humidity and no predicted rainfall.

7. Trafficability: I've shown the Meteoblue "trafficability" forecast before. It is for farming, not military vehicles. The model has largely "flat-lined" (predicting "go" for using farm equipment in fields) due to extended drying. Model is probably too optimistic (but useful).

8. Extended Forecasts (2 weeks to 1 month): Good confidence the dry spell will continue through June 1st, thereafter, rain is likely to return per the ECMWF C3S ensemble forecast. Annually, June typically receives the most rainfall, over 50 mm rain in some locations.

9. Water balance and seasonal trends: It's not shocking annual soil moisture is the least in months with greatest minutes of sunlight causing a moisture deficit of 2 mm per day in the spring/summer. June's rainfall increases soil moisture but overall soil stays dry until October.

10. In summary, 2023 spring #MudSeason is over (e.g., extended period of limited vehicle trafficability) due to May's high ET and low rainfall. June will likely see a return of rain but that moisture will rapidly be removed from soil due to high rates of ET. /end

.@threadreaderapp please unroll