Thread by @davidhelms570

1/ Soil moisture update: While #MudSeason is "officially over", locally heavy rain can and will degrade trafficability for periods of time. A #NAFOWeather 🧵

https://twitter.com/davidhelms570/status/1658093469015973889?s=20

2/ BLUF: Updated soil moisture/trafficability matrix similar to 25 April forecast with a 1 month delay in seasonal drying conditions due to above average April rain. Last week of May had several thunderstorm days & locally heavy rain but overall dry conditions since May 1st.

3/ As stated in previous tweet, some locations had heavy rain including eastern Kherson/northwest Zaporizhzhia, northeast Donetsk and southern Luhansk in the last week of May. However, June has been mostly rain free.

4/ Heavy rain from thunderstorms definitely did some damage reversing the soil drying trend and making some trenches into fishing holes!

https://twitter.com/SanderRegter/status/1665069608544468993?s=20

5/ Some locations in Kherson & Zaporizhzhia a day with very heavy rain from thunderstorms but much of this rain ran-off the land instead infiltrating into the ground causing sustained trafficability problems. Note mechanized UA attack in northwest Luhansk.

https://twitter.com/J_JHelin/status/1665510652318822402?s=20

6/ A deeper dive on May 2023 rainfall, Noteable is the large area of above normal rainfall right of a line from Novoazovs'k-Donetsk-Soledar-Luhansk (southeast Ukraine). This region likely continues to have limited trafficability for the next two weeks.

https://twitter.com/davidhelms570/status/1664637641394999296?s=20

7/ Latest available Soil Water Index (proxy for soil strength) through 21 May 2023 (blue versus climate (dashed orange))... going in the right direction (seasonal drying); of course, the late May rain stopped the drying trend.

8/ SMAP Surface Soil Moisture (L4 analysis, m**3/m**3). Again, going in the right direction (drying) since 26 April (1 June values increase due to late May rain). The threshold for trafficability is 0.250 m**3 (water)/m**3 (soil) of less.

9/ Agricultural Meteogram (Forecast Timeline) shows daily evapotranspiration (lost soil moisture to atmosphere) 3.0-4.5 mm/day, e.g., it needs to rain more than 100 mm per month to keep soil from drying out; however, June monthly rain is far below that amount, typically 45 mm.

10/ The Meteoblue agriculture 6 day trafficability forecast (through 11 June) has soil rapidly drying to good (green) state. Caveat: This model is faster than most and probably not representative of soil moisture needed for military vehicles.

11/ 7-Day Rainfall forecast (through 12 June): ECMWF & other models have rain moving into southeast Ukraine by next Sunday (11 June). Rain predicted for the southeast along Sea of Azov coast. I don't think whatever rain falls will have significant impact to most of the LoC.

12/ GFS 15-Day soil moisture continues the drying trend with critical threshold [0.20-0.30 m**3/m**3 soil moisture] for trafficability region expanding southwest to northeast. Caveat: Soil moisture forecast is only as good as the rainfall forecast.

13/ Looking forward to mid-late June, C3S seasonal forecast for eastern Europe hints at additional rain, which is probably a good bet. Any rain will have regional impacts to soil moisture for 3-7 days before seasonal drying removes excess moisture.

14/ Additional information on #MudSeason
@tracey_shelton article @ABC, 12 May 2023, "What is Ukraine waiting for before beginning the much-anticipated 'spring offensive'?"
abc.net.au/news/2023-05-1…

15/ Additional information on #MudSeason
@FrankRHofmann article for @dwnews, 1 May 2023
dw.com/en/countdown-t…

16/ #MudSeason Backgrounder, 5 May 2023:

https://twitter.com/davidhelms570/status/1654516669383933956?s=20

17/ First #MudSeason forecast, 27 March 2023, with additional background info (amended with subsequent forecasts including this thread):

https://twitter.com/davidhelms570/status/1640434216419598336?s=20

18/ Soil moisture conditions will be updated periodically as conditions change including a weekly rainfall assessment every Monday. /end

.@threadreaderapp please unroll