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David Helms Profile picture
@davidhelms570
May 15 • 11 tweets • 5 min read Twitter logo Read on Twitter
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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.
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. Image
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. Image
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. Image
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. Image
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. Image
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). Image
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. ImageImageImage
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. ImageImage
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
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More from @davidhelms570

David Helms Profile picture
May 8
#KakhovkaReservoir #KakhovkaHPP Status Follow-up: 8 May 2023. Upon further analysis of 6 May 2023 Sentinel-2 imagery and consultation with @tom_bike @Gergyl & @BruckenRuski, we believe the #KakhovkaReservoir water is "over-topping" the #KakhovkaHPP dam. /1
Time-series loop from 27 March 2023 to 6 May 2023. Note the "brightening" downstream (left side) of the #KakhovkaHPP sluice gates last frame in loop which is water flowing over the top of the dam. Over-topping is particularly evident on the 3 northern most sluice gates. /2
Why is this happening? Recall the Russian occupiers blew up the road and rail deck above the #KakhovkaHPP dam sluice gates on 10 NOV 2022 as part of the RF retreat ("strategic repositioning") from the Dnipro right bank. /3
Read 12 tweets
David Helms Profile picture
May 7
1. Ruschist operation of Kakhovka HPP (K-HPP) dam has been reckless. Kakhovka Reservoir (KR) water level has alternated from record low to record high in just 3 months. Loop (6 FEB-6 MAY 2023) shows sand bars receding with rising KR water. #NAFOWeather🧵
2. These images are of the K-HPP from Left: 6 FEB, and Right: 6 MAY 2023 (enhanced from data included in loop). ImageImage
3. North Crimean Canal intake, Left 20 FEB 2023 Right 6 May 2023: Latest image show water gushing through NCC intake gate at Tavrisk as record KR level is pushing water through gravity fed NCC at high rates. ImageImage
Read 7 tweets
David Helms Profile picture
May 6
1. Russians are once again attempting to frighten residents in occupied Kherson and Zaporizhzhia on the left bank of Kakhovka Reservoir into evacuating. This is part of a larger information operation ahead of the Ukrainian offensive. A #NAFOWeather 🧵
2. TASS reported (some western media repeated) that the Kakhovka HPP dam could burst and this would flood Zaporizhzhia NPP and surrounding communities. This is pure rubbish. If the Kakhovka HPP dam burst, Kakhovka Reservoir would dramatically LOWER as these location are upstream. ImageImage
3. Russian propaganda uses facts, often reported by the west, with other false statements to create an environment of fear and uncertainty. It is TRUE Kakhovka Reservoir is at record high levels and the K-HPP controls water discharge for K reservoir.
Read 15 tweets
David Helms Profile picture
May 5
1. A backgrounder on how soil moisture changes over time. A #NAFOWeather 🧵
2. Soil moisture is one element of the water balance / hydrologic cycle which includes precipitation, terrain, vegetation state, and atmosphere (temperature, humidity, winds, sunshine/solar radiation). Image
3. Rate of soil moisture changes over time:
Over Weeks to Months - Controlled by vegetation growth
Cite: Reference evapotranspiration in water requirement: Theory, concepts, and methods of estimation, Handbook of Hydroinformatics, 2023
sciencedirect.com/book/978012821… Image
Read 13 tweets
David Helms Profile picture
Apr 25
1/ It has been almost a month since I provided a #MudSeason trafficability forecast. My assumption of a "normal" spring rainfall & improving trafficability were way too optimistic as it has rained Every. Damn. Day. since late March 2023. A #NAFOWeather 🧵
2/ #BLUF The trafficability forecast (below) is based on current and predicted rainfall which are well above normal for near the Line of Conflict (LoC). In general, trafficability is delayed about 1 month versus normal. Image
3/ Some input on #MudSeason from authoritative sources: @DefenceHQ "severe mud is highly likely slowing operations vor both sides" but "conditions can be expected to improve in the coming weeks".
Read 17 tweets
David Helms Profile picture
Apr 4
1/ Some thoughts on the flooding in Kramatorsk today (4 April 2023).
2/ To be sure, it snowed in Kramatorsk recently, probably 20-25 cm on March 30-31.
3/ For Donetsk Oblast, area-wide precipitation received in the past 10 days was about 35 mm. This puts the most recent 30 day period +16% above normal, but the past 90 days are -16% below normal. Thus, recently precipitation was a nice catch-up from winter precipitation deficit.
Read 6 tweets

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