Mika Rantanen
@mikarantane.bsky.social
Researcher in Finnish Meteorological Institute. Climate change, extreme weather, and attribution of extreme events. PhD in meteorology in University of Helsinki.
During the satellite era, no November SSW events are known to have occurred; the last robustly documented case was in 1968 (csl.noaa.gov/groups/csl8/...).
In a large sample of seasonal reforecasts (Ineson et al), November SSWs seem to be even rarer.
rmets.onlinelibrary.wiley.com/doi/full/10....
In a large sample of seasonal reforecasts (Ineson et al), November SSWs seem to be even rarer.
rmets.onlinelibrary.wiley.com/doi/full/10....
November 10, 2025 at 11:52 AM
During the satellite era, no November SSW events are known to have occurred; the last robustly documented case was in 1968 (csl.noaa.gov/groups/csl8/...).
In a large sample of seasonal reforecasts (Ineson et al), November SSWs seem to be even rarer.
rmets.onlinelibrary.wiley.com/doi/full/10....
In a large sample of seasonal reforecasts (Ineson et al), November SSWs seem to be even rarer.
rmets.onlinelibrary.wiley.com/doi/full/10....
Latest ECMWF subseasonal forecast shows ensemble mean zonal wind of about 5 m/s at 10 hPa in late November, with roughly 20–30 % of ensemble members indicating a reversal to easterlies (i.e. going < 0 m/s).
This suggests a non-zero probabilty for a major SSW event!
This suggests a non-zero probabilty for a major SSW event!
November 10, 2025 at 11:52 AM
Latest ECMWF subseasonal forecast shows ensemble mean zonal wind of about 5 m/s at 10 hPa in late November, with roughly 20–30 % of ensemble members indicating a reversal to easterlies (i.e. going < 0 m/s).
This suggests a non-zero probabilty for a major SSW event!
This suggests a non-zero probabilty for a major SSW event!
The first week of November (1.-7.11.) was record-warm in Helsinki, Finland. The average temperature was 9.3 °C.
Records have been kept since 1882.
Records have been kept since 1882.
November 8, 2025 at 3:26 PM
The first week of November (1.-7.11.) was record-warm in Helsinki, Finland. The average temperature was 9.3 °C.
Records have been kept since 1882.
Records have been kept since 1882.
Numerot muuttuvat jotenkin maagisesti valkoiseksi.
November 6, 2025 at 11:21 AM
Numerot muuttuvat jotenkin maagisesti valkoiseksi.
Unprecedentedly warm November day in eastern Finland, especially in North Karelia.
Multiple monthly heat records, including
Tohmajärvi Kemie 11.8 °C
Liperi Joensuu airport 11.1 °C
Juuka Niemelä 11.2 °C
Lieksa Lampela 10.9 °C
Nurmes Valtimo 10.8 °C
(shown with magenta in the map)
Multiple monthly heat records, including
Tohmajärvi Kemie 11.8 °C
Liperi Joensuu airport 11.1 °C
Juuka Niemelä 11.2 °C
Lieksa Lampela 10.9 °C
Nurmes Valtimo 10.8 °C
(shown with magenta in the map)
November 5, 2025 at 1:17 PM
Unprecedentedly warm November day in eastern Finland, especially in North Karelia.
Multiple monthly heat records, including
Tohmajärvi Kemie 11.8 °C
Liperi Joensuu airport 11.1 °C
Juuka Niemelä 11.2 °C
Lieksa Lampela 10.9 °C
Nurmes Valtimo 10.8 °C
(shown with magenta in the map)
Multiple monthly heat records, including
Tohmajärvi Kemie 11.8 °C
Liperi Joensuu airport 11.1 °C
Juuka Niemelä 11.2 °C
Lieksa Lampela 10.9 °C
Nurmes Valtimo 10.8 °C
(shown with magenta in the map)
Exceptionally mild airflow over central Finland today.
Liperi Joensuu airport just set a new November heat record with a temperature of 10.8 °C.
The reading is provisional and may still rise during the day.
Liperi Joensuu airport just set a new November heat record with a temperature of 10.8 °C.
The reading is provisional and may still rise during the day.
November 5, 2025 at 8:13 AM
Exceptionally mild airflow over central Finland today.
Liperi Joensuu airport just set a new November heat record with a temperature of 10.8 °C.
The reading is provisional and may still rise during the day.
Liperi Joensuu airport just set a new November heat record with a temperature of 10.8 °C.
The reading is provisional and may still rise during the day.
Here's Berkeley Earth dataset for Adelaide coordinates (-34.89N, 138.6E), nearest grid cell values.
1914 is there as 8th warmest, with 2013 ranking 1st.
1914 is there as 8th warmest, with 2013 ranking 1st.
November 3, 2025 at 9:38 AM
Here's Berkeley Earth dataset for Adelaide coordinates (-34.89N, 138.6E), nearest grid cell values.
1914 is there as 8th warmest, with 2013 ranking 1st.
1914 is there as 8th warmest, with 2013 ranking 1st.
In the current climate, it is extremely rare for the annual temperature record to be so far in the past, like it is in Finnish Lapland (year 1938).
Only 0.6 % of the land surface area (excluding Antarctica) had their warmest year in the 1930s.
Only 0.6 % of the land surface area (excluding Antarctica) had their warmest year in the 1930s.
November 3, 2025 at 9:05 AM
In the current climate, it is extremely rare for the annual temperature record to be so far in the past, like it is in Finnish Lapland (year 1938).
Only 0.6 % of the land surface area (excluding Antarctica) had their warmest year in the 1930s.
Only 0.6 % of the land surface area (excluding Antarctica) had their warmest year in the 1930s.
Year-to-date temperatures in Sodankylä Tähtelä (northern Fennoscandia) are currently tracking record-high and exceeding the long-standing 1938 record.
The best chance so far to beat the 1938 annual temperature record but it would still require anomalously warm end to the year.
The best chance so far to beat the 1938 annual temperature record but it would still require anomalously warm end to the year.
November 3, 2025 at 9:05 AM
Year-to-date temperatures in Sodankylä Tähtelä (northern Fennoscandia) are currently tracking record-high and exceeding the long-standing 1938 record.
The best chance so far to beat the 1938 annual temperature record but it would still require anomalously warm end to the year.
The best chance so far to beat the 1938 annual temperature record but it would still require anomalously warm end to the year.
It's hard to get a more symmetric and well-defined hurricane structure than the latest satellite images of Melissa.
One of the most intense storms the Atlantic has ever seen and unfortunately, just at the landfall.
One of the most intense storms the Atlantic has ever seen and unfortunately, just at the landfall.
October 28, 2025 at 2:35 PM
It's hard to get a more symmetric and well-defined hurricane structure than the latest satellite images of Melissa.
One of the most intense storms the Atlantic has ever seen and unfortunately, just at the landfall.
One of the most intense storms the Atlantic has ever seen and unfortunately, just at the landfall.
Voimistuminen jatkuu. Nyt 892 hPa ja 185 mph. Jenkkien hurrikaanikeskuksen tiedote on suorasanainen:
THIS IS AN EXTREMELY DANGEROUS AND LIFE-THREATENING SITUATION! TAKE COVER NOW!
Melissa tulee olemaan kaikkien aikojen voimakkain rantautuva hurrikaani Atlantilla.
THIS IS AN EXTREMELY DANGEROUS AND LIFE-THREATENING SITUATION! TAKE COVER NOW!
Melissa tulee olemaan kaikkien aikojen voimakkain rantautuva hurrikaani Atlantilla.
October 28, 2025 at 2:10 PM
Voimistuminen jatkuu. Nyt 892 hPa ja 185 mph. Jenkkien hurrikaanikeskuksen tiedote on suorasanainen:
THIS IS AN EXTREMELY DANGEROUS AND LIFE-THREATENING SITUATION! TAKE COVER NOW!
Melissa tulee olemaan kaikkien aikojen voimakkain rantautuva hurrikaani Atlantilla.
THIS IS AN EXTREMELY DANGEROUS AND LIFE-THREATENING SITUATION! TAKE COVER NOW!
Melissa tulee olemaan kaikkien aikojen voimakkain rantautuva hurrikaani Atlantilla.
Oikeastaan pahin mahdollinen skenaario näyttäisi toteutuvan. Hurrikaani Melissa on jatkanut voimistumistaan juuri ennen rantautumistaan Jamakaille. Maksimikeskituulet puhaltavat nyt 80 m/s, ja pintapaine on laskenut 896 hPa:iin.
Yksi kaikkien aikojen voimakkaimmista myrskyistä Atlantilla.
Yksi kaikkien aikojen voimakkaimmista myrskyistä Atlantilla.
October 28, 2025 at 1:18 PM
Oikeastaan pahin mahdollinen skenaario näyttäisi toteutuvan. Hurrikaani Melissa on jatkanut voimistumistaan juuri ennen rantautumistaan Jamakaille. Maksimikeskituulet puhaltavat nyt 80 m/s, ja pintapaine on laskenut 896 hPa:iin.
Yksi kaikkien aikojen voimakkaimmista myrskyistä Atlantilla.
Yksi kaikkien aikojen voimakkaimmista myrskyistä Atlantilla.
Under the RCP4.5 scenario and collapsed AMOC, René van Westen shows how especially the cold extremes would get worse in the Nordics.
-47 °C in Helsinki would be once in a 10 year event!
-47 °C in Helsinki would be once in a 10 year event!
October 21, 2025 at 11:20 AM
Under the RCP4.5 scenario and collapsed AMOC, René van Westen shows how especially the cold extremes would get worse in the Nordics.
-47 °C in Helsinki would be once in a 10 year event!
-47 °C in Helsinki would be once in a 10 year event!
Nordic Tipping Week in Helsinki. @rahmstorf.bsky.social gave a nice overview on the state of latest research on the risk of AMOC change.
October 21, 2025 at 10:45 AM
Nordic Tipping Week in Helsinki. @rahmstorf.bsky.social gave a nice overview on the state of latest research on the risk of AMOC change.
First snow of the season in Finland has fallen today morning in Enontekiö, Lapland.
This year, the first snow was about three weeks late. Usually the first measurable snow is registered somewhere in the country in late September.
This year, the first snow was about three weeks late. Usually the first measurable snow is registered somewhere in the country in late September.
October 16, 2025 at 6:18 AM
First snow of the season in Finland has fallen today morning in Enontekiö, Lapland.
This year, the first snow was about three weeks late. Usually the first measurable snow is registered somewhere in the country in late September.
This year, the first snow was about three weeks late. Usually the first measurable snow is registered somewhere in the country in late September.
Wow, autumn-to-date mean temperature in Sodankylä, Lapland is currently a full two degrees (!) higher than the previous record.
In Sodankylä, records have been kept since 1908.
In Sodankylä, records have been kept since 1908.
October 9, 2025 at 7:23 AM
Wow, autumn-to-date mean temperature in Sodankylä, Lapland is currently a full two degrees (!) higher than the previous record.
In Sodankylä, records have been kept since 1908.
In Sodankylä, records have been kept since 1908.
The rapid deepening of Storm Amy has begun.
Over the next hours, the storm will travel across the jet stream and move to the left exit region of the jet stream where the most explosive deepening will take place.
Over the next hours, the storm will travel across the jet stream and move to the left exit region of the jet stream where the most explosive deepening will take place.
October 3, 2025 at 8:03 AM
The rapid deepening of Storm Amy has begun.
Over the next hours, the storm will travel across the jet stream and move to the left exit region of the jet stream where the most explosive deepening will take place.
Over the next hours, the storm will travel across the jet stream and move to the left exit region of the jet stream where the most explosive deepening will take place.
Finland's regionally averaged temperature in September was the 3rd highest on record, but here you can see how Septembers 2023–2025 surpass all previous years since 1900.
October 1, 2025 at 10:58 AM
Finland's regionally averaged temperature in September was the 3rd highest on record, but here you can see how Septembers 2023–2025 surpass all previous years since 1900.
Those estimates were based on climate change information from CMIP6 models, but the experimental observation-based method that only takes into account the change in mean temperature (not in variability), generally agree with PR ~50 and ΔI ~2 °C.
October 1, 2025 at 8:23 AM
Those estimates were based on climate change information from CMIP6 models, but the experimental observation-based method that only takes into account the change in mean temperature (not in variability), generally agree with PR ~50 and ΔI ~2 °C.
With our statistical attribution, we can estimate that September this warm in Sodankylä occurs every ~90 years in today's climate. In the climate of 1900, the event is almost impossible (~4700 years).
So we estimate that the month was ~50 times more likely and 1.9 °C warmer due to climate change.
So we estimate that the month was ~50 times more likely and 1.9 °C warmer due to climate change.
October 1, 2025 at 8:23 AM
With our statistical attribution, we can estimate that September this warm in Sodankylä occurs every ~90 years in today's climate. In the climate of 1900, the event is almost impossible (~4700 years).
So we estimate that the month was ~50 times more likely and 1.9 °C warmer due to climate change.
So we estimate that the month was ~50 times more likely and 1.9 °C warmer due to climate change.
September 2025 featured very optimal large-scale circulation for persistent warmth in northern Fennoscandia.
The ridge was situated east of Fennoscandia with low pressure anomaly over the North Atlantic. This favoured southerly flow that kept temperatures above freezing almost the whole month.
The ridge was situated east of Fennoscandia with low pressure anomaly over the North Atlantic. This favoured southerly flow that kept temperatures above freezing almost the whole month.
October 1, 2025 at 8:23 AM
September 2025 featured very optimal large-scale circulation for persistent warmth in northern Fennoscandia.
The ridge was situated east of Fennoscandia with low pressure anomaly over the North Atlantic. This favoured southerly flow that kept temperatures above freezing almost the whole month.
The ridge was situated east of Fennoscandia with low pressure anomaly over the North Atlantic. This favoured southerly flow that kept temperatures above freezing almost the whole month.
Breaking: September 2025 was record-warm in Finnish Lapland, for the third time in a row.
Monthly mean temperature in Sodankylä Tähtelä was 11.0 °C, exceeding the previous record of 10.3 °C set in 2024 (which itself had exceeded the previous record of 10.0 °C set in 2023 and 1934).
Monthly mean temperature in Sodankylä Tähtelä was 11.0 °C, exceeding the previous record of 10.3 °C set in 2024 (which itself had exceeded the previous record of 10.0 °C set in 2023 and 1934).
October 1, 2025 at 8:23 AM
Breaking: September 2025 was record-warm in Finnish Lapland, for the third time in a row.
Monthly mean temperature in Sodankylä Tähtelä was 11.0 °C, exceeding the previous record of 10.3 °C set in 2024 (which itself had exceeded the previous record of 10.0 °C set in 2023 and 1934).
Monthly mean temperature in Sodankylä Tähtelä was 11.0 °C, exceeding the previous record of 10.3 °C set in 2024 (which itself had exceeded the previous record of 10.0 °C set in 2023 and 1934).
Quite worrying solutions recently in the global weather models regarding Humberto's post-tropical intensification. The system is forecast to deepen explosively while arriving Europe.
The northern British Isles might be hit hard. 👀
The northern British Isles might be hit hard. 👀
September 30, 2025 at 5:02 AM
Quite worrying solutions recently in the global weather models regarding Humberto's post-tropical intensification. The system is forecast to deepen explosively while arriving Europe.
The northern British Isles might be hit hard. 👀
The northern British Isles might be hit hard. 👀
The highlight of this week was meeting with @mattpriestley.bsky.social here in Helsinki and his seminar about constraining future windstorm trends for Europe. Very interesting work!
September 25, 2025 at 12:33 PM
The highlight of this week was meeting with @mattpriestley.bsky.social here in Helsinki and his seminar about constraining future windstorm trends for Europe. Very interesting work!
Blocking high in action. The newest ECMWF forecast keeps Finland completely dry for the next 10 days.
September 25, 2025 at 8:17 AM
Blocking high in action. The newest ECMWF forecast keeps Finland completely dry for the next 10 days.