Blessed Weather

A stunning panorama taken by Iain Cameron on Sat 22nd Sept with a dusting of snow on the tops. View from Aonach Mor towards Carn Mor Dearg with the Allt Daim snaking northwards. https://twitter.com/theiaincameron/status/1044126657496461312

It won't be long now! And to wet our appetites for the upcoming winter a great photo of the first snowfall at Moraine Lake, Banff, on 14th Sept. https://twitter.com/attila_thefun/status/1040740567670353920

With the official stats now out, here's the Met Office chart comparing Summer 2018 with other similar years. For much of our Region 2018 was the hottest, but with some variations such as Norfolk and Kent. The second chart is a great 'zoom in' by Dan Holley showing the variances across East Anglia. https://twitter.com/danholley_/status/1036680299252510727

An interesting chart from Neil Kaye, Climate Scientist at the UK Met Office. "Looking at the patterns it is possible to see global warming emerge. Up to 1920, warm and cold seem randomly distributed. Between 1940 and 1980 warmer years are more recent, but warmest year is not always near the end of series. From 2000, the warmest year is always very recent!" https://twitter.com/neilrkaye/status/1034410752260628480

Hi Paul. I'm afraid the biggest losses are taking place in our very own Alps. This from the full report: "Mass losses were especially dramatic in the European Alps, where 9 reference glaciers from Austria, France, Italy, and Switzerland, had an average mass loss of 1,664 millimeters of water equivalent (5.5 feet)." And the situation is getting worse: "The report also notes that mass loss from mountain glaciers is accelerating each decade: -228 millimeters of water equivalent (9 inches) in the 1980s, -443 millimeters (17 inches) in the 1990s, -676 millimeters (27 inches) in the 2000s, and -896 millimeters (35 inches) for 2010–2017." https://www.climate.gov/news-features/featured-images/2017-state-climate-mountain-glaciers

Mountain glaciers (1980–2017) Based on the preliminary data, 2017, is likely to be the 38th year in a row of mass loss of mountain glaciers worldwide. According to the State of the Climate in 2017, “The cumulative mass balance loss from 1980 to 2016 is -19.9 meters, the equivalent of cutting a 22-meter-thick (72-foot-thick) slice off the top of the average glacier." Graph of yearly loss 1980 - 2017: Full report: https://www.climate.gov/news-features/understanding-climate/state-climate-highlights/2017

Yes Steve. Maybe last season was a good example - the stratosphere and troposphere remained uncoupled through Autumn and it wasn't until late November that the two finally coupled, but interestingly it was the troposphere engaging and coupling with the lower/middle stratosphere, rather than the upper stratosphere driving its influence downwards.

Another two interesting pieces of research that move our understanding forward, although the first paper maybe rather heavy on 'scientific theory' to test extreme scenarios and paper two acknowledging it ignores many important secondary factors that may negate their findings. I am left wondering whether (a) maybe the papers in my post are somewhat more realistic regarding medium term impact, and (b) much more work is needed before we can be certain about the likely future impact of climate warming in this area. These statements, both from the conclusions of the respective papers, illustrate what I'm trying to say: First Paper "It should be noted that the analysis here is based on a highly idealized model, where the MJO is not explicitly simulated and moisture feedbacks are ignored, among other simplifications. While this allows a deeper under-standing of the results, a verification using more complete GCMs is required. We also note that, because of the relative low model top being used (3 mb), the SSW simulated in the idealized model may be not realistic. The strongest MJO forcing used here is 10 K day. This value is significantly larger than current values of 2–4 K day, but maybe possible in a 4 x CO2 or even more extreme warming scenarios. At a 10 K day forcing amplitude, the mean atmospheric state is significantly modified by the forcing. We discussed how these mean state changes affect the teleconnection mechanism, yet it is useful to keep in mind that the mean state is very different from the present-day atmosphere in this case, making it likely an unrealistic scenario, even if useful for understanding purposes." Second Paper "This work focused on the anticipated strengthening of the MJO in a warmer climate but did not take the expected change of the static stability, storm track, and other general circulation features into account. Such changes may affect the Arctic stratosphere directly and may also change the way the MJO impacts SSWs. Future work will need to consider not only changes to the MJO but also many other intervening factors that may change in response to a global warming (e.g., blocking events, stationary wave patterns, storm track structure, El Niño–Southern Oscillation, and Quasi-Biennial-Oscillation."

There's been some very interesting research lately into the impact of a warming climate on the future frequency of SSW's. Here are two such papers. "No robust evidence of future changes in major stratospheric sudden warmings: a multi-model assessment from CCMI" This August 2018 paper looks at the results from the 12 models involved in the 'Chemistry-Climate Model Initiative' and concludes: No statistically significant changes in the frequency of occurrence of SSWs are to be expected in the coming decades and until the end of the 21st century. This result is robust, as it is obtained with three different identification criteria. Other features of SSWs – such as their duration, deceleration of the polar night jet, and the tropospheric precursor wave fluxes – do not change in the future either in the model simulations, in agreement with other studies, such as McLandress and Shepherd (2009) and Bell et al. (2010). The absence of a future change in SSWs is a robust result across all models examined here, regardless of their biases or different representation of the QBO, coupling to the ocean, solar variability, etc. https://www.atmos-chem-phys.net/18/11277/2018/acp-18-11277-2018.pdf On the other hand, this July 2017 paper finds there will be an impact: "More Frequent Sudden Stratospheric Warming Events due to Enhanced MJO Forcing Expected in a Warmer Climate." Given that the MJO is predicted to be stronger in a warmer climate, these results suggest that SSW events may become more frequent, with possible implications on tropospheric high-latitude weather. https://www.seas.harvard.edu/climate/eli/reprints/Kang-Tziperman-2017.pdf

Arctic sea ice usually reaches its minimum around early/mid September. But this year (August 16th) it's already below the minimums from the 1980, 1990, and 2000 decadal averages. https://twitter.com/ZLabe/status/1030128092545576960

Yes, GEFS forecasting the Zonal Mean Zonal Winds at 10hPa 60N switch to a gentle westerly on 24th August 2018. The Polar Vortex returns after its summer holiday - welcome back....... although we look forward to you having a very disturbed winter!

Well here's another very interesting chart produced by Zach Labe. A great way of looking at how Arctic air temperatures have been steadily increasing during the satellite era (since 1979). There seems to have been a notable 'flip' as we entered the 2000's. Did the Arctic cross a tipping point or is some other aspect of global climate at play?? Ranks: 1=warmest (red), 40=coldest (blue) https://twitter.com/ZLabe/status/1029219662536396801

With the latest Colorado State University (CSU) forecast for the Atlantic season going for 12 named storms, 5 hurricanes and now only 1 major hurricane (cat 3 or stronger), Phil Klotzbach has provided some interesting analysis showing that in every "one major only" season since 1950, each of those hurricanes made continental USA landfall. CSU update: https://source.colostate.edu/csu-team-continues-to-predict-below-average-2018-atlantic-hurricane-season/ Klotzbach tweet: https://twitter.com/philklotzbach/status/1027933953993269249

An excellent (but worrying) chart from Zack Labe showing the decreasing volume of Arctic sea ice each year in the three decades since the advent of satellite monitoring. The trend is clear to see. https://twitter.com/ZLabe/status/1027420787324608512

As others have mentioned, lots of cloud around this evening, which ironically seems to be helping to hold the temp up. Still 24C at 21.00. But at least it provided a really nice sunset! @Lauren You noticed too! Yes, beautiful colours!

More excellent analysis from Phil Klotzbach: https://twitter.com/philklotzbach/status/1025070459300143104

A very interesting chart placing each summer into a cool/warm/hot/wet/dry quadrant. No surprise to see how close 1976 and 2018 are! "Using the period May-June-July as a proxy for 'summer' (since we've still got 1 month of meteorological summer to go), it appears that 1976 is the closest match to 2018 - at least for temperature and rainfall. Highlights how extreme this summer has been relative to the norm." With thanks to Dan Holley: https://twitter.com/danholley_/status/1024921132154204160

For the record, July in the East: - 2nd warmest July on record [1910] - Joint 2nd warmest MONTH on record [1910] - 8th driest July on record [1910] - THE sunniest July on record [1929] - 2nd sunniest MONTH on record [1929] - also looks like the 2nd driest June-July period on record (1976 was 3rd) With thanks to Dan Holley: https://twitter.com/danholley_/status/1024729741859987456

For us mountain lovers this report from NOAA/Climate makes very depressing reading: Mountain glaciers (1980–2017) Based on the preliminary data, 2017, is likely to be the 38th year in a row of mass loss of mountain glaciers worldwide. According to the State of the Climate in 2017, “The cumulative mass balance loss from 1980 to 2016 is -19.9 meters, the equivalent of cutting a 22-meter-thick (72-foot-thick) slice off the top of the average glacier." Graph of yearly loss 1980 - 2017: Full report: https://www.climate.gov/news-features/understanding-climate/state-climate-highlights/2017

Zack Labe tweet today (30th July): Sea ice extent has dropped to a record low on the Atlantic side of the Arctic. https://twitter.com/ZLabe/status/1023956612443066369

"Look South, ENSO Forecasters" Prof. Jason Furtado has just written a very interesting 'guest article' for the NOAA/Climate.gov website giving details of his research into the role that the South Pacific Oscillation (SPO) plays in helping determine the type and strength of developing EL Ninos. The article includes many informative charts. Key extracts: ......let’s consider the evolution and development of an El Niño event. In June when an El Niño event is developing, warm water anomalies are already present in the central tropical Pacific. For development to continue, those warm central tropical Pacific SSTs have to build eastward and amplify during Northern Hemisphere summer and early fall. This eastward propagation of anomalies is driven by westerly winds and the formation of Kelvin Waves in the ocean in the eastern tropical Pacific, thus allowing waters to get warmer there. Since the SPO modulates the strength of the South Pacific trade winds in the eastern tropical Pacific, and it is most active during JJA, the phase and magnitude of the SPO can either help or hurt those Kelvin waves and the winds during the critical growth phase for ENSO. If the SPO is in the positive phase (i.e., a weaker South Pacific subtropical high), then the southeasterly trade winds weaken, which reduces the cold-water upwelling in the eastern tropical Pacific and allows for easier eastward propagation of the warm waters from the central tropical Pacific to the eastern tropical Pacific. However, if the SPO is in the negative phase (i.e., a stronger South Pacific subtropical high), then the southeasterly trade winds intensify, and the cold-water upwelling in the eastern tropical Pacific also increases. These two factors create an environment hostile for eastward expansion of the warm waters. Thus, the warm SST anomalies tend to remain in the central tropical Pacific. .......we identified all El Niño events (regardless of flavor) from 1950-present and then examined what the magnitude and sign of the JJA SPO was for that year. Using only that information, we predicted what the flavor of that El Niño event would be the following winter. The results indicate that our simple prediction scheme correctly predicted the flavor of the event nearly 3 out of 4 times. What does the SPO have to say about the expected flavor of this year’s El Niño event? The figure above illustrates that the SST warming thus far over the eastern tropical Pacific is spotty with evidence of subsurface warming present. Note that south of the Equator, however, there is an expanse of quite cold waters. More importantly, the SLP pattern in the South Pacific resembles a negative SPO signature. Indeed, for June 2018, the SPO index was about -1.3, and the SLP anomaly pattern in the South Pacific thus far for July also suggests a negative SPO value for the month. Without a substantial turnaround for the SPO in August, the JJA SPO for 2018 could turn out negative. Thus, based on what I argued above, if an El Niño event forms this upcoming winter, it will most likely be a weak/CP El Niño event. Luckily, I am not totally alone in this prediction. The latest forecast from the NMME models (below) hints at a weaker/CP El Niño event evolving this winter. Full article: https://www.climate.gov/news-features/blogs/enso/look-south-enso-forecasters

Great streamer going on here in Dinas Powys (just west of Cardiff) this pm, originating over the SW peninsular, particularly Exmoor as the SW'ly winds 'bend' around the high ground. The finger of rain seems to be happily following the M50 right up into the Midlands! 13.00 14.35 15.00

Excellent tweet from Ben Noll: "The late-July SST anomaly pattern in the tropical Atlantic during 2018 is the complete opposite of 2005, which was the most active Atlantic hurricane season on record. The difference is striking." July 2005 July 2018 https://twitter.com/BenNollWeather/status/1023188777198530560

Some rather large discrepancies in the number of UK lightning strikes over the last 24 hours. Can anybody shed some light on why that might be? Netweather: 27,000 MeteoGroup: 50,000 Convective Weather: 215,000

Interesting Research Article published in the last few days: A stratospheric pathway linking a colder Siberia to Barents-Kara Sea sea ice loss Abstract: Previous studies have extensively investigated the impact of Arctic sea ice anomalies on the mid-latitude circulation and associated surface climate in winter. However, there is an ongoing scientific debate regarding whether and how sea ice retreat results in the observed cold anomaly over the adjacent continents. We present a robust “cold Siberia” pattern in the winter following sea ice loss over the Barents-Kara seas in late autumn in an advanced atmospheric general circulation model, with a well-resolved stratosphere. Additional targeted experiments reveal that the stratospheric response to sea ice forcing is crucial in the development of cold conditions over Siberia, indicating the dominant role of the stratospheric pathway compared with the direct response within the troposphere. In particular, the downward influence of the stratospheric circulation anomaly significantly intensifies the ridge near the Ural Mountains and the trough over East Asia. The persistently intensified ridge and trough favor more frequent cold air outbreaks and colder winters over Siberia. This finding has important implications for improving seasonal climate prediction of mid-latitude cold events. The results also suggest that the model performance in representing the stratosphere-troposphere coupling could be an important source of the discrepancy between recent studies. Link to article: http://advances.sciencemag.org/content/4/7/eaat6025