bluewave

We’ll probably have to rely on these convective events for our rainfall chances a while longer. Some hints from the EPS weeklies that the tropics will become active in September. https://mobile.twitter.com/BenNollWeather/status/1158519860537651201 ECMWF weekly guidance FINALLY suggests a relaxation of the sinking branch over the Atlantic after September 10th. This could coincide with an increase in tropical cyclone activity across the basin.

That’s what it’s looking like.

Large 166k daily drop in NSIDC extent. We are entering the big decline week when 2012 pulled ahead of all other years. This was during the period of the Great Arctic Cyclone. NSIDC extent  Date....2012......2019....2019 difference 8-4......5.990.... .5.762.....+228k lead 8-5......5.768......5.596.....+172k lead 8-6......5.632 8-7......5.467 8-8......5.256 8-9......5.088 8-10....5.118 8-11....5.021 No let up in sight for the continuing record dipole pattern.

The steam makes a return for Wednesday. Mid 70’s dewpoints coupled with PWATS around 2.00”. Plenty of high octane juice for heavy convection.

https://mobile.twitter.com/RyanMaue/status/1158565610860814338 Just a warning about using one of my (really) old maps that still circulates. NCEP CFSR reanalysis has a significant problem after March 2011 when the model switched from T382 to T574. This creates a mismatch if you compare months before & after. Only use the JRA-55 or ERA5. https://mobile.twitter.com/RyanMaue/status/1157318343482888192 July 2019 average temperature was 16.77°C and is hottest month in instrumental record maybe tied with July 2016 by a hundredth of a degree. Regardless of the significant figures, the Earth was quite warm overall last month.

Dewpoints already on the rise ahead the Wednesday night heavy convection potential. Euro has another surge into the mid-70’s on Wednesday,

Brian Brettschneider has a great series of posts on this. But a recent study finds that this local irrigation effect will be overcome with continued global warming. https://news.wisc.edu/irrigated-farming-in-wisconsins-central-sands-cools-the-regions-climate/ While the cooling effect of irrigation mitigates global climate change on the regional scale, climate models suggest that regional warming attributed to the global trend will eventually overcome the magnitude of mitigation offered by irrigated agriculture. Farmers, who are partially buffered for now from more extreme heat, would quickly face increasing stress in that scenario. “Farmers in irrigated regions may experience more abrupt temperature increases that will cause them to have to adapt more quickly than other groups who are already coping with a warming climate,” says Kucharik. “It’s that timeframe in which people have time to adapt that concerns me.” The current study is the first to definitively link irrigation in the Midwest U.S. to an altered regional climate. These results could improve weather and climate forecasts, help farmers plan better, and, the researchers hope, better prepare agricultural areas to deal with a warming climate when the irrigation effect is washed out. https://mobile.twitter.com/Climatologist49/status/1139633305958014976 Map animation showing the 100-year change in monthly temperatures using NCEI county-level temperature data. In the summer months, the central U.S. is the only region on Earth showing a notable temperature decline. Likely related to irrigation. https://mobile.twitter.com/Climatologist49/status/1140048246477168640 https://mobile.twitter.com/Climatologist49/status/1140059426847461376 https://mobile.twitter.com/Climatologist49/status/1140057959973572609 https://mobile.twitter.com/Climatologist49/status/1140059253857640448 https://mobile.twitter.com/Climatologist49/status/1126293596909367301

From Climate Signals and Brian Brettschneider: https://mobile.twitter.com/ClimateSignals/status/1156929127414403074 In a stable climate, record high and low temps are about even. Globally, in July 2019, there were 132 all-time high temp records and only 2 all-time lows. Human-caused warming is driving this imbalance. https://mobile.twitter.com/Climatologist49/status/1158129812738699265 July 2019 temperatures mapped as percentile of all July temperatures (min 50 years). 134 stations with warmest July. 2 stations with coldest July. Spatial average of 71st percentile good for either 1st or 2nd warmest July on record globally.

We are entering the big decline week when 2012 pulled ahead of all other years. This was during the period of the Great Arctic Cyclone. NSIDC extent Date....2012......2019....2019 difference 8-4......5.990.... 5.762.....+228k lead 8-5......5.768 8-6......5.632 8-7......5.467 8-8......5.256 8-9......5.088 8-10....5.118 8-11....5.021

While the high temperatures have stepped down from the steamy July levels, the minimum temperatures are still staying up. NYC is currently at the 6th longest streak of 67 degrees or higher. Islip has the 2nd longest 64 degrees or warmer streak. A continuation of the less warm is the new cool theme. Number of Consecutive Days Min Temperature >= 67 for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Run Length Ending Date 1 46 2005-08-24 2 44 1988-08-18 3 42 2015-08-27 4 36 1939-08-28 5 35 1938-08-11 6 34 2019-08-04 Number of Consecutive Days Min Temperature >= 64 for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Run Length Ending Date 1 46 1988-08-18 2 41 2019-08-04 3 33 1980-08-16 4 32 2013-07-24 5 31 2006-08-08

Brief moderate shower here with the sun out. Just enough to wet the ground. Good thing for modern sprinkler systems with very little rain over the last 11 days.

3 top 5 warmest Augusts in 4 years was a very impressive streak. It appears we are backing off a bit from the extreme August heat of recent years. Time Series Summary for LA GUARDIA AP, NY - Month of Aug Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2016 81.6 0 2 2018 81.0 0 3 2005 80.9 0 4 2001 79.8 0 5 2015 79.3 0

NCEP/NCAR Reanalysis monthly means. https://www.esrl.noaa.gov/psd/data/timeseries/

May through July set new Arctic records for warmth, surface pressure, and 500 mb heights.

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL082914 During recent decades, there has been dramatic Arctic sea ice retreat. This has reduced the top‐of‐atmosphere albedo, adding more solar energy to the climate system. There is substantial uncertainty regarding how much ice retreat and associated solar heating will occur in the future. This is relevant to future climate projections, including the timescale for reaching global warming stabilization targets. Here we use satellite observations to estimate the amount of solar energy that would be added in the worst‐case scenario of a complete disappearance of Arctic sea ice throughout the sunlit part of the year. Assuming constant cloudiness, we calculate a global radiative heating of 0.71 W/m2 relative to the 1979 baseline state. This is equivalent to the effect of one trillion tons of CO2 emissions. These results suggest that the additional heating due to complete Arctic sea ice loss would hasten global warming by an estimated 25 years. https://scripps.ucsd.edu/news/research-highlight-loss-arctics-reflective-sea-ice-will-advance-global-warming-25-years Losing the remaining Arctic sea ice and its ability to reflect incoming solar energy back to space would be equivalent to adding one trillion tons of CO2 to the atmosphere, on top of the 2.4 trillion tons emitted since the Industrial Age, according to current and former researchers from Scripps Institution of Oceanography at the University of California San Diego. At current rates, this roughly equates to 25 years of global CO2 emissions. It would consequently speed up the arrival of a global threshold of warming of 2ºC beyond temperatures the world experienced before the Industrial Revolution. Scientists and analysts, including the authors of an Intergovernmental Panel on Climate Change Special Report released in October 2018, have stated that the planet runs the risk of catastrophic damage ranging from more intense heat waves and coastal flooding to extinction of terrestrial species and threats to food supply if that threshold is passed. The results were published June 20 in the journal Geophysical Research Letters. In “Radiative Heating of an Ice-Free Arctic Ocean,” former Scripps graduate student Kristina Pistone, now with the Bay Area Environmental Research Institute based at NASA Ames Research Center, and Scripps climate scientists Ian Eisenman and Veerabhadran Ramanathan used direct satellite observations to assess the impact of a potential ice-free Arctic Ocean. The authors of the study conclude that the loss of sea ice will add a globally-averaged 0.7 watts per square meter (W/m2) of solar heating to the Earth system, 0.21 W/m2 of which has already occurred between 1979 and 2016. The amount of additional heat introduced into the Earth system because of Arctic melt is equivalent to an increase in CO2 concentration from 400 to 456.7 parts per million. “Losing the reflective power of Arctic sea ice will lead to warming equivalent to one trillion tons of CO2 and advance the 2ºC threshold by 25 years. Any rational policy would make preventing this a top climate priority for world leaders,” said Ramanathan, a professor of atmospheric and climate sciences at Scripps. The research was primarily supported by grants from the National Science Foundation and the NASA Postdoctoral Program. While the paper presents a worst-case scenario, scientists’ observations show the Arctic is rapidly losing ice, and computer forecast models are actually underestimating the extent of this trend. “We analyzed 40 climate models from modeling centers around the world,” said Eisenman, a professor of climate, atmospheric science, and physical oceanography at Scripps. “Not a single one of the models simulated as much Arctic sea ice retreat per degree of global warming as has been observed during recent decades. This motivated us to use an observationally focused approach to investigate the scenario in which all of the remaining Arctic sea ice disappears considerably faster than the models simulate.” An earlier study by the same team calculated that the ice lost in the Arctic between 1979 and 2011 added 6.4 W/m2 to the Arctic, which averaged globally is equivalent to as much as 25 percent of the effect of CO2 during the same time period. Additional research shows that the thicker multi-year ice which survives year to year is down to 1 percent of the existing ice. There is great uncertainty about the timing of when the Arctic could become seasonally ice-free, with some research suggesting that recent trends could lead to an ice-free Arctic as early as the 2020s and others suggesting 2030 or substantially later depending on factors including future warming and natural variability. For the baseline calculations, the authors assumed that cloud cover would remain constant. However, they calculate that if the loss of the Arctic ice is accompanied by complete loss of cloud cover, the total added warming could be three times greater. “One of the really interesting, but somewhat expected, aspects of this study was quantifying just how much impact the potential change in cloud coverage has on the amount of reflected sunlight,” said Pistone. Conversely, if the Arctic experienced complete cloud cover, the total warming could be half as much. Under all scenarios considered, the study concludes that the radiative heating of complete Arctic sea ice loss could substantially accelerate the rate of future global warming. It would advance global warming by 25 years in the baseline scenario. This would drastically shorten the time available to adapt to climate change and the time for achieving carbon neutrality, the authors said. “It’s important to remember that the amount of warming isn’t limited to just the ice-free time,” said Pistone. “Even as September becomes ice-free, we will likely see less ice in other parts of the year as well, so for example June could end up having a greater warming impact even with some remaining ice simply because there is more sunlight in that month.” “Because the Arctic’s role in regulating the global climate is a critical link in the chain of climate protection it should be the focus of an all-out effort to keep it strong and safe,” said Durwood Zaelke, president of the Institute for Governance & Sustainable Development which partially funded the research. – Robert Monroe and IGSD

The ridge that dominated the Northeast with record heat in July will take a break for a while.

Surface conditions have quickly dried out along the Long Island South Shore since July 24th. Most of the grass and vegetation not regularly watered turned brown. Best recent sea breeze front convection has been favoring the North Shore. The last 10 period has been the 3rd driest on record at Islip. Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Precipitation Jul 24 to Aug 2 Missing Count 1 2006-08-02 0.02 0 2 1972-08-02 0.04 0 3 2019-08-02 0.05 0 4 2005-08-02 0.07 0 5 1999-08-02 0.13 0

It looks like it will make it difficult for the August temperature departure to beat July. Our warmer summers since 2015 all had a greater August temperature departure than July. 2015 LGA....JUL...+1.8.....AUG...+3.0 2016 LGA....JUL...+3.7....AUG....+5.3 2018 LGA....JUL...+2.4....AUG....+4.7 2019 LGA....JUL...+4.1 Plenty of unknowns concerning next winter at this time. Will the raging Pacific jet relax? Will the record summer -NAO extend into winter? What will happen with ENSO? Will the amped up MJO continue for another winter? How will the extreme Arctic summer warmth and low sea ice impact the fall and winter circulation?

The duration of that eventual Northeast trough may come down to the MJO. The MJO is finally becoming active again. Phase 4 in August favors a trough over the region. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml https://ds.data.jma.go.jp/tcc/tcc/products/clisys/mjo/composite.html

https://eos.org/articles/greenland-ice-sheet-beats-all-time-1-day-melt-record The Greenland ice sheet broke records on 1 August 2019 by losing more water volume in 1 day than on than any other day since records began in 1950, shedding 12.5 billion tons of water into the sea.

Large -299k drop in NSIDC extent over the last 2 days. This puts 2019 +259 k ahead of 2012 as of August 2nd. 2019 needs to maintain an average daily decline rate of 97k over the next 9 days to hold even with 2012 by the 11th. NSIDC extent 8-2-19.....5.893 8-2-12.....6.152 8-11-12....5.021

The epic Pacific firehose jet just won’t let up. This time it was nearly forced up to the Arctic circle with record rains in Nome,Alaska. https://mobile.twitter.com/AlaskaWx/status/1157502080392712192 There it is: Nome, Alaska, with one of the longest climate records in the state (since 1907) sets all-time 24 hour precipitation record: 10pm AKDT Thursday to 8pm Friday rainfall 2.43" (61.7mm) breaks previous record 2.38" (60.5mm) Aug 8-9, 1956. https://mobile.twitter.com/AlaskaWx/status/1157352074373259264 Remember the atmospheric river forecast from a few days ago? It's here: Nome received 2.09" (53.1mm) in 12-hours between 10pm Thursday & 10am Friday. The greatest 24-hour rainfall at Nome is 2.38" (60.5mm) Aug 8-9, 1956.

Zack Labe is reporting that July set the new lowest NSIDC average extent for the month. The only months not to set a new record low since 2016 so far have been ASO. 9 new monthly records in 3 years shows how much the Arctic has warmed. https://mobile.twitter.com/ZLabe/status/1156938182832693249 New Record* -- 2019 averaged the lowest #Arctic sea extent in the satellite-era for the month of July. It was 1,880,000 km² below the 1981-2010 average. Data from @NSIDC https://mobile.twitter.com/ZLabe/status/1157122835409596416 Updated record low #Arctic sea ice extent months - @NSIDC data (satellite-era from 1978/1979) -------------- 2018 : January 2018 : February 2017 : March 2019 : April 2016 : May 2016 : June 2019 : July 2012 : August 2012 : September 2012 : October 2016 : November 2016 : December

https://news.wisc.edu/irrigated-farming-in-wisconsins-central-sands-cools-the-regions-climate/ New research finds that irrigated farms within Wisconsin’s vegetable-growing Central Sands region significantly cool the local climate compared to nearby rain-fed farms or forests. Irrigation dropped maximum temperatures by one to three degrees Fahrenheit on average while increasing minimum temperatures up to four degrees compared to unirrigated farms or forests. In all, irrigated farms experienced a three- to seven-degree smaller range in daily temperatures compared to other land uses. These effects persisted throughout the year. A map of the Central Sands region of Wisconsin where researchers studied the effects of irrigation on the local climate. A sensor was placed at each pink dot to mark a line across the region as it changed from pine plantations to farms to forests. IMAGE COURTESY MALLIKA NOCCO/CHRISTOPHER KUCHARIK The results show that the conversion of land to irrigated agriculture can have a significant effect on the regional climate, which in turn can affect plant growth, pest pressure and human health in ways that could be overlooked unless land uses are accounted for in forecasts and planning. Such a cooling effect mitigates — and obscures — a global warming trend induced by the accumulation of greenhouses gases in the atmosphere. Irrigated farming, like all agriculture, also generates greenhouses gases. The work was led by Mallika Nocco, who recently completed her doctorate in the Nelson Institute for Environmental Studies at the University of Wisconsin–Madison. Nocco worked with Christopher Kucharik of the Nelson Institute and the UW–Madison agronomy department and Robert Smail from the Wisconsin Department of Natural Resources. The team published their findings July 2 in the journal Global Change Biology. “We’re finding that weather forecasts can be wrong if they don’t take these land uses into account,” says Nocco, now a postdoctoral researcher at the University of Minnesota. “That will affect both farmers and plants.” Irrigation, and agriculture generally, cools the air due to the evaporation of water through crop leaves, much like how evaporating sweat cools people. This evaporation also increases the water content of the air. The scientists wanted to determine if the naturally humid Wisconsin climate would respond as strongly to irrigation as drier regions, such as California, do. To find out, Nocco worked with private landowners to install 28 temperature and humidity sensors in a line that crossed through the Central Sands. The 37-mile transect extended from pine plantations in the west, over irrigated farms toward forests in the east. The researchers collected data across 32 months from the beginning of 2014 through the summer of 2016. Each of the 28 sensors was matched to nearby irrigation levels through a regional well withdrawal database managed by Smail of the Department of Natural Resources. Nocco’s team found that irrigation lowered the maximum daily temperature about three and half degrees compared to nearby rainfed farms. Adjacent forests were slightly warmer than either rainfed or irrigated farms. Somewhat surprisingly, the lower maximum temperatures on irrigated farms were accompanied by higher minimum temperatures. Saturated soils can hold more heat than dry soils. When that heat is released at night, it keeps nighttime minimum temperatures somewhat higher. Wet soils may also be darker, helping them absorb more sunlight during the day. The researchers found that if all land in the study area were converted to irrigated agriculture, the daily range in temperatures would shrink nearly five degrees Fahrenheit on average, and up to eight degrees at the high end. This smaller difference between daily maximum and minimum temperatures can significantly affect plant growth or insect pest lifecycles, both of which are sensitive to daily temperatures. “If you’re adjusting the range of temperatures, you’re changing who or what can live in an area,” says Nocco. The temperature differences between irrigated fields and rain-fed fields or forests were pronounced during the growing season, when fields were being irrigated, but extended throughout the year. Open fields of snow reflect more winter sunlight than forests do, keeping the air above cooler, but it’s not entirely clear what drives winter temperature differences between irrigated and non-irrigated farms. While the cooling effect of irrigation mitigates global climate change on the regional scale, climate models suggest that regional warming attributed to the global trend will eventually overcome the magnitude of mitigation offered by irrigated agriculture. Farmers, who are partially buffered for now from more extreme heat, would quickly face increasing stress in that scenario. “Farmers in irrigated regions may experience more abrupt temperature increases that will cause them to have to adapt more quickly than other groups who are already coping with a warming climate,” says Kucharik. “It’s that timeframe in which people have time to adapt that concerns me.” The current study is the first to definitively link irrigation in the Midwest U.S. to an altered regional climate. These results could improve weather and climate forecasts, help farmers plan better, and, the researchers hope, better prepare agricultural areas to deal with a warming climate when the irrigation effect is washed out. “Irrigation is a land use with effects on climate in the Midwest, and we need to account for this in our climate models,” says Nocco. This work was supported in part by the U.S. Environmental Protection Agency, the U.S. Department of Agriculture Sustainable Agriculture Research and Education program and the Wisconsin Department of Natural Resources.

JFK came out ahead of last July for the new dewpoint record. But the extreme dewpoints continued into September last year.