bluewave

They have been getting the areas of the positive and negative 500mb height anomalies correct for North America. But the magnitude of the anomalies will always get refined the closer in we get. Maybe they corrected stronger on the blocking this month due to the lagged effect from the SSW and individual wave breaks? Jan 4 forecast for Jan 25-Feb 1 Jan 11 forecast for Jan 25-Feb 1 Jan 18 forecast for Jan 25- Feb 1

Parts of the region usually see heavier snow squalls when the mid level lapse rates are this steep. Could be the type of morning when the visibility briefly falls to 1/4 of a mile in a few spots. Winds may also beat expectations since the low level lapse rates become so steep by the afternoon.

Yeah, we need to ease up on the south based blocking suppression risk for the OP Euro to work out. The 0z Euro run was showing what needs to happen with the 2 storms. There aren’t that many years with the strongest AO blocking sitting just east of The Canadian Maritimes. The record holders for the previous strongest south based blocking for the entire winter were 2005, 1969, and 1951.

Record low snow extent for North America on January 17th for the last 16 years.

We are doing better than Northern New England with cold temperatures relative to averages. It was a tie for the warmest first half of winter at Caribou. BTV finished at the 4th warmest. NYC is further down the list at 19th warmest. Time Series Summary for Caribou Area, ME (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Jan 15 Missing Count 1 2021-01-15 25.0 0 - 2016-01-15 25.0 0 2 2011-01-15 24.3 0 3 2007-01-15 23.6 0 4 2002-01-15 23.5 0 5 1997-01-15 22.8 0 Time Series Summary for Burlington Area, VT (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Jan 15 Missing Count 1 2016-01-15 34.7 0 2 2007-01-15 33.2 0 3 2002-01-15 30.9 0 4 2021-01-15 30.0 0 5 1997-01-15 29.4 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Dec 1 to Jan 15 Missing Count 1 2016-01-15 45.7 0 2 2007-01-15 44.5 0 3 1932-01-15 41.9 0 4 2002-01-15 41.7 0 5 2012-01-15 41.2 0 6 1983-01-15 41.0 0 7 2013-01-15 40.7 0 - 1950-01-15 40.7 0 8 1995-01-15 40.6 0 9 1890-01-15 40.2 0 10 2000-01-15 40.1 0 11 1998-01-15 39.9 0 - 1992-01-15 39.9 0 - 1985-01-15 39.9 0 12 2020-01-15 39.8 0 13 1972-01-15 39.7 0 - 1937-01-15 39.7 0 - 1892-01-15 39.7 0 14 2005-01-15 39.6 0 - 1991-01-15 39.6 0 15 1966-01-15 39.2 0 - 1913-01-15 39.2 0 16 1975-01-15 39.1 0 - 1924-01-15 39.1 0 17 1997-01-15 39.0 0 - 1980-01-15 39.0 0 18 1933-01-15 38.8 0 19 2021-01-15 38.6 0

NYC will extend the above 20° streak for at least another week as temperatures still average above normal for mid to late January. KNYC GFSX MOS GUIDANCE 1/16/2021 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 SAT 16| SUN 17| MON 18| TUE 19| WED 20| THU 21| FRI 22| SAT 23 CLIMO X/N 52| 35 46| 35 46| 32 42| 26 35| 29 42| 31 37| 24 33 24 38

Heaviest rainstorm for portions of the South Shore since December 5th. 1/16/2021 7:00 AM NY-NS-46 Massapequa Park 1.2 N 1.35 NA | NA NA | NA NY Nassau

I guess it goes with the big snowfall swings that have become common in recent times. It’s been a rollercoaster ride between record highs and lows. The North America snow extent anomalies since October followed this pattern.

Only the 4th time that NYC didn’t drop below 20° by mid-January. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Lowest Min Temperature Oct 1 to Jan 15 Missing Count 1 2013-01-15 22 0 2 2021-01-15 20 1 - 2002-01-15 20 0 - 1932-01-15 20 0

We always run the risk of suppression when there is a -strong -PNA trough in the West and a strong 50/50 low to our east.

The definition of luck these days is getting the Pacific to cooperate. Notice how the -PNA amps of the Pacific Jet as it crosses the country around the 22nd. This 200KT Jet max allows the primary low to scoot by to our north. The secondary gets going further to the east as it squeezes under the 50/50.

The biggest change for the first week of February is more poleward extension of the global ridges. So heights are a little higher over the SW U.S. up to the Aleutians and Pole. We may end up with further improvements in later runs. New run Feb 1-7 Old run

The EPS weeklies are slightly less warm for February than previous runs. Perhaps, the MJO signal getting over to 7-8 is responsible for the change. The VP anomalies indicate a 4-5...7-8 forcing split. Root for more toward phase 8.

https://www.nies.go.jp/whatsnew/20210114-2/20210114-2-e.html Human-induced climate change caused the northwestern Pacific warming record in August 2020 A once-in-1000-year warming event has been already altered to occur once per 15 years because of past human activities Observed sea surface temperatures in August over the northwestern Pacific Ocean The white boxes are the region focused on in this new study. The COBE SST2 dataset from JMA-MRI is used. A new study led by National Institute for Environmental Studies researchers, published in the journal Geophysical Research Letters, revealed that the record-warm sea surface temperature over the northwestern Pacific in August 2020 could not be expected to occur without human-induced climate changes. Such extremely warm condition is likely to become a new normal climate in August by the mid-21st century, needing the prompt implementation of adaptation measures for anthropogenic global warming. August 2020 set new record high sea surface temperatures (SSTs) in the northwestern Pacific Ocean and around the Japan coasts. A new study led by National Institute for Environmental Studies (NIES) researchers revealed that this warming record could not happen without human-induced climate changes. The northwestern Pacific sea surface becomes warm seasonally around August every year. However, it was unprecedentedly high in August 2020, according to the Japan Meteorological Agency and the National Oceanic and Atmospheric Administration. The extremely high SSTs exceeding 30°C, which lasted until mid-September, may have intensified tropical cyclones such as Typhoon Haisheng, causing severe damages to the East Asian countries. Although human-induced greenhouse gas emissions such as carbon dioxide have gradually warmed the northwestern Pacific Ocean since the mid-20th century, it remains unclear yet how much past human activities may increase the occurrence likelihood of such regional record-warm SSTs. “Understanding the tropical warm water expansion in the Indo-Pacific and Atlantic Oceans is essential for projecting changes in the characteristics of tropical cyclones and other weather events in the future,” said Hideo Shiogama, a co-author and the head of Climate Risk Assessment Section at the Center for Global Environmental Research, NIES. “A quantitative evaluation of what drives regional extreme temperatures happening recently is necessary to take appropriate measures to reduce greenhouse gas emissions and the impacts of global warming.” The paper published in Geophysical Research Letters illustrates the quantitative impact of greenhouse gases emitted by human activities on the unprecedentedly high SSTs in the northwestern Pacific Ocean in August 2020. By analyzing multiple observational datasets from 1901 to 2020 and a large number of experimental outputs from the state-of-the-art numerical climate models, a climate research group at NIES statistically estimated changes in the occurrence probability of the northwestern Pacific Ocean (120°E–180° and 20°N–35°N) condition exceeding the record-warm SST in August 2020 from the past to future. The scientists revealed that its probability in the present climate was increased from once-in-1000 years to once-in-15 years because of human-induced climate changes. Detecting human-induced climate changes “The numerical climate model ensembles are powerful tools to quantitatively distinguish between natural variability of the Earth system and climate changes caused by human activities,” said corresponding lead author Michiya Hayashi, a research associate at NIES. The ensemble of 31 climate models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6) consists of a series of historical experiments and future scenario experiments forced by greenhouse gas- and aerosol emissions from human activities and natural volcanic and solar variations from 1850 to 2100. “We can compare the historical and future experiments with a sub-ensemble of the CMIP6 climate models forced only by the natural volcanic and solar activities to estimate to what extent human-caused climate changes have altered the northwestern Pacific Ocean condition until today.” “The northwestern Pacific Ocean has heated up clearly since the 1980s,” stated Shiogama. “The warming speed has been accelerated in the last four decades as the reduced aerosol emissions do not cancel the warming signal forced by increasing greenhouse gas concentration anymore.” The results show that the CMIP6 ensemble well reproduces the observed long-term change in the northwestern Pacific August SST within the range of ‘once-in-20-year’ events in the historical simulations. “The SSTs that exceed the pre-industrial range are rarely observed during the 20th century but have occurred frequently since 2010, indicating that human influences on the northwestern Pacific Ocean are already detectable in observations,” noted a co-author Seita Emori, deputy director of the Center for Global Environmental Research at NIES. Time series of the northwestern Pacific sea surface temperature in August Showings are the observational datasets and the simulation results from the climate model (CMIP6) ensemble: the global warming signal (solid black line) and the ranges of ‘once-in-20-year’ events (95% probability range) in the historical and future experiments (gray shading) and pre-industrial experiments (dashed lines). This new study estimates that the occurrence frequency of high northwestern Pacific SSTs exceeding the August 2020 level has been increased from once-in-600 years in the 20th century (1901-2000) to once-in-15 years in the present climate (2001-2020) using the CMIP6 ensemble. On the other hand, in the sub-ensemble forced only by natural volcanic and solar activities, the frequency for 2001-2020 is estimated to be once-in-1000 years or less. “The record high level of the northwestern Pacific SST in August could have occurred approximately once per 15 years in 2001-2020, as observed, but it never likely occurred without human-induced greenhouse gases or in the 20th century,” said Hayashi. Importantly, the scientists also imply from the future scenario experiments that the 2020 record high SST is becoming a new normal climate condition in August at the northwestern Pacific region by 2031-2050 when the globally averaged air temperature relative to pre-industrial levels would exceed 1.5°C. In this case, the tropical warm sea surface water, exceeding 28°C, may reach Japan, the Korean Peninsula, the west coast of India, the east coast of the U.S. mainland, and the west of the Hawaiian Islands. “We might need to prepare for living with such warm ocean conditions even if we humans could achieve the 1.5°C goal of the Paris Agreement,” said Hayashi. “The human-induced ocean warming may have impacted tropical cyclones, heavy rainfall, and marine life from the past to present and will continue in the future unless tremendous mitigation measures would be implemented,” added Emori. “It is time to take prompt actions to transform our society for reducing the greenhouse gas emissions and for adapting to a changing climate.” Probability distributions for the northwestern Pacific sea surface temperature in August For 1901-2000, the climate model (CMIP6) ensemble (solid black line) reproduces the observational values (gray shading). For 2001-2020, the observed values (red triangles) are well covered by the CMIP6 ensemble (solid red line) but not by the sub-ensemble forced by natural variations only (thin blue line). For 2031-2050, the most likely level of the projected probability (solid yellow line) exceeds the 2020 level (dashed red line).

First time since 1875 that NYC only had a T of snow through mid-January following 10+ in mid-December. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Snowfall Dec 10 to Dec 20 Dec 21 Jan 14 1 1948-12-20 21.1 5.7 2 1960-12-20 16.6 2.0 3 1916-12-20 13.8 0.7 4 1904-12-20 13.3 10.7 5 1945-12-20 12.1 3.5 6 2009-12-20 10.9 2.3 7 2020-12-20 10.5 T 8 1917-12-20 10.1 2.0 - 1874-12-20 10.1 T

We are actually doing better here relative to the means than areas closer to the Northern Tier. NYC is still ahead of Grand Rapids in snowfall through January 13th. Bismarck has gone the latest ever without a reading below 0°.Their average first below 0° date since 1980 is December 1st. So this would be like NYC not going below freezing until January. Time Series Summary for Bismarck Area, ND (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Ending Date Lowest Min Temperature Oct 1 to Jan 13 Missing Count 1 2021-01-13 0 0 2 1955-01-13 -6 0 3 2012-01-13 -7 0 - 2003-01-13 -7 0 - 1983-01-13 -7 0 - 1908-01-13 -7 0 - 1891-01-13 -7 0

The Pacific Jet continues to make headlines.

Coming up on the 5th anniversary of one of the greatest snowstorms of all time.

The Northern Tier will eventually cool with the more Niña-like -EPO -PNA -AO pattern.

Warmest start to January on record for Bismarck, ND at +18.5. Time Series Summary for Bismarck Area, ND (ThreadEx) Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Jan 1 to Jan 12 Missing Count 1 2021-01-12 30.8 0 2 2012-01-12 29.2 0 3 1990-01-12 27.5 0 4 2002-01-12 27.1 0 - 1987-01-12 27.1 0 5 1983-01-12 26.9 0

It appears that the new GFS v16 scheduled to go operational in February has fixed the cold bias. https://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/

https://www.sciencedaily.com/releases/2019/08/190801120209.htm US infrastructure unprepared for increasing frequency of extreme storms August 1, 2019 American Geophysical Union Current design standards for United States hydrologic infrastructure are unprepared for the increasing frequency and severity of extreme rainstorms, meaning structures like retention ponds and dams will face more frequent and severe flooding, according to a new study. Extreme weather events are on the rise, but U.S. water management systems use outdated design guidelines. New research, published in the AGU journal Geophysical Research Letters, analyzed data from multiple regions throughout the U.S. and found the rising number of extreme storms combined with outdated building criteria could overwhelm hydrologic structures like stormwater systems. The new study is particularly timely in light of recent storms and flash floods along the East Coast. "The take-home message is that infrastructure in most parts of the country is no longer performing at the level that it's supposed to, because of the big changes that we've seen in extreme rainfall," said Daniel Wright, a hydrologist at the University of Wisconsin-Madison and lead author of the new study. Engineers often use statistical estimates called IDF curves to describe the intensity, duration, and frequency of rainfall in each area. The curves, published by the National Oceanic and Atmospheric Administration (NOAA), are created using statistical methods that assume weather patterns remain static over time. "Design engineers at cities, consulting companies, and counties use this for different purposes, like infrastructure design management, infrastructure risk assessment and so forth. It has a lot of engineering applications," said Amir Aghakouchak, a hydrologist at the University of California, Irvine who was not involved with the new study. But climate change is causing extreme rainfall events to occur more often in many regions of the world, something IDF curves don't take into account. One measure of extreme rainfall is the 100-year storm, a storm that has a one percent chance of happening in a given year, or a statistical likelihood of happening once in 100 years on average. Wright and his colleagues wanted to know how existing IDF curves compare with recent changes in extreme rainfall. They analyzed records from more than 900 weather stations across the U.S. from 1950 to 2017 and recorded the number of times extreme storms, like 100-year storms, exceeded design standards. For example, in the eastern United States, extreme rainstorm events are happening 85 percent more often in 2017, than they did in 1950. In the western U.S., these storms are appearing 51 percent more often now than they once did. The scientists found that in most of the country the growing number of extreme rainstorms can be linked to warming temperatures from climate change, although natural events, such as El Niño, also occasionally affect the Southeast's climate. By comparing the number of storms that actually happened against the number predicted by IDF curves, the researchers also showed the potential consequences for U.S. infrastructure. In some regions, for example, infrastructure designed to withstand extreme rainstorms could face these storms every 40 years instead of every 100 years. "Infrastructure that has been designed to these commonly-used standards is likely to be overwhelmed more often than it is supposed to be," Wright said. The researchers hope the findings will encourage climate scientists, hydrologists, and engineers to collaborate and improve U.S. hydrologic infrastructure guidelines. "We really need to get the word out about just how far behind our design standards are from there they should be," Wright said. Story Source: Materials provided by American Geophysical Union. Original written by Abigail Eisenstadt. Note: Content may be edited for style and length. Journal Reference: Daniel B. Wright, Christopher D. Bosma, Tania Lopez‐Cantu. U.S. Hydrologic Design Standards Insufficient Due to Large Increases in Frequency of Rainfall Extremes. Geophysical Research Letters, 2019; DOI: 10.1029/2019GL083235 https://www.nytimes.com/interactive/2020/06/29/climate/hidden-flood-risk-maps.html Nearly twice as many properties may be susceptible to flood damage than previously thought, according to a new effort to map the danger. Across much of the United States, the flood risk is far greater than government estimates show, new calculations suggest, exposing millions of people to a hidden threat — and one that will only grow as climate change worsens. That new calculation, which takes into account sea-level rise, rainfall and flooding along smaller creeks not mapped federally, estimates that 14.6 million properties are at risk from what experts call a 100-year flood, far more than the 8.7 million properties shown on federal government flood maps. A 100-year flood is one with a 1 percent chance of striking in any given year. The federal government’s flood maps guide where and how to build, whether homeowners should buy flood insurance, and how much risk mortgage lenders take on. If the new estimates are broadly accurate, it would mean that homeowners, builders, banks, insurers and government officials nationwide have been making decisions with information that understates their true physical and financial risks. Numerous cities nationwide — as diverse as Fort Lauderdale, Fla., Buffalo, N.Y., and Chattanooga, Tenn. — show the startling gap in the risks. In Chicago alone, 75,000 properties have a previously undisclosed flood risk. And minority communities often face a bigger share of hidden risk. “Millions of home and property owners have had no way of knowing the significant risk they face,” said Matthew Eby, founder and executive director of the First Street Foundation, a group of academics and experts based in New York City who compiled the data, creating a website where people can check their own address.

Long Island used to get normal snowfall before the mid1990s. But since then, we switched to all or nothing mode. More frequent very high or very low snowfall winters. Fewer closer to the mid range. https://www.bnl.gov/weather/4cast/MonthlySnowfall.htm

This is the composite for the last 10 La Niña events to reach 6” or more in NYC during January and February. That’s why we need that -PNA trough out West to pull back off the West Coast at storm time. Like I said in the post above, relevant details like that may not be known for a while yet. And there may have probably been lesser than 6” storms that had more leeway.