bluewave

It’s easy to lose track of all the new extremes in recent years.

Another warmer than average start to September across the area. The first week came in at +2.3 to +4.1. EWR...+2.7 NYC...+2.3 LGA....+4.1 JFK....+2.5 ISP.....+3.8 BDR...+4.1

More record breaking 500 mb heights.

We had several more 70° minimums since the start of September. So our local sites are still moving up on the list. We could add a few more this week as the higher dew points return. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature >= 70 Missing Count 1 1973 62 0 2 2011 59 0 3 2005 58 0 4 2010 57 0 5 2020 55 116 - 1993 55 0 Time Series Summary for NY CITY CENTRAL PARK, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature >= 70 Missing Count 1 1906 61 0 2 2005 60 0 3 2020 57 116 4 2015 56 0 5 2018 55 0 - 2010 55 0 Time Series Summary for LAGUARDIA AIRPORT, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature >= 70 Missing Count 1 2018 78 0 2 2005 77 0 3 2016 73 0 4 2020 71 116 - 2012 71 0 5 2015 69 0 - 2010 69 0 Time Series Summary for JFK INTERNATIONAL AIRPORT, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature >= 70 Missing Count 1 2016 55 0 2 2015 53 0 3 2010 51 0 4 2018 49 0 5 2020 48 116 - 2012 48 0 - 1983 48 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature >= 70 Missing Count 1 2018 41 0 2 2010 36 0 - 1980 36 0 3 2020 35 116 - 2016 35 0 4 2013 34 0 - 1999 34 0

First time since 2012 that the 5 day NSIDC extent dropped below 4 million sq km. Also the first 5 year period with 3 years below 4.2 million sq km. 9-6-20.......3.928 September 5-day date 3.387 2012-09-17 4.155 2007-09-18 4.165 2016-09-10 4.192 2019-09-18

Plenty of onshore flow coming up with high pressure to our north and east. So no 90° potential for the foreseeable future. The last time Newark didn’t reach 90° in September was 2011 and 2012 for LGA.

A recent study was able to determine just how extreme the Bering wintertime sea ice low in 2018 was.

It would be really odd if LGA didn’t have another 90° day this year. LGA never reached 30 days before without any 90° days in the spring or fall. LGA is currently in 4th place with 34 days reaching 90°. LGA finished JJA with the 2nd highest number of 90° days behind 2010. Monthly Number of Days Max Temperature >= 90 for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Year Apr May Jun Jul Aug Sep Oct Season 2010 1 2 12 18 11 4 0 48 2018 0 4 4 10 16 4 0 38 2002 2 0 5 14 13 1 0 35 2020 0 0 5 19 10 0 M 34 1991 0 4 9 10 9 2 0 34 2016 0 3 1 15 10 3 0 32 1983 0 0 5 11 8 7 0 31 2005 0 0 7 10 10 3 0 30 1953 0 1 7 10 9 3 0 30 Monthly Number of Days Max Temperature >= 90 for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Year Jun Jul Aug Season 2010 12 18 11 41 2020 5 19 10 34

According to Brian B, the US record for earliest measurable snowfall after a 100° was 5 days at Rapid City, SD in September 2000. So Denver could potentially see their latest 100° and then one of their earliest measurable snowfalls. 2000-09-17 101 53 77.0 16.8 0 12 T 0.0 0 2000-09-18 93 64 78.5 18.8 0 14 T 0.0 0 2000-09-19 65 48 56.5 -2.7 8 0 0.04 0.0 0 2000-09-20 61 43 52.0 -6.7 13 0 0.00 0.0 0 2000-09-21 66 41 53.5 -4.8 11 0 0.00 0.0 0 2000-09-22 46 34 40.0 -17.8 25 0 0.27 0.5 0 First/Last Summary for Denver Area, CO (ThreadEx) Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year First Value Last Value Difference 2019 07-19 (2019) 101 09-02 (2019) 100 44 2002 08-16 (2002) 100 08-16 (2002) 100 0 1962 08-10 (1962) 100 08-14 (1962) 100 3 1876 07-06 (1876) 101 08-12 (1876) 100 36 1969 08-08 (1969) 100 08-08 (1969) 100 0 First/Last Summary for Denver Area, CO (ThreadEx) Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Difference 1961 05-13 (1961) 6.4 09-03 (1961) 4.2 112 1962 04-30 (1962) 0.1 09-08 (1962) 0.7 130 1974 04-29 (1974) 0.2 09-12 (1974) 1.8 135 1989 04-30 (1989) 3.7 09-12 (1989) 2.3 134 1993 04-24 (1993) 1.0 09-13 (1993) 5.4 141 1971 04-22 (1971) 4.5 09-16 (1971) 2.7 146

Looks like we will experience near record 500 mb heights for September. But the high will be to our NE with onshore flow.

Yeah, the number of new weather extremes since around 2010 has almost become too numerous to keep track of. Don, thanks for those stats. I guess our version of that near sea level would be February 8th- 9th, 2017. ISP 2017-02-08 62 39 50.5 18.8 14 0 T 0.0 0 2017-02-09 42 18 30.0 -1.8 35 0 1.30 14.3 1

I wonder if this will be the first time that a part of the US experiences snow so soon after highs near 100°? RECORD HEAT THIS WEEKEND TO POSSIBLE SNOW TUESDAY... Upper level ridge centered over the Great Basin will retrograde westward Sunday over California and Nevada. By Monday, what`s left of the ridge is just off the California coast. This ridge will keep it hot and dry Saturday and Sunday. Highs across northeast Colorado are expected to reach the mid 90s to lower 100s. A low pressure trough across eastern Colorado and a short wave trough passing to the north of Colorado will cause west to northwest winds to increase Sunday. This downslope flow will produce very dry conditions. It will likely offset any minor cooling associated with the short wave trough. A weak cold front drops south across the area Sunday night. Gusty east winds behind it are expected for Monday. This will usher in cooler air into northeast Colorado. For Monday, models still showing a strong open trough over the Northern Rockies. This trough then dives south and strengthens into a closed low over somewhere near the Four Corner Tuesday. A strong cold front associated with this system pushes south through the state late Monday afternoon through Monday night. Precipitation develops Monday evening and becomes widespread overnight Monday night and Tuesday. The 00Z GFS, GEM, and ECMWF are quite impressive with the amount of cold that accompanies this storm system. If the current solutions are right or close, it will be cold enough for snow to fall along the Front Range Urban Corridor and nearby plains. Accumulating snow on trees may cause considerable tree damage and related impacts will be possible. This system is four days away and models will likely change some. Confidence is becoming high that snow will occur in the mountains and foothills Monday night through Tuesday evening. A slight change in storm track or a slightly weaker closed low may keep the lower elevations warm enough for rain. Main message is cold and heavy snow is possible Monday night through Tuesday night. Monitor the latest forecasts and consider changing outdoor or travel plans if cold and snow still look on track.

Just an unbelievable temperature and weather swing in the forecast for the Rockies.

This was the warmest melt season on record. A new paper is out on the continuing Atlantification of the Arctic Ocean. This year the sea ice edge made it to 85°N on the Atlantic side. https://nsidc.org/arcticseaicenews/ Atlantification continues As discussed in a recent paper in the Journal of Climate led by colleague Igor Polyakov of the University of Alaska, the process of “Atlantification” of the Arctic Ocean, first noted in the Barents Sea, is continuing, with significant effects on the sea ice cover during the winter season in the Eastern Eurasian Basin. The relatively fresh surface layer of the Arctic Ocean is underlain by warm, salty water that is imported from the northern Atlantic Ocean. The cold fresh surface layer, because of its lower density, largely prevents the warm, salty Atlantic waters from mixing upwards. However, the underlying Atlantic water appears to have moved closer to the surface in recent years, reducing the density contrast with the water above it. Recent observations show this warm water “blob,” usually found at about 150 meters (492 feet) below the surface, has shifted within 80 meters (263 feet) of the surface. This has resulted in an increase in the upward winter ocean heat flow to the underside of the ice from typical values of 3 to 4 watts per square meter in 2007 to 2008 to greater than 10 watts per square meter from 2016 to 2018. Polyakov estimates that this is equivalent to a two-fold reduction in winter ice growth.

Yeah, the record amplitude may allow allow a piece of energy to cutoff near the Rockies. So some rapidly changing conditions even by Rockies standards are possible. I guess we’ll have to see how this trough evolution influences the Western Atlantic pattern regarding any tropical systems. Courtesy of wx.us and Ryan Maue on twitter.

The first half of the month was cold enough to compensate for the milder second half. But even the second half of the month only made to 56° in NYC with the historic flood cutter. January 1996 finished 30.5° and -2.1. That was like a grand finale in a fireworks show. I never expected in 1996 that we would see such a snow drought from 96-97 to 01-02. It was my biggest weather surprise since the winter of 89-90 historic reversal from the record cold December.

95-96 was the last time for NYC that every month from November to March was below normal. Came close in 02-03 but March finished above normal. 13-14 and 14-15 got interrupted by the warmth in December.

Looks like any major heat will be limited by clouds and onshore flow. But the warmer than normal minimums may take the lead with the higher dew points and winds off the still warm ocean.

Less warm is the new cool.

Extremely amplified pattern coming up. Record 500mb heights forecast along the West Coast by the weekend. Then we see how strong the ridge off the East Coast can get in 7-10 days.

Yeah, those warming WPAC SSTs lead to the record MJO 4-6 activity during recent winters. This served to enhance the La Niña background state over the last 4 winters. It resulted in mild to record warm winters with the SE Ridge dominating and setting a new record in February 2018. But the location of the NPAC ridge made the difference between snowy and nearly snowless winter outcomes. 2017 to 2018 featured the ridge near the Aluetians and more NATL blocking with a snowy pattern. During the 2019 to 2020 period ,the ridge was much flatter near Hawaii. So we got the two recent nearly snowless DJF periods along with a strong NATL PV. While it looks like we could experience a 5th La Niña background state winter, we’ll have to see how the NPAC ridge and NATL pattern influence the snowfall potential.

Updated for August 2020. 8....2020...EWR...10..LGA...5...BDR...3...ISP....6

I wonder what the 500MB height record is for Newfoundland in September? All the models are going near 600 DM In about 10 days.

It looks like we will have a trough in the Great Lakes and Midwest at least into early September. There should also be plenty of high pressure to our north and east with onshore flow here. But we will just have to wait and see how many of the AEWs coming off Africa can actually develop into named systems.