bluewave

You know it’s a warm pattern when Islip reaches 81° on a NE wind in mid-September.

Yeah, we needed the strong SE ridge to boost the SSTs for heavier snows. Luckily, the years that the SE Ridge ran the table without blocking like 2012 and 2020 were in the minority. Some of our best snowfalls have occurred a month after the record SE Ridge was replaced by blocking. The historic January 30” blizzard followed the historic +13.3 SE Ridge December 2015. The historic February 2018 SE Ridge and 80° at Newark was followed by the March historic 30” snows on Long Island.

We now have a new AI based sea ice forecasting system.The paper was just published in late August. So their first official forecast was issued a few weeks ago on the ARCUS site. The September daily minimum was very close to their September average monthly forecast. The September average extent will come in a little higher which is always the case due to the higher average extent in early and late September. Name of contributor or name of contributing organization: IceNet1 https://www.arcus.org/files/sio/32360/icenet1_2021_sio_august_individual_report.pdf a) Pan-Arctic September extent prediction in million square kilometers. 4.75 IceNet is a sea ice forecasting AI system which predicts monthly-averaged sea ice probability (SIP; probability of sea ice concentration > 15%) up to 6 months ahead at 25 km resolution on an EASE2 grid. IceNet is based on a deep learning U-Net architecture, and has been trained on climate simulations (CMIP6) covering 1850-2100 and observational data (OSI-SAF SIC and ERA5) from 1979-2011. IceNet’s monthly-averaged inputs comprise SIC, 11 climate variables, statistical SIC forecasts, and metadata. IceNet is introduced in the following pre-print, with the study soon to be published in Nature Communications: https://doi.org/10.31223/X5430P. IceNet was also presented at the Oxford ML and Physics Seminar Series: https://youtu.be/JAKWhEU09Xo. Brief explanation of Outlook method (using 300 words or less). At each 25x25 km ocean grid cell in the Arctic and at each forecast lead time from 1 to 6 months ahead, IceNet produces a probability that the SIC will be less than 15% (no ice), between 15% and 80% (marginal ice), or above 80% (full ice). To compute the SIP map for this SIO submission, we sum the probability of the two ice classes to obtain P(SIC > 15%). IceNet comprises 25 different U-Net models, whose output SIPs are averaged to produce the final SIP forecast. To compute the SIE, we sum the area of grid cells whose SIP > 0.5.

The increased blocking and milder winter temperatures have worked wonders for our snowfall since 2002-2003.

This was only the 2nd 40-40 year for Newark. 41 days reaching 90°after 45.7” of snow. The other 3 years with at least 30” of snow were strong to super El Niño’s. I guess it fits since winter was more El Niño-like. Year /snowfall/ #90°days/peak ENSO ONI 2021…..45.7”…41...-1.3 2010….47.9”….54…+1.6…strong El Niño 2016….32.8”….40.+2.6…super El Niño 1983….31.0”….40.+2.2….super El Nino https://www.climate.gov/news-features/blogs/enso/did-northern-hemisphere-get-memo-years-la-niña That means you can argue that the Northern Hemisphere atmosphere looked a little more like El Niño than La Niña!

Some late season Miami dew points into New England today. New Haven MOSUNNY 83 75

Warmest summer minimums on record this year north of NYC Metro with the continuing record high dew points. Time Series Summary for DANBURY MUNICIPAL AP, CT Click column heading to sort ascending, click again to sort descending. Rank Year Mean Min Temperature Missing Count 1 2021 63.8 0 2 2020 61.6 0 3 2018 61.3 0 - 2005 61.3 0 4 2013 60.9 0 5 2010 60.5 0

High of 78° at HPN. Another very warm start to the day across the area. We’ll see if HPN can add another 65°minimum to the list making it to 54 days. The higher dew points in recent years allowed record numbers of 65° or warmer minimums. Time Series Summary for WESTCHESTER CO AP, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature >= 65 Missing Count 1 2018 63 1 2 2011 60 2 3 2020 59 1 - 2012 59 2 - 1969 59 0 4 1959 58 0 5 1999 56 58 6 2010 54 2 - 1961 54 3 7 2021 53 110 - 2016 53 0 - 2005 53 5 - 1985 53 11 - 1983 53 5 8 2017 51 6 - 2013 51 1 - 1970 51 5 9 1973 50 0

Yeah, 1993 was the latest 80° day on record at Newark. First/Last Summary for NEWARK LIBERTY INTL AP, NJ 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 1993 04-20 (1993) 80 11-15 (1993) 80 208 1948 05-10 (1948) 87 11-06 (1948) 80 179 2003 04-15 (2003) 81 11-03 (2003) 81 201

The other impressive 80° day statistic for Newark is how early the first 80° of the year has been arriving. The 2-21 -18 earliest is one of the more extreme high temperature records that our area has seen in recent years. 5 of the top 10 earliest have occurred since 2011. But the cooler recent Novembers relative to the rest of the fall hasn’t allowed any late 80° records to be challenged recently. First/Last Summary for NEWARK LIBERTY INTL AP, NJ 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 2018 02-21 (2018) 80 10-11 (2018) 81 231 2016 03-09 (2016) 82 10-19 (2016) 87 223 1990 03-13 (1990) 86 10-14 (1990) 83 214 1945 03-16 (1945) 81 10-19 (1945) 82 216 2011 03-18 (2011) 80 10-10 (2011) 85 205 2020 03-20 (2020) 80 09-28 (2020) 81 191 1938 03-22 (1938) 80 10-17 (1938) 90 208 2021 03-26 (2021) 84 - - - 1998 03-27 (1998) 84 09-27 (1998) 91 183 2007 03-27 (2007) 80 10-23 (2007) 80 209 1989 03-28 (1989) 83 10-16 (1989) 80 201

Another 80° day at Newark. 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 Max Temperature >= 80 Missing Count 1 2015 118 0 2 1994 114 0 3 2016 113 0 - 1993 113 0 - 1991 113 0 4 2011 111 0 - 2010 111 0 5 1959 108 0 6 2007 106 0 7 2005 105 0 8 2002 104 0 9 1990 103 0 - 1957 103 0 2021 103 109

With Newark adding another 70° low yesterday, it’s getting closer to the all-time record. 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 2021 57 109 - 2020 57 0 - 2010 57 0 5 1993 55 0

Latest EPS continues the above normal temperatures into October. 9-13 to 9-20 9-20 to 9-27 9-27 to 10-04

We will have to monitor for severe storms later into tonight with the record breaking September midlevel lapse rates nearby.

Warm offshore flow day with the the 850 mb temperature peaking at +18C this morning on the OKX sounding.

The monthly temperature increases from 81-10 to 91-20 have been more pronounced during certain months. Newark and Islip are compared below. The +1.0 or warmer months for either station were bolded. So we get an extension of summer into September. ……….EWR…..ISP Dec…+1.5….+1.5 Jan….+1.2…+1.3 Feb….+0.5….+0.5 Mar….+0.4….+0.6 Apr….+0.5…..+0.6 May...+0.6….+0.9 Jun….+0.3….+0.6 Jul…..+1.4…..+1.1 Aug...+0.6….+0.9 Sep….+1.0….+1.3 Oct…..+0.9..+1.4 Nov….+0.2..+0.5

This will be the tenth year since 2007 with a daily NSIDC minimum extent in the 4s. Two years finished below 4 million sq km and three slightly above 5 million sq km. Following 2007, no year has been able to finish above 6 million sq km in a much warmer Arctic.

Pretty good agreement between Euro and GFS on above normal temperatures for the rest of September.

1980 and 1995 were much further down the list. But 1988 finished close to the 10 highest summer temperature. The top 10 is mostly filled with recent years. 202106 - 202108 74.01°F 127 2.61°F 193606 - 193608 74.00°F 126 2.60°F 201206 - 201208 73.70°F 125 2.30°F 201106 - 201108 73.65°F 124 2.25°F 202006 - 202008 73.55°F 123 2.15°F 193406 - 193408 73.53°F 122 2.13°F 200606 - 200608 73.52°F 121 2.12°F 201606 - 201608 73.50°F 120 2.10°F 201806 - 201808 73.50°F 120 2.10°F 200206 - 200208 73.19°F 118 1.79°F 198806 - 198808 73.11°F 117 1.71°F

Must be like a tropical rainforest canopy covering the NYC ASOS. Highs today… JFK….76° NYC…76° ISP…..76° LGA….79° EWR…81°

As Don pointed out earlier, the smoke will return with the warm up starting tomorrow.

The unusual El Niño Niño-like response for such a strong La Niña from December into January may have acted as a SSW precursor pattern. https://www.climate.gov/news-features/blogs/enso/did-northern-hemisphere-get-memo-years-la-niña Did the Northern Hemisphere get the memo on this year's La Niña? Was the mismatch that we saw in December-January really that unusual? We know from previous blog posts (like this one) that the atmosphere varies quite a bit from one La Niña to the next, and the atmosphere never fully resembles the average of all events. To address this question, I evaluated the similarity between the individual December-January 500 hPa maps and the average La Niña pattern (for the 13 moderate-to-strong La Niña episodes). For this calculation, I use the pattern correlation, a metric that summarizes the similarity in a single number: a value of 1 means perfect match, 0 means complete mismatch, and -1 means mirror opposites (3). Pattern correlations between the individual La Niña and average La Niña December – January 500 hPa geopotential height anomalies north of 15°N for the 13 strongest La Niña episodes since 1950. Positive values indicate at least some degree of pattern matching, with 1 indicating a perfect match, and negative values indicate a mismatch between the two patterns. NOAA Climate.gov figure with NCEP/NCAR Reanalysis dataobtained from the NOAA Physical Sciences Laboratory. The pattern correlations are usually substantially positive for moderate-to-strong La Niñas, which indicates that most events share some basic similarity with the average La Niña pattern. This confirms that La Niña is a reliable source of predictability outside of the tropics (and a big reason that we have an ENSO Blog!). However, the pattern correlation for the December 2020 – January of 2021 is the lowest of the 13 events and is actually slightly negative. That means you can argue that the Northern Hemisphere atmosphere looked a little more like El Niño than La Niña! On the sudden stratospheric warming and polar vortex of early 2021 https://www.climate.gov/news-features/blogs/enso/sudden-stratospheric-warming-and-polar-vortex-early-2021 Butler: While it’s not entirely clear yet what led this SSW to occur, in the weeks leading up to the SSW there was a fairly persistent low pressure weather system over the North Pacific and high pressure weather system over the North Atlantic and Eurasia. This pattern represents a really large (planetary-scale) “atmospheric wave”, which can grow bigger as it extends upward into the stratosphere given the right location and wind conditions. These same weather patterns have been linked to prior SSWs. An extratropical bomb cyclone in the North Pacific just days before the SSW might have reinforced this pattern, but this connection will have to be investigated further. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL074611 Classifying the tropospheric precursor patterns of sudden stratospheric warmings Abstract Classifying the tropospheric precursor patterns of sudden stratospheric warmings (SSWs) may provide insight into the different physical mechanisms of SSWs. Based on 37 major SSWs during the 1958–2014 winters in the ERA reanalysis data sets, the self-organizing maps method is used to classify the tropospheric precursor patterns of SSWs. The cluster analysis indicates that one of the precursor patterns appears as a mixed pattern consisting of the negative-signed Western Hemisphere circulation pattern and the positive phase of the Pacific-North America pattern. The mixed pattern exhibits higher statistical significance as a precursor pattern of SSWs than other previously identified precursors such as the subpolar North Pacific low, Atlantic blocking, and the western Pacific pattern. Other clusters confirm northern European blocking and Gulf of Alaska blocking as precursors of SSWs. Linear interference with the climatological planetary waves provides a simple interpretation for the precursors. The relationship between the classified precursor patterns of SSWs and ENSO phases as well as the types of SSWs is discussed.

This will be our coolest morning for a while with 40s in the local cool spots. Westhampton CLEAR 45 43 93 East Hampton FAIR 49 48 97 Somerville CLEAR 49 48 97 Sussex CLEAR 49 47 93