bluewave
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It’s tough to know if this one test case means the big upgrade improved East Coast storm tracks. But suppression seems to have been an issue since the January 2016 blizzard. Last February was the most recent winter example. https://confluence.ecmwf.int/display/FCST/201601+-+Snowstorm+-+US+east+coast 5. Good and bad aspects of the forecasts for the event Early signal (from Sunday 17 Jan 00z) and very consistent forecasts Too low accumulation over NYC Question about snow density for the case
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The Euro came south before the GFS and CMC which were too amped up. We usually don’t start tracking until around 120 hrs out. So the Euro did the best from 120hrs to the present.
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You can see why the models keep correcting warmer from the weekend going forward. They now how one of the deepest -PNA +EPO troughs near NW Canada on record for December. This is accompanied by a 6 sigma Jet max. So a continuation of the fall record breaking +EPO and Pacific Jet pattern.
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This start of December was a great example of models correcting warmer with an unfavorable -PNA and +AO pattern. The first week of December was originally forecast to be around -2. But the 5 station average is +4.5 through the 6th. EWR….+5.9 NYC….+3.6 LGA…..+4.4 JFK…..+4.4 ISP…….+4.1 AVG…..+4.5
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Maybe this means they fixed the East Coast storm track issue with the Euro since all the other models were too amped up for such a fast Pacific flow.
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This happens all the time with rain and convection events. But people aren’t paying such close attention unless it’s snow. When was the last 36-48 hr forecast rainfall -convection event that the models nailed to within a T to .3 of an inch of liquid? This is all with in the margin of error at 36 to 48 hours out.
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A west based -EPO with a -PNA and +AO is a warm pattern for us. This is what happened in February 2018. We want a -EPO to link up with a -AO like March 2018. So it may require a stratospheric warming event near the start of January to fully shift the pattern.
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The latest extended EPS continues the warm -PNA +AO pattern into late December. It develops a west based EPO ridge near Alaska during late December. But still has a SE Ridge here due to the -PNA and +AO. So Western Canada gets much colder. The MJO eventually gets over to 7, but it’s forecast to destructively interfere with the La Niña. So that may be why it takes longer to build the ridge into Alaska. We would probably need a cleaner MJO 7 response to start pushing the gradient closer to the Northeast during the last week of December. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf • A Pacific MJO event is likely to destructively interfere with La Niña, and there remains uncertainty as to whether the MJO will maintain an organized structure, as evidenced by large ensemble spread in the RMM forecasts through mid-December. Dec 6-13 Dec 13-20 Dec 20-27
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Winter version of the Ambrose Jet. Cooler conditions and winds gusting near 35 mph along the South Shore. Mid-60s at the usual spots in NJ. Kennedy Intl PTSUNNY 53 51 93 S29G37 29.74F FOG Breezy Point N/A 52 N/A N/A S25G35 N/A Newark/Liberty PTSUNNY 65 52 62 S15G29 29.69F Teterboro MOSUNNY 62 53 72 S17G25 29.68F Caldwell LGT RAIN 64 52 64 VRB7 29.69F Somerville PTSUNNY 64 54 69 S8 29.66F Linden PTSUNNY 65 50 59 SW10G21 29.69F Perth Amboy N/A 63 N/A N/A S18G25 N/A
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Going warm has been the winning forecast for 9 out of the last 10 Decembers. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Year Mean Avg Temperature Departure 2020 39.2 +1.7 2019 38.3 +0.8 2018 40.1 +2.5 2017 35.0 -2.5 2016 38.3 +0.8 2015 50.8 +13.3 2014 40.5 +3.0 2013 38.5 +1.0 2012 41.5 +4.0 2011 43.3 +5.8
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That’s not how it works. December has been warming at close to 1° per decade over the last 40 years. We started out closer to 35° and now are approaching 40° in the averaged means for our whole climate division. So by mid-century, averages closer to 45° will become the norm. The warming baseline makes it easier for the more extreme years like 2015 to occur. We saw this in February 2018 with our first 80. So one of these Decembers in the future will eventually produce an 80° reading also.
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While December 2015 has been the most extreme expression of the US December warming trend, the composite of the other years since 2011 shows the same pattern.
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December has been the warmest winter departure month over the last decade. It’s no surprise that the models have corrected so much warmer in recent days. Summer has been extended into fall and fall into early winter.
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You know it’s a very warm December pattern when Long Island is approaching 60° early in the morning. CITY SKY/WX TMP DP RH WIND PRES REMARKS Jones Beach N/A 57 N/A N/A S13G18 N/A Wantagh N/A 57 55 94 S10 N/A Hempstead NOT AVBL Matinecock Pt N/A 52 N/A N/A N1 N/A Farmingdale CLOUDY 57 55 93 S15G24 29.94F MacArthur/ISP CLOUDY 57 56 96 S14 29.94F Stony Brook N/A 55 54 94 S7 N/A Shirley MOCLDY 57 54 89 SE14G23 29.97F Mt Sinai Harb N/A 55 N/A N/A S10 N/A Westhampton CLOUDY 55 53 93 SE14G21 29.98F East Hampton CLOUDY 53 51 94 SE15G23 29.98F Southold N/A 54 52 94 S18 N/A Montauk N/A 54 52 93 S12G21 30.02F
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The latest Euro monthly has a low heating bill special for the US in December.
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The CMC came south from yesterday due to a faster Pacific Jet flattening the ridge near California. New run Old run
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That’s why many people were disappointed when the NCEP chose the FV3 core over the MPAS. https://blogs.agu.org/wildwildscience/2016/07/28/noaa-makes-decision-new-global-weather-model-controversy-likely/
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The NAM looks like it could be a possibility with the fast flow putting us in the NW edge of the precipitation shield. This may mean that the recent Euro fix worked for East Coast storms. Those tucked in low solutions from the GFS don’t really match the pattern.
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The record storm near Japan and the typhoon are probably a big part of why the current MJO phase 6 pattern is getting disrupted. A -PNA is the opposite of what we would expect from a MJO 6 La Niña December composite. The near record Aleutians Ridge and deep -PNA trough for mid-December will probably take time to shift.
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Our actual pattern in late November was a perfect match for a November La Niña phase 5. We had the classic +PNA and -NAO pattern. But the block in the North Atlantic was more south based probably due to the record SSTs off the East Coast.
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The last few weeks have been classic MJO phase 5. The strongest VP anomalies were too far west to be in the phase 6 region. The wave break a few days ago disrupted the whole pattern. Notice the big VP anomalies jump into Eastern Siberia. That’s probably a part of what all the models have a big -PNA in mid-December going against the Phase 6 +PNA for December.
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The last few weeks have been a November phase 5 for a La Niña. We are just going into December phase 6 right now. The mid-December -PNA that the models have been adverting is the opposite of what to expect from a La Niña phase 6 in December. My guess is that losing the +PNA is related to the big West PAC wave break amplifying the Aleutians Ridge . That being said, it’s possible that the MJO can start having a bigger influence later in December. It could take another wave break to shake things up again.
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A thread the needle SWFE has been our storm track of choice when the general pattern was challenging. The models seem struggle even more when a storm follows another one by only a few days. But I don’t really trust individual model forecasts for coastals until we get under 72 hrs.
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The only trends that seem to matter for us are the ones that occur under 72 hrs. It would be great if we had a model that could get a 96-120 hr coastal storm track correct. Funny how models usually can get cutters right from a week out.
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Another indicator that the pattern driving the fall record +EPO and current -PNA is on steroids.
