bluewave

I already gave the JMA credit for seeing the record TNH pattern for the 13-14 winter.

To be fair, our really warm winters like 22-23 and 23-24 weren’t forecast to be that warm. The seasonal models had a pretty extensive cold bias for both those winters. The seasonal forecasts for years like 15-16, 16-17, and 19-20 were also much cooler than the record warmth which verified. I believe from memory that the 01-02 and 11-12 seasonal model forecasts missed the warmth also. So most of the time as the winters have been warming these seasonal forecasts have been too cold. Last October I was pointing out the colder La Niña mismatch potential that some of the seasonal models could have been missing. So I wasn’t surprised at the colder pattern last January than some of the seasonals had many months in advance.

The one particular month shows the greater bias of being too cold in the Northeast which is the same as the collection of all the months averaged out we have been discussing. Seasonal models beyond a month out are usually a crapshoot even when looking at the 500mb forecasts and not taking into account the general temperature biases for said patterns. The last time one of these seasonal models had a great winter forecast in October and verified close to having a great actual winter was the JMA winter 13-14 forecast with the wall of Pacific blocking which verified.

You are using an example of the CanSIPS missing the 500mb forecast from multiple months out. My observation is based on the months when the 500mb forecast is reasonably close. The updated January 2025 forecast which came out on January 1st was too cold in the Great Lakes and Northeast even though the 500mb forecast did better once we got closer in.

Thanks. I have kept a running tally of past model forecasts and where their errors or biases have been. I use them in the various threads for my forecast discussions. While AI models on their own haven’t been very good with real world use compared to the numerical models, they may have some promise if they could figure out how to incorporate AI to bias correct the numerical models in real time. I think the ECMWF is trying to do this. But the computer power involved in that is pretty demanding.

Yeah, these forecast soundings are really loaded with tropical moisture. Also weak steering flow could lead to stalling and training convection. Somebody could see some very heavy rains in a short time period.

Models having inherent biases have nothing to do with cherry picking. They are a function of the way the models work. The CanSIPS is well known for showing too much cold where the troughs are forecast especially in the East. One of the few parts of the country that can verify colder than these seasonal forecasts is the Rockies and Upper Plains. But that doesn’t do the posters living in the I-95 corridor any good. Plus the forecasts beyond one month are a crap shoot anyway. So don’t get too attached to what any of the seasonal models are showing now for next winter. The CanSIPS and other models don’t have a ton of skill forecasting the 500mb pattern more than 30 days out. So we have to wait until the 1st of each month for the monthly forecast. Then adjust the temperatures warmer in the spots where a trough is indicated for models like the CanSIPS. With the exception of Western areas which can sometimes verify colder. But usually not the East. The one model truism over the years is that the Southeast Ridge or general 500 mb heights in the East verify higher than forecast. This is why the heavy snows which were indicated as far south as NY Metro last February got pushed up into Canada from Toronto to Montreal. So understanding these model biases is essential if you want to have a better handle on the medium to long range and seasonal forecasts.

Just look at all the new mesonet sites that have multiple elevation temperature observations. Temperatures most times decline with elevation from 2m to 10m and 30m to over 100m at some sites. The exceptions are during radiational cooling inversions and strong winter WAA when the higher levels warm more than the surface and we get fog.

Higher dew points and more clouds with onshore flow mean more rain chances. So your area usually sees at least 30-40 days reaching 90° each season. But the chances of going 20 straight days reaching 90° like in 1988 when it was much drier without interruption are very low. But the overall 90° day counts in NJ are much higher than the 1980s and 1990s. Just no really long extended heatwaves. So a bunch of shorter heatwaves giving you more total 90° days than you used to get.

No problem. We need some levity in here after what has happened since 2018-2019. My only comment on the CanSIPS is that temperatures never match the forecasted 500 mb pattern. Just look at the one month forecast for June to see what I am talking about. The 500mb forecast for June wasn’t bad. But the cold pool to the south was way overdone. So this has also been happening with the La Niña winters showing so much cold to the north around the Great Lakes, Northeast, and Canada. If that Southeast Ridge verifies like it’s showing for the winter, there will be much less cold to the north and the warmth to the south will be much more expansive. 500 mb pattern forecast not bad Cold pool to the south never verified

We have been fortunate from Philly to Boston that it hasn’t happened yet. But it has come close at Philly. They managed to narrowly miss a complete shutout twice with 0.3” in 19-20 and 22-23. So they avoided the T from 72-73. NYC also has avoided a complete shutout with their lowest season out of the last 7 coming in at 2.3” in 22-23. Boston was able to stay over 5” with their low season coming in at 9.8” in 23-24. People would really start to say it’s never going to snow again if Philly had a T or their first 0.0”. With a T to 0.9” in NYC and under 5.0” at Boston. Thankfully we are yet to see a snowfall season this low from Philly to Boston.

Great Lakes cutters, I-95 to I84 huggers, and suppressed Southern Stream storm tracks have been dominant since the 2018-2019 winter. This is what we have had with the much stronger Pacific Jet. With the Great Lakes Cutter track the fast Pacific flow carves out a trough out West and pumps the Southeast Ridge with an I-95 rainstorm. The hugger track has wave spacing issues due to too many short waves in the fast Pacific flow. So we get the brief light to sometimes moderate snows changing to rain. Then there is the suppressed Southern Stream low due to the fast Pacific flow having a kicker trough coming into the West Coast. This doesn’t allow the Gulf low like the one last winter which gave record snows to the Gulf Coast to turn the corner and come up the coast. Then sometimes the lows come far enough north for DC to get snows but not areas further north. So the fast Pacific flow effectively turns off the benchmark snowstorm track. I hope we can see at least a small relaxation of this pattern in the coming years even if we still stay warm. Would take a warm and snowy La Niña winter like 16-17 and a weaker Pacific Jet in a second if I could get it. Wouldn’t mind a 60° day before of after some of the blizzards that season. Now we just get the 60° days without the great snows.

Absolutely. Just compare the old photos of the site from the recent ones. Most of those 100° readings from the 1930s into the early 1990s would have only been mid to upper 90s if the they had the same tree cover back then. The strongest wind gust is still 78 mph set back in December of 1974 when the trees were much lower. So there could have been higher gusts in the interim but the tress could be interfering like with the temperatures.

As I have pointed out, you are putting way too much stock in what the teleconnections have been to the north of the subtropics. No combination of WPO, EPO, PNA, AO, or NAO is going to produce a cold and snowy outcome along the I-95 corridor in the Northeast provided that the winter subtropical ridge remains so robust. We need a weaker Southeast Ridge/ Western Atlantic Ridge along with a much slower Pacific Jet. This is why even the -WPO, -EPO, +PNA, and record -AO -NAO block last February still produced a cutter with record snows in Toronto and Montreal with a rainstorm along the coast. The -5 sigma Greenland block linked up with the Southeast Ridge when in the past there would have been a deep trough underneath and a benchmark I-95 blizzard. The issue is the fast Pacific flow and robust subtropical ridges from Japan to Western Europe. So these ridges to the south joining with the ridges associated with the -WPO, -EPO, +PNA, -AO, and -NAO don’t leave any room for cold trough development under the ridges.

The heliport gets sea breezes off the NY Harbor. So it’s not really representative of the areas of NYC away from the shore. I would have them decommission the site by the castle since the park conservancy would never allow any of those trees to be cut down. The one thing I learned over the years is that people love their trees. Back on the South Shore were I used to live there were big disputes which emerged when some trees were going to be removed from my community. Several trees were damaged and were at a risk of falling on some of the houses. I was glad to have them removed. But some residents tried to block the tree removal guys from doing their job. As several fallen weak trees caused property damage prior to the crews arrival. So if NYC every tried to remove those trees around the ASOS, their would be a big protest. I would give the NYC mesonet the opportunity to pick a spot Central Park in a clearing to install a new site like below. So no trees would have to be disturbed.

A grassy clearing in Central Park like the Great Lawn is among of the warmest parts of Manhattan Island and NYC. It’s one of the few spots that gets full sun during the summer. As the midtown streets are often in the shade with the increase in the ultra tall skyscrapers. Plus Central Park has an unusual amount of exposed bedrock which really heats up. This is why Central Park would often have similar temperatures as Newark and sometimes warmer during the summer from the 1930s to around 1980.

The Euro brings in Chantal’s remnants Monday into Tuesday. 2.00-2.50 PWATS and mid 70s dewpoints for heavy rain potential. Will probably have to within the SPC HREF range to guess the peak amounts.

None of our current teleconnection indices accurately capture the changes we have seen in the North Pacific since 2018-2019 that I have highlighted in my previous posts. The record ridge near the Aleutians and to the east of Japan and attendant shift north in the storm track doesn’t fit neatly into either the Western Pacific oscillation of the North Pacific oscillation. Same goes for the record SSTs across the mid-latitudes of the North Pacific and Atlantic and subtropical ridge expansion. This is why the snowfall outcome was the same last winter with the strong -WPO interval in February as it had been with prior +WPO intervals. Both outcomes featured very strong Southeast Ridge patterns.

This was the reason that the NWS didn’t like to substitute readings at LGA back in the 1970s when the NWS equipment was out of service. Before the tree growth issue in the 1970s, LGA ran cooler than NYC did. So the NWS recognized that an open area of Central Park in the middle of Manhattan was a warmer part of NYC for summer high temperatures than right on the bay in Northern Queens. Central Park is our one ASOS in or around NYC which is the furthest distance from the water and local cooling breezes. So my estimate is that the placement of the ASOS under the trees has resulted in nearly 10 fewer 90° days reaching annually then they would be getting if the equipment was sited the same way prior to the 1990s. Annual 90° day counts for EWR, NYC and LGA during the 1961-1990 era prior to the ASOS being placed under the trees in the deep shade. EWR…..23 days NYC…..18 days LGA…..14 days Annual 90° day counts for EWR, NYC, and LGA during the most recent 15 year period of maximum tree growth and summer warming from 2010 to 2024. 12 out of the last 15 summers warmer to record warm across the region. EWR…..33 days for a 43% increase over 1961-1990 averages NYC…..19 days for only a 5% increase over 1961-1990 averages LGA…..25 days for a 78% increase over 1961-1990 averages The actual number of 90° days Central Park would be getting if the ASOS wasn’t under the trees would be around 28 a year. I arrived at this number by averaging the 43% increase at LGA and 78% at LGA. The average number was a 60% increase or 10 days more up to 28 days from 18 days. So the 5% increase from 1961-1990 should actually be 60%. So an annual undercount of 55% for 90° days if the ASOS was in a grassy clearing like the Great Lawn rather than beneath a densely wooded area of Central Park next to the castle. https://www.nytimes.com/1977/07/22/archives/vandals-in-central-park-forcing-weather-service-to-seek-new-site.html When the devices at the castle are not functioning, the Weather Service substitutes readings from La Guardia Airport. But Mr. Gibson said those readings do not really reflect conditions in the city, because they may be several degrees cooler in summer or warmer in winter than those in Central Park.

We have been seeing these lulls in recent years when the subtropical warming has increased faster than the tropics. But often by later in the season SST anomalies between the tropics and subtropics balance out. So the tropics sit quietly gaining record amounts of heat through the season with suppressed convection. But when the hurricanes do finally form later on, we get these rapidly intensifying hurricanes becoming majors right before landfall on the Gulf Coast. Different from the old days when most hurricanes seemed to weaken right before landfalling.

Severe storms usually overperform when we have steep lapse rates and such unstable soundings.

The record WPAC warm pool and Aleutian Ridge are much more amplified than we typically see from +WPO patterns. Same goes for the new way the -PDO has played out in the 2020s. So the hemispheric expansion of the subtropical ridges are creating their own pattern.

Early split picture showing up in the data. It was a warmer than average May across the Arctic. But not as warm as 2020 was which lead to all the preconditioning that year. June was the coolest in the Arctic over the last decade. Yet the extent is currently in 1st place for lowest in early July. But the area is only 8th lowest. Area and melt pond fraction are more important this time of year than extent in trying to guess a September low. Unfortunately, the May melt pond data still hasn’t been released. This is what the statistical model uses to forecast a June September low. If I had to take an early guess, the higher area now than extent could mean that the extent will fall behind the steep 2012 drop which happened back in early August 2012. So it’s possible that the 2012 record low will hold for another year. But I want to see the May melt pond fraction first before making a final call. I will update this if the ARCUS SPIN site gets around to posting the model forecasts for September. They have been delayed in their update.

Looks like the next warm up in mid-July will be another over the top one leaving room for moisture undercutting the ridge before then.

Yeah, unusually cool and wet July 4th following the snowiest winter of the 1970s. Climatological Data for ISLIP-LI MACARTHUR AP, NY - July 1978 Click column heading to sort ascending, click again to sort descending. 1978-07-01 78 58 68.0 -5.5 0 3 0.00 0.0 0 1978-07-02 73 55 64.0 -9.7 1 0 0.00 0.0 0 1978-07-03 70 60 65.0 -8.9 0 0 0.99 0.0 0 1978-07-04 61 56 58.5 -15.6 6 0 1.56 0.0 0 Climatological Data for JFK INTERNATIONAL AIRPORT, NY - July 1978 Click column heading to sort ascending, click again to sort descending. 1978-07-01 84 66 75.0 0.3 0 10 0.00 0.0 0 1978-07-02 78 57 67.5 -7.4 0 3 0.00 0.0 0 1978-07-03 71 60 65.5 -9.6 0 1 1.73 0.0 0 1978-07-04 65 60 62.5 -12.7 2 0 0.50 0.0 0 Snowfall Data for October 1, 1977 through April 30, 1978 Click column heading to sort ascending, click again to sort descending. NY PORT JERVIS COOP 70.5 NY PATCHOGUE 2 N COOP 68.7 NY ISLIP-LI MACARTHUR AP WBAN 68.0 CT DANBURY COOP 67.0 NY NY WESTERLEIGH STAT IS COOP 66.7 NJ PLAINFIELD COOP 65.2 NJ NEWARK LIBERTY INTL AP WBAN 64.9 NY MIDDLETOWN 2 COOP 64.7 CT MOUNT CARMEL COOP 64.1 NJ CHARLOTTEBURG RESERVOIR COOP 62.3 NY DOBBS FERRY-ARDSLEY COOP 61.6 NJ CRANFORD COOP 60.7 CT MIDDLETOWN 4 W COOP 60.2 NY WESTCHESTER CO AP WBAN 59.7 NY SCARSDALE COOP 59.6 NY BRIDGEHAMPTON COOP 59.1 NJ GREENWOOD LAKE COOP 59.0 NY NEW YORK AVE V BROOKLYN COOP 58.0 NY RIVERHEAD RESEARCH FARM COOP 57.5 NY YORKTOWN HEIGHTS 1W COOP 57.1 CT STAMFORD 5 N COOP 56.0 NY MINEOLA COOP 55.8 NJ WANAQUE RAYMOND DAM COOP 55.6 NY WALDEN 1 ESE COOP 54.2 CT IGOR I SIKORSKY MEMORIAL AIRPORT WBAN 52.7 NY NEW YORK LAUREL HILL COOP 51.6 NJ CANOE BROOK COOP 51.4 NY NY CITY CENTRAL PARK WBAN 50.7 NJ MIDLAND PARK COOP 49.1 CT GROTON COOP 48.9 NY JFK INTERNATIONAL AIRPORT WBAN 48.5 NJ TETERBORO AIRPORT WBAN 48.3 NY SETAUKET STRONG COOP 46.5 NJ LITTLE FALLS COOP 45.6 NY LAGUARDIA AIRPORT WBAN 43.5