bluewave

The Euro, CMC, and UKMET don’t have much rain. So the GFS is the only regular global trying to show a PRE-like feature Wed into Thurs. It’s still an outlier compared to the other globals. GFS only global that tries to connect front to Helene also much deeper GEM more separate and weaker system like Euro and UKMET

The record SST warmth is much more expansive than just 150E. It encompasses the entire area from the Maritime Continent to around the Dateline. The +30C warm pool area is much larger than anything we have ever seen before. The previous record holder was the summer of 2016. But you can see this summer was a leap above the levels heading into the 16-17 La Niña winter.

Full suppression mode with one the lowest daily -NAO readings for the month of September coming up with the near record +49 dm Greenland Block.

Places like Newark are on track for one of their driest Septembers on record. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Sep Click column heading to sort ascending, click again to sort descending. 1 2024 0.08 9 2 1941 0.14 0 3 2005 0.45 0 4 1951 0.95 0 5 1972 1.03 0 6 1948 1.14 0 - 1939 1.14 0 7 1931 1.19 0 8 1953 1.25 0 9 1964 1.30 0 10 1967 1.35 0

Who would have thought it would be so difficult to get another tropical system up here after Debby.

Plenty of rain out on Cape Cod with over 6.00” as the low cutoff under the record block.

This may be the first time I can remember seeing surface high pressure build west from Newfoundland to north of the Great Lakes. The highs usually start out north of the Great Lakes and move off the coast a few days later. So this really isn’t a typical looking set up. Just goes to show how extreme these blocking patterns are getting. It’s no wonder there are a number of models showing a dry slot near the area with heavier totals east and west.

I think the forecast details for the closed low positions are going to be tricky since the blocking is even stronger on the 12z run today near a record 580 dm block for Greenland. So it’s going to be challenge forecasting how much moisture can stream into the area with so much blocking to our north. Models really struggle with blocking and cutoffs. So not putting much stock yet in any rainfall details. A +48 dm 500 mb anomaly is as extreme as we have seen during September.

The GFS recent wetter solution for next week weakened the blocking ridge over the Northeast enough. Notice the upper low getting closer to the area. The tropical input also helps. New run Old run

This a new type of -PDO which is associated with record mid-latitude SST warming east of Japan to south of the Aleutians along with to the east of New England and Maritime Canada. This most recent phase began in 2017 following the shorter 2014 to 2016 +PDO which was also associated with a record marine heatwave known as the blob off the West Coast. So these record mid-latitude marine heatwaves are becoming associated the patterns which in the past didn’t have this type of extreme oceanic heat content.

They did a great job putting all the research together. https://www.science.org/doi/10.1126/science.adk3705 This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time," Tierney said. "When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm." The findings also reveal that the Earth's current global temperature of 59 degrees Fahrenheit is cooler than Earth has been over much of the Phanerozoic. But greenhouse gas emissions from human-caused climate change are currently warming the planet at a much faster rate than even the fastest warming events of the Phanerozoic, the researchers say. That speed of warming puts species and ecosystems around the world at risk and is causing a rapid rise in sea level. Some other episodes of rapid climate change during the Phanerozoic have sparked mass extinctions. Rapidly moving toward a warmer climate could spell danger for humans who have mostly lived in a 10 degree Fahrenheit range for global temperature, compared to the 45 degree span of temperatures over the last 485 million years, the researchers say. The collaboration between Tierney and researchers at the Smithsonian began in 2018. The team wanted to provide museum visitors with a curve that charted Earth's global temperature across the Phanerozoic, which began around 540 million years ago and continues into the present day. The team collected more than 150,000 estimates of ancient temperature calculated from five different chemical indicators for temperature that are preserved in fossilized shells and other types of ancient organic matter. Their colleagues at the University of Bristol created more than 850 model simulations of what Earth's climate could have looked like at different periods of the distant past based on continental position and atmospheric composition. The researchers then combined these two lines of evidence to create the most accurate curve of how Earth's temperature has varied over the past 485 million years. Another finding from the study pertains to climate sensitivity, a metric of how much the climate warms for the doubling of carbon dioxide. "We found that carbon dioxide and temperature are not only really closely related, but related in the same way across 485 million years. We don't see that the climate is more sensitive when it's hot or cold," Tierney said. In addition to Judd, Tierney and Wing, co-authors on the study are Brian Huber of the Smithsonian, Daniel Lunt and Paul Valdes of the University of Bristol and Isabel Montañez of the University of California, Davis.

The Euro has been struggling with East Coast low tracks since the blizzard miss in January 2015. The model had the big win with Sandy’s track back in 2012 and was the first model to show the Nemo phase in February 2013. This lead to the model taking on a legendary status. But there appears to have been some upgrades in 14 and 15 which caused it to struggle. The next big error was with the historic Jan 2016 snowstorm. Was too suppressed with the heavy snows forecast to remain to our south. Then other issues with low tracks being too close to the coast like the other day have been occurring. A suppressed bias has also been occurring like in early February 2021 and other more recent events. Not sure exactly changed with the model. It’s a bit unusual that it’s the top scoring model for North America and the world. But it struggles with East Coast storm tracks. Would be nice if we had someone from the modeling center join these threads and go over what they think is the issue. My guess is that it’s related to the convection scheme and interactions with the Gulf Stream and the North American landmass to the West.

Yes, I am aware of that. Unfortunately the charts on the NOAA site calculate a little differently from the CPC. But the theme is the same though the magnitudes are a little different. Even using the CPC we noticed a shift to stronger winter +NAOs since around 2015. But the AO has been very variable with record swings from positive to negative over this period. This link calculates a little differently from CPC. https://psl.noaa.gov/data/climateindices/ It would be nice if the CPC provided a way to print out the graphs. This is also why I use the 500 mb height anomaly charts to illustrate the point. Lower winter heights near Iceland since 2015 and variable heights near Greenland averaging slightly positive though as an average of big swings. The strongest blocking has actually been over the KB regions shifted toward the Russian Arctic. The vortex near Iceland has been responsible for that cold pool which shows up due to the stronger winds.

Remember that the NAO and AO have been out of sync in recent winters. Yes, most winters have had a +NAO in recent years. So it would not be a surprise if the trend continues. Most of our blocking intervals have been AO dominant with a vortex east of Greenland and a +NAO. The main takeaway with these blocking patterns has been the propensity of the Greenland blocks to link up with the Southeast Ridge. This coming event will be no different as it’s even linking up with the Southeast Ridge during a +PNA. Forecast Dominant winter pattern since 15-16 favors +NAO with vortex near Iceland. But variable AO due to blocks shifting west and linking up with the Southeast Ridge. Very large AO swings have become evident between month and season. AO and NAO blocking more in sync during the 2010-2013 era with more uniform 500mb blocking from Iceland to Greenland and no Southeast Ridge linkage. Dominant winter +NAO since 15-16 Variable AO with big swings

JFK and BDR got to within 3° of the record high today as the +8 to +11 departure will continue to shrink the monthly cool departure. CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 432 PM EDT THU SEP 19 2024 ................................... ...THE KENNEDY NY CLIMATE SUMMARY FOR SEPTEMBER 19 2024... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1948 TO 2024 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 87 259 PM 90 1983 75 12 76 MINIMUM 69 709 AM 47 1956 60 9 59 1959 AVERAGE 78 67 11 68 CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 432 PM EDT THU SEP 19 2024 ................................... ...THE BRIDGEPORT CT CLIMATE SUMMARY FOR SEPTEMBER 19 2024... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1948 TO 2024 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 85 259 PM 88 1983 74 11 74 MINIMUM 65 618 AM 42 1959 59 6 57 AVERAGE 75 67 8 66

After the lowest August 500mb heights on record for Iceland, Greenland is getting ready to experience some of its strongest 500mb blocking on record for the month of September. We have been seeing these big swings in the AO and NAO since just after 2010. So this makes extended forecasting of those indices very tricky at any interval beyond the 1 or 2 week range.

An unusual strom track is always possible when we get such extreme near record Greenland blocking.

Yeah, we want a more easterly track in order for a place like Newark to avoid the first under 1.00” month since May 2023 and July 2022. Monthly Total Precipitation for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. 2024 5.52 1.75 7.99 3.85 2.79 1.75 3.59 6.69 0.08 M M M 34.01 2023 4.31 1.41 3.32 8.07 0.89 2.66 6.26 4.27 8.31 4.02 2.91 7.55 53.98 2022 4.06 2.65 2.38 4.36 5.23 2.40 0.55

Yeah, the drier pattern here after the very wet summer is becoming evident now. Lawns have started turning brown with considerable leaf drop. Tough to get a happy medium these days between the brief dry patterns and big deluges.

Just pointing out the early September pattern. Very tough to get any year to play out exactly as a previous one especially with the evident amplitude differences going back the last several months. But I will say that some of the seasonal models lowest skill with La Nina’s in recent years seems to have been with the Western Trough details.It was one of the biggest surprises was with the 16-17 La Niña. It was as if the 15-16 super El Niño precipitation got delayed a year for California. So won’t try to pinpoint Western details this early in the game.

It was the first time that the summer 500mb ridge was this strong from east of Japan to south of the Aleutians .

After the historic flood in Suffolk last month September is off to the driest start on record at Islip. Time Series Summary for Islip Area, NY (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 2024-09-18 0.06 0 2 2019-09-18 0.33 0 - 1986-09-18 0.33 0 3 1985-09-18 0.36 0 4 1983-09-18 0.38 0 5 1979-09-18 0.49 0 6 1997-09-18 0.54 0 7 2001-09-18 0.64 0 8 1994-09-18 0.68 0 9 1965-09-18 0.69 0 10 1982-09-18 0.70 0

The September 500mb pattern so far is most similar to 2022. The 500 mb anomaly center locations are far are fairly close. But this time the Aleutian Ridge is stronger and the North Atlantic ridge east of Canada a little weaker. But its forecast to strengthen in the coming days.

We will probably need some help from the tropics next week to see a pickup in the rainfall. The best bet would be a system in the gulf with some type of inverted trough or PRE extending northward into the region. Then the rest of the forecast into early October would be contingent on development and track details.

This is another season which confirms that the big shift in the Arctic occurred with the record multiyear ice drop back in 2007. We have had over a decade now without the extended May to August dipole patterns from 2007 to 2012. But none of the years since have been able to recover back to the extent, area, or multiyear ice levels which were common before 2007. https://www.nature.com/articles/s41586-022-05686-x Manifestations of climate change are often shown as gradual changes in physical or biogeochemical properties1. Components of the climate system, however, can show stepwise shifts from one regime to another, as a nonlinear response of the system to a changing forcing2. Here we show that the Arctic sea ice regime shifted in 2007 from thicker and deformed to thinner and more uniform ice cover. Continuous sea ice monitoring in the Fram Strait over the last three decades revealed the shift. After the shift, the fraction of thick and deformed ice dropped by half and has not recovered to date. The timing of the shift was preceded by a two-step reduction in residence time of sea ice in the Arctic Basin, initiated first in 2005 and followed by 2007. We demonstrate that a simple model describing the stochastic process of dynamic sea ice thickening explains the observed ice thickness changes as a result of the reduced residence time. Our study highlights the long-lasting impact of climate change on the Arctic sea ice through reduced residence time and its connection to the coupled ocean–sea ice processes in the adjacent marginal seas and shelves of the Arctic Ocean.