bluewave

I like the Euro monthly forecasts issued on the 5th which have been doing a pretty good job compared to some of the other guidance.

Overlapping forecast signal showing up near the start of October. A more traditional Nino ridge south of Hudson Bay developing. With the lingering mid-latitude ridge underneath.

Especially with the most recent runs moving to cutoff the upper low under the big ridge.

The continuing record WWBs are making this the strongest east based event for so early in the season.

Yeah, looks like a very wet pattern coming up with lows and stalled fronts undercutting the big high to our north and plenty of easterly flow.

Yeah, we could see a subtropical or tropical system eventually form next 2 weeks somewhere to our south. Not what the waterlogged parts of the region want to hear. Even if we don’t get a well defined system, the high moisture could lead to heavy downpours with weak lows and stalled fronts.

September 500mb ridge axis continues to be much further south and stronger than past developing super El Niño events. This has lead to the record warmth across the CONUS this month. At the least the trough near the West Coast matches with the other years. But it’s a weaker area of low pressure than 1997.

More of the same since the big 2007 shift. So most years making a forecast for a minimum in the 4s has done very well. The exceptions were a little above in 2009, 2013 and 2014. The only years below 4 million sq km were 2012 and 2020. My guess is that we would need a strong dipole pattern like we saw from 2007-2012 to challenge the 2012 record. 2020 came the closest but quickly fell behind during the early August period which had the big storm back in 2012. I suppose the other possibility is that we get a really warm Arctic winter into spring some day that allows us to surpass the 2012 with a less extreme summer. But that hasn’t been the case so far as all these weak dipole summers since 2013 have made the 2012 minimum to challenging to pass. The volume remains so low with the loss of older sea ice that even a very favorable pressure pattern this summer like this one can’t get us back to pre 2005-2007 extents. While there was significant cold near the North Pole at times early this summer, it was too narrowly focused to do much. The overall Arctic was near the warmest summer on record. This became obvious with the recent record open water close to the North Pole. https://nsidc.org/sea-ice-today/analyses/new-abnormal The new abnormal THURSDAY, OCTOBER 3, 2024 Since 2007, the Arctic sea ice minimum has dropped below 5 million square kilometers (1.93 million square miles) every year, except in 2009, 2013, and 2014, when extent barely crossed the 5 million square kilometer mark. Such low extents would have been hard to imagine in the 1990s, when extent averaged 6.46 million square kilometers (2.49 million square miles). This persistent new normal, and the related losses of most of the old and thick ice, are prominent characteristics of the new, warmer Arctic—resiliently low in ice cover despite more than a decade of variations in seasonal climate patterns and oceanconditions.

Starting the day out with minimums near 70°. So the warmer minimum departures this month have been a bit more impressive than the maxes. The cool down next week follows this theme. Clouds, easterly flow, and rain will keep the maximum departures cooler than the minimum departures.

https://forecast.weather.gov/product.php?site=NWS&issuedby=OHX&product=AFD&format=CI&version=1&glossary=1 Dangerous heat is the main concern this week, especially during the afternoon hours. A powerful 6000+ meter 500 mb ridge over the region will keep conditions hot and humid with no meaningful rain potential. BNA reached a record-setting 100 degrees Tuesday and there is no reason to doubt it will happen again Wednesday as the ridge intensifies directly overhead. Record high temperatures are in jeopardy each day this week.

NYC was one of the coolest spots in the city at 57° as most other stations didn’t drop below 60°. TEMPERATURE (F) YESTERDAY MAXIMUM 72 229 PM 92 1927 77 -5 79 MINIMUM 57 621 AM 44 1873 63 -6 66 AVERAGE 65 70 -5 73 St./16th / Alphabet City 75 62 67 75 62 66 38 0.00 18 1:00am 9 12:50am 20.5 160th Ave. / Howard Beach 70 59 65 70 59 69 45 0.00 28th St. / Chelsea 75 62 67 75 62 65 41 0.00 16 4:40pm 7 8:45pm 18.3 Astoria 73 60 66 73 60 68 45 0.00 13 1:00am 6 12:55am 15.7 Bensonhurst / Mapleton 73 61 67 73 61 69 44 0.00 20.1 Blooming Grove 71 47 59 71 47 94 44 0.00 14 11:10pm 7 11:10pm 21.0 Bronx Mesonet 73 56 65 73 56 71 45 0.00 18 9:15am 9 9:15am 19.9 Brooklyn Mesonet 69 61 65 69 61 70 44 0.00 18 1:25am 11 1:45am 21.3 Brownsville 73 61 67 73 61 68 40 0.00 Corona 75 60 67 75 60 69 43 0.00 E 40th St. / Murray Hill 72 63 67 72 63 66 41 0.00 East River at Alphabet City Fresh Kills 86 41 0.00 15 2:20pm 7 12:25pm 20.9 Glendale / Maspeth 73 60 66 73 60 67 44 0.00 Gold Street / Navy Yard 73 62 67 73 62 67 42 0.00 17 1:15am 8 12:40am 21.4 Lefferts / South Ozone Park 72 60 66 72 60 68 44 0.00 Manhattan Mesonet 72 61 66 72 61 67 45 0.00 22 8:00am 12 8:00am 20.6 Mount Ivy 73 47 59 73 47 95 42 0.00 10 1:40pm 4 3:55pm 20.7 Newtown / Long Island City 74 61 67 74 61 65 40 0.00 17 1:15am 10 1:15am 19.3 Otisville Mesonet 70 42 56 70 42 99 45 0.00 13 4:15pm 8 3:20pm 20.9 Port Jervis 73 46 58 73 45 96 40 0.00 12 4:05pm 5 4:25pm 20.3 Queens Mesonet 72 59 65 72 59 70 44 0.00 19 6:30pm 11 6:30pm 20.1 Queensbridge / Dutch Kills 76 61 68 76 61 65 41 0.00 16.5 Staten Island Mesonet 71 57 64 71 57 83 44 0.00 16 12:40pm 9 2:45pm 20.1 Suffern Mesonet 71 50 60 71 50 94 44 0.00 10 2:30pm 5 11:35am 19.3 TLC Center 73 61 66 73 61 66 41 0.00 16 12:35am 12 6:55pm 21.3 Tremont / Van Nest 73 58 66 73 58 67 45 0.00

Plenty of easterly flow reducing the maxes is the main reason. It will be interesting to see if we can get a tropical connection established. Since lows often develop underneath the big highs east of New England this time of year.

Even single model forecasts have been missing the magnitudes of the ridges and the warmth underneath. But this is to be expected due to the much lower resolution and nature of long range forecasts beyond 15 days. In our rapidly warming climate there have been many more opportunities for the models to be biased too cold than too warm. So it’s beyond technology of present day weather forecast models to have been able to see the historic 600 dm ridge this week from beyond 5-10 days out.

The C3S model blend had the general temperature spatial pattern correct for the CONUS this summer. But as usual it was too cool especially where the all-time warmth occurred out West. Plus the ridge axis verified further south which has become a reoccurring theme in recent years. Many outlets that do seasonal forecasting use this blend as the basis for their forecasts which you see online. That’s why it’s a useful piece of guidance even if it often misses the magnitude of the warmth under the ridges. https://climate.copernicus.eu/charts/packages/c3s_seasonal/products/c3s_seasonal_spatial_mm_2mtm_3m?area=area06&base_time=202605010000&type=ensm&valid_time=202606010000

This record breaking 600 dm ridge is ridiculous for September.