bluewave

The -PDO composite was a great match for this summer. The composites below are for a +PDO pattern in summer and winter. So they have to be reversed. The classic -PDO is a ridge south of the Aleutians and east of New England during the summer. We got one of the strongest ridges on record south of the Aleutians and east of New England. So if this -PDO state continues through the winter then it would feature a strong Aleutian Ridge and Southeast Ridge. Pretty much identical to a robust La Niña 500 mb atmospheric response. We would need to get some type of mismatch like we saw in 21-22 when the MJO 8 shifted us away from the La Niña and -PDO background for January and gave us at least one good winter month even if the winter was still warmer overall the Northeast. Otherwise, the inverse of the below composite would prevail. We probably need to see how things go in October to get some better hints. +PDO summer 500 mb pattern needs to be reversed for -PDO Summer 2024 strong -PDO +PDO winter composite needs to be reversed like summer was

The upper atmosphere warmed faster than the surface leading the record low lapse rates. So this August 20th to 31st is unusually quiet. Last year over the same period we had 6 named storms form. But the record SSTs around the Gulf are concerning since it will only take one wave to get in there and rapidly deepen. So it will be interesting to see how the rest of the season goes as we approach the peak. Hurricane seasons are mostly evaluated on land impacts which are largely unknown until we reach the peak later in the season.

The wild card for ACE this season may be the upper atmosphere warming faster than the surface. So we’ll have to see what happens once we reach the peak of the season in September. This may be why most of the other developing La Niña summers since 1995 had major hurricanes between August 20th and 31st without any this year. Perhaps if the upper atmosphere begins to cool off faster we’ll see an uptick in activity during the coming weeks. The record SSTs in the Gulf are concerning for any waves that can find a way in there since they could rapidly intensity. I know we like to focus on total ACE for judging a season but in actuality it’s mostly about landfall impacts which are usually a big unknown until we reach the heart of the season. So as always it only takes one hitting a populated area to have a big season regardless of ACE or total storm counts. La Niña years since 1995 major hurricanes August 20th September 1st 2022….none 2021….Ida….Cat 4…..Larry Cat 3 2020…Laura Cat 4 2017….Harvey Cat 4…Irma Cat 5 2016….Gaston Cat 3 2011….Irene Cat 3 2010…Danielle Cat 4….Earl Cat 4 2008….Gaston Cat 4 2007…..Dean….Cat 5 2005…..Katrina Cat 5 2000…..none 1999…..Brett Cat 4….Cindy Cat 4 1998…..Bonnie Cat 3 1995…..Louis Cat 4

After the big ACE jump with Beryl earlier in the season the ACE will be closer to average near the start of September. https://kouya.has.arizona.edu/tropics/index.html

A large number of stations over 10.00” on the month. Monthly Data for August 2024 for Upton NY NWS CWA Click column heading to sort ascending, click again to sort descending. NY PORT JEFFERSON STATION 0.3 SSW CoCoRaHS 15.58 CT NEWTOWN 4.6 SE CoCoRaHS 15.45 NY ST. JAMES COOP 15.16 CT NEWTOWN 5.3 S CoCoRaHS 13.58 CT NAUGATUCK 1.7 NNE CoCoRaHS 13.29 CT SOUTHBURY 2.3 W CoCoRaHS 12.70 CT STAMFORD 1.0 S CoCoRaHS 12.70 NY CENTEREACH 1.3 NE CoCoRaHS 12.64 NJ NORTH ARLINGTON 0.7 WNW CoCoRaHS 12.35 CT RIDGEFIELD 2.4 NNE CoCoRaHS 12.29 CT DANBURY COOP 12.24 CT BETHEL 4.5 SSE CoCoRaHS 12.01 CT RIDGEFIELD 3.7 NNE CoCoRaHS 12.00 CT MONROE 0.8 W CoCoRaHS 11.97 CT RIDGEFIELD 3.6 N CoCoRaHS 11.74 CT NEW CANAAN 3.8 N CoCoRaHS 11.66 NJ MAPLEWOOD TWP 0.9 SE CoCoRaHS 11.59 NY SETAUKET-EAST SETAUKET 0.7 SSW CoCoRaHS 11.54 CT HERITAGE VILLAGE 0.2 E CoCoRaHS 11.00 CT BETHEL 3.5 NNE CoCoRaHS 10.94 NY MOUNT SINAI COOP 10.85 NJ MONTVALE 1.8 ESE CoCoRaHS 10.81 CT BROOKFIELD 3.3 SSE CoCoRaHS 10.78 NJ WANAQUE RAYMOND DAM COOP 10.66 CT BETHEL 0.5 E CoCoRaHS 10.64 NJ OAKLAND 1.0 ESE CoCoRaHS 10.55 NJ CHARLOTTEBURG RESERVOIR COOP 10.47 CT PROSPECT 1.9 ENE CoCoRaHS 10.25 NJ MONTCLAIR 0.7 N CoCoRaHS 10.22 NY SELDEN 1.6 ESE CoCoRaHS 10.13 NJ LITTLE FALLS TWP 0.5 WNW CoCoRaHS 10.12 NJ WAYNE TWP 0.8 SSW CoCoRaHS 10.11

At least we were able to balance out the 60°+ warmth with blizzards the next day prior to recent years. But the last few years it has just been 60s and no snow. Hard to believe our last actual winter month was in January 2022. https://www.weather.gov/okx/Blizzard_Feb92017 The day before the blizzard (Wednesday February 8), record warmth was observed across the Tri-State area. Record highs ranged from 62 at Central Park, NY to 65 at Newark, NJ. Temperatures dropped 30-40 degrees in 12-15 hours as readings were in the middle-upper 20s during the height of the blizzard.

The reason the blocking in December 22 and March 23 didn’t work was due to it linking up with the Southeast Ridge. In the 50s to early 70s when we had much cooler SSTs along the East Coast a deep -PNA trough out West also had a trough near the East instead of Southeast Ridge. These days we need to establish a +PNA first to keep the Southeast Ridge in check for -NAO -AO intervals. Remember the strong +PNA in December into January 20-21 worked in concert with the -AO keeping the trough near the East Coast. But even the +PNA -AO allowed a more south based blocking than usual with the record SSTs east of New England so BGM got the 40” record snowfall instead of NYC to Boston. The low was too tucked in near ACY for the coast to jackpot. But due to the early season +PNA trough lingering near the East Coast when the PNA turned negative in late January, it was the only time in the 2020s that the coast had over 12” around NYC with a -PNA. The snowy January 2022 was all on the -EPO+PNA MJO 8 pattern even though the AO was more positive. But this favored the coast on Long Island over areas just west of NYC which didn’t do as well.

Wednesday could be the first EML of the summer. So we’ll have to monitor for severe once within the range of the CAMS. Could be a decent MCS pattern from the Great Lakes into the Northeast.

He is going to have to update this map.

Near record 500 mb ridge for late August building to our west next few days with our next heatwave. Low 90s possible Sunday into Monday. Then mid 90s possible by around Wednesday for the usual warm spots.

The Pacific Ridge pattern or Aleutian ridge as it’s also called was displaced a little further SW this June and July. So a bit of a hybrid pattern also allowing a ridge in the PNA region. The 500 MB anomaly just west of the Dateline was the highest on record for June and July. Another case of record breaking 500 mb height anomalies which have become so common. That’s roughly where the winter ridge axis has been since the 15 -16 super El Niño. https://simonleewx.com/north-american-weather-regimes/

The better La Niña winters for snowfall were associated with very high ACE and storm totals. Not exactly sure whether it was a cause and effect relationship or they were both just part of the same pattern with another underlying cause. 2005…second most active hurricane season for ACE at 245 with the 2nd highest named storms at 28. 1995…227 ACE which was 5th highest with 19 named storms 2017…224 ACE which was 6th highest 2020..180 ACE….With the highest named storm count at 30 2010…165 ACE…with 19 named storms

2023 and 2017 were the only summers a little cooler than average since the super El Niño in 2015. So we have had 9 out of 9 warmer to record warmer winters and 8 out of 10 warmer than average to record warm summers.

The Euro seasonal had a good summer forecast. The smaller cool spot was centered further north over the Midwest rather than down near Texas. This cooler in the middle and warmer near the coasts has been the summer temperature pattern since the 15-16 super El Niño.

Record breaking 100” of precipitation since last July in parts of the area. Data for July 1, 2023 through August 23, 2024 Click column heading to sort ascending, click again to sort descending. CT PROSPECT 1.9 ENE CoCoRaHS 100.47 CT NEWTOWN 4.6 SE CoCoRaHS 98.18 CT NAUGATUCK 1.7 NNE CoCoRaHS 97.40 CT BROOKFIELD 3.3 SSE CoCoRaHS 96.58 CT SOUTHBURY 2.3 W CoCoRaHS 95.62 CT MIDDLEFIELD 1.4 W CoCoRaHS 95.48 NY WEST POINT COOP 94.95

It looks this season will have 5 named storms by September 1st as the Atlantic experiences break in the action for late August. All the seasons that have made it to 19 or more named storms since 1995 had at least 7 named storms by September 1st and most 11 or more. But the concern going forward is how warm the Gulf Of Mexico is. Any tropical wave that makes it in there could rapidly intensify. It only takes one major hitting a populated area to have a big hurricane season regardless of total numbers or ACE. But actual land impacts for any given season are very challenging to forecast before the season starts. 19 or more named storms since 1995 and storm count by September 1st 2024…..5 projected named storms by September 1st 2023…..11 named storms by September 1st and 20 total named storms 2021…..12 named storms by September 1st and 21 total named storms 2020….14 named storms by September 1st and 30 total named storms 2012….12 named storms by September 1st and 19 total named storms 2011….11 named storms by September 1st and 19 total named storms 2010….7 named storms by September 1st and 19 total named storms 2005….13 named storms by September 1st and 28 total named storms 1995….12 named storms by September 1st and 19 total named storms

This is a continuation of the theme needing record blocking and rainfall to get a briefly cooler pattern. Looks like we go back to the usual warmer near the coast and cooler over the Midwest later August into early September. So more 90° potential for the regular warm spots in NJ. Record blocking north of Hudson Bay with cool down. More 90° heat potential from ensembles for the usual warm spots in NJ Midwest cool and warmer Northeast as we head into September

46° at FOK with the strong radiational cooling. https://www.weather.gov/wrh/timeseries?site=kfok

The MDR SSTs have come down a bit since Beryl but are still high relative to before 2023 which set the second.

The upper low was so strong that today was once of the lowest departures of the year in NYC. Departures of -10 or lower have been pretty rare this time of year. This is even more unusual since the daily departure of -11 isn’t that much lower than the lowest of the year at -12.8 on January 17th. TEMPERATURE (F) TODAY MAXIMUM 73 237 PM 96 1955 83 -10 88 MINIMUM 57 532 AM 53 1922 69 -12 73 AVERAGE 65 76 -11 81 2024-01-17 24 17 20.5 -12.8

You know it’s an impressive cold pool when we are able to get convection with dew points in the 40s this time of year.

The La Niña background state is so strong that it’s actually creating easterly shear in the Atlantic. This is why the models are quiet for late August instead of very active which we usually see during La Ninas. So we’ll have to wait until September for our next period of tropical development. https://michaelrlowry.substack.com/p/the-bell-has-rung-so-why-are-forecast Too much of a good thing? As regular readers of this newsletter know, wind shear – the change in wind direction or speed with altitude – is one of the big hurdles to tropical development. Typically it’s the strong winds at upper levels (30,000-40,000 feet) which blow from west to east (known as upper-level westerlies) through the deep tropical Atlantic and the Main Development Region or MDR that create most of the wind shear issues. So when upper-level winds in the tropical Atlantic turn more east-to-west (easterly winds) and against the west-to-east grain, it usually helps to reduce wind shear, which in turn favors hurricane development. This is especially true during La Niña years like we’re experiencing and when rising air settles in over Africa and the North Indian Ocean as it has recently – a big upper-level disturbance we track across the tropics called the Madden Julian Oscillation or MJO. The combination of La Niña with the part of the MJO that usually reduces wind shear would normally suggest a conducive period for development. However, the upper-level winds have switched so far out of the east that they’re creating easterly wind shear issues across the Atlantic, an unusual problem not often seen in the basin. It means that the MJO will need to move to a less conducive phase to bring back the seasonal upper-level westerlies and tamp down on easterly shear issues plaguing the basin right now. The easterly shear is also worsened by the low-level westerly winds from the northward displaced ITCZ we discussed earlier. The MJO naturally propagates eastward across the globe and extended range models are already showing the easterly shear issues abating toward the end of the month. So when will activity pick back up? Putting all the pieces together, it should be another week or two before the current impediments clear out. It’s possible our next spurt of activity is delayed until the beginning of September, but we should see the transition as August comes to a close late next week. Traditionally 70% of tropical activity, including most hurricane formations, happens from September onward. Still a long way to go in the game, but for now we’ll soak up the unforeseen late August lull.

First time in August since 2012 that the CT Shoreline dropped to 55° or lower as the surrounding sites did. https://www.weather.gov/wrh/timeseries?site=kbdr Time Series Summary for Bridgeport Area, CT (ThreadEx) - Month of Aug Click column heading to sort ascending, click again to sort descending. 2024 55 11 2023 59 0 2022 60 0 2021 60 0 2020 59 0 2019 57 0 2018 59 0 2017 58 0 2016 59 0 2015 60 0 2014 58 0 2013 56 0 2012 55 0