bluewave

Development of convection that holds together is always the wild card in determining our wind gust potential in these situations. The gradient looks tight enough for southerly gusts in the 40-50 mph range on Long Island ahead of the front. Could see similar winds immediately behind the front. But more significant gusts usually require an intense squall line holding together that can mix down the stronger winds. Either way, the leaf blowers should be busy this weekend.

Daniel Swain is probably one of the best sources of information on this topic. While all these California wildfire posts probably belong in a different thread, the information below helps people understand the issues involved. https://insideclimatenews.org/news/13112018/california-deadly-wildfires-climate-change-dry-autumn-late-rainy-season-swain-interview What does the recent data show in California? And how are these changes impacting overall rainfall? We are starting to see a trend towards drier autumns in California. It's somewhat new, it's just emerging from the noise, one might say, but it is actually there. This year is going to add another data point in that direction. It matches climate projections. There has long been an expectation that California's so-called shoulder season precipitation would probably decrease—that's autumn and spring. Now what we're starting to see is, especially in the autumn, that process now appears to be underway. It's both an emerging observation but also a projection for the future, a future that maybe isn't really the future any more. That actually doesn't necessarily mean the overall amount of precipitation is decreasing. There's a growing overall concentration of water in the rainy season. Our research suggests that concentration will be a pretty strong indicator of California's future climate. You've made the point that it's problematic to ask whether climate change causes a specific event. Why is that? In any sort of natural system there's never really, in any context, a singular cause of anything. It depends how you define causation, which then is a non-trivial task. It ends up being more meaningful to say, look, we're going to have fires no matter what. Whether they're caused naturally by lightning, by totally innocent human error or by more malicious human intent. It doesn't really matter what started the fire. But the question is, what factors contribute to what happened after the fire starts. The real question is not so much what caused it, because ultimately it doesn't really matter. The question is what made it as bad as it was. Then you can get an answer that, yes, there is a link between wildfire behavior intensity and climate change. As climate change progresses, what is expected to happen with wildfire season? When it comes to wildfire trends, the last five years in California have really been something else. It's really been hard to watch. it's pretty rare to see such large, dramatic step changes as what we've seen in California in the last five to 10 years. We've broken every record, and we've broken them several times. Largest, most destructive, deadliest—all

Dewpoints may approach near record high levels in spots for so late in the season with the Halloween storm. The highest dewpoint that I could find at JFK for November is 65 degrees. The Euro gets close to this early on the 1st. A tropical air mass could also be more convective. So we have to monitor later runs for convection strong enough to mix down the extremely strong LLJ in the heaviest downpours.

Probably the most extreme temperature dipole across the the US for the month of October.

https://www.pnas.org/content/early/2019/10/15/1911130116 PNAS first published October 21, 2019 Significance How the magnitude of El Niño will change is of great societal concern, yet it remains largely unknown. Here we show analysis of how changing El Niño properties, due to 20th century climate change, can shed light on changes to the intensity of El Niño in the future. Since the 1970s, El Niño has changed its origination from the eastern Pacific to the western Pacific, along with increased strong El Niño events due to a background warming in the western Pacific warm pool. This suggests the controlling factors that may lead to increased extreme El Niño events in the future. If the observed background changes continue under future anthropogenic forcing, more frequent extreme El Niño events will induce profound socioeconomic consequences. Abstract El Niño’s intensity change under anthropogenic warming is of great importance to society, yet current climate models’ projections remain largely uncertain. The current classification of El Niño does not distinguish the strong from the moderate El Niño events, making it difficult to project future change of El Niño’s intensity. Here we classify 33 El Niño events from 1901 to 2017 by cluster analysis of the onset and amplification processes, and the resultant 4 types of El Niño distinguish the strong from the moderate events and the onset from successive events. The 3 categories of El Niño onset exhibit distinct development mechanisms. We find El Niño onset regime has changed from eastern Pacific origin to western Pacific origin with more frequent occurrence of extreme events since the 1970s. This regime change is hypothesized to arise from a background warming in the western Pacific and the associated increased zonal and vertical sea-surface temperature (SST) gradients in the equatorial central Pacific, which reveals a controlling factor that could lead to increased extreme El Niño events in the future. The Coupled Model Intercomparison Project phase 5 (CMIP5) models’ projections demonstrate that both the frequency and intensity of the strong El Niño events will increase significantly if the projected central Pacific zonal SST gradients become enhanced. If the currently observed background changes continue under future anthropogenic forcing, more frequent strong El Niño events are anticipated. The models’ uncertainty in the projected equatorial zonal SST gradients, however, remains a major roadblock for faithful prediction of El Niño’s future changes. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL083906?af=R First published: 25 October 2019 Abstract The El Niño‐Southern Oscillation (ENSO) represents the largest source of year‐to‐year global climate variability. While earth system models suggest a range of possible shifts in ENSO properties under continued greenhouse gas forcing, many centuries of preindustrial climate data are required to detect a potential shift in the properties of recent ENSO extremes. Here, we reconstruct the strength of ENSO variations over the last 7,000 years with a new ensemble of fossil coral oxygen isotope records from the Line Islands, located in the central equatorial Pacific. The corals document a significant decrease in ENSO variance of ~20% from 3,000 to 5,000 years ago, coinciding with changes in spring/fall precessional insolation. We find that ENSO variability over the last five decades is ~25% stronger than during the preindustrial. Our results provide empirical support for recent climate model projections showing an intensification of ENSO extremes under greenhouse forcing. Plain Language Summary Recent modeling studies suggest El Niño will intensify due to greenhouse warming. Here, new coral reconstructions of the El Niño‐Southern Oscillation (ENSO) record sustained, significant changes in ENSO variability over the last 7,000yrs, and imply that ENSO extremes of the last 50 years are significantly stronger than those of the pre‐industrial era in the central tropical Pacific. These records suggest that El Niño events already may be intensifying due to anthropogenic climate change. Key Points Line Island corals provide 1,751 years of monthly‐resolved ENSO variability from the mid‐Holocene to present ENSO strength is significantly weaker between 3,000 and 5,000 years ago compared to the 2,000‐year periods both before and after ENSO extremes of the last 50 years are significantly stronger than those of the pre‐industrial era in the central tropical Pacific

If the EPS is correct about the early month cold pattern, then perhaps NYC gets the first freeze by the 15th. This has been the case during the last 2 years. Frost/Freeze Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Season Length Minimum 03-23 (2017) 11-06 (2012) 215 Mean 04-01 11-21 234 Maximum 04-16 (2014) 12-10 (2011) 255 2018 04-09 (2018) 32 11-14 (2018) 32 218 2017 03-23 (2017) 23 11-10 (2017) 25 231 2016 04-10 (2016) 31 12-09 (2016) 29 242 2015 04-01 (2015) 32 11-24 (2015) 32 236 2014 04-16 (2014) 31 11-18 (2014) 24 215 2013 03-23 (2013) 32 11-12 (2013) 31 233 2012 03-27 (2012) 30 11-06 (2012) 31 223 2011 03-29 (2011) 31 12-10 (2011) 32 255 2010 03-27 (2010) 29 12-04 (2010) 32 251

November has been the only fall month this decade able to generate any cold in our area. The count is 5 colder than normal Novembers to 4 warmer since 2010. So the trough coming east with colder temperatures early in the month matches this new fall climo. But can the colder pattern persist beyond the early part of the month? 2010’s November temperature departures Nov....EWR...NYC...LGA 2018...-3.1....-3.3....-2.7 2017...-.0.7....-1.1....-0.3 2016...+2.9...+2.1...+4.1 2015...+5.2...+5.1...+5.0 2014...-2.9....-2.4....-2.9 2013...-2.4....-2.4....-2.8 2012...-3.5....-3.8....-3.2 2011..+4.1...+4.2...+3.8 2010..+0.5....+0.2...+1.1

HPN went from 2nd driest September to 8th wettest October so far. Time Series Summary for WESTCHESTER COUNTY AP, NY - Month of Sep Click column heading to sort ascending, click again to sort descending. Rank Year Total Precipitation Missing Count 1 2009 0.60 0 2 2019 0.72 0 3 2014 0.75 2 4 1948 1.13 0 5 1986 1.15 0 6 1990 1.23 0 7 1964 1.37 0 8 2013 1.38 0 Time Series Summary for WESTCHESTER COUNTY AP, NY - Month of Oct Click column heading to sort ascending, click again to sort descending. Rank Year Total Precipitation Missing Count 1 2005 15.66 0 2 1955 13.85 0 3 1983 10.20 0 4 1989 9.81 0 5 1995 8.27 0 6 1996 8.12 0 7 2006 7.90 0 8 2019 7.30 4

Models coming close to 2.00” PWATS all the way up into New England.

The most impressive part of the Euro run is the early Friday squall line. Wind gusts over 50 mph and very heavy downpours.

Highest rainfall total in CT again. https://nwschat.weather.gov/p.php?pid=201910280141-KOKX-NOUS41-PNSOKX WESTPORT 3.04 801 PM 10/27 CWOP

No surprise that the models are correcting warmer for Halloween from earlier forecasts. Looks like the warm spots can make it to 70 later on the 31st into early on the 1st. Low topped squall potential with gusty winds and heavy downpours early on the 1st. The SE Ridge continues to overperform.

Euro has our next shot at 70 around Halloween. w

Another new hurricane record to add to the list.

70 degrees now at LGA with breaks of sun. http://wxweb.meteostar.com/meteogram/link.shtml?choice=Klga

Looks like their wettest October of the decade. They pulled ahead of 1990 for 8 wettest October. Time Series Summary for WESTCHESTER COUNTY AP, NY - Month of Oct Click column heading to sort ascending, click again to sort descending. Year Total Precipitation Missing Count 2019 7.18 4 2018 4.50 0 2017 4.99 0 2016 3.47 1 2015 4.07 0 2014 5.31 0 2013 0.86 0 2012 4.61 0 2011 4.90 0 2010 4.70 0

Lightning detection picked up lightning in Nassau.

Heavy thunderstorms on Long Island with the back edge coming through.

The heaviest downpours should come near the back edge early this afternoon. Thunderstorms developing now to our SW.

Yeah, the back edge of the cloud deck may be crossing eastern sections around sunset.

The HRRR has sun and 70+ in NJ by around 3 pm. Clearing a few hours later further to the east.

The warm and wet SE Ridge pattern rolls on. Many stations in Florida are experiencing their warmest October on record. We weren’t alone this month with the latest 95 degree heat on record.

Posters will be happy as long as we don’t get one in late December like 2013 and 2015. First/Last Summary for NEWARK LIBERTY INTL AP, NJ Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year First Value Last Value Difference Minimum 02-18 (2011) 10-22 (2012) 223 Mean 03-15 11-17 246 Maximum 04-13 (2015) 12-24 (2015) 282 2019 03-15 (2019) 77 - - - 2018 02-21 (2018) 80 11-02 (2018) 73 253 2017 02-24 (2017) 74 11-03 (2017) 76 251 2016 03-09 (2016) 82 11-03 (2016) 74 238 2015 04-13 (2015) 71 12-24 (2015) 71 254 2014 04-11 (2014) 77 11-24 (2014) 74 226 2013 04-08 (2013) 72 12-22 (2013) 71 257 2012 03-08 (2012) 72 10-22 (2012) 71 227 2011 02-18 (2011) 71 11-28 (2011) 72 282 2010 03-18 (2010) 71 10-28 (2010) 76 223

We get warm sectored later in the day after the rain ends. Deep SW flow and 850 mb temps around +15C. Best chance of 70 may be the usual warm spots in NJ.

Euro has a very wet and mild Sunday. Rainfall totals in the 1 to 2 inch range with highs near 70.