bluewave

The 50s dew points are very noticeable following another top 5 highest dew point summer.

Updated for Ida https://nwschat.weather.gov/p.php?pid=202109022136-KOKX-NOUS41-PNSOKX 9-1…Staten Island……9.64…….Manhattan…..9.55……Cranford….9.05….Ida

I just posted this paper a few days ago in the increase of 10” rainfall months in our area since around 2003 thread. A recent study also found an abrupt shift to more extreme precipitation in the Northeast over this same time period. https://journals.ametsoc.org/view/journals/hydr/18/6/jhm-d-16-0195_1.xml Abstract The northeastern United States has experienced a large increase in precipitation over recent decades. Annual and seasonal changes of total and extreme precipitation from station observations in the Northeast were assessed over multiple time periods spanning 1901–2014. Spatially averaged, both annual total and extreme precipitation across the Northeast increased significantly since 1901, with changepoints occurring in 2002 and 1996, respectively. Annual extreme precipitation experienced a larger increase than total precipitation; extreme precipitation from 1996 to 2014 is 53% higher than from 1901 to 1995. Spatially, coastal areas receive more total and extreme precipitation on average, but increases across the changepoints are distributed fairly uniformly across the domain. Increases in annual total precipitation across the 2002 changepoint are driven by significant total precipitation increases in fall and summer, while increases in annual extreme precipitation across the 1996 changepoint are driven by significant extreme precipitation increases in fall and spring. The ability of gridded observed and reanalysis precipitation data to reproduce station observations was also evaluated. Gridded observations perform well in reproducing averages and trends of annual and seasonal total precipitation, but extreme precipitation trends show significantly different spatial and domain-averaged trends than station data. The North American Regional Reanalysis generally underestimates annual and seasonal total and extreme precipitation means and trends relative to station observations, and also shows substantial differences in the spatial pattern of total and extreme precipitation trends within the Northeast. 1. Introduction Multiple studies have found increasing total and extreme precipitation across the northeastern United States (Kunkel et al. 2013a; Peterson et al. 2013; Hayhoe et al. 2007), and extreme precipitation events have increased faster over the Northeast region than in any other part of the United States (Kunkel et al. 2013a). Hayhoe et al. (2007) found an increase of 10 mm decade−1 in annual total precipitation from 1900 to 1999 using the 93 stations in the U.S. Historical Climatology Network in the states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, and Pennsylvania. Using the U.S. Climate Divisional Dataset, version 2, over the domain of Hayhoe et al. (2007) plus Maryland, Delaware, West Virginia, and Washington, D.C., Kunkel et al. (2013b) found a 10.2 mm decade−1 increase in annual total precipitation over 1895–2011. However, across a similar time period (1901–2000) as Hayhoe et al. (2007), Walsh et al. (2014) and Kunkel et al. (2013b) found a trend of approximately 5.6 mm decade−1. Extreme precipitation events have also been increasing across the Northeast, both in intensity and frequency, particularly over the past three decades (Walsh et al. 2014; Kunkel et al. 2013a; Hoerling et al. 2016). This increase in extreme precipitation events is consistent with expected impacts of climate change on precipitation, primarily more extreme events driven by the ability of the atmosphere to hold more water as described by the Clausius–Clapeyron relationship (e.g., Trenberth 1998; Mishra et al. 2012; Prein et al. 2017). Kunkel et al. (2013a) found significant increases in both 2-day precipitation events that occur once every 5 years and the amount of precipitation falling on the 1% wettest days during the time period 1957–2010 for the Northeast. Hoerling et al. (2016) discovered a 2%–3% increase per decade in both the total amount and frequency of heavy precipitation events (5% wettest days) in the Northeast over 1901–2013, with the increases in heavy precipitation total amount, frequency, and intensity accelerating after 1979. Walsh et al. (2014) also evaluated trends in the amount of precipitation falling in the Northeast on the 1% wettest days using the Global Historical Climatology Network-Daily (GHCN-D) dataset, finding a striking increase of 71% from 1958 to 2012. Given the growing consensus on the recent dramatic increase of extreme precipitation across the Northeast, our motivation is to explore the temporal and spatial attributes of precipitation increases in greater detail, as well as to assess the ability of gridded observational and reanalysis datasets to capture this precipitation increase. Specifically, we add to this literature by 1) assessing the sensitivity of total and extreme precipitation changes to the time period of analysis [sections 3a(1), 3a(3)]; 2) exploring the spatial distribution of total and extreme precipitation across the Northeast [sections 3a(2), 3a(4)]; 3) analyzing seasonal changes in total and extreme precipitation [section 3a(5)]; and 4) evaluating the consistency of means and trends in precipitation across station, gridded, and reanalysis data (section 3b). 4. Conclusions Over the 1901–2014 station observational record in the Northeast, we find a significant 6.8% (0.6% decade−1) increase in annual total precipitation and a much larger 41% (3.6% decade−1) increase in annual extreme precipitation. However, a key conclusion of our study is that the recent increases in annual total and extreme precipitation in the Northeast are best characterized as abrupt shifts in 2002 and 1996, respectively, rather than long-term increases over several decades as could be implied from a linear trend. While the pre-changepoint trends in annual total (1901–2001; −1.6 mm decade−1) and annual extreme (1901–95; 0.1 mm decade−1) precipitation are not statistically significant, total precipitation from 2002 to 2014 was 13% higher than from 1901 to 2001 and extreme precipitation from 1996 to 2014 was 53% higher than from 1901 to 1995, with both increases being statistically significant. The fact that these wetter periods both abut the end of our record in 2014 means that any long-term linear trends are highly dependent on their start date and should therefore be interpreted with caution, particularly when extrapolating into the future. Of note, the recent 2015–16 drought in the Northeast is not included in our analyses, although it is not likely to change the significance of the post-changepoint increases. Spatially, we find that the increases in annual total and extreme precipitation are widespread across the Northeast domain, with the exception of smaller increases and even some significant decreases to the east of Lake Erie, and in the southern part of the domain in West Virginia, Maryland, and Delaware. Our seasonal analysis reveals that fall and summer total precipitation have statistically significant increases after changepoints in 2002 and 2003, respectively, suggesting that they contribute to the annual total precipitation changepoint in 2002. The extreme precipitation increase across the 1996 changepoint is associated with 83% and 85% increases in spring and fall extreme precipitation, respectively, and may indicate common atmospheric forcing of spring and fall extreme precipitation in the mid- to late 1990s. The increase in fall precipitation across the 1995 changepoint is consistent with the finding of Kunkel et al. (2010) that increased heavy precipitation associated with tropical cyclones after 1994 is an important driver of the overall increase in extreme precipitation. Our ongoing investigations into the underlying dynamical causes for Northeast annual total and extreme precipitation increases are focusing on these critical time periods in the late 1990s and early 2000s. Our comparison of spatial and temporal extreme precipitation patterns in station (GHCN-D), gridded (LI2013), and reanalysis (NARR) datasets shows that LI2013 is more consistent with station data than NARR. LI2013 reasonably captures the mean (within 2%) and seasonality (within 11%) of GHCN-D extreme precipitation, but contains significant differences in its trends. NARR underestimates regionally averaged extreme precipitation across all seasons by 1%–16%, and the annual extreme trends show significant differences in their spatial distribution, particularly over New England. Perhaps more importantly, both the NARR and LI2013 annual extreme time series have no significant changepoints. LI2013 does, however, reproduce GHCN-D regionally averaged annual and seasonal total precipitation within 5% (and usually within 3%), and its trends faithfully capture those from station observations both across the region and averaged over the Northeast. In addition, LI2013 has a changepoint in 2003, only one year later than the changepoint identified in GHCN-D annual total precipitation. However, NARR underestimates annual and seasonal total precipitation by 3%–10% and has annual total precipitation trends that are a factor of 2–9 times smaller than GHCN-D trends. Spatially, NARR is also less accurate than LI2013, with decreasing 1979–2014 trends over much of the coastal and western portions of the domain where GHCN-D trends are positive. This comparison of LI2013 and NARR to GHCN-D provides important information on the strengths and limitations of these products for use in analyzing hydroclimate, forcing climate impacts models, and identifying drivers of total and extreme precipitation.

Break in the heat following the historic rainfall and flooding. But looks like a temperature rebound by mid-September. Tough to sustain a cooler to near normal pattern for extended periods. EPS 9-6 to 9-13 9-13 to 9-20

Flemington,NJ Cocorahs at 11.00”. Daily Precipitation Report Station Number: NJ-HN-58 Station Name: Flemington 2.9 ESE Observation Date 9/2/2021 7:00 AM Submitted 9/02/2021 8:09 AM Total Precip Amount 11.00 in. Notes -- Taken at registered location Yes Snow Information New Snow Depth NA New Snow Water Equivalent NA Total Snow Depth NA Total Snow Water Equivalent NA Duration Information Precipitation Began -- Precipitation Ended -- Heavy Precip Began -- Heavy Precip Lasted -- Duration Time Accuracy -- Additional Information Additional Data Recorded No Submitted 9/02/2021 8:09 AM Flooding --

I am guessing that some spots may have approached 1000 year rainfall levels. NYC recorded a 500 year return interval for our old climate. But these return intervals will be shorter in our wetter climate.

The HREF was the only piece of guidance that had the 10”+ potential correct. Notice how tucked in near the 1-95 corridor it was. The team of scientists that developed this system deserves an award. Most impressive model performance in an extreme event since the Euro in Sandy.

Lambertville, NJ just one of the many parts of the area to get historic flooding.

1.08” in 10 min at SI mesonet. https://www2.nysmesonet.org/weather/meteogram#network=nysm&stid=stat

10.52” at Harrison. PRECIP ACCUM 10.52 in PRECIP RATE 6.25 in/hr https://www.wunderground.com/dashboard/pws/KNJHARRI36/table/2021-09-1/2021-09-1/daily

Very busy evening for the rescue crews.

4.27” already at the Harrison, NJ wxflow. https://www.wunderground.com/dashboard/pws/KNJHARRI36/table/2021-09-1/2021-09-1/daily 7:45 PM 66.4 °F 64.0 °F 92 % South 7.4 mph 17.2 mph 29.55 in 2.18 in 4.27 in

One of the many flash flood reports coming in:

This is the storm report:

CAMS like the HREF are doing a great job on how rapidly the convection would fill in ahead of Ida this evening. The HREF was the only model to indicate that this would go 10”+ in the wettest spots.

Several 5”+ reports in PA. Bedford County... Saxton 5.10 in 0130 PM 09/01 CWOP Blair County... Claysburg 5.52 in 0135 PM 09/01 CWOP AWS ...Lancaster County... Middletown 5.66 in 0131 PM 09/01 CWOP

The heaviest snowfall axis for January 2015 would up about 60 miles further east than forecast the day before. I believe that is within the margin of error for 24 hr model forecasts. We only noticed this since NYC is the most densely populated part of the country. A similar miss out on the Great Plains would hardly make news since it could easily fall between the spread out population centers. January 2000 was my most recent memory of a big model bust. The forecast the day before was for no storm at all for NC up to New England. Parts of the NC had one of their biggest snowstorms on record. Jan 87 was a big model bust since we got 10” of snow instead of modeled snow quickly changing to rain. Jan 20, 78 had a nighttime forecast of rain heavy at times. But 12-18” of snow verified the next morning. So most of the model misses since the 2000 event have been minor in comparison. There were many other examples in the pre-1990 era of winter storm warming’s that verified as partly sunny or the moon visible through a thin cloud layer.

Actual busts are pretty rare in the age of better modeling. Models do a great job at identifying when heavy precipitation potential exists for the region. It’s just very difficult to pinpoint the exact locations for summer convection and winter snowstorm banding. Since I grew up in the 70s and 80s, one of my definitions off a bust is the models completely missing a storm. The most recent example of this was models the day before the Jan 25, 2000 snowstorm forecasting no precipitation here. Another type of bust is getting the p-type wrong. Like the January 2008 event that would up mostly rain instead of snow. These two types of model busts were par for the course before the early 90s. While January 2015 was a big forecast amount miss, the blizzard just shifted to a further east part of the forum. NYC got lower amounts than forecast but still a significant snow. So all I really need to see from a model in the warm season is being correct with the the general heavy convection signal. I have learned to be patient on where the specific heaviest rainfall verifies. We often need to rely more on nowcast location of mesoscale features.

Localized 10”+ where the best training of convection sets up. Since the rainfall rates will be so extreme, areas near and west of NYC could see most of their rainfall accumulation between 0z and 6z. The storm should be well to our east by early on Wednesday.

HREF has its localized 10”+ potential just north and west of a line from Philly to NYC and NE into SNE.