bluewave

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.

Updated for August 2021. 8….2021….EWR…..2…..LGA…..6…..JFK……10…..BDR….3…..ISP….5

Models haven’t been of much use with the placement of the heaviest rain this summer before nowcast time. But the heavy convection signals were very good. So it will be interesting to see if they get the location right this time or we get more shifts right through 12z tomorrow. The ingredients are there for somebody in the wider MA to NE region to get near a localized 10”+ max.

Thanks. I think that setting you highlighted when a new thread is started determines what format the thread will be. So I guess it’s up to the thread starter as to how wide the columns will be. I just noticed that the various threads have different looks.

Islip beat out all the other stations in the August 90° day rankings. They finished with 7 days in 2nd place. 13 days at Newark was only good enough for the 4th highest number of days. JFK was further back in the list with only 4 days. 10 was the record there set in 2005 and 1959. Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Month of Aug Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Max Temperature >= 90 Missing Count 1 1980 8 0 2 2021 7 1 - 2016 7 0 - 2005 7 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Aug Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Max Temperature >= 90 Missing Count 1 1988 17 0 2 1959 15 0 3 2018 14 0 - 2002 14 0 - 1995 14 0 4 2021 13 1 - 2016 13 0 - 2015 13 0

JFK finished with the 11th warmest August temperature due to the sea breeze arriving earlier than the other stations which ranked higher. Time Series Summary for JFK INTERNATIONAL AIRPORT, NY - Month of Aug Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2016 78.9 0 2 2015 78.5 0 3 2005 78.4 0 4 1980 78.0 0 5 2018 77.5 0 - 1984 77.5 0 6 1978 77.4 0 - 1969 77.4 0 7 1970 77.3 0 8 2001 77.2 0 9 1995 77.0 0 10 1955 76.9 0 11 2021 76.8 1 - 1991 76.8 0 - 1959 76.8 0

Ida will be the first storm this summer that finally begins a break in the 90° heat potential. Very strong blocking for early September will develop. Long range guidance is hinting at a resurgence of the WAR by mid to late September.