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On 4/11/2024 at 5:59 PM, LibertyBell said:

it's why our summers don't have the length of heatwaves they used to.  Look at the length of heatwaves from the 50s to the 90s vs what passes for heatwave now-- the differences are eyeopening.

 

Interesting. I don't see much evidence for this, but [assuming you are using data from first-order sites to draw this conclusion] it seems to coincide with the move to automated weather observing systems. 

Based on a study of 76 first-order sites from September 1, 1994 to August 31, 1995, ASOS averaged +0.79F COOLER* than the temperatures measured from conventional hygrothermometers - more specifically 0.90F COOLER for daytime maxima and 0.66F COOLER for overnight minima. Of the 76 sites studied, all but nine had a cooling bias with the installation of the ASOS. The study estimated +0.53F as a systemic bias, with an additional +0.37F bias due to improper solar shielding in the conventional hygrothermometer in the daytime, and an additional bias of +0.13F [but variable] for overnight temperatures resulting from the move of the station from sites close to airport buildings to more remote areas of the airport by the runways.

What's interesting to me if you look at the temperature traces from first order sites today, it's warmed so much that this step change of nearly 1F is not even detectable. Can't help but wonder if the change in instrumentation isn't at play here if the data truly shows a decrease in heatwave length. It's certainly WAY hotter nowadays than it used to be in the summertime.

Source: https://climate.colostate.edu/pdfs/climo_rpt_96_2.pdf

Edit: Sorry, originally had warmer here. Just got the comparison mixed up, should read cooler.

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13 minutes ago, TheClimateChanger said:

Interesting. I don't see much evidence for this, but [assuming you are using data from first-order sites to draw this conclusion] it seems to coincide with the move to automated weather observing systems. 

Based on a study of 76 first-order sites from September 1, 1994 to August 31, 1995, ASOS averaged +0.79F COOLER* than the temperatures measured from conventional hygrothermometers - more specifically 0.90F COOLER for daytime maxima and 0.66F COOLER for overnight minima. Of the 76 sites studied, all but nine had a cooling bias with the installation of the ASOS. The study estimated +0.53F as a systemic bias, with an additional +0.37F bias due to improper solar shielding in the conventional hygrothermometer in the daytime, and an additional bias of +0.13F [but variable] for overnight temperatures resulting from the move of the station from sites close to airport buildings to more remote areas of the airport by the runways.

What's interesting to me if you look at the temperature traces from first order sites today, it's warmed so much that this step change of nearly 1F is not even detectable. Can't help but wonder if the change in instrumentation isn't at play here if the data truly shows a decrease in heatwave length. It's certainly WAY hotter nowadays than it used to be in the summertime.

Source: https://climate.colostate.edu/pdfs/climo_rpt_96_2.pdf

Edit: Sorry, originally had warmer here. Just got the comparison mixed up, should read cooler.

As a follow-up, this looks to be something specific to NYC (Central Park) ASOS. In addition to switching to an automated system at Central Park, they've also allowed a veritable jungle to encroach on the site in contravention of standard siting rules. So I would say it probably reflects a more substantial warm-season daytime cooling bias at NYC.

9 of the 20 longest streaks of 90+ at EWR are from the 21st century.

image.png.bad8982a23771d6ca8780f723e87be45.png

And 10 of 20 at LGA.

image.png.c2541bef625a2373c1f8d50b6fd366c4.png

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39 minutes ago, TWCCraig said:

Beautiful day, the HRDPS or the GEM-LAM hinted 80 degree temps briefly even for the island. Wouldn't be achievable without the offshore flow. Absolutely loves days like this!

78 now. Well hit 80

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Records:
 

Highs:

EWR: 88 (1960)
NYC: 87 (1941)
LGA: 86 (1941)


Lows:

EWR: 25 (1943)
NYC: 28 (1943)
LGA: 28 (1943)

Historical:


 

1921 - Two mile high Silver Lake, CO, received 76 inches of snow in 24 hours, the heaviest 24 hour total of record for North America. The storm left a total of 87 inches in twenty-seven and a half hours. (David Ludlum)

1927 - New Orleans LA was drenched with 14.01 inches of rain, which established a 24 hour rainfall record for the state. (The Weather Channel)

1949 - A hailstone five inches by five and a half inches in size, and weighing four pounds, was measured at Troy NY. (The Weather Channel)

1958 - A tornado 300 yards in width skipped along a five mile path near Frostproof FL. A 2500 gallon water tank was found one mile from its original position (it is not known how much water was in the tank at the time). (The Weather Channel)

1987 - Thunderstorms developing along a cold front produced severe weather in the Southern Atlantic Coast Region. A tornado killed one person and injured seven others near Mount Dora FL. Drifts of hail up to two feet deep were reported in Davidson and Rowan counties in North Carolina. Myrtle Beach SC was deluged with seven inches of rain in three hours. (The National Weather Summary) (Storm Data)

1988 - Death Valley, CA, was soaked with 1.53 inches of rain in 24 hours. Snow fell in the mountains of southern California. (The National Weather Summary) (Storm Data)

1989 - Showers and thunderstorms soaked the eastern U.S. with heavy rain, pushing the rainfall total for the month at Cape Hatteras NC past their previous April record of 7.10 inches. (Storm Data) (The National Weather Summary)

1990 - Thunderstorms developing along a stationary front produced severe weather from west central Texas to west central Arkansas during the late afternoon and evening. Thunderstorms spawned a tornado which caused more than half a million dollars damage at Fort Stockton TX, produced wind gusts to 65 mph at Dennison TX, produced baseball size hail at Silo OK and near Capps Corner TX, and drenched southeastern Oklahoma with up to 4 inches of rain in two hours. (The National Weather Summary) (Storm Data)

 

1998: An F3 tornado hits downtown Nashville causing extensive damage but no loss of life. An additional 62 tornadoes touched down in Arkansas, Kentucky, and Tennessee. These tornadoes caused 12 fatalities and approximately 120 injuries. Click HERE for more information from the NWS Office in Nashville.

 

2000: What a difference a day made (with the help of a strong cold front). Yesterday's 86 degrees in Goodland, Kansas, tied the record high for the date. Today's high of 29 degrees was also a date record high, but a record low high. It was a new record by 3 degrees.

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4 hours ago, TheClimateChanger said:

Interesting. I don't see much evidence for this, but [assuming you are using data from first-order sites to draw this conclusion] it seems to coincide with the move to automated weather observing systems. 

Based on a study of 76 first-order sites from September 1, 1994 to August 31, 1995, ASOS averaged +0.79F COOLER* than the temperatures measured from conventional hygrothermometers - more specifically 0.90F COOLER for daytime maxima and 0.66F COOLER for overnight minima. Of the 76 sites studied, all but nine had a cooling bias with the installation of the ASOS. The study estimated +0.53F as a systemic bias, with an additional +0.37F bias due to improper solar shielding in the conventional hygrothermometer in the daytime, and an additional bias of +0.13F [but variable] for overnight temperatures resulting from the move of the station from sites close to airport buildings to more remote areas of the airport by the runways.

What's interesting to me if you look at the temperature traces from first order sites today, it's warmed so much that this step change of nearly 1F is not even detectable. Can't help but wonder if the change in instrumentation isn't at play here if the data truly shows a decrease in heatwave length. It's certainly WAY hotter nowadays than it used to be in the summertime.

Source: https://climate.colostate.edu/pdfs/climo_rpt_96_2.pdf

Edit: Sorry, originally had warmer here. Just got the comparison mixed up, should read cooler.

Speaking from a suspect memory, I seem to remember heat waves in the 1960s and 1970s, but then we would get cool fronts in between.  Now it seems it gets hot, then hotter, then back to just hot?

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The temperature soared into the 80s across much of the region today. It was even hotter in the southern Mid-Atlantic region where the temperature topped out at 90° in Norfolk (old record: 89°, 1941) and Richmond.

Tomorrow will be another warm day with readings rising toward or above 70°. Afterward, it will turn somewhat cooler with unsettled conditions before a stronger cold shot arrives during the next weekend.

The ENSO Region 1+2 anomaly was -0.1°C and the Region 3.4 anomaly was +1.2°C for the week centered around April 3. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.28°C and the ENSO Region 3.4 anomaly has averaged +1.22°C. The ongoing basinwide El Niño event is fading. Neutral conditions could develop later in the spring.

The SOI was -4.69 today.

The preliminary Arctic Oscillation (AO) was +3.405 today.

Based on sensitivity analysis applied to the latest guidance, there is an implied 63% probability that New York City will have a warmer than normal April (1991-2020 normal). April will likely finish with a mean temperature near 55.2° (1.5° above normal).

 

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