donsutherland1

The 8/20 0z HREF:

A dramatic change to a sustained period of cooler weather has now occurred. High temperatures will likely reach the middle and upper 70s through Thursday and then the lower 80s on Friday through the weekend. Some showers or periods of rain are possible Wednesday afternoon into Thursday. Most of the region will see less than 0.50" or rain, though widely scattered areas of heavier rainfall are possible. The Jersey shore could see heavier rain and a gusty wind. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, rip currents, and some showers or periods of rain would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. There will be higher-than-climatological risk of at least one period in September with highs in the upper 80s or perhaps 90s. Summers similar to the current one have had September highs of 90 or above about 10 percentage points above that for all other years. The ENSO Region 1+2 anomaly was +0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.53°C and the ENSO Region 3.4 anomaly has averaged -0.20°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was -17.72 today. The preliminary Arctic Oscillation (AO) was -0.771 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 80% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 74.8° (1.3° below normal). Supplemental Information: The projected mean would be 0.4° below the 1981-2010 normal monthly value.

Yes, that’s correct. Phoenix has a pronounced UHI effect. One sees it particularly in the explosive increase in 90 or above low temperatures.

A dramatic change to a sustained period of cooler weather has now occurred. High temperatures will likely reach the middle and upper 70s through Wednesday and then the lower 80s on Thursday and Friday. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, and rip currents would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. There will be higher-than-climatological risk of at least one period in September with highs in the upper 80s or perhaps 90s. Summers similar to the current one have had September highs of 90 or above about 10 percentage points above that for all other years. The ENSO Region 1+2 anomaly was +0.6°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.53°C and the ENSO Region 3.4 anomaly has averaged -0.20°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was -4.73 today. The preliminary Arctic Oscillation (AO) was -0.721 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 70% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 75.2° (0.9° below normal). Supplemental Information: The projected mean would be at the 1981-2010 normal monthly value.

A cooler regime is now in place and it will remain in place for an extended period of time. Here's where things currently stand with respect to select high temperature thresholds for 2025:

Those findings aren't too surprising. The UHI Effect grows most rapidly when an area first begins to urbanize. From 1950-1980, Phoenix's population grew 6.9% per year (Phoenix metro area: 6.4% per year). Since 1980, Phoenix's population has been growing 1.7% per year (Phoenix metro area: 2.7% per year). Since 2000, those rates have slowed further to 1.0% per year and 2.0% per year respectively. Phoenix's suburbs are currently growing faster than the City.

Central Park picked up 0.64" rain in an hour. While impressive, that was just half of the hourly record of 1.28" for August 17 that was set in 1974.

I've often noted that Phoenix's warmth is a combination of UHI and climate change. The scientific literature describes numerous impacts on the Southwest monsoon in a warmer climate, particularly a drier monsoon season, fewer rain events, and higher temperatures during monsoon season. This evolution is currently in its early stages. The outcome described in the literature won't happen all at once or uniformly. Phoenix deserves focused attention because it represents both an extreme case and an early signal of how climate change and aridification interact in the desert Southwest. Phoenix’s accelerated warming, even as UHI amplifies the impact of ongoing warming, makes it a valuable barometer of what other communities may face as aridification deepens across the state.

Today saw hot temperatures across much of the region. Highs included: Bridgeport: 88° Islip: 86° New Haven: 89° New York City-Central Park: 91° New York City-JFK Airport: 85° New York City-LaGuardia Airport: 91° Newark: 94° White Plains: 89° A dramatic change to a sustained period of cooler weather now lies ahead. A cold front will cross the region this evening or tonight bringing some showers or thundershowers. In the wake of the frontal passage, noticeably cooler air will overspread the region. High temperatures will likely reach the upper 70s Monday through Wednesday and then the lower 80s on Thursday and Friday. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, and rip currents would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. The ENSO Region 1+2 anomaly was +0.8°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged -0.15°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was +4.49 today. The preliminary Arctic Oscillation (AO) was -0.220 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 66% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 75.4° (0.7° below normal). Supplemental Information: The projected mean would be 0.2° above the 1981-2010 normal monthly value.

Yes. I ran the numbers this morning to see what the coefficient of determination was. It is .0.0143. This was even lower than I had thought when I had run the scatter diagram earlier today.

When it comes to ACE and winter temperatures (using NYC), the long-term warming already overwhelms the ACE. Here's what it looks like (anomalies are against the Winter 1869-70 through 2024-25 mean temperature for purposes of standardization): Here's what happens when one detrends the data for the ongoing warming (takes out the warming signal):

For NYC, the coefficient of determination for ACE and seasonal snowfall is just 0.014.

The ACE connection is somewhat positive but very noisy for Central Park.

Tomorrow will turn briefly warmer with highs reaching the upper 80s and lower 90s acros the region. Afterward, a shift toward cooler weather lies ahead. Noticeably cooler air will overspread the region tomorrow night and Monday. High temperatures will likely reach the upper 70s Monday through Wednesday and then the lower 80s on Thursday. The extended range guidance continues to suggest that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, and rip currents would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. The ENSO Region 1+2 anomaly was +0.8°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged -0.15°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was -4.37 today. The preliminary Arctic Oscillation (AO) was +0.333 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 57% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 75.6° (0.5° below normal). Supplemental Information: The projected mean would be 0.4° above the 1981-2010 normal monthly value.

Three things: 1. The focus of my post was Phoenix's monsoon season where recent years have seen disappointing monsoon season outcomes. It was not intended to focus on all of Arizona's monsoon season. 2. The expected impacts of climate change for the Phoenix area were fewer rainfalls, lower monsoon season rainfall and a warming monsoon season. All three are present in Phoenix. 3. The Phoenix area, precisely because it has warmed faster than much of Arizona, could be a barometer of what lies ahead in coming decades as the climate continues to warm elsewhere in Arizona. Aridification won't have a uniform impact in Arizona. Indeed, a prior aridification regime might well have led to the demise of the Hohokam people who resided in the vicinity of where Phoenix is today.

Here it is:

The hourly guidance showed mostly cloudy skies this morning. The clouds should break late morning/early afternoon yielding to partly sunny skies.

Congratulations and best wishes.

Today, the low temperature at Phoenix was only 76, its coolest since June 4 due to some monsoonal moisture.

Tomorrow will turn cooler before it turns briefly warmer on Sunday. Highs on Sunday could reach the upper 80s. Parts of the region could reach the lower 90s. Noticeably cooler air will then overspread the region. High temperatures will likely reach the upper 70s Monday through Wednesday and then the lower 80s on Thursday. The extended range guidance increasingly suggests that the closing week of August could feature below normal temperatures. Precipitation could be near normal. The synoptic pattern should limit direct tropical cyclone threats for the foreseeable future. Impacts from elevated tides, surf, and rip currents would be the most likely effects produced by Erin as it tracks well offshore between the U.S. East Coast and Bermuda. The ENSO Region 1+2 anomaly was +0.8°C and the Region 3.4 anomaly was -0.3°C for the week centered around August 6. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.50°C and the ENSO Region 3.4 anomaly has averaged -0.15°C. Neutral ENSO conditions will likely continue into early autumn. The SOI was -4.61 today. The preliminary Arctic Oscillation (AO) was -0.285 today. Based on sensitivity analysis applied to the latest guidance, there is an implied 57% probability that New York City will have a cooler than normal August (1991-2020 normal). August will likely finish with a mean temperature near 75.6° (0.5° below normal). Supplemental Information: The projected mean would be 0.4° above the 1981-2010 normal monthly value.

I ran the numbers for 1995 and 1993 where summer mean temperature was weighted at 50% and where the remaining 50% weight was equally divided among the other three variables. In that case, 1993 tops 1995. 2010 remains at the top.

Here's the breakdown: 1993: Mean Temperature Z-Score: 1.653 Max Temperature Z-Score: 1.638 Min Temperature Z-Score: 0.813 Number of 90°F+ Days Z-Score: 3.025 Summer Score: 1.782 1995: Mean Temperature Z-Score: 1.451 Max Temperature Z-Score: 1.638 Min Temperature Z-Score: 2.366 Number of 90°F+ Days Z-Score: 1.908 Summer Score: 1.841 All variables are equally weighted. Personally, I wouldn't give equal weight to each variable e.g.., I'd place greater weight on the summer mean temperature.

Here are the standardized scores for Central Park. I used the same criteria as for JFK Airport.

It's highly unlikely. Both LGA and Central Park had too few 90° or above days during 1948 and the summer mean was 0.4°-0.5° below that of 1949. Using just the 1948-2024 period, 1948 ranked 13 spots below 1949 at LGA and 19 spots below Central Park.

I cleaned up my typos. 1983 would remain second, but the difference between 2010 and 1983 would narrow were September added.