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August 2020 General Discussions & Observations Thread


Rtd208
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8 minutes ago, bluewave said:

This reminds me of severe weather setups in Oklahoma. Sometimes the day before severe weather, the dewpoints can be really low, in the low to mid 50s. At night, the floodgates open up and the moisture starts streaming up from the gulf. 

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Temperatures will rebound tomorrow and Friday. In addition, tomorrow could see a widespread severe thunderstorm outbreak. However, the month could end on a cool note before temperatures again return to above normal levels during the first week of September. Overall, the September 1-15 period could run several degrees above normal in the Middle Atlantic region.

Laura will likely exit off the Delmarva Peninsula late Saturday night or very early Sunday morning. The system has the potential to bring an area of 1"-3" rain with locally higher amounts across parts of Virginia and the Delmarva Peninsula, along with another area with pockets of moderate to heavy rain along a frontal boundary to its north. The New York City area and adjacent suburbs could pick up 0.50" or more rain if some of the guidance verifies. There remains some uncertainty concerning the location of the front.

The current predominantly warmer than normal pattern will likely persist through much of September, providing a warm start to fall throughout the region. Occasional short-lived cool shots remain possible.

Parts of the West continued to experience near record and record high temperatures. Select high temperatures included:

Death Valley, CA: 117°
Denver: 97° (tied record set in 1936 and tied in 1985 and 2015)
Flagstaff: 86°
Kingman, AZ: 106° (tied daily record set in 1924)
Lake Havasu City, AZ: 118°
Las Vegas: 108°
Needles, CA: 117°
Palm Springs, CA: 118° (old record: 116°, 1924, 1944 and 1967)
Phoenix: 112°
Pueblo, CO: 98°
Tucson: 101°
Yuma, AZ: 115° (old record: 113°, 1879, 1910, 1944, 2011 and 2017)

Phoenix has an implied near 100% probability of having its warmest summer on record. Phoenix will likely finish with a summer mean temperature near 96.8°. The existing record is 95.1°, which was set in summer 2013 and tied in summer 2015. July 2020 was Phoenix's warmest month on record with a mean temperature of 98.9°. August 2020 could approach or exceed that figure. There is currently an implied 67% probability that August will exceed July's monthly record.

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.8°C for the week centered around August 19. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.17°C and the ENSO Region 3.4 anomaly has averaged -0.55°C. Neutral-cool conditions will likely evolve into La Niña conditions during the fall.

The SOI was -6.13.

Today, the preliminary Arctic Oscillation (AO) figure was +0.325.

On August 25, daily MJO data was unavailable.

Last year, the MJO went through a very strong passage through Phase 1 during the closing days of May. About four weeks later, a warmer than normal pattern locked in and predominated through early autumn. This year, the MJO was in Phase 1 for 3 consecutive days with an amplitude of 1.500 or above during the June 1-3 period.

Last year, the SOI fell to -42.04 on June 22 when the MJO was in Phase 6. This year, the SOI plunged below -46.68 on June 5, its lowest level in more than three years. The dramatic plunge in the SOI could be the proverbial spark that kicks off a sequence of events leading to the development of a sustained warmer than normal period. The cases that saw both the MJO and SOI thresholds satisfied generally saw 10-20 days where the temperature reached or exceeded 90° in New York City during the July 1-August 31 period.

Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO.   

Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal August. August will likely finish with a mean temperature near 77.0°.

Summer 2020 will likely finish with a mean temperature near 76.9°, which would tie 2020 as Central Park's 4th warmest summer with 1949, 1983, and 1993. At LaGuardia Airport, summer 2020 will likely finish with a mean temperature of 79.4°. That would surpass the summer record of 79.2°, which was set in 2010.

Finally, on August 25, Arctic sea ice extent was 4.205 million square kilometers (JAXA). There is an implied 92% probability that Arctic sea ice extent will reach a minimum figure below 4.000 million square kilometers for the second consecutive year and third time on record. The highest 25% bound is 3.835 million square kilometers. The lowest 25% bound is 3.539 million square kilometers.

 

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The last 5 days of August are averaging 78degs., or 4.5 degs. AN.

Month to date is  +1.8[77.2].       August should end at  +1.9[77.3].       Correcting the GFS bias of +4 at this range, August should end at  +1.4[76.6].

Cat. 3 threatens EC around Sept. 13.    Long runner.     Takes shape off Africa Sept. 1-3.

73*(66%RH) at 6am, ground wet, overcast.         72*(68%RH) at7am.          78*(73&RH) by Noon.         86*(65%RH) by 2pm.        89*(58%RH) by 4pm.          90* at 6pm with a HX of 98*.

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74/67.  early morning showers and clouds clearing out.  Dewpoints on the rise.   36 hours of some late summer heat with storm chances tonight and and Friday.  Hotter spots mid to perhaps upper 90s today and tomorrow maxing out in low to perhaps mid 90s.  Storms and cloud the only caveat.  Saturday looks like a wet day with front near by and Laura's remnants tracking through the DelMarVa area. Sunday (8/30) and Mon (8/31) we dry out and cool off similar to Wed with highs in upper 70s low 80s.

By Tue 9/1 Western Atlantic Ridge is expanding back west as we are warming back . The next 90s look to arrive between 9/2 and 9/5 before brief cool down Labor day.  ECm has 850s >16c starting next Wed (9/2).  The W.A.R looks close by and expanding west again towards 9/9 with sustained ridging into the east which should bring continued warmth / above temps with additional 90s potential especially in the warmer spots..  Tropics look more of a threat to SE coast in that period.

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77* in the bronx. Very unlikely to get to mid to upper 90's here. I checked several forecast not one has a higher temperature than 90 degrees for any part of our area today. That would be Northern New Jersey New York City metro Long Island Southeast New York and Southwest Connecticut don't know where those mid and Upper 90 are coming from. Maybe Central Southern New Jersey and the Philly area

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15 hours ago, psv88 said:

Today was beautiful. A great day to work remotely...

Yeah, it felt great. Looks like the warm front is further north today than expected. The NAM has us warming into the 90s as the flow becomes more WSW this afternoon.

0C9E3FCD-A3F5-424F-9331-CF93DD5C1BE9.thumb.gif.728e9382f8762bf2e2344781294d4f93.gif

 

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Parts of southern New York State and Connecticut saw severe thunderstorms this afternoon. North of the frontal boundary, readings stayed mainly in the 60s and 70s. South of the front, temperatures topped out into the upper 80s and lower 90s.

High temperatures included:

Albany: 69°
Allentown: 93°
Baltimore: 94°
Bridgeport: 88°
Harrisburg: 95°
Hartford: 77°
Islip: 90°
New York City-JFK: 92°
New York City-LGA: 94°
New York City-NYC: 90°
Newark: 93°
Philadelphia: 93°
Washington, DC: 93°

90° Days for Select Cities (through August 27):

Albany: 13 (2019: 12 days)
Allentown: 24 (2019: 24 days)
Baltimore: 44 (2019: 59 days)
Boston: 14 (2019: 15 days)
Burlington: 20 (2019: 8 days)
Harrisburg: 34 (2019: 33 days)
Hartford: 39 (2019: 27 days)
Islip: 8 (2019: 8 days)
New York City-JFK: 12 (2019: 7 days)
New York City-LGA: 34 (2019: 26 days)
New York City-NYC: 20 (2019: 15 days)
Newark: 31 (2019: 28 days)
Philadelphia: 35 (2019: 35 days)
Scranton: 25 (2019: 12 days)
Washington, DC: 43 (2019: 62 days)

New York City-Newark Average: 24 (2019: 19 days)
...Expected: 25 (based on regression equation tied to JFK-LGA-EWR data)

Tomorrow will be another very warm day. However, the month could end on a cool note before temperatures again return to above normal levels during the first week of September. Overall, the September 1-15 period could run several degrees above normal in the Middle Atlantic region.

After having made landfall as a Category 4 hurricane with maximum sustained winds of 150 mph near Cameron, LA, Laura weakened but continued to bring heavy rain to parts of the Gulf region. Through 8 pm, select daily rainfall amounts included:

Lafayette, LA: 5.71" (old record: 3.77", 1967)
Little Rock: 2.78"
Pine Bluff, AR: 2.69" (old record: 1.37", 2017)
Shreveport: 2.04" (old record: 1.76", 1940)

Laura will likely exit off the Delmarva Peninsula late Saturday night. The system has the potential to bring an area of 1"-3" rain with locally higher amounts across parts of Virginia and the Delmarva Peninsula, along with another area with pockets of moderate to heavy rain along a frontal boundary to its north. The New York City area and adjacent suburbs could pick up 0.25"-0.75" rain.

The current predominantly warmer than normal pattern will likely persist through much of September, providing a warm start to fall throughout the region. Occasional short-lived cool shots remain possible.

Parts of the West continued to experience near record and record high temperatures. Select high temperatures included:

Death Valley, CA: 114°
Denver: 96°
Flagstaff: 87°
Kingman, AZ: 104°
Lake Havasu City, AZ 113°
Las Vegas: 106°
Needles, CA: 115°
Palm Springs, CA: 116°
Phoenix: 113° (tied record set in 1981 and tied in 2009)
Pueblo, CO: 98°
Tucson: 107°
Yuma, AZ: 115°

Phoenix has an implied near 100% probability of having its warmest summer on record. Phoenix will likely finish with a summer mean temperature near 96.8°. The existing record is 95.1°, which was set in summer 2013 and tied in summer 2015. July 2020 was Phoenix's warmest month on record with a mean temperature of 98.9°. August 2020 could approach or exceed that figure. There is currently an implied 61% probability that August will exceed July's monthly record.

The ENSO Region 1+2 anomaly was -1.1°C and the Region 3.4 anomaly was -0.8°C for the week centered around August 19. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.17°C and the ENSO Region 3.4 anomaly has averaged -0.55°C. Neutral-cool conditions will likely evolve into La Niña conditions during the fall.

The SOI was -0.67.

Today, the preliminary Arctic Oscillation (AO) figure was -0.507.

On August 26, daily MJO data was unavailable.

Last year, the MJO went through a very strong passage through Phase 1 during the closing days of May. About four weeks later, a warmer than normal pattern locked in and predominated through early autumn. This year, the MJO was in Phase 1 for 3 consecutive days with an amplitude of 1.500 or above during the June 1-3 period.

Last year, the SOI fell to -42.04 on June 22 when the MJO was in Phase 6. This year, the SOI plunged below -46.68 on June 5, its lowest level in more than three years. The dramatic plunge in the SOI could be the proverbial spark that kicks off a sequence of events leading to the development of a sustained warmer than normal period. The cases that saw both the MJO and SOI thresholds satisfied generally saw 10-20 days where the temperature reached or exceeded 90° in New York City during the July 1-August 31 period. New York City has had 18 days on which the temperature reached 90° or above during July-August 2020.

Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO.   

Based on sensitivity analysis applied to the latest guidance, there is an implied 99% probability that New York City will have a warmer than normal August. August will likely finish with a mean temperature near 76.9°.

Summer 2020 will likely finish with a mean temperature near 76.9°, which would tie 2020 as Central Park's 4th warmest summer with 1949, 1983, and 1993. At LaGuardia Airport, summer 2020 will likely finish with a mean temperature of 79.4°. That would surpass the existing summer record of 79.2°, which was set in 2010.

Finally, on August 25, Arctic sea ice extent was 4.173 million square kilometers (JAXA). There is an implied 93% probability that Arctic sea ice extent will reach a minimum figure below 4.000 million square kilometers for the second consecutive year and third time on record. The highest 25% bound is 3.840 million square kilometers. The lowest 25% bound is 3.575 million square kilometers.

 

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