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July 2020 General Discussions & Observations Thread


Rtd208
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Ahead of a backdoor cold front that produced scattered thunderstorms this evening, temperatures surged to 90° or above from New York City and southward. High temperatures included:

Allentown: 92°
Baltimore: 96°
Bridgeport: 87°
Harrisburg: 97°
Hartford: 87°
Islip: 88°
New York City: 90°
Newark: 93°
Philadelphia: 97°
Washington, DC: 97°

Somewhat cooler air will return for the July 4 weekend. The modest respite from the heat will be short-lived. Excessive heat will likely build over the Central Plains next week. Some of that heat will then expand eastward. The potential for the season's first heat wave in New York City is on the table for later next week.

A predominantly warmer than normal pattern will likely persist through at least August, paving the way for a solidly warmer than normal summer throughout the region. Occasional short-lived cool shots remain possible Initially, extreme heat is unlikely, but that could change as July progresses, especially if the emerging drought continues to deepen. One or more heatwaves are likely in July across the region.

The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was +0.1°C for the week centered around June 24. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.48°C and the ENSO Region 3.4 anomaly has averaged -0.37°C. Neutral-cool conditions will likely prevail through mid-summer. The probability of the development of a La Niña event during late summer or early autumn has increased in recent weeks.

The SOI was +11.02.

Today, the preliminary Arctic Oscillation (AO) figure was -0.331.

On July 2, the MJO was in Phase 1 at an amplitude of 1.331 (RMM). The July 1-adjusted amplitude was 1.254.

That was the 13th consecutive day the MJO was in Phase 1. The last time the MJO had a longer stretch in Phase 1 occurred during September 21-October 8, 2019 when the MJO was in Phase 1 for 18 consecutive days. In addition, the MJO has been in either Phase 1 or Phase 2 for 33 consecutive days.

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.

 

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