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October 2019 General Discussions & Observations Thread


Rtd208
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19 minutes ago, donsutherland1 said:

With 2.08" rain through 2 pm, White Plains set a new daily precipitation record for October 27. The previous record was 1.78", which was set in 2003.

Looks like their wettest October of the decade. They pulled ahead of 1990 for 8 wettest October.

Time Series Summary for WESTCHESTER COUNTY AP, NY - Month of Oct
Click column heading to sort ascending, click again to sort descending.
Year
Total Precipitation 
Missing Count
2019 7.18 4
2018 4.50 0
2017 4.99 0
2016 3.47 1
2015 4.07 0
2014 5.31 0
2013 0.86 0
2012 4.61 0
2011 4.90 0
2010 4.70 0
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The remnants of Tropical Storm Olga brought a general 1.00"-1.50" rainfall to the region today. Several locations exceeded 2.00" rain. Daily precipitation records for October 27 were set at:

Bridgeport: 2.12" (old record: 1.90", 2016)
Islip: 1.58" (old record: 1.50", 2018)
New Haven: 2.19" (old record: 1.39", 2003)
White Plains: 2.20" (old record: 1.78", 2003)

Year-to-date precipitation totals for select sites include: Allentown: 53.30" (11th wettest year); Harrisburg: 39.03"; Islip: 38.63"; New York City: 43.32"; Newark: 49.67" (20th wettest year); Philadelphia: 40.34"; and, Scranton: 43.70" (17th wettest year).

In the wake of today's rainfall, the implied probability of New York City picking up 50" or more precipitation this year (1971-2018 data) has increased to 73%.

The remainder of October will likely see readings mainly above normal. Cooler air will move into the region Friday or Saturday during the first week of November. The coolest period now appears likely to be the second week of November. Afterward, a prolonged return to above and occasionally much above normal temperatures could return. However, uncertainty about the second half of November has increased in recent days. Nevertheless, the base case remains a warmer than normal November.

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was +0.8°C for the week centered around October 16. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.82°C and the ENSO Region 3.4 anomaly has averaged +0.28°C. A neutral ENSO is currently the base case for Winter 2019-20.

Since 1981, approximately one out of every seven December cases involved a neutral ENSO. In general, a neutral ENSO in which Region 1+2 had a cold anomaly and Region 3.4 had a warm anomaly (as has been the case in the 6 week moving average) saw a warmer than normal December. Such neutral ENSO cases accounted for about 27% of all neutral ENSO December cases during the 1981-2018 period. This data does not consider blocking, as it is too soon to be confident about that factor in December. However, the greatest warmth coincided with a negative PDO while the coldest outcome coincided with a strongly positive PDO (+1.00 or above for December). Therefore, the first part of winter could start off milder than normal in the Middle Atlantic and southern New England regions.

The SOI was +1.42 today.

Today, the preliminary Arctic Oscillation (AO) figure was -0.183.

Since 1950, there have been five prior cases when the AO averaged -0.500 or below in both July and August: 1950, 1958, 1960, 1968, and 2015. The average temperature for September through November in New York City was 58.9° (59.6° adjusted). All cases featured a warmer than normal fall. There remains a potential for autumn 2019 to rank among the 30 warmest cases on record. For New York City, that would translate into a September-November mean temperature of at least 58.8°.

On October 26, the MJO was in Phase 3 at an amplitude of 0.842 (RMM). The October 25-adjusted amplitude was 0.841.

In the two prior cases when the MJO moved into Phase 1 in late September or early October and then remained in Phase 1 for 12 or more consecutive days as occurred this year, the average decline in the 14-day average temperature for the 2-3 weeks that followed the MJO's moving out of Phase 1 was gradual. The current long-duration Phase 1 episode suggests that the second half of October could be warmer than normal. For New York City, an October mean temperature of 58.5°-59.5° (1.6° to 2.6° above normal) would be implied by those earlier long-duration Phase 1 cases. Based on the sensitivity analysis, the estimated October mean temperature is currently near 59.8°.

Since 1974, there were 3 cases that saw the MJO in Phase 2 at an amplitude of 1.500 or above for at least 3 days during the October 15-25 period, as occurred this year: 1990, 2011, and 2015. All three cases featured a warmer than normal November in New York City and readings that were 3° or more above normal during the second half of November.

Based on sensitivity analysis applied to the latest guidance, the implied probability of New York City having a warmer than normal October is currently near 100%.

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