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October 2019 General Discussions & Observations Thread


Rtd208
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A warmer than normal October is poised to end on a warmer than normal note. Before then, a moderate to significant rainstorm could affect the region Saturday night and Sunday. A general 0.50"-1.50" rain is possible. A few areas could pick up around 2.00" rain.

The following are year-to-date rainfall totals for select sites:

Allentown: 51.88" (14th wettest year on record); Baltimore: 30.86"; Boston: 39.25"; Harrisburg: 37.53"; Islip: 37.05"; New York City: 41.93"; Newark: 48.28" (24th wettest year on record); Philadelphia: 39.70"; Poughkeepsie: 31.45"; Providence: 39.36"; Scranton: 42.62" (22nd wettest year on record); and, Washington, DC: 34.70".

Cooler air will move into the region to start November. Afterward, the cool conditions will likely persist through the first week of November before slowly yielding to milder than normal temperatures during the second week of 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 -10.96 today.

Today, the preliminary Arctic Oscillation (AO) figure was +0.792.

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°.

In August, the AO averaged -0.722 and in September the AO rose to +0.306. The possible transition to predominantly positive values from September into October has been a relatively uncommon occurrence. Since 1950, only 1963 and 2011 saw a transition of an August value of -0.500 or below to positive values in September and a positive average in October. Both cases featured a warmer than normal November in the Middle Atlantic and southern New England areas. Despite what might be a somewhat cooler than normal start to November, a warmer than normal outcome for the month as a whole remains likely.

On October 25, the MJO was in Phase 3 at an amplitude of 0.841 (RMM). The October 24-adjusted amplitude was 1.177.

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 59.5°.

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 greater than 99%.

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The last 5 days of October are still averaging near 60degs., or about 8degs. AN.

Month to date is  +2.2[59.8].           October should end near  +3.0[59.9].

The first 3 days of November are averaging 53degs., or about 2degs. AN.

59.9* here at 6am.

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What criteria must be met for them to issue flash flood warnings on our phones? The roads near where I live are flooded and driving conditions are dangerous. There have been times in the past where we didn’t get much rain and still had warnings issued.

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1.66” and counting with rates north of 2” per hour. Flash flood conditions in some areas, parked in a shopping center and came back 20 minutes later to find that the water was ankle deep, my shoes and pants are soaked as a result.

Also, a perfect time for the RainX to wear off. :rolleyes:

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