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October 2018 Discussions & Observations Thread


Rtd208
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Through the first 15 days of October, New York City had a mean temperature of 66.2°, ranking that period the 11th warmest 10/1-15 period on record. Records go back to 1869. Since then, the temperature has averaged 51.0°.

Given the latest guidance, it is likely that the 10/16-31 period will rank among the 10 coldest on record. The 10 coldest 10/16-31 periods are:

1. 46.8°, 1940
2. 47.3°, 1886
3. 47.5°, 1925 and 1976
5. 47.7°, 1888
6. 48.1°, 1887
7. 48.6°, 1882
8. 48.7°, 1907
9. 48.8°, 1879
10. 49.0°, 2002

Applying sensitivity analysis to the guidance, the implied probability of a mean 10/16-31 average temperature of 49.0° or below was 60%. The implied probability of a 10/16-31 mean temperature below 46.8° was 36%.

Looking at the larger record, 13 years had a mean temperature below 50° for the 10/16-31 period. Select snowfall data for the subsequent winters is below:

Mean snowfall: 35.0”
Median snowfall: 32.9”
Least snowfall: 16.5”, 1888-89
Most snowfall: 60.4”, 1922-23

Frequency of Select Outcomes (13 cases with a 10/16-31 mean temperature < 50°):
< 20” snow: 8% (historic frequency: 32%)
30” or more snow: 62% (historic frequency: 41%)
40” or more snow: 31% (historic frequency: 24%)

 

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12z GFS really tones down the November warmup. The ridge is much flatter. Still past 240 hours though, which is the point where GFS temp forecasts seem to become more accurate and consistent run to run.

 

E: Also worth noting that the GEFS continues to show only a minor moderation of temps during the first week of November.

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5 hours ago, Juliancolton said:

Some thunder and epic double rainbow with distinct supernumerary bands, this hour. Sweet

I'm connected with a few of you guys on Facebook so some may have already seen it, but I liked this shot from tonight. I've always enjoyed the illusion of having an unobscured view of the end of the rainbow.

WBUpimN.jpg

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50 minutes ago, Juliancolton said:

I'm connected with a few of you guys on Facebook so some may have already seen it, but I liked this shot from tonight. I've always enjoyed the illusion of having an unobscured view of the end of the rainbow.

WBUpimN.jpg

Beautiful. “Where funny little blue birds fly beyond the rainbow why oh why can’t I” perhaps soon ........

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4 hours ago, Juliancolton said:

I'm connected with a few of you guys on Facebook so some may have already seen it, but I liked this shot from tonight. I've always enjoyed the illusion of having an unobscured view of the end of the rainbow.

WBUpimN.jpg

Did you find your two pots of gold?!  Maybe you won the 1.6 billion dollar megalottery today and will win the 600 million dollar powerball lottery tomorrow lol.

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On 10/23/2018 at 5:43 AM, CIK62 said:

Next 8 days averaging 47degs., or about 6degs. BN.

Month to date is +2.8[61.1].    Should be just +0.40[57.4] by the 30th.

 

45 minutes ago, CIK62 said:

Remainder of Oct. averaging 50degs., or about 3 degs. BN.

Month to date is +2.7[60.9].    Should end month at +1.2[58.1].

Damn, halloween is gonna be hot!

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Over the past two days, the guidance has moved aggressively toward paring back the magnitude of the cold that the models had suggested would predominate during the closing week of October.  As a result, the implied probability for an October 16-31 period with a mean temperature of 49° or below has tumbled from 60% to 34%. That period could average within 0.5° of 50°, which is still remarkably cool for cases when the first 15 days of October had a mean temperature of 65° or above. The implied probability for October’s having an above normal monthly anomaly is currently 76% (estimated range: 57.2°-58.6°).

Going into November, there are growing indications that the first half of the month could see the pattern turn warmer than normal as the trough retreats to the center of the CONUS and ridging tries to take hold in the East. The EPS weekly forecast favors a continuation of below normal temperatures through most of the first half of November, but the possible rise in the AO, decline in the PNA, and near neutral to somewhat positive EPO favor an evolution toward the kind of milder pattern that has predominated for the most part during the autumn. However, the warmth likely won’t be as extreme relative to normal as it had been. The latest CFSv2 weekly forecast is particularly aggressive with the return to warmer anomalies.  Taking into consideration the preponderance of the guidance and teleconnection forecast, the odds likely favor an evolution to a milder pattern during the first half of November. This could favor November’s winding up somewhat warmer than normal as a whole.

 

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59 minutes ago, uncle W said:

the ao/nao are negative together for the first time in months...temps are cool and a storm is lurking...this is what we need in January...

It would be ridiculously cold today if it were January. Highs in the 20s lows in the teens type of weather. But we would all be freaking out over the low track this weekend as it would most likely be a snow to rain event for our entire region

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33 minutes ago, LongBeachSurfFreak said:

It would be ridiculously cold today if it were January. Highs in the 20s lows in the teens type of weather. But we would all be freaking out over the low track this weekend as it would most likely be a snow to rain event for our entire region

L.B.S.F. Just made an accurate forcast predicting the end of our forums “G” behavior rating.

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23 hours ago, donsutherland1 said:

Over the past two days, the guidance has moved aggressively toward paring back the magnitude of the cold that the models had suggested would predominate during the closing week of October.  As a result, the implied probability for an October 16-31 period with a mean temperature of 49° or below has tumbled from 60% to 34%. That period could average within 0.5° of 50°, which is still remarkably cool for cases when the first 15 days of October had a mean temperature of 65° or above. The implied probability for October’s having an above normal monthly anomaly is currently 76% (estimated range: 57.2°-58.6°).

Going into November, there are growing indications that the first half of the month could see the pattern turn warmer than normal as the trough retreats to the center of the CONUS and ridging tries to take hold in the East. The EPS weekly forecast favors a continuation of below normal temperatures through most of the first half of November, but the possible rise in the AO, decline in the PNA, and near neutral to somewhat positive EPO favor an evolution toward the kind of milder pattern that has predominated for the most part during the autumn. However, the warmth likely won’t be as extreme relative to normal as it had been. The latest CFSv2 weekly forecast is particularly aggressive with the return to warmer anomalies.  Taking into consideration the preponderance of the guidance and teleconnection forecast, the odds likely favor an evolution to a milder pattern during the first half of November. This could favor November’s winding up somewhat warmer than normal as a whole.

 

Yeah, the cold got modified coming on the tail of such a warm early fall pattern. The coldest days of the cool down couldn't match the magnitude of the warmest departure days.

Peak warm and cold daily temperature departures for October so far:

NYC...+17...-10

LGA....+17...-9

JFK.....+15...-9

ISP......+17...-9

BDR.....+18...-10

EWR.....+17...-10

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Previously, the forecast state of the teleconnectiions suggested that the upcoming storm's heaviest precipitation would likely miss the Philadelphia to New York City corridor. Instead, areas on Long Island and New England would have a better chance at seeing 1" or more precipitation.

https://www.americanwx.com/bb/topic/51583-october-2018-discussions-observations-thread/?do=findComment&comment=5006049

The caveat was that the event was still 9-12 days away and that much could change (as often happens in the guidance).

Now that the event is less than 48 hours away, the details are coming into place. The general idea that the heaviest precipitation would wind up in the area suggested by a probabalistic look at the teleconnection indices (parts of Long Island and New England) still looks reasonable.

However, a widespread area of 1"-1.5" rain appears likely. That area includes Philadelphia to New York City. However, the region most likely to see 1.5" or more extends from eastern Suffolk County, across eastern Massachusetts and then parts of Maine (10/25 12z GFS).

Select GFS figures:

Baltimore: 1.7”
Bangor: 1.9”
Boston: 1.7”
Harrisburg: 1.4”
Montauk Point: 2.0”
New York City: 1.5”
Newark: 1.5”
Philadelphia: 1.3”
Plymouth: 2.9”
Washington, DC: 1.7”

Select NAM figures:

Baltimore: 0.8”
Bangor: 0.8”
Boston: 1.2”
Harrisburg: 0.9”
Montauk Point: 1.4”
New York City: 0.9”
Newark: 0.9”
Philadelphia: 0.7”
Plymouth: 1.6”
Washington, DC: 0.9”

Those rainfall totals will add to the excessive precipitation that has fallen across parts of the Middle Atlantic region this year. Select figures through 10/24:

Baltimore: 55.72” (7th highest annual figure)
Harrisburg: 51.47” (8th highest annual figure)
New York City: 50.05” (33rd highest annual figure)
Philadelphia: 44.92” (45th highest annual figure)
Richmond: 52.50” (16th highest annual figure)
Scranton: 50.05” (3rd highest annual figure)
Washington, DC: 51.64” (13th highest annual figure)
Wilmington, NC: 87.46” (highest annual figure on record)

 

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Reminder of Oct. averaging 53degs. , or just NORMAL.

Month to date is +2.0[59.8].    Should end month at +1.6[58.5].

All 8 days averaging 55degs., or about 3degs. AN.

RRWT warning of a record hot Nov., with BN coming late, but maybe holding.   Something to wait for anyway.  

Gotta love these models, GFS and CMC differ by 30 degrees+ for Nov. 4th. 

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12 minutes ago, bluewave said:

Looks like a warm Halloween coming up as the WAR begins to flex again.

ecmwf-ens_T850a_us_7.thumb.png.0146eadabcf92eefc150533bf4150bdc.png

 

Remember I said a month ago to get ready to wear a light colored, loose fitting costume for Halloween. lol.   The RRWT did not let me down, on that one, it seems.

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11 minutes ago, LurkerBoy said:

Looks to be low/mid 60s...that's like, +5...not too bad. Doesn't hang around too long either

60's on Halloween during the 2010's hasn't been a common occurrence for NYC. It looks to be the first time in NYC since 2013. 

10-31 high temperatures in NYC since 2010

2017...57/45

2016...54/44

2015...56/42

2014...55/45

2013...66/53

2012...50/44

2011...53/37

2010...58/42

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