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September 2021


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The last 7 days of September are averaging 68degs.(60/77) or +3

Month to date is  72.0[+1.5].      September should end at  71.1[+1.9]

59*(88%RH) here at 6am, cloudy, drizzle.      60* at 7am with clearing skies.        67* at Noon.         71* at 3pm        73* at 4pm.      74* at 4:30pm.

Latest GFS has no more rain this month---previous run had 0.3".

SAM, around Oct. 03, seems most trapped on the GFS, but it still escapes.      The CMC blocks it--- but it goes into the SE US.

Today. 68-73, w. wind., some sun by the PM,


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Morning thoughts…

At 7:10 am, the front responsible for the heavy rainfall that commenced yesterday continued to move slowly eastward. Central Park picked up 2.03” of rain bringing its monthly total to 9.76”. 2021 is the first year on record with 3 consecutive months of 9.50” or more rainfall. Annual rainfall in New York City has reached 51.69”. That surpassed the 51.38” that fell in 1871 to make 2021 New York City’s 34th wettest year on record.

Today will see rainfall shift slowly eastward on Long Island. Clouds will break, especially west of Suffolk County allowing for some sunshine. Areas to the south and west of Newark could see a lot of sunshine. It will be cool for the season. High temperatures will likely reach the lower and middle 70s in most of the region.  Where clouds linger longest, temperatures will hold in the 60s. Likely high temperatures around the region include:

New York City (Central Park): 71°

Newark: 76°

Philadelphia: 74°


New York City: 30-Year: 73.1°; 15-Year: 74.3°

Newark: 30-Year: 74.7°; 15-Year: 76.0°

Philadelphia: 30-Year: 75.9°; 15-Year: 77.0°

A sun-filled weekend lies ahead.

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53 minutes ago, bluewave said:

It will be interesting to see how close NYC can come to the warmest September minimum of 57°. All our other local stations are near the warmest levels also. The NBM blend gets NYC down to 57° on the last day of September. 


 KNYC    NBM V4.0 NBE GUIDANCE    9/24/2021  0700 UTC                    
        SAT 25| SUN 26| MON 27| TUE 28| WED 29| THU 30| FRI 01|SAT CLIMO 
 UTC    00  12| 00  12| 00  12| 00  12| 00  12| 00  12| 00  12| 00       
 FHR    17  29| 41  53| 65  77| 89 101|113 125|137 149|161 173|185       
 TXN    71  59| 75  61| 73  59| 73  62| 74  59| 70  57| 69  58| 69  56 71
Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Sep
Click column heading to sort ascending, click again to sort descending.
Lowest Min Temperature 
Missing Count
  2021 59 7
  1910 57 0
  2015 56 0
- 1921 56 0
  2018 54 0
- 2017 54 0
- 2016 54 0
- 2010 54 0
- 2002 54 0
- 1982 54 0
- 1960 54 0
- 1891 54 0


Central Park was 57 degrees this morning.

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2 hours ago, wdrag said:

Unsure about EWR Sept record.  Not starting SAM related thread, as yet...  wait a couple of days to see if indeed there is a more direct interaction with the mid-Atlantic coast low pressure system. What I see on some 6AM weathercasts are tooo optimistically dry forecasts tomorrow and middle-end of next week for NYC-LI-NJ. 

I hope Bluewave and Don have some stats to share on Sept and will recheck late today. 

Newark is currently in 2nd place for wettest September at 10.08”.


Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Sep
Click column heading to sort ascending, click again to sort descending.
Total Precipitation 
Missing Count
1 1944 10.28 0
2 2021 10.08 7
3 1999 9.38 0
4 1975 9.00 0
5 1933 8.33 0
6 1934 8.15 0
7 2011 8.13 0
8 2004 8.01 0
9 1971 7.88 0
10 1966 7.86 0
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SAM update:       

The CMC comes closest to us as it hits in Maine.     EURO is similar till very end of its run and only scrapes Maine.         GFS  is way out to sea at Maine's latitude.


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In the wake of the frontal passage that brought a widespread 1"-2" rainfall into today, clouds and rain shifted eastward and the sun returned. Abundant sunshine occurred near New York City and westward. There, readings soared into the 70s.

Tomorrow, the entire region will benefit from abundant sunshine. It will be a warm day with temperatures rising into the middle and upper 70s. A few locations could reach or exceed 80°. Sunday will be a similar but perhaps slightly cooler day.

The MJO had recently been locked in Phase 3 at a high amplitude, frequently in excess of 1.500. Only 2006 and 2009 saw the MJO in Phase 3 at an amplitude of 1.500 or above for 2 or more days during September 10-20. Both years saw September end with a cold shot that continued into the first days of October. Both days saw Central Park's temperature fall to 49° on September 30. A fairly sharp rebound in temperatures followed. October wound up wetter than normal with 7.07" rainfall in 2006 and 5.58" of rainfall in 2009. Normal rainfall (1991-2020) is 4.38".

Despite the guidance of a few days ago and a likely cold shot to end the month, 2021 is still on course to become the 6th out of the last 7 years during which September has had a mean temperature of 70° or above in New York City. Prior to 2000, New York City saw such warmth on average once every five years. In short, September has become more an extension of summer than a gateway to autumn in the New York City area.

There is increasing consensus on the long-range guidance that October will be an unseasonably warm month. The first half could feature much above normal readings in the Northern Plains into Central Canada.

Fall 2021 will likely be wetter to much wetter than normal in the northern Middle Atlantic region. Since 1869, there have been 9 August cases where New York City picked up 20.00" or more rainfall during the summer. Two thirds of those cases (and 4/5 of those with summer mean temperatures of 73.0° or above) had 17.00" or more fall precipitation in New York City. 2011 is probably the closest match in terms of precipitation and a nearly identical summer mean temperature. Mean fall precipitation for those 9 cases was 14.86". The median was 17.35". The 1991-2020 normal value is 12.27".

The ENSO Region 1+2 anomaly was +0.2°C and the Region 3.4 anomaly was -0.4°C for the week centered around September 15. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +0.03°C and the ENSO Region 3.4 anomaly has averaged -0.45°C. Neutral ENSO conditions will likely prevail through September. Afterward, La Niña conditions could begin to develop.

The SOI was -18.18 today.

The preliminary Arctic Oscillation (AO) figure was +0.787 today.

On September 22 the MJO was in Phase 4 at an amplitude of 1.305 (RMM). The September 21-adjusted amplitude was 1.553 (RMM).

Based on sensitivity analysis applied to the latest guidance, there is an implied 86% probability that New York City will have a warmer than normal September (1991-2020 normal). September will likely finish with a mean temperature near 70.5° (1.3° above normal).


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How is this for a hurricane season. 1954, Carol at the end of August caused widespread damage across our area and New England. A few weeks later Edna crossed Cape Cod causing widespread damage and very heavy rains and strong winds across our area. Over 9 inches at Brookhaven Labs on Long Island. Then about 3 weeks later in the beginning of October, Hazel well to our west gave some of the highest wind gusts in our area, ever recorded. The next season in August Connie and Dianne gave some of the worst flooding our area has ever seen, especially in Connecticut. All this in one years time.

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The last 6 days of September  are averaging 67degs.(60/75), or +2.

Month to date is  71.7[1+4].         September should end near  70.8[+1.6].

Reached 76* here yesterday.

Today: 73-76, variable wind, some clouds late.

9/27-10/03....N, BN.  10/04-11+....AN

61*(76%RH) here at 6am, m. clear.     65* at 9am.       67* at 10am.       70* at Noon         73* at 3pm.       76* at 4pm.       Reached 77* at 4:30pm.


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For now, very little to favor widespread qpf late Sept 30-Oct3 with 00z/25 ensembles a little further se.  Still think it's not impossible for a closer in low (separate from Sam).

In the meantime, if we cant muster the quarter inch late Monday-Wed morning, then we will probably miss out on a 10" Sept for CP.  UK is drier on this than most other modeling.

Tonight: Still interesting to watch this neg tilt 500MB short wave response NYC eastward late today/tonight. 

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Morning thoughts…

Today will be mostly sunny and pleasantly warm. High temperatures will likely reach the middle and upper 70s in most of the region. A few locations could reach or exceed 80°.  Likely high temperatures around the region include:

New York City (Central Park): 75°

Newark: 79°

Philadelphia: 77°


New York City: 30-Year: 72.7°; 15-Year: 73.9°

Newark: 30-Year: 74.3°; 15-Year: 75.6°

Philadelphia: 30-Year: 75.5°; 15-Year: 76.6°

Tomorrow will be another sun-filled day.

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1 hour ago, bluewave said:

Looks like your area will probably finish with a top 3 warmest September minimum temperature. Model blends have a low near 50° at HPN for the last day of September. But lows closer to normal for the last week of September definitely feel more fall-like compared to recent experience.

1991-2020 new average low for HPN on 9-30 is 51°

White Plains, NY
   Sunny    Sunny    Sunny    Ptcldy   Ptcldy   Ptcldy   Ptcldy
     /73    56/71    54/73    58/72    52/67    50/66    50/66
      /00    10/10    00/00    20/30    30/20    10/10    10/10


Time Series Summary for WESTCHESTER CO AP, NY - Month of Sep
Click column heading to sort ascending, click again to sort descending.
Lowest Min Temperature 
Missing Count
1 2021 52 6
2 2018 51 0
3 2008 48 0
- 2002 48 0
- 1999 48 2
- 1968 48 0

52 this morning

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Down to 50 and now up to 68 and bright sunshine. This will make three very nice weekends in a row.   GFS would have a 4 peat and ECM not so much next weekend.  ECM is cut off ULL city from mid week  9/30 on the GFS keeps the ULL into northeast.  SO will be a matter of progression to see much rain/clouds cool we can get in the 10/2 - 10/5 period.  Sam looks just a bit outside the coast.  beyond that heights look to rise towards the second week of Oct.  12 hours of daylight today as we descend into the dregs of the longer days.


Just a great next fews days at least in tap 70s / 50s and lots of sun.

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I probably should throw in the towel on anything significant Sept 30-Oct 3;  but 12z/25 GEFS still wants to separate the streams with a closed low 'trying' to form near the mid Atlantic coast, whereas the EPS has vigorous closed low up near Maine and no opportunity for significant qpf after Wednesday morning. Strange, that the EPS brings SAM closer than then the GEFS in this pattern.  

I guess I look at it like this: climatologically it rains every 3 days or so (trace included).  I think we're pretty much assured of measurable Tuesday. After that, next measurable??

I'll check back if 12z/25 GEFS looks to be more accurate than the 12z/25 EPS, or Tuesday, whichever comes first. 

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