September 2020 wx discussion

[uncle W]

last year was the ninth time NYC had a higher temperature in October than in September...its possible it can happen again though chances are not great at this time...from 1938-1941 it happened three times in four years...

year....Sept....Oct....

2019....89........93

1997....83........85

1975....81........83

1949....87........88

1941....93........94

1939....88........91

1938....86........90

1928....85........86

1883....79........80

[CIK62]

The last 2 days of September are averaging 71degs.      Making it 68, or +3.5.

Month to date is  +0.5[68.5].        September should end at 68.4, within +1.0.

The first 10 days of October are averaging 62.5 on the GFS-just Normal.     With its +6 to +8 bias at this range, BN for the period seems certain.

68%(97%RH) here at 6am.   69* at 6:30am, overcast.

[EastonSN+]

11 hours ago, donsutherland1 said:

Clouds broke for sunshine this afternoon. In response, the temperature rose into the upper 70s and lower 80s. A frontal boundary will approach the region later tomorrow and a storm will develop along the front and move northward. Late Tuesday into Wednesday, the region will likely see a general 0.50"-1.50" of rain with some locally higher amounts. Temperatures will likely remain at generally above normal levels for the remainder of September.

Phoenix has an implied near 100% probability of recording just its 13th September on record with a mean temperature of 90° or above. The most recent such occurrence was 2018 with a mean temperature of 91.8°. Phoenix will very likely record its hottest June-September period on record with a four-month mean temperature of near 95.4°. That would exceed the previous June-August record of 95.1°, which was set in 2013 and tied in 2015. The existing record is 93.9°, which was set in 2011.

A cool shot is likely during the opening week of October, but warmer readings could return during the following week. The latest EPS weeklies favor the development of a sustained warmer than normal pattern for the second half of October.  

October could be wetter than September in and around the New York City area. Since 1950, 10 of the 12 (83%) of the La Niña cases that followed an El Niño winter saw October receive more precipitation than September, including 7 of the 8 (88%) cases since 1980. October 1954 and October 1998 were the exceptions. The largest increase in precipitation occurred in 2005. September 2005 saw just 0.48" precipitation in New York City. October 2005 received 16.73" precipitation.  

The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.0°C for the week centered around September 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.92°C and the ENSO Region 3.4 anomaly has averaged -0.87°C. La Niña conditions will likely prevail into at least the start of winter.

The SOI was +8.62.

Today, the preliminary Arctic Oscillation (AO) figure was +0.139.

On September 27 the MJO was in Phase 5 at an amplitude of 1.275 (RMM). The September 26-adjusted amplitude was 1.392.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO.   

Based on sensitivity analysis applied to the latest guidance, there is an implied 98% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.7°.

 

Thanks Don!

2016 2017 was a surprisingly good winter with 2 major snow events and above average snowfall for the year. Hopefully this winter mimic's.

[donsutherland1]

7 minutes ago, EastonSN+ said:

Thanks Don!

2016 2017 was a surprisingly good winter with 2 major snow events and above average snowfall for the year. Hopefully this winter mimic's.

2016-17 would be a major upgrade from the non-winter we just went through. Hopefully, the coming winter will be far better. 

[donsutherland1]

Morning thoughts...

At 9:10 am, a cold front stretched from central Alabama to central Quebec. Showers and thundershowers accompanied that front. A storm will develop along that front and bring a widespread 0.50"-1.50" rainfall to much of the region from later today into tomorrow. Some areas could pick up enhanced rainfall amounts in excess of 2.50". Overall, today will be mainly cloudy with some showers and perhaps thundershowers. Steadier rain will likely develop during the afternoon or evening. Temperatures will likely reach the middle 70s across the region. Likely high temperatures around the region include:

New York City (Central Park): 76°
Newark: 77°
Philadelphia: 76°

Tomorrow will still be mild, but cooler air will arrive to start October.

 

[bluewave]

Looking like our first year with 30 or more 90° days and  none in the spring or fall. 
 

Monthly Number of Days Max Temperature >= 90 for LAGUARDIA AIRPORT, NY
Click column heading to sort ascending, click again to sort descending.

Year	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Annual
2010	0	0	0	1	2	12	18	11	4	0	0	0	48
2018	0	0	0	0	4	4	10	16	4	0	0	0	38
2002	0	0	0	2	0	5	14	13	1	0	0	0	35
2020	0	0	0	0	0	5	19	10	0	M	M	M	34
1991	0	0	0	0	4	9	10	9	2	0	0	0	34
2016	0	0	0	0	3	1	15	10	3	0	0	0	32
1983	0	0	0	0	0	5	11	8	7	0	0	0	31
2005	0	0	0	0	0	7	10	10	3	0	0	0	30
1953	0	0	0	0	1	7	10	9	3	0	0	0	30

 

[frd]

1 minute ago, bluewave said:

Looking like our first year with 30 or more 90° days and  none in the spring or fall. 

Hmm, maybe late season blocking combined with early season blocking. And, the positioning of the WAR further North leading to all that heat up in New England.  ( East/ESE  flow below ) Not sure honestly the reason(s), but very interesting stat. Some climate stations in certain locations in the US are totally opposite from this time last year, whether that is a clue for the future remains to be seen.    

[SACRUS]

73/ 68 cloudy off a low of 61.  Front nearby with showers into PA.  Clouds and rain next 36 hours with areas in the >1 inch range later on Wednesday (first measurable rain since 9/11 three weeks ago .  Cooler air reinforced with another front Friday some showers and light rain, again airmass is not as cool as the 9/19 - 9/22 airmass.  Trouh deepens again ealry next week Mon (10/5  and Tue 10/6 with more rain.  Cooler air 10/5 - 10/7 or 8 before a potential major more sustained warmup.  Initially yesterday seemed like the warmest day till next year but may need to rethink that for the 10/10 and beyond timeframe.  Also cant rule out southeast tropics in the same timeframe..

[frd]

14 minutes ago, SACRUS said:

Initially yesterday seemed like the warmest day till next year but may need to rethink that for the 10/10 and beyond timeframe.  Also cant rule out southeast tropics in the same timeframe..

 

Warming would be acceptable without the crazy dews please.

As you mentioned,  warming seems likely as the EPS and the weeklies like the idea of moderation after the 10th, or so. Might be able to do one last beach trip. Granted surf zones temps have lost that mid summer feel, but will still give it a go if we can maintain above 65 degrees.     

 

[winterwx21]

31 minutes ago, SACRUS said:

73/ 68 cloudy off a low of 61.  Front nearby with showers into PA.  Clouds and rain next 36 hours with areas in the >1 inch range later on Wednesday (first measurable rain since 9/11 three weeks ago .  Cooler air reinforced with another front Friday some showers and light rain, again airmass is not as cool as the 9/19 - 9/22 airmass.  Trouh deepens again ealry next week Mon (10/5  and Tue 10/6 with more rain.  Cooler air 10/5 - 10/7 or 8 before a potential major more sustained warmup.  Initially yesterday seemed like the warmest day till next year but may need to rethink that for the 10/10 and beyond timeframe.  Also cant rule out southeast tropics in the same timeframe..

This thing is moving very quickly ... the rain is going to be ending early in the morning tomorrow. So I'm not sure where you're getting the 36 hours. It isn't even going to be 24 hours.

[Stormlover74]

43 minutes ago, winterwx21 said:

This thing is moving very quickly ... the rain is going to be ending early in the morning tomorrow. So I'm not sure where you're getting the 36 hours. It isn't even going to be 24 hours.

Yeah the sun will be out by 9am

[SnoSki14]

1 hour ago, frd said:

 

Warming would be acceptable without the crazy dews please.

As you mentioned,  warming seems likely as the EPS and the weeklies like the idea of moderation after the 10th, or so. Might be able to do one last beach trip. Granted surf zones temps have lost that mid summer feel, but will still give it a go if we can maintain above 65 degrees.     

 

The problem with these long range forecasts is the hyper fast pacific jet will keep causing rapid shifts. 

I'm not convinced we see a big warmup after October 10. So far there's been a tendency for ridging to build out west and that could continue.

[bluewave]

64th day this year at JFK with a 70° or higher dew point. This brings JFK into 4th place. The top 4 years were all since 2016.
 

Kennedy Intl   LGT RAIN  72  70  

 

[frd]

1 hour ago, SnoSki14 said:

The problem with these long range forecasts is the hyper fast pacific jet will keep causing rapid shifts. 

I'm not convinced we see a big warmup after October 10. So far there's been a tendency for ridging to build out west and that could continue.

Rational possibility. Also, on a related note, the average temps continue to drop at a good clip, as does the length of daylight. DST begins in about a month on November 1 st. 

[Allsnow]

I have noticed some foliage starting to pop around town the past few days 

[donsutherland1]

A frontal boundary will cross the region tonight into tomorrow with a storm moving northward along that front. The region will likely see a general 1.00"-2.00" rainfall by the time the storm departs tomorrow. Eastern New England will likely see lesser amounts. Some pockets of amounts in excess of 2.50" are likely. The month will end on a mild note.

Phoenix has an implied near 100% probability of recording just its 13th September on record with a mean temperature of 90° or above. The most recent such occurrence was 2018 with a mean temperature of 91.8°. Phoenix will record its hottest June-September period on record with a four-month mean temperature of near 95.4°. That would exceed the previous June-August record of 95.1°, which was set in 2013 and tied in 2015. The existing record is 93.9°, which was set in 2011.

A cool shot is likely during the opening week of October, but warmer readings could return during the following week. The latest EPS weeklies favor the development of a sustained warmer than normal pattern for the second half of October. Overall, October will likely be somewhat warmer than normal in much of the region.  

October could be wetter than September in and around the New York City area. Since 1950, 10 of the 12 (83%) of the La Niña cases that followed an El Niño winter saw October receive more precipitation than September, including 7 of the 8 (88%) cases since 1980. October 1954 and October 1998 were the exceptions. The largest increase in precipitation occurred in 2005. September 2005 saw just 0.48" precipitation in New York City. October 2005 received 16.73" precipitation.  

The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.0°C for the week centered around September 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.92°C and the ENSO Region 3.4 anomaly has averaged -0.87°C. La Niña conditions will likely prevail into at least the start of winter.

The SOI was +7.01.

Today, the preliminary Arctic Oscillation (AO) figure was +0.139.

On September 28 the MJO was in Phase 5 at an amplitude of 1.495 (RMM). The September 27-adjusted amplitude was 1.277.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO.   

Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.8°.

 

[doncat]

73/65 split today...0.35" rain so far.

[Rtd208]

Picked up 0.52" of rain for the day.

[SACRUS]

9/29

New Brnswck: 77
PHL: 77
ACY: 76
BLM: 76
ISP: 75
EWR: 74
LGA: 74
TEB: 74
TTN: 74
NYC: 74
JFK: 72

[Rtd208]

Moderate to heavy rain falling here.

[Rtd208]

Have picked up 0.80" of rain since midnight. Storm total of 1.32" of rain so far.

[CIK62]

The last day of September is averaging 69degs.      Making it 66degs., or +1.5.    [[The first 7 days of October are averaging 65degs, making it 60degs., or -3.0]]

Month to date is  +0.7[68.9].       September should end at +0.8[68.8].      Remember my 1968 Almanac had a 30-Year Normal of 68.5 back then---it caught the Dirty 30's---in that.     September has LOST 0.5 degree because of global warming?! 

63*(97%RH) here at 6am, streets wet, mean looking overcast with breaks.    61*(91%RH) by 9am, breezy and clearing up.         67*(RH62%). by 2pm.       71*(53%) by 4pm.

[bluewave]

Record 7th consecutive September above 70° at LGA. The NYC and EWR version of this is 7 consecutive years above 68°.

Monthly Mean Avg Temperature for LAGUARDIA AIRPORT, NY
Click column heading to sort ascending, click again to sort descending.

Year	Sep	Season
2020	71.2	71.2
2019	72.1	72.1
2018	72.8	72.8
2017	71.5	71.5
2016	73.8	73.8
2015	74.1	74.1
2014	70.4	70.4
2013	68.1	68.1

Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY
Click column heading to sort ascending, click again to sort descending.

Year	Sep	Season
2020	68.9	68.9
2019	70.4	70.4
2018	70.7	70.7
2017	70.5	70.5
2016	71.8	71.8
2015	74.5	74.5
2014	69.7	69.7
2013	67.9	67.9

 

Monthly Mean Avg Temperature for NEWARK LIBERTY INTL AP, NJ
Click column heading to sort ascending, click again to sort descending.

Year	Sep	Season
2020	69.2	69.2
2019	70.8	70.8
2018	71.4	71.4
2017	70.9	70.9
2016	71.8	71.8
2015	73.4	73.4
2014	69.8	69.8
2013	67.2	67.2

 

 

 

[donsutherland1]

Morning thoughts...

A storm that moved along an advancing cold front brought a soaking rain to much of the region into early this morning. Rainfall totals through 8 am included:

Allentown: 1.49"
Bridgeport: 0.85"
Islip: 0.39"
New York City: 1.61"
Newark: 1.48"
Philadelphia: 2.13"
Poughkeepsie: 2.54"
Scranton: 1.37"
White Plains: 1.55"

As the storm pulls away, clouds will give way to sunshine. Temperatures will likely reach the upper 60s and lower 70s across the region. Likely afternoon high temperatures around the region include:

New York City (Central Park): 69°
Newark: 71°
Philadelphia: 70°

The first week of October will likely be cooler than normal.

 

[doncat]

Rain wise, this month featured a 17 day dry spell and just 3 real rain events...they were all significant however so station rainfall of 4.85" was above normal.

[Rtd208]

Storm total rainfall of 1.33" here.

[thunderbolt]

Just over 2 inches in the rain gauge Langhorne PA

[donsutherland1]

New York City is concluding September with a monthly mean temperature of 68.8° (0.8° above normal). A somewhat warmer than normal October lies ahead, with the second half of the month likely to be warmer relative to normal than the first half.

Phoenix recorded just its 13th September on record with a mean temperature of 90° or above with a monthly mean temperature of 91.5°. That made September 2020 the 3rd warmest September on record. Phoenix also registered its hottest June-September period on record with a four-month mean temperature of 95.4°. The previous record was 93.9°, which was set in 2011. The June-September 2020 figure also exceeded the previous summer (June-August) record of 95.1°, which was set in 2013 and tied in 2015.

Climate change contributed to this most recent heat event. Climate change has increased the frequency, magnitude, and duration of extreme heat events in the United States and worldwide. Further increases are likely in coming decades as the world's climate continues to warm (for more information, refer to the links in the note below this discussion).

The opening week of October will see generally cooler than normal conditions. No exceptional cold is likely. Warmer readings could return during the following week, though a renewed push of cool air remains possible. The latest EPS weeklies favor the development of a sustained warmer than normal pattern for the second half of October. The development of this warmth also shows up on the 63-ensemble MME subseasonal guidance and latest weekly CFSv2 guidance. Overall, October will likely be somewhat warmer than normal in much of the region with temperatures generally 0.5° - 1.5° above normal.

October could also be wetter than September in and around the New York City area. Since 1950, 10 of the 12 (83%) of the La Niña cases that followed an El Niño winter saw October receive more precipitation than September, including 7 of the 8 (88%) cases since 1980. October 1954 and October 1998 were the exceptions. The largest increase in precipitation occurred in 2005. September 2005 saw just 0.48" precipitation in New York City. October 2005 received 16.73" precipitation.  

The ENSO Region 1+2 anomaly was -0.8°C and the Region 3.4 anomaly was -1.0°C for the week centered around September 23. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.92°C and the ENSO Region 3.4 anomaly has averaged -0.87°C. La Niña conditions will likely prevail into at least the start of winter.

The SOI was +16.11.

Today, the preliminary Arctic Oscillation (AO) figure was -1.039.

On September 29 the MJO was in Phase 5 at an amplitude of 1.555 (RMM). The September 28-adjusted amplitude was 1.498.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 9/10 (90%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO.   

Note:

1. https://www.globalchange.gov/browse/indicator-details/3983
2. https://advances.sciencemag.org/content/6/12/eaay2368
3. https://www.researchgate.net/publication/234114398_Global_increase_in_record-breaking_monthly-mean_temperatures

 

[forkyfork]

every model but the gfs shows a potential nor'easter next week

[SACRUS]

9/30

LGA: 73
EWR: 73
ACY: 73
New Brnswck: 72
BLM: 72
ISP: 72
TEB: 72
JFK: 72
PHL: 71
TTN: 71
NYC: 71