September 2020 wx discussion

[uofmiami]

48 minutes ago, lee59 said:

As many named storms as we have had this season, so far, it really has not been as bad as it could have been. Many of the storms were weak and fortunately we have had only a few hurricanes and one major. It is now mid September and in a few weeks we will be past peak, very active right now and even though the waters are warm, wind shear has been helping to keep many of the storms this season at bay. Of course things can change fast.

Don’t go jinxing us. 

[bluewave]

22 hours ago, LibertyBell said:

I was wondering about the winter implications of this sudden switch

 

22 hours ago, LibertyBell said:

meh if thats the reason then it wont stop us from having another mild winter.  I remember a few years in the late 80s and early 90s were like this (cold falls, mild winters).....

 

We have a pretty good idea that this will be the 5th consecutive winter with a La Niña-like base state. The North Pacific Ridge was able to extend NE into Alaska in 16-17 and 17-18 allowing for snowy and warm. The El Niño couldn’t couple in 18-19 due to all the record Niña-like SST warmth in the WPAC. So we had the La Niña ridge north of Hawaii and SE ridge for a mild and nearly snowless DJF. The record WPAC warmth in 19-20 set new records north of Australia. So we got a continuation of record MJO 4-6 amplitude and the Niña-like ridge north of Hawaii and SE Ridge. Warm and even less snowy overall than the previous year since we didn’t get the Nov and Mar snows. This fall we will be looking for clues as to which type of La Niña winter we will have this year. It often comes down to how much snow NYC can pick up in December. All the Niña-like Decembers with under 3.0” of snow in NYC since 1995 featured below normal snowfall seasons. While all above 3.0” finished normal to above normal.

Monthly Total Snowfall for NY CITY CENTRAL PARK, NY
Click column heading to sort ascending, click again to sort descending.

Year	Oct	Nov	Dec	Jan	Feb	Mar	Apr	Season
2019-2020	0.0	0.0	2.5	2.3	T	T	T	4.8
2018-2019	0.0	6.4	T	1.1	2.6	10.4	0.0	20.5
2017-2018	0.0	T	7.7	11.2	4.9	11.6	5.5	40.9
2016-2017	0.0	T	3.2	7.9	9.4	9.7	0.0	30.2

 

 

2011-2012	2.9	0.0	0.0	4.3	0.2	0.0	0.0	7.4
2010-2011	0.0	T	20.1	36.0	4.8	1.0	T	61.9

 

2008-2009	0.0	T	6.0	9.0	4.3	8.3	T	27.6
2007-2008	0.0	T	2.9	T	9.0	T	0.0	11.9

 

2005-2006

0.0

T

9.7

2.0

26.9

1.3

0.1

40.0

 

2001-2002	0.0	0.0	T	3.5	T	T	T	3.5
2000-2001	T	0.0	13.4	8.3	9.5	3.8	0.0	35.0
1999-2000	0.0	0.0	T	9.5	5.2	0.4	1.2	16.3
1998-1999	0.0	0.0	2.0	4.5	1.7	4.5	0.0	12.7

 

1996-1997	0.0	0.1	T	4.4	3.8	1.7	T	10.0
1995-1996	0.0	2.9	11.5	26.1	21.2	13.2	0.7	75.6

[dWave]

Partly cloudy 71, after a low of 61

[MJO812]

Will Sally give the area rain next week ?

[wdrag]

34 minutes ago, MJO812 said:

Will Sally give the area rain next week ?

So it's trending closer for late Thursday or Friday. Added 12z GEFS/EPS tracks which are decidedly closer than the 820AM post.  Also NAEFS 52 member mean which offers us on the northern fringe of near 1/2" (10MM).  NAEFS probs for 2" are not in yet.  Fast moving but a possibility of rainfall enhancement Friday, if it doesn't pass too far south.  For now, the trends in the past 12 hours are slightly more favorable.

 

[forkyfork]

8 hours ago, wdrag said:

Forgot to add the radar appearance quote from mweisenfeld. 

 

Not Birds:  AP with temperature inversion developing near or after sunset. Shows some nearby non-moving targets near radar and not too distant hills. Here is more information below. Extracted from sensAgent.com

 

The position of the radar echoes depend heavily on the standard decrease of temperature hypothesis. However, the real atmosphere can vary greatly from the norm. Anomalous Propagation (AP) refers to false radar echoes usually observed when calm, stable atmospheric conditions, often associated with super refraction in a temperature inversion, direct the radar beam toward the ground. The processing program will then wrongly place the return echoes at the height and distance it would have been in normal conditions.^[2]

This type of false return is relatively easy to spot on a time loop if it is due to night cooling or marine inversion as one sees very strong echoes developing over an area, spreading in size laterally, not moving but varying greatly in intensity with time. After sunrise, the inversion disappears gradually and the area diminishes correspondingly. Inversion of temperature exists too ahead of warm fronts, and around thunderstorms' cold pool. Since precipitation exists in those circumstances, the abnormal propagation echoes are then mixed with real rain and/or targets of interest, which make them more difficult to separate.

Anomalous Propagation is different from ground clutter, ocean reflections (sea clutter), biological returns from birds and insects, debris, chaff, sand storms, volcanic eruption plumes, and other non-precipitation meteorological phenomena. Ground and sea clutters are permanent reflection from fixed areas on the surface with stable reflective characteristics. Biological scatterer gives weak echoes over a large surface. These can vary in size with time but not much in intensity. Debris and chaff are transient and move in height with time. They are all indicating something actually there and either relevant to the radar operator and/or readily explicable and theoretically able to be reproduced. AP in the sense of radar is colloquially known as "garbish" and ground clutter as "rubbage".

Doppler radars and Pulse-Doppler radars are extracting the velocities of the targets. Since AP comes from stables targets, it is possible to subtract the reflectivity data having a null speed and clean the radar images. Ground, sea clutter and the energy spike from the sun setting can be distinguished the same way but not other artifacts.^[2][3] This method is used in most modern radars, including air traffic control and weather radars.

birds.

[Tatamy]

4 hours ago, SACRUS said:

Lots of clouds

 

 

Any one take notice of the shadowing effect on the cloud deck caused by the easterly flow drying out slightly as it crossed LI and NYC extending into eastern PA.  This has been seen on visible satellite almost all day.  This is not something that I can recall seeing.

[donsutherland1]

At Jones Beach, the temperature rose into the lower 70s, but there was a stiff onshore breeze. Three photos from this afternoon:

[donsutherland1]

Despite bright sunshine, today provide a preview of autumn. High temperatures reached only the lower and middle 70s in most areas. Select high temperatures included:

Baltimore: 75°
Boston: 67°
Islip: 71°
New York City: 74°
Newark: 74°
Philadelphia: 76°
Washington, DC: 75°

Tomorrow will be partly cloudy and somewhat warmer.

The season's coolest air mass so far could arrive next week. The temperature will very likely fall into the 50s in New York City's Central Park for the first time since June 15. Generally below normal readings could persist into at least the last week of September.

The ENSO Region 1+2 anomaly was -1.6°C and the Region 3.4 anomaly was -0.9°C for the week centered around September 2. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.08°C and the ENSO Region 3.4 anomaly has averaged -0.72°C. La Niña conditions have developed and will likely prevail through the remainder of autumn.

The SOI was +6.30.

Today, the preliminary Arctic Oscillation (AO) figure was +1.146.

On September 11, the MJO was in Phase 4 at an amplitude of 0.931 (RMM). The September 10-adjusted amplitude was 0.899.

Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°. Overall, the evolution of ENSO, along with the observed ongoing monthly warming (1.6°/decade in NYC and 1.5°/decade in the Northeast Region during September 1990-2019), favors a warmer than normal September.

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 54% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.9°.

Finally, on September 11, Arctic sea ice extent was 3.571 million square kilometers (JAXA). Based on 2010-2019 data, the highest 25% bound was 3.742 million square kilometers. The lowest 25% bound was 3.581 million square kilometers. The lowest 10% bound is 3.465 million square kilometers. 2020 is the second consecutive year with a minimum extent figure below 4.000 million square kilometers and the third such year on record. 2020 also has, by far, the second lowest figure on record.

 

[doncat]

3 hours ago, Tatamy said:

Any one take notice of the shadowing effect on the cloud deck caused by the easterly flow drying out slightly as it crossed LI and NYC extending into eastern PA.  This has been seen on visible satellite almost all day.  This is not something that I can recall seeing.

Yeah I love looking at the visible loops and searching out things like that.

[JustinRP37]

7 hours ago, MJO812 said:

Will Sally give the area rain next week ?

Would be nice if she would drop off some tomato pies. A joke for those from CT. Mmm I could go for some Sally’s right about now. In all seriousness though hopefully this one doesn’t strengthen. Louisiana is in very rough shape.

[SACRUS]

9/12

PHL: 76
EWR: 74
NYC: 74
LGA: 73
TEB: 73
ACY: 73
TTN: 73
JFK: 72
New brnswck: 72
ISP: 71
BLM: 70

[CIK62]

The next 8 days are averaging 68degs.    Make it 63degs., or -5.5.      This agrees with the EURO for the next 8.      We could be   -0.4   by the 21st.

66*(77%RH) at 6am, overcast.      71*(81%RH) by 10am.

The Tropics:    27N 85W(watch me work), 29N 61W,  26N 47W( a twerp), 11N 36W.    Maybe quieter after this last one.

All the models look incapable of dealing with all these multiple vorticities.

[wdrag]

15 hours ago, forkyfork said:

birds.

I don 't think so. Not likely after sundown... and the best way to see is a loop where you can see them moving, best time tends to be near sunrise. 

[wdrag]

On Sally: not starting a topic until I see a decent chance of 2+" of rain in our forum(would have to be southeast edge) or resultant pressure gradient creating gale-tropical northeast wind gusts. Right now the NAEFS prob for 2" is less than 20%.  Most of the guidance is a potential grazer contributing impact for the southern edge of our NYC forum. So yes, Sally might contribute-enhance potential for a brief nor'easter??  but I don't think it's worth a topic at this point due to likelihood of main hazard risk being only for marine (gale gusts s&e of LI?). You're welcome to start a topic-just doesn't look abnormal to me (at least for rain, and should  not be much, if any, player in se NYS which missed a lot of this past Thursday's rain).

Graphics: Added 00z/13 EPS, 06z GEFS 24 hr rainfall ending 00z/Sat, and 00z EPS Sally tracks, plus 24 hr NAEFS rainfall for Wed, Thu, Fri-just check the legends. Isohyets In MM, so 10 MM, is about 4 tenths of an inch. Variability of ensemble rainfall is color coded in the legends.

Basically this post is in agreement with WPC D1-7 QPF from earlier this morning. 753A/13

[donsutherland1]

Morning thoughts...

Today will be partly cloudy and a bit warmer than yesterday. A shower or thundershower is possible during the afternoon or evening as a cold front moves across the region. Temperatures will likely reach the middle and upper 70s across much of the region. Likely high temperatures around the region include:

New York City (Central Park): 76°
Newark: 78°
Philadelphia: 80°

Cooler air will arrive for tomorrow. Much of the coming week will feel like early autumn. An even colder air mass could arrive late in the week.  

 

[MJO812]

66 right now in Sheepshead  Bay

 

Beautiful  weather coming up with highs in the low 70s this week and possibly highs in the mid to upper 60s next weekend. 

[lee59]

Sally seems to want to follow a similar path as Laura after it makes landfall. I barely got a shower out of Laura.

[SACRUS]

Low of 55.  Now 74 / 64 with sunshine.  Fri and Sat were more cloudy than forecast and today so far more sunny..  Back and forth pattern the next 5 - 6 days warm Sun / Mon cooler Tue and Wed AM before more warmth and humid air Wed PM through  Fri.  Wed and Thu 850s reach >16C but clouds and rain from sally will keep temps capped in the low 80s.  Any delay or miss from Sally Thu could be sneaky hot day especially in the hotter spots.

9/19 - 9/24 = Coolest since May peaking Mon (9/21) and Tue (9/22).  Beyond there cool pocket slow to erode over the northeast but warmer end to the month looks likely with more ridging sustained in the east.

[bluewave]

This could be our first year with 30 or more 90° days with 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

 

 

 

[Brian5671]

59 minutes ago, lee59 said:

Sally seems to want to follow a similar path as Laura after it makes landfall. I barely got a shower out of Laura.

with the fast Pac flow, I could see a sharp recurve to the east and we get nothing.

[qg_omega]

2 minutes ago, Brian5671 said:

with the fast Pac flow, I could see a sharp recurve to the east and we get nothing.

Remember when the WAR was forecasted for early September and always under forecasted?

[MJO812]

14 minutes ago, qg_omega said:

Remember when the WAR was forecasted for early September and always under forecasted?

Yep

This time frame was supposed to be dangerous for the east coast with the big ridge 

[bluewave]

The strong  WAR without a deep trough in the MW/GL favors the SE and GOM like we are seeing with Sally. Notice how the trough remained up near Hudson Bay and couldn’t dig.We’ll have to see if the Euro stronger WAR verifies later in the week with the northern fringe of the remnant Sally moisture streaming into our area. 

 

 

 

 

[forkyfork]

4 hours ago, wdrag said:

I don 't think so. Not likely after sundown... and the best way to see is a loop where you can see them moving, best time tends to be near sunrise. 

they are mass migrating at several hundred feet up and it shows on velocity

[forkyfork]

https://birdcast.info/news/a-primer-for-using-weather-surveillance-radar-to-study-bird-migration/

[Nibor]

1 hour ago, forkyfork said:

they are mass migrating at several hundred feet up and it shows on velocity

I was just in the Adirondacks where autumn is becoming visually apparent and found it eerie how there were virtually no birds chirping. The migration is definitely happening. 

[SnoSki14]

1 hour ago, bluewave said:

The strong  WAR without a deep trough in the MW/GL favors the SE and GOM like we are seeing with Sally. Notice how the trough remained up near Hudson Bay and couldn’t dig.We’ll have to see if the Euro stronger WAR verifies later in the week with the northern fringe of the remnant Sally moisture streaming into our area. 

 

 

 

 

That looks a bit more favorable for winter if that type of pattern were to hold. Maybe more like 16/17. 

[bluewave]

3 hours ago, SnoSki14 said:

That looks a bit more favorable for winter if that type of pattern were to hold. Maybe more like 16/17. 

The NPM is remaining strongly positive even with the developing La Niña and -PDO. At least right now, we are getting more ridging out there than we typically see this time of year with a La Niña. But it’s still too early to know if this is a temporary pattern or can hold on into the fall and winter. Last winter the NPM dropped as the +EPO vortex took over.

 

[donsutherland1]

Under variably cloudy skies, temperatures reached the lower and middle 70s. The season's coolest air mass so far will arrive tomorrow.

Strengthening Tropical Storm Sally brought heavy rain to parts of southwestern Florida today. At Naples: 3.47" fell. The 2-day total was 5.06". At Fort Myers, daily rainfall was 1.84" (old record: 1.33", 1975). Sally will likely continue to strengthen overnight before making landfall along the Louisiana coast on Monday night.

During Monday night, the temperature will fall into the 50s in New York City's Central Park for the first time since June 15. An even cooler air mass could arrive late in the week. Generally below normal readings could persist into at least the last week of September. There is an increasing possibility that September could wind up on the cool side of normal, which would be an uncommon event in recent cases preceding La Niña winters.

The newly-released subseasonal guidance is in strong consensus that a generally cool regime could last through the first week of October. The latest EPS weeklies forecast an end to the cool anomalies near the end of September.

The ENSO Region 1+2 anomaly was -1.6°C and the Region 3.4 anomaly was -0.9°C for the week centered around September 2. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -1.08°C and the ENSO Region 3.4 anomaly has averaged -0.72°C. La Niña conditions have developed and will likely prevail through the remainder of autumn.

The SOI was +3.03.

Today, the preliminary Arctic Oscillation (AO) figure was +0.636.

On September 12, the MJO was in Phase 4 at an amplitude of 0.813 (RMM). The September 11-adjusted amplitude was 0.935.

Since 1990, there have been 11 La Niña events, 6 of which followed an El Niño winter. 10/11 (91%) case saw warmer than normal September. All 6 following an El Niño winter were warmer than normal. September mean temperatures for New York City for those cases were: 11 cases: 69.9°; Subset of 6 cases: 70.8°; Entire 1990-2019 period: 69.0°. The September mean temperature for all La Niña and neutral-cool cases following an El Niño winter (1950-2019: n=13) was 69.9°.

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 50% probability that New York City will have a warmer than normal September. September will likely finish with a mean temperature near 68.5°.

Finally,on September 12, Arctic sea ice extent was 3.564 million square kilometers (JAXA). That was just above the figure of 3.562 million square kilometers reached on September 11. Based on 2010-2019 data, the highest 25% bound was 3.742 million square kilometers. The lowest 25% bound was 3.581 million square kilometers. The lowest 10% bound is 3.465 million square kilometers. 2020 is the second consecutive year with a minimum extent figure below 4.000 million square kilometers and the third such year on record. 2020 also has, by far, the second lowest extent on record.