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Isotherm's Summer Outlook 2019 VERIFICATION

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Nice forecast. One thing I'm happy about seeing in your forecast is the less present tropical dews. It was horribly excessive last year.

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9 hours ago, Event Horizon said:

Nice forecast. One thing I'm happy about seeing in your forecast is the less present tropical dews. It was horribly excessive last year.

 

 

Thanks. And yes, I don't anticipate months on end of 70F dew points akin to last year, although periods of very high dew points are likely.

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Hi Isotherm, thanks for that, interesting read.

 

However, just want to flesh out some details on one point you make, which I quote below;

 

"However, recent weeks have seen increasingly negative frictional torque, negative EA MT, which will be reflected in an AAM decline, to a certain extent."

 

However, as I believe it, should the -ve FT not be increasing angular momentum? - This would tie in well with the plots of recent months (see below) in which has seen FT clearly negative for large portions of it, but with, overall, significant amounts of +AAM, especially through the sub-tropics but, temporarily, at more northern latitudes too. Clearly, however, this general +AAM trend continues to be related to a more Nino atmospheric profile which has, at times, continued to promote several northern blocking regimes across the N Atlantic and UK domain, noticeably at present and through large portions of April which were, obviously, in association with increased E'ly momentum through the mid-lats. This was, however, interspersed with more W'ly regimes through late April, which brought a more cyclonic early May profile and, noticeably during early March, but that was also linked to the potent strat vortex too.

 

Just one piece of information, gained in recent months which discusses both variables below and as I have thought is the way things work. 

 

"If there is a net global surface westerly wind, the atmosphere will speed up the earth’s rotation (positive FT), transfer angular momentum to the earth and the atmosphere loses angular momentum. If there is a net easterly surface wind, the atmosphere slows down the earth’s rotation (negative FT) and the atmosphere gains angular momentum"

 

Please do correct me if I'm wrong here, but certainly, hope I'm not!

 

Regards, Matt.

image.png.dda230cd195065fb35ac52af70f8f87e.png

 

 

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Any chance this Autumn will be cooler and start earlier then the previous two?

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48 minutes ago, Weathergeek said:

Any chance this Autumn will be cooler and start earlier then the previous two?

 

 

Well, considering last autumn started October 12th - high chance it will begin earlier than that. But as far as an objectively, "cool," autumn -- low chance right now.

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I wish we had an AAM plot that showed both the tendency and the total AAM anomaly values together. 

 

Then it would be very clear how AAM tendency inevitably oscillates between positive and negative as the atmosphere seeks balance, with large-scale forcing phenomena such as the warm and cool ENSO phases determining how close to true neutrality (i.e. zero total AAM anomaly) the total AAM anomaly can reach; the warm phase (El Nino) tending to keep it above the line and the cool phase (La Nina) below the line.

 

This oscillation on top of the base forcing is what makes it impossible - at least until we have many decades more historical data - to effectively classify historical months by AAM behaviour; there's  a multitude of different factors to that behaviour that are important, such as the number of complete oscillations and how many stayed in line with the base state suggested by the ENSO region SST anomalies versus how many contradicted it.

 

Perhaps a useful approach would be a rigorous classification of historically observed AAM tendency oscillation alongside total AAM anomaly into cycles of different types... hmm, where have I seen something like that before...?

 

Ah yes, the GSDM 😉. Though from personal experience, it's not as simple as going by the phase numbers - it also matters a great deal how large the tendency and total anomaly values are. At which point you start finding that your classes contain only a few years at best, and so we come back to the 'need more data' problem. It's a shame GSDM wasn't monitored pre-1970s, but given the lack of reliable satellite data, it's hardly surprising that it wasn't 🤪.

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2 hours ago, Isotherm said:

Screen_Shot_2019_05_27_at_8_00_35_AM.png

 

Screen_Shot_2019_05_27_at_8_00_22_AM.png

 

Courtesy: Joe Bastardi.

 

The top image is 2018; bottom is now. Note material diminution in warm pool, which played a pivotal role in the interminable WAR and high dew points last summer. We'll see high dew intrusion this summer, but it should be more typical intervals rather than weeks consecutively of 70F dews.

 

Wow. They look nothing alike. Crazy how much of a difference one year can make. 👀

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5 hours ago, Event Horizon said:

 

Wow. They look nothing alike. Crazy how much of a difference one year can make. 👀

 

 

The SSTA profile similarities b/t present [2019] and late May 2002 are quite striking. The degree of structural symmetry is impressive, on a hemispheric and even global scale.

 

qqpav9.png

 

rapzlz.gif

 
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1 hour ago, Isotherm said:

 

 

The SSTA profile similarities b/t present [2019] and late May 2002 are quite striking. The degree of structural symmetry is impressive, on a hemispheric and even global scale.

 

qqpav9.png

 

rapzlz.gif

 

 

Wow. The similarities are all too real here. Now I'm curious about the evolution of this summer. The differences I see here are west of Chile, The Azore to the Carribean Corridor, the Bering Sea, Southern Indian Ocean, and North of Iceland. Everything else seems almost like the same of some variation or similar.   

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On 6/6/2019 at 9:37 PM, Armando S said:

Excellent analysis, discussion, and conversation Isotherm and others (from the teleconnection thread as well - for some reason, I can't comment on there); Tom - excellent summer forecast as there is no such surprise with how superb you are in conveying and output! 

 

 

Thank you very much for those kind comments, @Armando S!

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there were four double el nino years   the second years were 1958, 1977, 1987, 2015...if this el nino we are in continues 2019 will become the fifth time an el nino lasted two years...this is how the temperatures looked for those summers...

summer analogs june.png

summer analogs july.png

summer analogs aug.png

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11 minutes ago, Isotherm said:

http://www.lightinthestorm.com/archives/1195

 

 

VERIFICATION

 

Temperature Departure Forecast JJA: +1 to +2

NYC/NJ Local Station Departures:

NYC: +1.2
LGA: +2
EWR: +1.3
JFK: +1.2
BDR: +1.9

 

ISP: +2.1
 
Mean of all stations: +1.6
 
This fell directly within the target range. The notion that June would be near normal with increasing heat and humidity in July and August was correct, as well as the forecast for at least one major heat spell.
 
Precipitation Forecast for JJA was wetter than normal. Results:
 
NYC: +0.49″
EWR: +2.1″
LGA: +0.53″
JFK: +0.75″
BDR: +0.92″
ISP: -0.35″
 
Mean of all stations = +0.74″ wetter than normal
 
This was a wet and active T-storm season overall, as anticipated in the Northeast and Mid-Atlantic.
 
90 degree day projections / actual:
 
90 Degree Day Projections / actual  through 9/2/2019:

BOS: 14 / 14 error: 0
NYC: 26 / 14 error: +12
LGA: 30 / 23 error: +7

EWR: 33 / 24 error: +9
PHL: 36 / 31 error: +5
DCA: 45 / 52 error: -7
RDU: 52  / 61 error: -9

 

 
Total error: +17 [overall, slightly warmer than anticipated]
 
This was a very good forecast considering the high level of difficulty; the numbers were virtually on target for the Mid-Atlantic and New England. It was slightly too many for the PHL-NYC corridor.
 
Summer Outlook 2019 Grade:
 
This will be considered a hit. The forecast was “A” locally. Including the nation-wide picture, the expectation for a very hot West Coast and Mid-atlantic/SE US was correct, and warmer than normal most other locations. The primary flaw was slightly cooler anomalies in the N/C Plains. The nationwide grade is therefore a B+.
 
The overall final grade is A-
 
 
 
image.thumb.png.4144bd7b4a5cdbbb2d8730f244f6fd8f.png
 
 
 
 
image.thumb.png.9084cad5d9de3312b542beb00b044d2c.png

 

 

Nice isotherm! Any early winter thoughts or still too early?

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2 hours ago, dmillz25 said:

Nice isotherm! Any early winter thoughts or still too early?

 

 

Thanks and not yet but I will be sure to share as we progress through the next month or so.

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