My Summer Outlook 2015

[Isotherm]

The upcoming summer will feature a combination of factors that has not been present for many years. This past winter we saw the return of El Nino conditions in the Pacific (a weak criteria event), for the first time since the winter of 2009-10. The El Nino has intensified significantly over the past couple months, evidenced by frequent, strong westerly wind bursts (WWB’s), dips in SOI daily values to very negative levels, and cooling water temperatures around Australia (which aids in the maintenance / build-up of higher pressures, feeding WWB’s). The SSTA profile in the Pacific indicates a classic basin wide moderate El Nino signature right now, and the latest ENSO forecast models are in strong agreement that we will see further strengthening to at least high-end moderate levels (1.3-1.5c in region 3.4 of the tropical Pacific). The question becomes: does the El Nino reach strong status, and can it possibly attain “super” Nino criteria (2.0c or greater in region 3.4)? Based upon the recent trends, the uptick in strengthening has not been as impressive as super Nino years like 1982 or 1997, for example. However, it’s possible that this El Nino becomes the strongest Nino event since 1997, with peak region 3.4 temperatures slightly warmer than the low-end strong El Nino of 2009-10.

 

 

 

 

This will be a double / second year Nino, since the winter of 2014-15 already featured a weak Nino. The analogs for this type of occurrence are not numerous; there’s very few years that share similarities in terms of ENSO progression. It is possible that the El Nino peaks relatively early – late summer/early autumn – much like the 1986-88 double Nino event which featured a region 3.4 peak of approximately +1.75c in late summer. Many of the forecast models are supporting that notion. The latest IRI model mean is projecting a +1.5c peak in early autumn with a weakening trend to +1.2c by the middle of next winter. Of that model mean, the statistical guidance has a moderate Nino peak of +1.2c while the dynamical model mean has a strong Nino peak of +1.7c. Both sets of model data fall under the 2.0c, super Nino classification. While it is still a somewhat fickle time of year for model data, I think it’s unlikely that we’ll see a super Nino on par with 1982, 1972, or 1997 intensity. We don’t appear to be strengthening quickly enough, and the conditions for rapid intensification are not ideal. However, currently, I would anticipate high-end moderate to possible strong Nino conditions by later this summer. Thus, one will notice that my chosen analogs do reflect the opinion that the El Nino will reach strong criteria.

 

Northern hemispheric teleconnection indices such as the NAO / AO become less important in the summer months in terms of their correlation with CONUS weather; however, they still do play a role in determining the overall ridge/trough orientation. The PDO and EPO are important indicators that have been mentioned quite a bit lately, especially given their role in this recent winter’s excessive mid-level ridging over Alaska. Right now, the PDO remains in a strongly positive modality (+1 to +2). Looking back through history, there were not many oncoming moderate/strong Nino’s with strongly positive PDO’s. 1965, 1972, and 1982 were all strong Nino’s that featured neutral or negative PDO’s (cooler water in the NE/E PAC). The most similar years in terms of the expectation of a moderate-strong Nino and +PDO state are 1957, 1987, and 1997. Interestingly though, there’s an inverse correlation between the PDO and temperatures for much of the USA during the summer months. This implicates that a +PDO tends to induce cooler than normal temperatures across much of the United States.

 

 

 

The EPO has been predominately negative (for most of the past two years), and looks to remain that way overall in the coming months. The analog years featured a dominating –EPO, as it the case in the majority of strong El Nino summers, and like the winter season, -EPO signals the maintenance of the mid-level ridge near Alaska/NW Canada. Forecast modelling, the SSTA profile, and tropical forcing also supports the continuation of West Coast ridging in the means for June-July-August (JJA). However, there will be some variation of that mean regime over the coming months.

With regards to sensible weather conditions, oncoming strong El Nino’s featured an active sub-tropical jet (STJ) which often delivers copious rains to the South/Plains and MS/OH valleys – as we’ve already seen this month (record wettest May in parts of Texas). A pattern of wetter than normal conditions should persist for much of the South/Plains, and extending into at least interior portions of the Eastern US for the summer months. The SW US should see an uptick in precipitation later this summer. The East Coast is a bit of a wildcard because some strong Nino summers feature a wet pattern, while others are dry. But by and large, the majority of years err on the drier side of normal for the immediate East Coast, with wetter than normal further inland. The May pattern is not necessarily correlated to the JJA mean precipitation pattern, but given the expected trough/ridge orientation, a tendency for dryness might occur near the coast.

 

 

 

Temperature wise, the anticipated –EPO/+PDO/Strong Nino regime tends to produce coolness from the SW US northeastward through the Plains and Lakes, with warmth in the NW US and SE US. The Northeast US should see a summer similar to last year – fairly temperate – and maybe slightly warmer. 90F degrees should be lower than normal once again in the Northeast corridor. If there are any heat waves, they will probably not be prolonged.

 

 

The mean NAO/AO states should transition neutral to negative for much of the summer, and this is supported by analogs and model guidance.

The totality of factors yields the following sensible weather result.

 

 

Forecast Summer 2015 for the NYC area stations:

 

June-July-August (JJA) Temperature Departures: -0.5 to +0.5

 

June-July-August (JJA) Precipitation Departures: Near normal

 

One month of the summer could be quite cool relative to normal in the Northeast – likely either July or August. This should be an active summer for convection given the mean trough position near the Great lakes and SE-ridge resistance to the south.

 

 

 

[PB GFI]

Tommy great piece. I think we finish the summer closer to plus 1. I have been riding a strong 1.8 in the 3.4 region.

The SST s in the 3.4 region are getting warmer and line with the modeling , water temps and heat potential in that region.

I like the look of the cfsv2 in the 1.2 region. It's latest run is weaker than its last run and once past October the slope steepens.

That may put us in decent shape for the winter .

The warm pool in the EPO region also looks to maintain that signature through DJF so I like the combination.

[SACRUS]

Iso - excellent write up as always.  I like your analogs and overall thinking, however I lean on the overall warmer side for the summer as a whole.  Liking '87 analog best with some others based on current ENSO/MEI index.

 

Good luck but hope youre too cool :-) 

[SnoSki14]

You did great last winter so it's tough to argue this forecast. I also feel it'll be slightly warmer (+1 overall) with a stronger Bermuda High influence than last year, but agree with everything else.

[snowman19]

Nice write up. We are also seeing quite a +PNA as well, which really doesn't favor extended eastern heat waves

[easternsnowman]

Good write up and I agree that NYC area will be near average,but I feel that philly on south will be above average.

[Isotherm]

Thanks guys! Tony, 1987 was one of my top analogs as well. Although, if I'm wrong I think it'll end up being slightly cooler than expected. Definitely looks like we're out of the prolonged heat pattern of 2010-2013. It'll probably be back next summer, especially if we transition into -ENSO.

[snowman19]

Thanks guys! Tony, 1987 was one of my top analogs as well. Although, if I'm wrong I think it'll end up being slightly cooler than expected. Definitely look like we're out of the prolonged heat pattern of 2010-2013. It'll probably be back next summer, especially if we transition into -ENSO.

I honestly think any periods of heat will be short lived this summer. Persistent +PNA doesn't scream heat in the east to me

[Isotherm]

I honestly think any periods of heat will be short lived this summer. Persistent +PNA doesn't scream heat in the east to me

 

 

I agree. Should be a very temperate summer like last year. Too much -EPO / +PNA for sustained heat waves. Thinking there will be a lot of near miss 85-89 type days.

[SACRUS]

Thanks guys! Tony, 1987 was one of my top analogs as well. Although, if I'm wrong I think it'll end up being slightly cooler than expected. Definitely looks like we're out of the prolonged heat pattern of 2010-2013. It'll probably be back next summer, especially if we transition into -ENSO.

 

Tom , I am going to hold you to that. Just kidding, but again really excellent writeup - concise and thorough!.  Keep up the great work and posts my friend.

 

As for this summer - if we can get back into what we saw in late April and May with ridging over us and at times connecting with the WAR - that's how we can get it warmer.  But agreed - I don't see anything prolonged.  Wetter than normal looks most likely.

[Isotherm]

Tom , I am going to hold you to that. Just kidding, but again really excellent writeup - concise and thorough!.  Keep up the great work and posts my friend.

 

As for this summer - if we can get back into what we saw in late April and May with ridging over us and at times connecting with the WAR - that's how we can get it warmer.  But agreed - I don't see anything prolonged.  Wetter than normal looks most likely.

 

 

Thanks for the kind words Tony! Would be nice if we saw some prolonged heat this summer. It may be another season more suited for golf than swimming, but there will be plenty of warmth and humidity as per usual (we almost never escape from that). I was struggling with precipitation a bit for this outlook. Some conflicting analog years, but I do agree that if I'm off on precipitation, it'll be a bit wetter than anticipated. Some oncoming strong Nino's feature a very dry East Coast, but I do not believe this will be one.

[JBG]

This will be a double / second year Nino, since the winter of 2014-15 already featured a weak Nino. The analogs for this type of occurrence are not numerous; there’s very few years that share similarities in terms of ENSO progression. It is possible that the El Nino peaks relatively early – late summer/early autumn – much like the 1986-88 double Nino event which featured a region 3.4 peak of approximately +1.75c in late summer. Many of the forecast models are supporting that notion. The latest IRI model mean is projecting a +1.5c peak in early autumn with a weakening trend to +1.2c by the middle of next winter.

One summer which was an early-peaking double  Niño was 1969.  How does that fit as an analog? After all we had a toasty and relatively dry May, similar to 1969, and June seems to be progressing along the same lines as June 1969, without the gelid first two days thrown in. Without those days we're about the same place we were at this time in June 1969.

 

Unfortunately this is not a forecast for a good summer; 1969 was generally dreary and cool, with a few good moments.

[Isotherm]

VERIFICATION FOR METEOROLOGICAL SUMMER 2015:

USA Temperature Departures June-July-August (JJA) -

Northeast USA Temperature Departures JJA –

USA Precipitation Departures JJA -

Northeast USA Precipitation Departures JJA -

Overall, I think this was a good to very good forecast nationwide for both precipitation and temperature. In the Northeast, precipitation totals were higher in the interior Northeast with respect to normal, which was expected. Temperature departures were cooler in the interior Northeast as forecasted. JJA temperature departures for the NJ-NY-CT corridor were generally 0 to +1.5 for most locations. However, some immediate urban areas exceeded +1.5 for the summer. Thus, for these areas, there was a larger discrepancy between outlook numbers and actual. For the vast majority in NJ-NY-CT corridor, departures finished slightly warmer than anticipated. The idea of the two major hot spots relative to normal being the SE US and NW US verified, with the coolness in the Mid-west/Lakes. Precipitation was good except for the southern Plains/southern MS valley, which finished drier than anticipated.

JJA Summer Temperature Departures for select locations in the NJ-NY area:

Newark: +1.36
NYC: +1.96
Trenton: +1.1
Atlantic City: +0.8
New Brunswick: +0.96
Freehold/Marlboro: +0.03
Sussex: +0.5

One can see that some/most locations finished slightly warmer than normal, while immediate urban areas like Central Park had a much warmer than normal summer. This is due in large part to the high frequency of dry days / nights with light winds, thus allowing suburbs to cool more effectively via radiational cooling.

Overall grade for Summer 2015: B+

[SACRUS]

Great job tom. Look fwd to your winter forecast. Discrepancy between inland and costal / metro areas enhance by warm waters. Ove extending the season may to sep will yield one of the warmest

[Isotherm]

Great job tom. Look fwd to your winter forecast. Discrepancy between inland and costal / metro areas enhance by warm waters. Ove extending the season may to sep will yield one of the warmest

 

 

Thanks Tony! This has felt like a nice, long summer this year given the warm May/September. Similar to the feel of an extended winter with a very cold November and March.

[winterwarlock]

Based on the temps that Sacrus has been posting for New Brunswick this year...I have a hard time believing they were only .96 above normal

[SACRUS]

Based on the temps that Sacrus has been posting for New Brunswick this year...I have a hard time believing they were only .96 above normal

 

There are 3 or 4 NB stations all of which radiate 4 - 8 degrees cooler than NYC/EWR/LGA.  I post the Rutgers weather station in the daily updates,

[Isotherm]

That's likely because you're selectively recalling only the high temperatures. The mean minima were close to or below normal for all three summer months.

 

Departures for each month at NB:

 

June: -0.1

July: +1.1

August: +1.9

 

Mean minima:

 

June: 60.2

July: 65.4

August: 62.5

[donsutherland1]

Very nice done.

[Isotherm]

Thanks Don!

[WEATHER53]

Yes a good solid B.  This is getting better each seasonal as people do these forecasts. Some are 50/50 or less but as we now get 10+ years at it there are a few who are closer to 70%, like you, and that says something.

[Isotherm]

Yes a good solid B.  This is getting better each seasonal as people do these forecasts. Some are 50/50 or less but as we now get 10+ years at it there are a few who are closer to 70%, like you, and that says something.

 

 

Thank you for the compliment, I appreciate it. You've done very well with long range forecasting as well. Hopefully the success can continue into this winter. I think it's a much more difficult forecast than some think. The broad-brush ENSO signal is risky to utilize given the small sample size.

[uncle W]

Isotherm is a must read... he's one of the best NYC posters...

[Rjay]

Isotherm is a must read... he's one of the best NYC posters...

Yup and so are you.

[Isotherm]

Thank you Uncle W & I agree with Rjay; you are a great poster and asset to the boards.