April outlook - will the warmth continue?

[Isotherm]

I wrote a post on my thoughts for the coming month.

http://www.lightinthestorm.com/

March has entered the record books as the second warmest March on record in NYC, after the warmest February on record, second warmest winter (DJF) on record, and warmest DJFM period on record. Truth be told, it’s been about as mild as it can get in our area for the cool season. Since November, we’ve seen countless days in the 50s and 60s, with very few days featuring sub freezing or even below normal temperatures. The growing season is off to a remarkably early start, about 3-4 weeks ahead of schedule for most in the tristate area, thanks to the record warmth of recent months. But this can’t last forever, or can it?

Looking ahead into April, it’s safe to say we can close the books on the winter 2011-12 dismal snowfall season for NYC and the coast, barring a freak mid/late spring storm (chances for that happening are slim to none). The weak/moderate La Nina is finally weakening, as evidenced by recent Southern Oscillation Index (SOI) values. When the index is in a predominately positive state, it indicates enhanced tropical easterly trade winds, more upwelling to the west of South America, and cooler waters (hence La Nina). When the SOI is in a negative state, generally we see weakened easterly trade winds, which allow the warm water in the west Pacific to gradually slide eastward and pile up (the development of an El Nino). The latter is what should occur over the next several months. Statistical and dynamic models are in fairly good consensus that we’ll reach warm neutral, potentially weak El Nino status, sometime this summer. Daily SOI values have been in the tank lately, with readings as low as -26 to -28. This means the environment is becoming rapidly less favorable for the maintenance of the La Nina.

Atmospheric angular momentum (AAM) is another good way to measure ENSO state, and unlike the SOI, when the AAM is in a positive state, it generally means the atmosphere is more El Nino-like. Over the past few months we’ve seen a predominately negative AAM, but over the past couple weeks, values have surged to near neutral. This is yet another indication of the dying La Nina.

A third factor to examine is the most obvious one — sea surface temperature anomalies (SSTA). Tropical Pacific SST’s have warmed quite significantly since late winter, and crucial ENSO region 3.4 is nearing neutral — now at -0.22c as of the latest weekly update. This suggests a cold neutral ENSO regime currently, a major rebound from the values down around moderate La Nina criteria a couple months ago. These SST’s will continue to warm, slowly but surely, over the coming weeks and months.

So what will April have in store? Here’s what the US looks like temp wise in the first three days of the month. Note a continuation of the big heat in the Mid-west, and a touch of coolness on the West and East Coasts.

While I don’t expect the month of April to finish with temperature departures as warm as they are right now in the Central US, I am anticipating another fairly warm month nationwide, with the West Coast and New England likely being the coolest spots.

ENSO region 3.4 will be near neutral in the .weeks, and looking at the other important teleconnections, both AO and PNA values should bounce around near 0 / slightly positive, while the NAO is the most negative its been since last October. However, the NAO should not tank significantly negative, and may actually rebound to neutral to slightly above by late April. What all this means is the atmosphere should be in a state that does not support the maintenance of well below normal temperature regimes or well above normal temp regimes. Rather, temperatures in the Northeast should average out close to normal in the next couple weeks.

Easter week (4/8 – 4/14) may end up slightly cooler than normal in the Northeast as a storm cuts off near Newfoundland, keeping mid levels rather chilly into the middle of the month. However, thereafter, that chilly pattern should breakdown even in the Northeast, giving way to more warm shots by the final 10 days of April. I’m most confident about the region from the Rockies to the Ohio Valley (most of the country) finishing warmer than normal for April. I’m a bit less confident but still believe the Northeastern part of the United States should end up warmer than normal for April, and also drier than average.

Given the expected ENSO and teleconnection pattern, I came up with 4 analogs for the next month: 1976, 1986, 2001, and 2009. All of them were warm from the Rockies to the Northeast coast, with a cool pattern on the West Coast. All of them had less precipitation than normal in the Eastern US, with a precip maximum in the central Plains.

H5 pattern for April based on the analogs:

Surface temp anomaly:

Precipitation anomaly:

Now that we’re near neutral ENSO, the MJO will have a greater influence on our pattern (it has had a significant influence this past winter). Tropical forcing can be helpful in determining mid latitude ridge/trough position and general temp/precip patterns. MJO will be swinging through phase 8 and phase 1 in the next couple weeks, which is a cool signal in the East. Thereafter, things become less certain, but MJO may enter the circle of death. As noted earlier, the cool period for Easter week seems reasonable, with warming temps thereafter.

MJO phase 1 map for the US in April — note the coolness in the East, but it should not be as impressive or expansive as this.

Conclusion:

– Near/slightly above normal the rest of this week, then a slightly cooler than normal week for 4/8-4/14 in the Northeast

– The Mid-west should continue well above normal temperatures

– West Coast cooler than average throughout most of April

– Northeast temps will begin to warm after mid month, with the possibility that some of the torch in the Central US shoots eastward by the end of the month

– Final temperature departures for April should be slightly above normal in the Northeast, but not as warm relative to averages as the past several motnhs (i.e., closer to “normal” than the past 4 months).

– Precip departures below average in the East, wetter in the Plains

[doncat]

Very nice write up as usual Isotherm. Will be interesting to see when we break out of the current dry pattern.

[NJwinter23]

Nice write up and I've also liked the idea of warmth returning by the final week of April. However, I am getting a little cold feet today looking at the CPC analog composite which mirrors Raleighwx's Phase 1 April MJO chart to a tee just about. Extrapolating that out to the end of the month and it is solidly below average from the northern Plains to the eastern U.S. IF the MJO were to stay amplified enough heading towards phases 2-4, this would seem to support that idea as well. Thoughts?

[uncle W]

the last time we had two years with mostly above normal months was January 1990 to February 1992...26 months...We have been torching since March 2010...25 months...I hope this is the last torch month and hope that May and the rest of the warm season will be cooler than average...

[Isotherm]

Very nice write up as usual Isotherm. Will be interesting to see when we break out of the current dry pattern.

Thanks Don. Looks to me like it probably won't be in the next few weeks. I haven't researched any farther than April, but I have a feeling the reversal will occur either by May or early summer.

Nice write up and I've also liked the idea of warmth returning by the final week of April. However, I am getting a little cold feet today looking at the CPC analog composite which mirrors Raleighwx's Phase 1 April MJO chart to a tee just about. Extrapolating that out to the end of the month and it is solidly below average from the northern Plains to the eastern U.S. IF the MJO were to stay amplified enough heading towards phases 2-4, this would seem to support that idea as well. Thoughts?

Thanks. Yeah I see your point about the cold East if the MJO were to progress through phases 2-4. At this time I don't believe that will occur - the ECMWF forecast looks most reasonable to me - phase 1, then weakening. Even if we were to go through those phases, I don't see the other indices providing much help wrt maintaining a cooler than normal pattern in the East w/ the NAO and AO hovering around neutral. The MJO composites for phases 2-4 looks to expansive/widespread with the cold considering the lack of high latitude blocking.

CPC has the East Coast painted blue the next 2 weeks which is the first time I've seen that in 6+ months. No doubt we're going to get some chilly days next week, after Easter. The second half of the month will be interesting to watch. Strong analog support for warming in that period.

[Isotherm]

the last time we had two years with mostly above normal months was January 1990 to February 1992...26 months...We have been torching since March 2010...25 months...I hope this is the last torch month and hope that May and the rest of the warm season will be cooler than average...

Yeah I think we're nearing the end of the above normal streak. I don't have a strong opinion on the summer yet, but right now I'm leaning cooler than normal JJA after a warm May.

[NJwinter23]

Thanks Don. Looks to me like it probably won't be in the next few weeks. I haven't researched any farther than April, but I have a feeling the reversal will occur either by May or early summer.

Thanks. Yeah I see your point about the cold East if the MJO were to progress through phases 2-4. At this time I don't believe that will occur - the ECMWF forecast looks most reasonable to me - phase 1, then weakening. Even if we were to go through those phases, I don't see the other indices providing much help wrt maintaining a cooler than normal pattern in the East w/ the NAO and AO hovering around neutral. The MJO composites for phases 2-4 looks to expansive/widespread with the cold considering the lack of high latitude blocking.

CPC has the East Coast painted blue the next 2 weeks which is the first time I've seen that in 6+ months. No doubt we're going to get some chilly days next week, after Easter. The second half of the month will be interesting to watch. Strong analog support for warming in that period.

Yeah that analog support has been there, at least going off the ones you have selected. i know Don is all over 1976 and 2009 in the main thread as well. Though it is a bit troubling to see the new CPC composite. Furthermore, the ensembles seem to be showing a lot of +anomalies across Greenland and the Arctic over the enxt 2 weeks...though who knows once we get into late April. Also, my original outlook for late April from weeks ago was cooler than average centered around the Great Lakes before I really considered those analogs. Now I'm wondering if that idea could end up being correct.

Any particular reason why you think the MJO is more likely to die after phase 1? What is going to stop the momentum of this thing now that its plowing through the former La Nina easterly death wall region?

[Isotherm]

Yeah that analog support has been there, at least going off the ones you have selected. i know Don is all over 1976 and 2009 in the main thread as well. Though it is a bit troubling to see the new CPC composite. Furthermore, the ensembles seem to be showing a lot of +anomalies across Greenland and the Arctic over the enxt 2 weeks...though who knows once we get into late April. Also, my original outlook for late April from weeks ago was cooler than average centered around the Great Lakes before I really considered those analogs. Now I'm wondering if that idea could end up being correct.

Any particular reason why you think the MJO is more likely to die after phase 1? What is going to stop the momentum of this thing now that its plowing through the former La Nina easterly death wall region?

I think the ECMWF has shown to have better verification scores in the medium-long range wrt tropical forcing. And this morning it's interesting to note that the GFS based NCEP model is already beginning to trend toward the Euro.

Today's NCEP MJO guidance depicts a weaker look going through phase 1, and if extrapolated further, probably wouldn't be too dissimilar from the Euro, nearing the COD after phase 1. Either way, there's now pretty good agreement that the amplitude of this MJO wave will be significantly less after early phase 1, and that will lessen its impacts on CONUS weather.

[Isotherm]

The NAEFS, which had us painted in red for the past 5 months, shows the brief break next week with more normal temps. I think it may be a bit underdone; we should see some slightly below normal air in the East.

http://www.cpc.ncep.noaa.gov/products/predictions/short_range/NAEFS/poeabn_h264.00.gif

[SACRUS]

Great stuff Iso and others. It will be interesting to track and see the eventual outcome for April and beyond into the the summer. I agree with others that this summer will likely be close to normal with one caveat being any prolonged dry pattern enhancing any heat. I wouldnt bet on a prolonged dry pattern in these parts, especially of late. We know the result of the past few dry patterns, they all seemed to be quickly reversed to excessive wetness. At some point that has to break but im not ready to bet on that yet.

I suspect Arpil finishes slightly above normal with the period of April 9th - the 15th the coolest relatiive to normal. Perhaps more persistant warmth returns towards the last 10 days. Should we stay dry id think we see that warmth stronger and longer into May.

[Isotherm]

Great stuff Iso and others. It will be interesting to track and see the eventual outcome for April and beyond into the the summer. I agree with others that this summer will likely be close to normal with one caveat being any prolonged dry pattern enhancing any heat. I wouldnt bet on a prolonged dry pattern in these parts, especially of late. We know the result of the past few dry patterns, they all seemed to be quickly reversed to excessive wetness. At some point that has to break but im not ready to bet on that yet.

I suspect Arpil finishes slightly above normal with the period of April 9th - the 15th the coolest relatiive to normal. Perhaps more persistant warmth returns towards the last 10 days. Should we stay dry id think we see that warmth stronger and longer into May.

Thanks Tony, and good post. I pretty much agree with your thoughts going forward. For what it's worth, here are my 4 analogs rolled forward into May and this summer.

Slightly milder than normal May in the Northeast, but we see the sern plains cooling:

Then JJA has a pretty solid cool pocket in the Lakes/OH valley, and near normal on the Northeast/Mid-atlantic coast.

Some modelling for this summer seems to agree with the notion of cooler Great Lakes, warm West, and east coast. At this point I don't think we're looking at a 2009 year w/o a summer.

[SACRUS]

The idea of warmer west/east coasts with cooler Lakes/OH valley is similar to 2008. Our warmth was aided by the June torch and mid July that summer. Looking a your analogs 2001 aside from the first week of August was rather cool. 1976/2009 we know how those summers stacked up for those who like warmth.

Im waiting for the MEI figures to come out the end of this week to assess analogs but 76 is clearly in there.

[Isotherm]

The idea oa warmer west/east coasts with cooler Lakes/OH valley is similar to 2008. Our wearmth was aided by the June torch and mid July that summer. Looking a your analogs 2001 aside from the first week of August was rather cool. 1976/2009 we know how those summers stacked up for those who like warmth.

Im waiting for the MEI figures to come out the end of this week to assess analogs but 76 is clearly in there.

Yeah, looking at the individual years, it's easy to see there's a much greater chance of a cool summer as opposed to a warm one this year. 1986, 1976, and 2009 were all coolish in the Northeast, and 2001 near normal.

[NJwinter23]

I think the ECMWF has shown to have better verification scores in the medium-long range wrt tropical forcing. And this morning it's interesting to note that the GFS based NCEP model is already beginning to trend toward the Euro.

Today's NCEP MJO guidance depicts a weaker look going through phase 1, and if extrapolated further, probably wouldn't be too dissimilar from the Euro, nearing the COD after phase 1. Either way, there's now pretty good agreement that the amplitude of this MJO wave will be significantly less after early phase 1, and that will lessen its impacts on CONUS weather.

Fair enough! And right on cue, the new gefs runs today are plowing this thing right into the circle in 2 weeks at phase 1.

[uncle W]

Yeah, looking at the individual years, it's easy to see there's a much greater chance of a cool summer as opposed to a warm one this year. 1986, 1976, and 2009 were all coolish in the Northeast, and 2001 near normal.

those years averaged 12 90+ days in NYC...Below the average...None of the years were above but 2001 did have a 103 degrees day...

[NYCSuburbs]

Nice post... the recent changes in the pattern aren't enough to make it a persistent colder than average one, and the first half of the month should end up at least seasonable in terms of temperatures, slightly below average for some areas, although in my opinion the warm pattern pretty much ended just after the March warm spell, when the first of several consecutive troughs moved into the Northeast; I don't remember seeing troughs dropping into the region this frequently, as well as ridging near Greenland lasting for more than a very short time, at any other time this winter, and now it's suddenly happening more frequently. I agree with the second half of the month ending up warmer; if the warm pattern has in fact ended, I would think that at least some warmth but without frequent significantly positive departures would be more likely for the second half of the month and possibly beyond, as opposed to significant warmth like the central US is now seeing.

[SACRUS]

Euro and several runs of the gfs hinting at the ridge building back east on/around the 16th. It will be interesting to see how April progresses and if we can see some rain as the ridge begins shifting east accompanied by more stronger warmth.

[jdrenken]

The Western trough will return and force the warmth to spread eastward. We will see above normal temperature departures this April. It won't be as strong as the past 2 months, but no matter how you look at it...it will be above average.

[bluewave]

80 degree or higher potential showing up on Euro and ensembles.

GFS ensembles are warm also.

[Weathergun]

Both the GFS and Euro ensembles have 850mb temps 12C into NYC area, by the 17th. I think it's a good signal, for some more well above normal temps again. I don't often see the ensembles this warm compared to operational, this early:

[SnoSki14]

Not surprised to see some very warm temps ahead of the trough, will see how high it can go I guess, it we could reach upper 70s to near 80F in mid March, then it should be an easy feat to get into the 80s in mid April.

[bluewave]

The interesting thing about the coming warm up is that the warmest temperatures relative to the means will be over

the East rather than the Upper Midwest and Plains like we have been seeing recently. May we be seeing the beginning

of the April and May pattern setting up? Stay tuned...

[SnoSki14]

I disagree about the warm focus being in the east. The reason it's showing high anomalies in the east is because the front is heading east and were warming ahead of it. It's not were locked into a big time ridge like in mid March, it's more typical April weather with warmups (meaning very warm temps this year) and cool downs (which this year means near normal).

[Sundog]

I disagree about the warm focus being in the east. The reason it's showing high anomalies in the east is because the front is heading east and were warming ahead of it. It's not were locked into a big time ridge like in mid March, it's more typical April weather with warmups (meaning very warm temps this year) and cool downs (which this year means near normal).

Actually you can see the progression of the warmest anomalies as the days progress in mid April. Some ensembles even have a classic cold front shape to the warm anomalies. Ill agree with you on this one.

[blizzardof09]

The interesting thing about the coming warm up is that the warmest temperatures relative to the means will be over

the East rather than the Upper Midwest and Plains like we have been seeing recently. May we be seeing the beginning

of the April and May pattern setting up? Stay tuned...

maybe, im hoping that we get back into the warm weather swing again. that march heat wave got me excited for the heat. btw bluewave you always got great input.

[bluewave]

I disagree about the warm focus being in the east. The reason it's showing high anomalies in the east is because the front is heading east and were warming ahead of it. It's not were locked into a big time ridge like in mid March, it's more typical April weather with warmups (meaning very warm temps this year) and cool downs (which this year means near normal).

The models are showing a shift in the medium range of the warmer anomalies a little further east than we have

seen recently.

[bluewave]

maybe, im hoping that we get back into the warm weather swing again. that march heat wave got me excited for the heat. btw bluewave you always got great input.

Thanks.I think that the pattern stays warmer than average in the East through the end of May. I am not sure how much of a

positive departure it will be but it should be above normal. The recent springs following a warm Canadian winter like

we saw this year have been warmer in the East than in the West. The summer signal for this type of pattern is

for a warmer than average summer across the US as a whole so it would not be surprising to see the positive

monthly departure streak here carry into the summer.

Winter 2012

Winter composite

Spring composite

Summer composite

[jdrenken]

Those maps show exactly what I've been thinking. Warmer anomalies in the Plains/MW then "bleeding" East to the coast.

[bluewave]

Those maps show exactly what I've been thinking. Warmer anomalies in the Plains/MW then "bleeding" East to the coast.

It's interesting to see the ECCA going with roughly the same theme.

[jdrenken]

I don't believe that the departures will be that extreme as our highs will obviously go up as time goes along which will mitigate the impact.