229 replies to this topic

[donsutherland1]

Due to the big success of the Winter 2011-12 thread, I'm starting a Spring 2012 thread. As the discussion for March continued in the winter thread, I'll post my April and May thoughts here.

April 2012 Forecast:

For April, I expect that the eastern half to eastern two-thirds of North America will likely see warmer than normal readings. However, there could be more variability than had been seen during much of the winter and during March. At the same time, the potential for at least one outbreak of impressive heat might exist given some of the analog cases that came up.

Key Assumptions:
• The ongoing La Niña will slowly give way to neutral ENSO conditions during April
• The AO will likely be predominantly positive
• The PNA will likely be predominantly positive (but generally < +1)

The top analog was 2009. The second closest analog was 1976. As had been the case with March, 1976 figured prominently in the outlook, so I also showed the reference case for 1976. The 1976 reference case has a lot of similarities to the CFSv2 forecast. Both 1976 and 2009 featured a significant outbreak of heat during the second half of the month (1976 just after mid-April and 2009 in late April). The first half of each of those two cases did feature some colder than normal readings, so some cold shots would appear plausible in eastern North America, especially during the first 1-2 weeks of April.

The charts on which my April idea is based are:

Top Left: Composite temperature anomalies based on ENSO/Teleconnection Analogs.
Top Right: 1976 Reference Case
Bottom Left: Observed Decadal Temperature Change for April
Bottom Right: CFSv2 Forecast for April (from March 20)



Based on the combination of the composite teleconnection analogs, the 1976 reference case, and the observed decadal temperature changes, my thoughts for April are as follows:

The eastern half to two-thirds of the U.S. and most of eastern Canada will likely be warmer than normal. Eastern Quebec and Labrador could see cooler readings. The warmest anomalies might be present in an area that includes the Great Lakes, Northeastern U.S. southern Ontario, and southern Quebec. The Western quarter of the U.S. and Canada will likely be cooler than normal. The northern half of Alaska could be warmer than normal with the observed decadal trends and CFSv2 being given greatest weight for that area, while the rest of the state is normal to cooler than normal.

[Met1985]

Hey great right up. What do you think about the southeast going through this spring?

[uncle W]

sooner or later (probably later) we'll have a cooler than normal month...I still won't rule out a late cold shot or snowfall but I'll bet NYC will reach 90 degrees in April again....1976 and 2009 are the only analogs that had its highest temperature for the year in April for NYC...

[michsnowfreak]

sooner or later (probably later) we'll have a cooler than normal month...I still won't rule out a late cold shot or snowfall but I'll bet NYC will reach 90 degrees in April again....1976 and 2009 are the only analogs that had its highest temperature for the year in April for NYC...

Hopefully when the cooler than normal weather arrives, it stays. Our last below normal month was April 2011, and that was the 5th consecutive month below normal. (Most of May was below normal, but we squeaked just enough out late to end up slightly above). Then June-Aug were above normal, Sep normal, Oct-Mar above normal.

[andyhb]

May have more severe wx problems down the road with this type of pattern:

[donsutherland1]

Hey great right up. What do you think about the southeast going through this spring?

The SE will probably be milder than normal, as will be the case through much of the East.

[donsutherland1]

Hopefully when the cooler than normal weather arrives, it stays.

I agree. It will be interesting to see if the generally warm pattern lasts into or through the summer. Hopefully, it won't persist into the next winter.

[Tropical]

I'm hoping above normal lasts for several more months. Haven't gotten my fix yet.

[buckeye]

I'm hoping above normal lasts for several more months. Haven't gotten my fix yet.

me too!

anyone who isn't enjoying this historic warmth for March needs to have their head examined!!! When I got out of bed this morning, it was 66 degrees, it's like July right now.

[mnweather]

I agree. It will be interesting to see if the generally warm pattern lasts into or through the summer. Hopefully, it won't persist into the next winter.

Hi Don, when looking at past winters, how often does it happen where 2 in a row are warmer than average? I want to say it's probably not as uncommon as I think but I'm interested to see what you have to say about it. Thanks.

[WxMidwest]

Don, Well Done, there is reason to believe that this Warm pattern will persist into April as Well. These should just give more congruence to Don's Thoughts..

The Jamstec April Forcast made March 1st... Shows it well...


 aprjamst.PNG   147.33K   8 downloads


Here is a a seasonal teleconnection model made in Fortran (imported into Excel), I've been working on for a few months:


I believe this supports your idea of warmth continuing, maybe with not the same anomalies, but still strong...


 composite.jpg   181.8K   6 downloads

[donsutherland1]

Very nice work, WxMidwest. Did you run your teleconnections model for the recent winter? It would be interesting to see how it fared.

The analogs you came up with and the JAMSTEC forecast are certainly consistent with the idea of a warmer than normal March in the East/Midwest. At the same time, I suspect there might be more days with cold anomalies than March. However, given the bouts of extreme heat that developed in 2009 and 1976 (two of my key analog cases for April), it would not surprise me if there is a period of much above normal temperatures.

[WxMidwest]

I have run it already for every month since Jan 1980, It just takes a load of time to make the composites. I'll probably check the winter 2010-11 out after Thursday's Synoptic Test. Eventually, I'm going to try to make a concatation code that will build these top 5 analog Http links in us climate composite form. That will take awhile to build the strings for that, then I can call Wget and receive the U.S. T/P map pngs/gifs automatically. I had another model that had 11 variable multiregression model for Midwestern U.S. temps with near 0.90 Coerrelation coeeficient for hindcasts with every winter since 81-82, and it busted huge this winter. Tested it for multicollinarity, passed fine, I really think this winter was quite even more an outliner then 2001-2002. Big time busts for nearly every wx outlet for 2011-2012. With this Major Warm Wing event March, I'm starting to wonder if there has been a some sort of major quirk in the entire system, like a decadal PDO switch..

[bluewave]

I have run it already for every month since Jan 1980, It just takes a load of time to make the composites. I'll probably check the winter 2010-11 out after Thursday's Synoptic Test. Eventually, I'm going to try to make a concatation code that will build these top 5 analog Http links in us climate composite form. That will take awhile to build the strings for that, then I can call Wget and receive the U.S. T/P map pngs/gifs automatically. I had another model that had 11 variable multiregression model for Midwestern U.S. temps with near 0.90 Coerrelation coeeficient for hindcasts with every winter since 81-82, and it busted huge this winter. Tested it for multicollinarity, passed fine, I really think this winter was quite even more an outliner then 2001-2002. Big time busts for nearly every wx outlet for 2011-2012. With this Major Warm Wing event March, I'm starting to wonder if there has been a some sort of major quirk in the entire system, like a decadal PDO switch..

It's probably the low sea ice which is throwing the model a curveball.
There is a paper explaining why the 2006 analog was at the top of your chart.

http://www.agu.org/p...9JD013568.shtml

http://www.scienceda...20213133056.htm

[donsutherland1]

April 1-7, 2012 Thoughts:

Given the forecast teleconnections, progression of the MJO, and weakening La Niña conditions, I suspect that the major stories for the April 1-7 timeframe will be:

1. Warmth in much of eastern North America, but focused on central Canada and the Central and Northern Plains States
2. Some cool anomalies in the eastern U.S. (a rare outcome in recent months)

The charts below are as follows:

Left: The composite temperature anomalies for ENSO Region 3.4 anomalies of -0.9°C to -0.2°C, a PNA of 0.00 to +0.75, and an AO of +1.00 to +2.00 for North America.

Right: The Objective Analogs centered on April 1, 2012 but rolled forward 3 days



It should be noted that the NAEFS, which run for the 3/29-4/4 timeframe (part of the timeframe in question) have the highest probability of warm anomalies where the above two charts show the greatest warmth.

Interestingly enough, years showing up in the teleconnection analogs include 1976, 1977, 2001, and 2009. All four of those years featured a period of much above normal readings later in April, with 1976, 1977, and 2009 featuring a period of exceptional warmth that saw temperatures reach 90° or above in the Northern Mid-Atlantic and even southern New England region. That fits quite well with the monthly idea (Message #1 in this thread) that had April 1976 and April 2009 as the top two analogs.

Conclusion:
Taking into consideration the observed decadal temperature trend, I believe the teleconnection analogs present a reasonable idea for the temperature anomalies during the first week in April. Adjustments would refine the Mid-Atlantic and New England areas to be somewhat below normal to near normal. The Southeast would probably wind up somewhat colder than normal. Most of the rest of the U.S. would be warmer than normal, except for the Pacific Northwest where some cool anomalies might also be present. Much of Canada would be warmer than normal except for Northwestern Canada where near normal readings with some cool anomalies could prevail.

[donsutherland1]

FWIW, the Canadian Ensembles show the MJO regressing from Phase 7 back into Phase 6 during the first week of April. Below is a chart showing temperature anomalies associated with Phase 6, Amplitude 1-2 (April 1-15, 1974-2011) with ENSO conditions similar to what I expect in my April 1-7, 2012 forecast:



The below charts were the basis of my April 1-7 thoughts:

[Roger Smith]

The current warm spell reminds me of mid-April 1976 which then brings to mind the possibility of a snowstorm developing after the deciduous trees have fully bloomed. That was a major problem in the snowstorm across the Great Lakes region in late April unlike some other April snowfall events that came well before blooming had really begun. For example the April 2-3 1975 storm came after a cold March, and heavy snow in April 1982 occurred after near-normal conditions in March.

Looks like an epic temperature fall on the way for Monday night into Tuesday although the interruption to the warm spell will apparently be short-lived. I do see signs of retrogression to place the core of the positive anomalies closer to Kansas-Nebraska in April, and this may end the spell of unsettled cold weather on the west coast if retrogression continues to about Utah-Idaho for the core of warmth. That could place the northeast in a deepening trough and perhaps April will turn out more like 1945 as well, with a warmish start but a colder finish.

I think there is going to be at least one late snowstorm in parts of the northeast, possibly more inland and certainly in the Great Lakes region and Midwest, would not be looking for this pattern to lock in for the entire season, but it may signal a hot summer with a 3-4 month period for the retrograde sequence then becoming stationary and slowly progressive again.

[uncle W]

The current warm spell reminds me of mid-April 1976 which then brings to mind the possibility of a snowstorm developing after the deciduous trees have fully bloomed. That was a major problem in the snowstorm across the Great Lakes region in late April unlike some other April snowfall events that came well before blooming had really begun. For example the April 2-3 1975 storm came after a cold March, and heavy snow in April 1982 occurred after near-normal conditions in March.

Looks like an epic temperature fall on the way for Monday night into Tuesday although the interruption to the warm spell will apparently be short-lived. I do see signs of retrogression to place the core of the positive anomalies closer to Kansas-Nebraska in April, and this may end the spell of unsettled cold weather on the west coast if retrogression continues to about Utah-Idaho for the core of warmth. That could place the northeast in a deepening trough and perhaps April will turn out more like 1945 as well, with a warmish start but a colder finish.

I think there is going to be at least one late snowstorm in parts of the northeast, possibly more inland and certainly in the Great Lakes region and Midwest, would not be looking for this pattern to lock in for the entire season, but it may signal a hot summer with a 3-4 month period for the retrograde sequence then becoming stationary and slowly progressive again.

April 1975 and 2002 had a significant cold spell early in the month...1976 had a cold spell just before the torch...2002 had a torch the same time 1976 did but 1975 torched in May...1976 and 1982 had a very cold January while 1975 and 2002 did not...so it is possible we get a late minute cold wave in April but I wouldn't bet on it...2002 had the only hot summer of the four analogs...

[VirginiaHippie]

What does precipitation look like for April? I've never quite understood why April has to be a rainy month (per the accepted archetype). We have a big outdoor community event here in SE VA planned for April 14th and NEED good weather for it to be successful.

[donsutherland1]

What does precipitation look like for April? I've never quite understood why April has to be a rainy month (per the accepted archetype). We have a big outdoor community event here in SE VA planned for April 14th and NEED good weather for it to be successful.

The Mid-Atlantic region looks to continue with drier than normal conditions in April. SE Virginia should have below normal precipitation.

[VirginiaHippie]

The Mid-Atlantic region looks to continue with drier than normal conditions in April. SE Virginia should have below normal precipitation.

Good. I hope that comes to fruition, Don. I know that doesn't guarantee Sunny weather on that particular day, but at least a drier regime would mean the chances for blue skies and sunshine would be higher.

Thank you for answering my question,

[donsutherland1]

In my discussion concerning the April 1-7 timeframe, I highlighted a number of analogs in the mix that later featured a period of much above normal readings later in April, with 1976, 1977, and 2009 featuring a period of exceptional warmth that saw temperatures reach 90° or above in the Northern Mid-Atlantic and even southern New England region. Using the 1981-2010 base period, the following are some probabilities for New York City:

Reaching or Exceeding:
80° Once every 0.8 years; Last reached: 2011
85° Once every 2.4 years; Last reached: 2010
90° Once every 9.6 years; Last reached: 2010
95° Once every 45.8 years; Last reached: 2002
100° Once every 273.4 years; No 100° temperatures on record

FWIW, 1976, 1977, and 2009 all saw NYC's highest temperature reach or exceed 90° in April.

[Amped]

MJO erupted in Phase 7 again.

[Geos]

I noticed developments in the teleconnection department, especially the AO and NAO. The AO has gone negative along with the NAO. Last time the NAO was negative was about Valentines Day.




This could result in a pattern shift in the eastern part of the US with more troughiness.

[Minnesota Meso]

I noticed developments in the teleconnection department, especially the AO and NAO. The AO has gone negative along with the NAO. Last time the NAO was negative was about Valentines Day.




This could result in a pattern shift in the eastern part of the US with more troughiness.

Sorry my computer skills are really bad so I have a hard time positing images. To your post, the PNA is almost neutral but slightly neg (trough off the US west coast) . The NAO goes negative, the MJO is locked in phased 7 for the 1st week of April (maybe longer), the EPO goes negative. This all points to big change coming up for the Northern Plains east to mid Atlantic area including the big cities of the North East. The other foot may be about to drop, major snow storm in the future anywhere from the Dakotas to Great Lakes area and points east is possible but where is the question. Way to early to tell but the GFS has been strongly hinting at this.

[Geos]

Sorry my computer skills are really bad so I have a hard time positing images. To your post, the PNA is almost neutral but slightly neg (trough off the US west coast) . The NAO goes negative, the MJO is locked in phased 7 for the 1st week of April (maybe longer), the EPO goes negative. This all points to big change coming up for the Northern Plains east to mid Atlantic area including the big cities of the North East. The other foot may be about to drop, major snow storm in the future anywhere from the Dakotas to Great Lakes area and points east is possible but where is the question. Way to early to tell but the GFS has been strongly hinting at this.

I know a -NAO means a trough somewhere in the eastern half of N. America. In the future, the ridge centered over the British Isles is forecast to retrograde back towards Greenland. We could be looking at a much different April with respect to this month. Looks like the MJO will make it's way into Phase 8 eventually -after doing a loop in 7.

http://raleighwx.ame...wx.com/MJO.html

[VirginiaHippie]

I know a -NAO means a trough somewhere in the eastern half of N. America. In the future, the ridge centered over the British Isles is forecast to retrograde back towards Greenland. We could be looking at a much different April with respect to this month. Looks like the MJO will make it's way into Phase 8 eventually -after doing a loop in 7.

http://raleighwx.ame...wx.com/MJO.html

Just being sensible here, a massive outbreak of cold is not impossible, but quite improbable given the time of year, sun angle, etc. Yeah, the teleconnections suggest such a thing in the *long* range...but we know how that goes.

The latest European shows most of April being warm to seasonable across N. America.

[Geos]

Just being sensible here, a massive outbreak of cold is not impossible, but quite improbable given the time of year, sun angle, etc. Yeah, the teleconnections suggest such a thing in the *long* range...but we know how that goes.

The latest European shows most of April being warm to seasonable across N. America.

I would expect to see a couple typical April cold punches come into Eastern North America. Typical around here would be a handful of days in the 30s and up to 10 days of 40s for highs.
It seems like the GFS long range is shifting the core of the warmth towards the Rocky Mountains and High Plains. I think April will be somewhat above normal in the east with in the exception of New England/Eastern Canada. We won't see insane high departures above normal next month like we did this month - that's like once in a lifetime early warmth! If the NAO does decide to stay more negative then the latest European outlook could be in trouble. The new 8-14 outlook shows more normal anomalies taking up resident across the Heartland and SouthEast.

[andyhb]

Pretty impressive severe setup showing up on the 18z GFS for next weekend/early the next week.

[Superstorm93]

Pretty impressive severe setup showing up on the 18z GFS for next weekend/early the next week.

[andyhb]

Fast forward that 3-9 hours as the mid/upper jet streak noses in and the LLJ intensifies...

[donsutherland1]

The following are some probabilities for Washington, DC (DCA):

Reaching or Exceeding:
80° Once every 0.4 years; Last reached: 2011
85° Once every 0.8 years; Last reached: 2011
90° Once every 2.6 years; Last reached: 2011
95° Once every 10.0 years; Last reached: 2002
100° Once every 47.2 years; No 100° temperatures on record

Keep in mind, these are statistical probabilities based on a normal curve using the 1981-2010 base period.

[Sstorm]

Don, before I ask my question I just want to say that I have been reading your thoughts and forcasts for quite a few years now. The strangest thing is that I live in Louisiana, but I've learned that you are the most accurate when it comes to medium/long range predictions.

My question pertains to the 1976 analog you are now referencing. At what point during any given year do you move from one analog year to a totally different one? My reason for asking is cause 1976/77 was an extremely cold year in the deep south from what I remember as a kid. So, will your reference analog year change? And when?

Thank you. Sstorm

[andyhb]

Pretty impressive severe setup showing up on the 18z GFS for next weekend/early the next week.

00z GFS too now, and of course it's from Palm Sunday to April 4th...

[Geos]

Noticed the new CPC outlook for the 6-10 day, 8-14 day has erased the positive anomalies in the GL states and the eastern 1/4 of the nation. Even below normal temperatures for the mid-Atlantic.