Medium Range Discussion Spring 2012

[easternsnowman]

I doubt anyone north of the mason dixon line gets to 90 except the usual hot spots like newark and philly airport which have a shot at it. This kind of weather is becoming more normal, the past few aprils have been well above the 1981-2010 averages.

[donsutherland1]

...past few aprils have been well above the 1981-2010 averages.

In the Northeast (defined by NCDC to include Connecticut, Delaware, Maryland, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, and Vermont), 7 of the last 8 years have seen a warmer than normal April (1981-2010 base period). Three of those years ranked among the five warmest Aprils during the 1981-2010 timeframe: 2006 (5th warmest), 2008 (2nd warmest), and 2010 (1st warmest). For the 1895-2011 timeframe, 2008 was the 7th warmest April and 2010 was the 2nd warmest April. Both April 2008 and April 2010 had departures that were more than 1 standard deviation above the 1981-2010 mean (2010 was 2.113 standard deviations above the mean). In contrast, only one of those 8 years and only 1 year since 2000 has been among the five coldest during the 1981-2010 timeframe: 2007 (4th coldest at 1.488 standard deviations below normal). Against the larger timeframe, April 2007 was the 25th coldest.

The trend line also had a very steep slope with a 1.35°F increase per decade.

[CoastalWx]

Might not be a bad idea to look back and see what the ocean water anomalies were when we had drought like conditions. I'll have to check on that and then see years of past droughts.

Are you more or less talking about the AMO? I think a larger scale feature like that has a better say on highs ridging into the SE.

[ezweather]

Oh, I wasn't even getting into the AMO discussion. I was curious what was the relationship if you had warm anomalies offshore and how it might keep areas inland drier than average. Its not a really clear answer to what I was thinking on.

Are you more or less talking about the AMO? I think a larger scale feature like that has a better say on highs ridging into the SE.

[donsutherland1]

In Message #120, I posted a map showing forecast temperature anomalies reaching 2 to perhaps 2 standard deviations above normal for the Mid-Atlantic region for Monday. If one backs up to the 48-hour forecast, one finds an incredible contrast of temperatures: An area of readings > 3.0 standard deviations below normal and another area of 1.5 to 2.0 standard deviations above normal. With a vigorous storm moving northward, that contrast will create ideal conditions for severe weather over part of the Plains. The worst impact will probably lie at the midpoint of the two anomalous areas where the air masses are most likely to clash.

Consistent with teh incredible contrast, SPC's categorical 2-day outlook shows a large area at moderate risk in the Plains States. Embedded in that area is a portion of Oklahoma and Kansas that is at high risk.

[ezweather]

Don,

That is an excellent showing of temperature contrast and why the risk is so high for severe weather. Looks like several days of rampaging severe weather again.. Wow..

Definitley gotta check out the livestreaming sites for the severe weather..

In Message #120, I posted a map showing forecast temperature anomalies reaching 2 to perhaps 2 standard deviations above normal for the Mid-Atlantic region for Monday. If one backs up to the 48-hour forecast, one finds an incredible contrast of temperatures: An area of readings > 3.0 standard deviations below normal and another area of 1.5 to 2.0 standard deviations above normal. With a vigorous storm moving northward, that contrast will create ideal conditions for severe weather over part of the Plains. The worst impact will probably lie at the midpoint of the two anomalous areas where the air masses are most likely to clash.

Consistent with teh incredible contrast, SPC's categorical 2-day outlook shows a large area at moderate risk in the Plains States. Embedded in that area is a portion of Oklahoma and Kansas that is at high risk.

[donsutherland1]

April 23-30, 2012 Thoughts:

The forecast for the April 23-30 timeframe is quite complex for a number of reasons. First, with the westerlies having strengthened somewhat, the warming of ENSO Region 3.4 could slow. In a worst case, there could be some cooling. Right now, I do not expect a return to La Niña conditions. Second, the AO is forecast to go negative. There remains some question as to how far negative it will drop. Run-to-run continuity is not consistent. Third, some of the guidance suggests a negative PNA. However, the PNA has not been negative since March 11. Moreover, the PNA has recently verified at the top of its forecast range or even above it. These trends suggest a dose of caution when it comes to the PNA. As a result, I'm favoring a mainly positive PNA.

Normally, the possibility of an AO- and PNA+ setup would suggest cold anomalies in parts of the U.S. and Canada that have generally seen a lot of warmth. However, if one looks northward to the Arctic source region, expansive warm anomalies are the rule. As a result, I suspect that the pattern will likely underperform with regard to cold. Early on, the Great Lakes, Ohio Valley, Northeast, Mid-Atlantic and portions of Ontario and Quebec could start cold. However, it is possible that the period could end on a warm note.

The charts below are as follows:

Left: ENSO Region 3.4 anomalies of -0.6°C to 0.0°C, a PNA of -0.25 to +0.50, and an AO of -0.75 to +0.25 for North America.

Right: NAEFS (April 21-27, 2012 timeframe)

Given the upstream conditions in the Arctic, I favor a compromise between the warmer NAEFS and colder teleconnection analogs.

My thoughts are as follows:

1. Areas of cool anomalies interspersed with near normal readings in the Great Lakes, Ohio Valley, northern Mid-Atlantic, and New England regions and somewhat cooler than normal to near normal across Quebec and Ontario.

2. Cooler than normal along the U.S. West Coast into perhaps southern British Columbia.

3. Generally warmer than normal elsewhere in the U.S., but near normal to perhaps somewhat below normal across the rest of Canada. The Rockes and Central Plains could be very warm for a time.

[Met1985]

Great work Don as always. I would like some normal weather just normal would be nice for this time of the year. Great Post always enjoy reading you opinions.

[cbmclean]

"However, if one looks northward to the Arctic source region, expansive warm anomalies are the rule."

Don, where do you to find current and forecast temperature anomalies for the arctic as a whole. I believe that I have had difficulty finding this information.

[donsutherland1]

"However, if one looks northward to the Arctic source region, expansive warm anomalies are the rule."

Don, where do you to find current and forecast temperature anomalies for the arctic as a whole. I believe that I have had difficulty finding this information.

To get the recent temperatures, I reference:

1. NCDC's re-analysis site and run the numbers: http://www.esrl.noaa.gov/psd/data/composites/day/

2. The Danish Meteorological Institute: http://ocean.dmi.dk/arctic/meant80n.uk.php

If there's a disparity in outcomes (infrequent), I take NCDC's numbers.

Forecasts are just based on the anomalies that show up on the operational models and ensembles.

[donsutherland1]

Some quick thoughts:

First, the excessive heat materialized with parts of the Mid-Atlantic and Northeast seeing maximum readings some 2 standard deviations above normal. NYC topped out at 88°, its warmest April reading since April 7, 2010 when the temperature soared to 92°.

Second, the ensembles continue to forecast a negative AO toward the end of April. As a result, it appears possible that today will mark the high point of April heat in the East.

Third, the recent model guidance pointing to a possible significant rainfall in parts of the East is consistent with the composite teleconnection indices for the April 23-30 timeframe used in Message #127. The composite pattern showed highest rainfall potential from the Carolinas east-northeastward and another area running across much of New York State through northern New England, with the heaviest amounts along the St. Lawrence River. The CFSv2 shows wet anomalies in the Northeast for around that timeframe.

As a result, I believe that it is possible that parts of the Mid-Atlantic region and Southeast could pick up a moderate to significant rainfall this coming weekend/early next week. I also believe that it is likely that the eastern Great Lakes region across New York State through western and northern New England could pick up a moderate to significant rain event. Even if such an event materialized, it remains to be seen whether it would be an infrequent event amidst a larger drought, or whether it offers the first hint of a denting of the growing drought or possible reversal.

[NJwinter23]

Some quick thoughts:

First, the excessive heat materialized with parts of the Mid-Atlantic and Northeast seeing maximum readings some 2 standard deviations above normal. NYC topped out at 88°, its warmest April reading since April 7, 2010 when the temperature soared to 92°.

Second, the ensembles continue to forecast a negative AO toward the end of April. As a result, it appears possible that today will mark the high point of April heat in the East.

Third, the recent model guidance pointing to a possible significant rainfall in parts of the East is consistent with the composite teleconnection indices for the April 23-30 timeframe used in Message #127. The composite pattern showed highest rainfall potential from the Carolinas east-northeastward and another area running across much of New York State through northern New England, with the heaviest amounts along the St. Lawrence River. The CFSv2 shows wet anomalies in the Northeast for around that timeframe.

As a result, I believe that it is possible that parts of the Mid-Atlantic region and Southeast could pick up a moderate to significant rainfall this coming weekend/early next week. I also believe that it is likely that the eastern Great Lakes region across New York State through western and northern New England could pick up a moderate to significant rain event. Even if such an event materialized, it remains to be seen whether it would be an infrequent event amidst a larger drought, or whether it offers the first hint of a denting of the growing drought or possible reversal.

Seems to be a lot of warm signals too though Don. The CFSv2 shows another blast of expansive heat pushing into the northeast near month's end and into early May... Roundy's OLR forecasts also would argue for some warm phase MJO activity by that time as well (though the models are against that). Rolling the CPC d+8 analogs forward past this cutoff situation also show this next heat wave around the same time. Finally, the GEFS superensemble analogs also show the warm shot coming back at this same period. Having trouble grasping the long range forecast through May, but I was leaning warm because of these signals.

[donsutherland1]

Seems to be a lot of warm signals too though Don. The CFSv2 shows another blast of expansive heat pushing into the northeast near month's end and into early May...

I agree. Going back to my April 23-30 discussion, I noted that the period could end on a warm note. As for May, a slowly increasing majority of my analogs is pointing to warmth. The continuing progression of the MJO could increase prospects for such an outcome.

[donsutherland1]

Some high temperatures from today. Parts of the Mid-Atlantic region saw maximum readings some 2 standard deviations above normal. In parts of southern New England, high temperatures were 2.5 standard deviations above normal.

Albany: 91° (broke daily record of 89° set in 2002; earliest 90° reading on record)

Baltimore: 90° (tied daily record set in 2002)

Boston: 87° (broke daily record of 84° set in 2003)

Concord: 90° (broke daily record of 88° set in 2002; earliest 90° reading on record)

Hartford: 92° (broke daily record of 90° set in 2002)

New York City: 88°

Newark: 88°

Philadelphia: 89°

Richmond: 90°

Washington, DC:

...DCA: 89°

...IAD: 88°

[JBG]

I doubt anyone north of the mason dixon line gets to 90 except the usual hot spots like newark and philly airport which have a shot at it. This kind of weather is becoming more normal, the past few aprils have been well above the 1981-2010 averages.

We were in "warm phase" for much of that period, through 2006 at least, and El Niños tend to feature toasty springs. Think 1969 (followed by lousy summer), 1986, 1987, 1990, 1991 (though heat persisted through summer), 1992, 1993 (though heat persisted through summer), 1994, 2004 and 2010 (transitioning to Niña). I don't think it's so much the "new normal" as a feature of an ENSO phase that tilted towards El Niños.

[Tropical]

Don,

What's your take on this? It looks like the models are completely reversing from their previous thoughts and are ready to plunge a cold air mass down into the CONUS.

End of the month warmth might be in trouble.

[donsutherland1]

Don,

What's your take on this? It looks like the models are completely reversing from their previous thoughts and are ready to plunge a cold air mass down into the CONUS.

End of the month warmth might be in trouble.

In recent days, there has been an expansion of cold anomalies across northern Canada. The guidance still leans toward at least an episode of AO-. It's still unclear whether the Great Lakes, Northeast, and Mid-Atlantic region will see a glancing blow from the cold or a more direct discharge. Persistence and a lack of a defined PNA+ argue for perhaps a transient shot of cold.

[JamieOber]

In recent days, there has been an expansion of cold anomalies across northern Canada. The guidance still leans toward at least an episode of AO-. It's still unclear whether the Great Lakes, Northeast, and Mid-Atlantic region will see a glancing blow from the cold or a more direct discharge. Persistence and a lack of a defined PNA+ argue for perhaps a transient shot of cold.

I noted JB tweeted the resemblance between last nights Euro and the upper air pattern on 4/28/28. As someone who enjoys historical weather, you might find it interesting that was the day of an epic Appalachian snowstorm that shattered records and probably some trees. One example, State College and the surrounding region saw 16-24 inches from that storm. Of course, we would need more than one run of the Euro to see anything like that.

[usedtobe]

I noted JB tweeted the resemblance between last nights Euro and the upper air pattern on 4/28/28. As someone who enjoys historical weather, you might find it interesting that was the day of an epic Appalachian snowstorm that shattered records and probably some trees. One example, State College and the surrounding region saw 16-24 inches from that storm. Of course, we would need more than one run of the Euro to see anything like that.

It does look like a pretty solid rain event for the mid atlantic, down here we really need it. The euro certainly is amped up. The gfs still shows some phasing and a wet system for the east. I remember a a strong closed low that crushed Mt Pisgah one year in early may so snow for the mountains would be possible from the euro. That said, it's the most amped solution and at times it likes jazzing up upper lows in that time range.

[Met1985]

It does look like a pretty solid rain event for the mid atlantic, down here we really need it. The euro certainly is amped up. The gfs still shows some phasing and a wet system for the east. I remember a a strong closed low that crushed Mt Pisgah one year in early may so snow for the mountains would be possible from the euro. That said, it's the most amped solution and at times it likes jazzing up upper lows in that time range.

You are right about that! I can see Mt Pisgah from my deck and we can have some suprising weather here in the spring. I remember a couple years ago were it snowed so much up there the people that work at the inn got stranded.

[donsutherland1]

I noted JB tweeted the resemblance between last nights Euro and the upper air pattern on 4/28/28. As someone who enjoys historical weather, you might find it interesting that was the day of an epic Appalachian snowstorm that shattered records and probably some trees. One example, State College and the surrounding region saw 16-24 inches from that storm. Of course, we would need more than one run of the Euro to see anything like that.

That's an interesting solution. The operational Euro seems more amplified than its ensemble mean or the GFS ensemble mean. Also, the best prospects for snow might be focused more on the Central and Southern Appalachians this time around based on that guidance. High elevations (>2500 feet) will probably do well. State College might be more marginal. It will be interesting to see what the later guidance shows.

[GaWx]

I noted JB tweeted the resemblance between last nights Euro and the upper air pattern on 4/28/28. As someone who enjoys historical weather, you might find it interesting that was the day of an epic Appalachian snowstorm that shattered records and probably some trees. One example, State College and the surrounding region saw 16-24 inches from that storm. Of course, we would need more than one run of the Euro to see anything like that.

A somewhat better analog might be the historic SE snowstorm of 4/25/1910, which dropped an incredible 1.5" of snow on Atlanta, its latest in the season accum. snowfall by far on record and several inches of snow to much of the SE US due to an upper level low that actually caused the snow to back westward per the old records and maps. That day also produced Atlanta's latest 32 on record. March 1910, like March 2012, was one of the warmest March's for the U.S. Also, this was during a La Nina albeit moderate instead of weak.

The 0Z Euro is the 3rd of the last 5 showing accumulating WNC/ETN snowfall. This run's output gives 2" near Greenville-Spartanburg and Knoxville, an incredible ~6" at Asheville, and an historic 12-14" at Johnson City! It also brings unseasonable cold to the SE US for the 4th run of the last 6. OTOH, no GFS run has had anything even close to the scenario and it is typically the colder model. So, we have a clear model battle that will be interesting to watch unfold.

Edit: I can't find any other current model run, including the 12Z GFS, that supports a SE Appalachian snow. That includes the UKMET, CDN, and JMA. So, from the standpoint of support, it isn't looking good at all for the Euro's chances. OTOH, three of the last five Euro runs have had the WNC/ETN snow. So, it is still worth following as a nontrivial possibility, especially considering the 1910 analog.

Edit #2: The 12Z Wed Euro not surprisingly says to the SE US "no big snow/upper level for you!" It caved pretty close to the 12Z GFS/other models.

[uncle W]

in April 1963 during a fading la nina the drought that was going on was temperarlly dashed by an end of month rain storm...Almost an inch of rain fell in Central Park and temperatures fell into the 30's May 1st with snow flurries as far south as Washington D.C....I don't think it will get that cold after the storm but we could see an inch of rain...

[donsutherland1]

"Summer in April" to Unfold in Parts of West...

While it is very likely that the East has experienced its highest readings for April, with some 90° or above highs in parts of the Mid-Atlantic and Southern New England regions, an even more spectacular bout of heat appears likely to unfold in parts of the West. The focus of the highest heat could be parts of Colorado, Idaho, Montana, Nevada, Utah, and Wyoming. The GFS ensembles are indicating 850 mb temperatures of 3 to 5 standard deviations above normal for the 4/20-25 period.

This could result in all-time April record highs in some of that area. For example, in Las Vegas, the all-time April high temperature is 99°, set on April 24, 1946 and tied on April 27, 2000 and April 30, 1981. If the GFS ensembles are correct, a 100° or above high could occur on one or two days during the upcoming heat.

For perspective, the following are high temperatures that are 2-3 standard deviations above the 4/20-25 norm (1981-2010 base period) for Las Vegas:

2.0∂: 97°

2.5∂: 101°

3.0∂: 106°

[donsutherland1]

Expanding on the post about upcoming heat in parts of the West during the weekend and perhaps into the middle of next week, today's guidance still has a signal for extreme April heat.

High temperatures of 2-3 standard deviations above normal, perhaps even more, continue to appear likely. Those deviations would translate into the following highs against the 4/20-25 norms (1981-2010 base period):

Casper:

2.0∂: 83°

2.5∂: 88°

3.0∂: 94°

Las Vegas:

2.0∂: 97°

2.5∂: 101°

3.0∂: 106°

Pocatello:

2.0∂: 79°

2.5∂: 83°

3.0∂: 88°

Provo-BYU:

2.0∂: 85°

2.5∂: 90°

3.0∂: 95°

The 4/19/2012 12z MOS Guidance shows the following highest temperatures for those locations during the 4/20-25 timeframe:

Casper: 84°

Las Vegas: 94°

Pocatello: 80°

Provo: 82°

At this time, I continue to expect that Las Vegas could see 1 or 2 days on which the temperature reaches or exceeds 100°. That would establish a new maximum temperature record for April. Casper could see the temperature soar into the middle and perhaps upper 80s. A 90° reading there is not out of the question. The all-time April mark for Casper is 84°, which was set on April 30, 1992. Pocatello could see a high temperature in the lower and middle 80s. The monthly record there is 86°, set on April 21, 1994, April 25, 1946, and April 29, 1992. Provo could approach or surpass 90°. The monthly record for Provo is 89°, which was established on April 29, 1992.

[donsutherland1]

Verification:

My April 8-15, 2012 thoughts (#42) were as follows:

Although the possibility exists that there cold be at least a moderate cold shot to the Ohio Valley and East Coast during the second week in April, the period could wind up somewhat warmer than normal in both areas. The warmth could follow a somewhat cooler than normal to near normal first week of April in that part of the U.S.

In contrast, a large part of Canada could see cooler than normal readings for the period as a whole. Eastern Canada, particularly Quebec, Nova Scotia, Newfoundland, New Brunswick, and PEI could be near normal to somewhat above normal.

.

The charts below are as follows:

Top Left: The composite temperature anomalies for ENSO Region 3.4 anomalies of -0.8°C to -0.1°C, a PNA of -1.00 to -0.25, and an AO of -0.75 to +0.25 for North America.

Top Right: NAEFS probabilities for the 4/6-12/2012 timeframe

Bottom Left: The Objective Analogs centered on April 9, 2012 but rolled forward 3 days

Bottom Right: Verification of the AO 14-day forecast

...At the same time, cold anomalies in the Arctic region are not very expansive. Barring a buildup of cold, there will be potential that cold anomalies in Canada could be more limited than what I anticipate. Pattern persistence has favored warmer-than-forecast outcomes.

Conclusion:

Taking into consideration the observed decadal temperature trend, I believe the eastern two-thirds of the U.S. will likely see generally somewhat above normal temperatures for the period as a whole. Eastern Canada could wind up with near normal to somewhat above normal readings, with some scattered cool anomalies. The rest of Canada, as well as the immediate West Coast of the U.S. could see cooler than normal readings. The western half of Alaska could also experience warmer than normal readings.

The anomalies were:

[Isotherm]

Verification:

My April 8-15, 2012 thoughts (#42) were as follows:

Although the possibility exists that there cold be at least a moderate cold shot to the Ohio Valley and East Coast during the second week in April, the period could wind up somewhat warmer than normal in both areas. The warmth could follow a somewhat cooler than normal to near normal first week of April in that part of the U.S.

In contrast, a large part of Canada could see cooler than normal readings for the period as a whole. Eastern Canada, particularly Quebec, Nova Scotia, Newfoundland, New Brunswick, and PEI could be near normal to somewhat above normal.

.

The charts below are as follows:

Top Left: The composite temperature anomalies for ENSO Region 3.4 anomalies of -0.8°C to -0.1°C, a PNA of -1.00 to -0.25, and an AO of -0.75 to +0.25 for North America.

Top Right: NAEFS probabilities for the 4/6-12/2012 timeframe

Bottom Left: The Objective Analogs centered on April 9, 2012 but rolled forward 3 days

Bottom Right: Verification of the AO 14-day forecast

...At the same time, cold anomalies in the Arctic region are not very expansive. Barring a buildup of cold, there will be potential that cold anomalies in Canada could be more limited than what I anticipate. Pattern persistence has favored warmer-than-forecast outcomes.

Conclusion:

Taking into consideration the observed decadal temperature trend, I believe the eastern two-thirds of the U.S. will likely see generally somewhat above normal temperatures for the period as a whole. Eastern Canada could wind up with near normal to somewhat above normal readings, with some scattered cool anomalies. The rest of Canada, as well as the immediate West Coast of the U.S. could see cooler than normal readings. The western half of Alaska could also experience warmer than normal readings.

The anomalies were:

Pretty remarkable how the warmth has been outdueling the cool recently. Note especially Canada -- your teleconnection/analog forecast vs observation. Positive anomalies virtually everywhere, and the areas that were cool, were only slightly so. April looks to go in the record books as a top 10 warmest for the US.

[donsutherland1]

Pretty remarkable how the warmth has been outdueling the cool recently. Note especially Canada -- your teleconnection/analog forecast vs observation. Positive anomalies virtually everywhere, and the areas that were cool, were only slightly so. April looks to go in the record books as a top 10 warmest for the US.

I agree. That's why, in part, I also take into consideration conditions in the Arctic source region, the observed decadal temperature trend, and persistence. Indeed, the lack of cold anomalies in the Arctic leading toward the period was a red flag of sorts. In the forecast, I noted, "At the same time, cold anomalies in the Arctic region are not very expansive. Barring a buildup of cold, there will be potential that cold anomalies in Canada could be more limited than what I anticipate. Pattern persistence has favored warmer-than-forecast outcomes."

In recent days, much of Canada has grown cold. That might allow for a seasonable or even somewhat cool start to May if a trough is present in the East. However, as the Arctic remains generally warmer than normal, any cold likely won't be sustained. It's a little soon to make that call, as things can still change, but a warmer than normal May is a distinct possibility.

[Isotherm]

I agree. That's why, in part, I also take into consideration conditions in the Arctic source region, the observed decadal temperature trend, and persistence. Indeed, the lack of cold anomalies in the Arctic leading toward the period was a red flag of sorts. In the forecast, I noted, "At the same time, cold anomalies in the Arctic region are not very expansive. Barring a buildup of cold, there will be potential that cold anomalies in Canada could be more limited than what I anticipate. Pattern persistence has favored warmer-than-forecast outcomes."

In recent days, much of Canada has grown cold. That might allow for a seasonable or even somewhat cool start to May if a trough is present during the East. However, as the Arctic remains generally warmer than normal, any cold likely won't be sustained. It's a little soon to make that call, as things can still change, but a warmer than normal May is a distinct possibility.

Agreed. While Canada is colder it still isn't impressive in terms of negative anomalies. I haven't made my call yet, but am currently leaning toward a warmer than normal May for much of the country.

Canadian 10 day ensemble. Note the limited chill.

[donsutherland1]

Agreed. While Canada is colder it still isn't impressive in terms of negative anomalies.

I agree that the cold is not very impressive in Canada.