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May Outlook: Another mild month on tap (Summer outlook posted)


Isotherm

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New thread / discussion on the month of May

http://www.lightinth...om/archives/525

It’s the battery that keeps recharging — an energizer bunny type pattern with regards to the warmth. In the Northeastern part of the United States, the 2010-2012 period has been the warmest on record for many cities. For the NYC local area, this past cold season, November through March, was the mildest on record. April will finish slightly warmer than normal as expected (probably +1 to +2 range in NYC), and not as anomalously mild as the previous months. The past several days have seen the longest stretch of negative departures since mid January, and before that, since October. However, it’s not saying much as this current stretch of moderately below normal temperatures should end by early next week. Prior to that time, late season frosts and freezes are likely in the suburbs of I-95 cities tonight and again late this weekend into Monday/Tuesday mornings.

Looking ahead to May, it doesn’t appear that we’ll break the seemingly eternal stretch of consecutive warmer than normal months. The weak-moderate La Nina event of 2011-2012 is slowly fading away, although SOI daily values have been positive in recent weeks, suggesting that we’re unlikely to see a rapid onset of an El Nino regime. Latest SSTA in ENSO region 3.4 indicates a reading of -0.17c, which is cold-neutral, and thus we’re not receiving any strong influence from ENSO right now. MJO tropical forcing patterns tend to be more noticable in times of weaker ENSO, and that will be spiraling toward phase 8 over the next couple weeks, a warm signal for much of the United States at this time of year.

NCEP model guidance projects a phase 8 MJO, while ECMWF based guidance essentially remains in the circle of death over the coming weeks. Either way, if the MJO does attain low amplitude phase 8, the signal produced for the eastern US will be a warm one.

Untitled1.png

Both the NAO and AO have remained fairly stable over the past several months, with predominately positive modalities for both indices. Although the AO has briefly turned negative this week (and we see the cool weather in response over the Northeast), models are in strong consensus that the AO will shoot slightly positive in early May. Meanwhile PNA forecast guidance suggests a slightly negative to near neutral look in the medium range.

When we combine the above factors, we get a May with near neutral ENSO conditions, a slightly positive NAO, AO, and near neutral PNA. MJO signalling will be weak, possibly low amplitude phase 8 in a couple weeks if anything.

The resultant analog package is as follows: Not many changes from the list of years that comprised the April forecast (and those years worked very well by the way with both temperature and precipitation departures in the US):

1951

1976

1986

2001

2009

The analog forecast May 500mb pattern:

153_104_187_53_116_18_31_34.png

Predicted May temperature anomalies:

153_104_187_53_116_18_32_21.png

Projected May precipitation anomalies:

153_104_187_53_116_18_33_53.png

Canadian temperature anomalies over the next 10 days — near to slightly above normal for the most part:

tenday.gif

Conclusion:

1.) May should feature slightly warmer than normal temperature departures in the Northeast US, with above normal temps stretching westward into the Great Lakes and Mid-west.

2.) Precipitation should increase over the southern Plains and Southeastern US

3.) Precipitation anomalies in the Northeast should be near normal (maybe slightly below avg), which is a step in the right direction after a very dry Jan-April period around here.

4.) May will start cool in the Northeast but trend milder. Bursts of 80s and summery weather is likely on a number of occasions.

5.) Summer outlook will be posted in late May. Early indications are that May “may” be the last month of the consecutive warmer than normal month stretch here in the Northeast. Our first “cooler than normal” temp month in awhile is likely to occur in either June or July.

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Mid to upper 80s look possible, particularly SW of NYC for Thursday and Friday, with 80s lingering into Saturday. 850mb temps rise to around +15c for a 48 hr period Thurs-Fri. The question is - can we get enough sunshine under SWLY flow to really torch us into the upper 80s? Right now it appears we'll be dealing w/ some differential advection / debris as we're not far from the warm front Thurs-Fri, so high temps may be held down in the 75-85 degree range. Difficult forecast temp wise late week; I could see numbers much higher than current MOS given less cloud cover.

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Looks likely that NYC will set the all time lowest heating degree days total record from July through June - previous number of 3887 set in 2001 -2002. NYC will be at about 3620 ending April . Since only one year has exceeded 267 combined May and June seems very likely we will set the record unless we have record cold in May and or June which seems very unlikely.

http://kamala.cod.ed...1.NYC.KOKX.html

http://www.erh.noaa....ingdegdays.html

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Looks likely that NYC will set the all time lowest heating degree days total record from July through June - previous number of 3887 set in 2001 -2002. NYC will be at about 3620 ending April . Since only one year has exceeded 267 combined May and June seems very likely we will set the record unless we have record cold in May and or June which seems very unlikely.

http://kamala.cod.ed...1.NYC.KOKX.html

http://www.erh.noaa....ingdegdays.html

it goes with the lowest amount of (freezing) 32 degrees or below days on record...

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  • 3 weeks later...

Mid month check of May thus far, temp and precip. The analog precip forecast is very good, with the wet anomalies across the East, save for a dry patch in the mid atlantic region. Temperature departures for May are likely to finish slightly above normal in NYC/Northeast as expected, but the Southern US looks to be much warmer than anticipated. What I found recently is the analog composite is often underdone with respect to the magnitude of the warmth. The orientation/positioning of the pos/neg temp and precip anomalies has been good over the past 2 months, with the years that I've been using. Will be interesting to see which years pop out as the main ones for June-July-August. I'm beginning to think June will be another warmer than normal month in the Northeast.

2mqrura.jpg

2u5rsc8.jpg

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The closest match of my analogs so far was 1986, with 2001 second.

May 1986:

2q89elj.jpg

The temp pattern for JJA was a colder than normal one for the Northeast, however, with the rest of the country on the mild side. We'll see how the next couple weeks progress.

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^86 was a developing Nino summer. While JJA was "cooler" than average overall in the Northeast, it wasn't that say south of NYC as both June and July were milder than normal in Philly and very warm in the South/Southeast. The West was hot/cool/mild respectively.

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developing El Nino years for May and June...

warmest years...

year...ave temp...

1991...68.7* warmest on record

1965...66.4

1986...66.0

2004...65.2

1982...64.1

middle years...

1972...63.3

1951...63.3

1957...63.1

2006...63.1

2009...62.5

coolest years...

1997...59.4

1968...59.6

1976...60.2

2002...60.7

1963...61.1

1994...61.8

norm...62.6

ave.....63.0

2012 could end up the fifth warmest with a warm ending to the month...

June during developing el nino years...

Warmest...

year...ave temp...

1994...75.2

1957...74.3

1991...74.1

1976...73.2

1986...71.6

middle years...

2002...71.4

2004...71.2

2006...71.0

1963...70.9

1997...70.9

coolest years...

1965...70.1

1951...69.8

1968...69.7

1982...68.6

1972...67.9

2009...67.5

norm...71.2

ave.....71.1

May has nine of 16 above normal...Seven below normal...the trend for developing el nino's for May is slightly above normal temperatures...This year looks to end up above normal...

Nine out of 16 Junes were below average...Six above and one average...

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  • 2 weeks later...

http://www.lightinth...om/archives/541

Here's my thoughts for the summer, posted in the main board as well. Any comments or questions would be appreciated!

Great job as usual Tom. I cant argue with your analysis and I especially agree with your above avg precip call . I think we continue an overall above normal temp regime but dont see any prolonged/severe heat like we did in 2010 and 2011. I have to also agree that June or Aug will be the warmest against the means.

I think EWR reaches 90 between 20 and 30 times NYC likely 15 - 20.

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Great job as usual Tom. I cant argue with your analysis and I especially agree with your above avg precip call . I think we continue an overall above normal temp regime but dont see any prolonged/severe heat like we did in 2010 and 2011. I have to also agree that June or Aug will be the warmest against the means.

I think EWR reaches 90 between 20 and 30 times NYC likely 15 - 20.

Thanks Tony, I agree about this summer being cooler than 10/11. Night time mins and high humidity probably more memorable this summer. I think we could be active T-storm wise as well, but that's always a long shot to predict

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I think above normal is the new normal. but if we keep it only a degree above the 1981-2010 averages it would seem cool for these times!

I think we'll get a below normal month this summer (slightly), but in terms of more than 1 in a row, it may be awhile. With any luck, it'll occur next winter.

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I think we'll get a below normal month this summer (slightly), but in terms of more than 1 in a row, it may be awhile. With any luck, it'll occur next winter.

Yes I think either july or august will be a little below and let's hope for next winter being below normal.

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