MONDAY: 14-DEC-15 / 3:00 PM CDT
NEXT WX CHART UPDATE WEDNESDAY
STORMY & COLD WEST - POTENTIAL RECORD WARMTH AHEAD IN THE EAST- AGAIN
Little change in the strong El Niño type WX Pattern is seen through the end of the month as strong storms continue to impact the nation from coast to coast – along with amazingly warm Temps in the East.
For the third time in the last 6 weeks, brief model ‘attempts’ at bringing more seasonal cold to the east have done a '180' back to a forecast for unusual warmth – including the potential for another week of record warmth starting next week and quite possibly again during the opening Week of the New Year as the mean upper level TROF remains anchored over western North America. While this general pattern is often experienced during strong El Nino’s, the extent and persistence of the warmth may push this DEC toward all-time national record territory.
While Temps will cool down this week to 'only' slightly above normal in the East - there is little doubt in the outlook for a return to very warm anomalies next week - though exactly how warm it gets will depend to a large extent on just how widespread and strong the storm systems are during the next 2 weeks - with the latest model runs showing 3 major, large-scale storms crossing the nation during the second half of the month. And while this morning’s 12Z GFS run is a bit colder than ALL previous runs since Friday afternoon, it’s still calling for Temps warm enough to make this one of the warmest Decembers on record.
MJO INTENSIFIES FOR FIRST TIME IN OVER A MONTHAfter remaining weak and incoherent since early NOV, the MJO (Madden-Julian Oscillation) has strengthened over the past few days – and appears to be centered in the far eastern Indian Ocean and is nearing Malaysia. The latest global model runs are forecasting it to reach moderate to near strong intensity during the week ahead with a slow progression eastward. The MJO is often quite weak during the mature phase of an El Niño event, and this ‘climatological influence’ may be playing a role in the longer range forecasts for the signal to weaken rapidly later this month as it moves towards the western equatorial Pacific. However, if it remains stronger and manages to cross the Pacific during JAN, it would almost certainly have a major influence on SST anomalies in the ENSO regions – so this potential needs to be monitored closely. Regardless, a moderate intensity MJO signal in the Phase 4 (Maritime Continent region) often leads (with a couple weeks lag) to very warm conditions in the eastern US – and is a ‘reinforcing signal’ for the warm anomalies over the US associated with El Niño and the latest operational model forecasts.
Fig 1: Temperature Anomalies for the Week Ending this Past Saturday Unusual nationwide warmth last week included weekly Temps averaging 16˚-20˚F above normal across the upper Midwest and Mississippi Valley.
Fig 2: Sub-Surface Temp Anomalies in the Equatorial Pacific As discussed last week – cooler sub-surface waters is working its way eastward across the central Pacific, undermining the very warm SST anomalies across ENSO region 4 – and is forecast to continue spreading eastward. This is a typical occurrence seen at the ‘beginning of the end’ for El Niño episodes.
CLICK IMAGE To Open FULL Size image in a new window
Fig 3: MJO Analysis / Global Model Forecasts (left Panels) and 850mb (~5,000 Ft) Temp Anomaly Composite (right panels) The MJO is now strengthening in the far eastern Indian Ocean and will move eastward across the Maritime Continent during the next 10 days – with most models calling for a rapid weakening as it approaches the western Pacific. A moderate to strong ‘Phase 4’ signal often leads to an upper air pattern favoring very warm low level Temp anomalies east of the Rockies – a thermal pattern strongly supportive of those associated with a strong El Niño and current, operational forecasts for late DEC.
CLICK IMAGE To Open FULL Size image in a new window
Fig 4: GFS 10 & 14 Day Forecasts for the Primary Teleconnections that impact North American Weather The latest forecasts for the primary Teleconnection indices (AO, NAO, PNA, EPO (eastern Pacific Oscillation) and WPO (Western Pacific Oscillation. The positive EPO, WPO, AO, and NAO - along with a negative phase of the PNA - are very supportive of warm anomalies in the eastern US – with little chance of any significant arctic outbreaks.
Fig 5: Temperature Anomaly Probability forecast for Week 2 from the GFS Ensemble (GEFS) model and the Experimental NAEFS model. The ensembles from the GFS (and the ECMWF – not shown) along with the NAEFs experimental model show an extremely high probability for above normal Temps over the eastern half of the nation for late DEC.
Figs 6a/b: 500mb (≈ 18,000 Ft) Height Forecast Loop for the next 2 Weeks (Top) and corresponding 250mb ( ≈35,000 Ft) Wind Forecast Loop (Bottom) The above loops show the wind patterns and location of TROF’s and Ridges, with shading indicating either above (reddish tones) or below (bluish tones) normal heights on the 500mb chart. The strong 500mb Low/TROF in the Midwest that brought heavy rain and severe WX to the central US this weekend will move quickly into SE Canada and weaken as the large upper level TROF in the west deepens and then ejects out to the E/NE later this week. The mean TROF over the west remains in place and is forecast to deepen into a full latitude, long wave TROF next week, bringing another surge of very warm air into the eastern US next week, and then weakens as it moves towards the east coast late next week. With such an active pattern, forecast accuracy for the timing, strength and exact track of individual short waves and storm systems is fairly low – though confidence in the overall pattern of warm and stormy conditions in the east and stormy but cold weather in the west, is very high.
Fig 7: GFS 15-Day Precipitation Pattern Loop (for mounts greater than 0.10” only). The animation shows total Precip forecasts during the preceding 24 hours in 3, 6 and then 12 hour time steps for the next 16 days. After rain passes off the east coast by tomorrow morning – cooler Temps will follow. The developing storm in the west will move eastward, with the heaviest Precip from this next system affecting mainly the eastern most states late this week. Next week, however, a series of strong systems hitting the west will move out over the Plains, and will develop into a major, complex storm event that will impact the central and then eastern US. A third major storm event also appears likely in the east just before New Years’ Eve. (At this time, it appears that only rain will occur next week in the east – with borderline probabilities of significant snow in the upper Midwest region – primarily dependent on exact storm tracks.)
Fig 8: Temperature ANOMALY forecast for Week 1 is based STRICTLY on the MOS data forecasts from the todays 12Z operational GFS model run with only minor adjustments towards the raw model data points for Days 6 and 8. Much Above normal Temps will fall off to modestly above normal as the week progresses will give way to a strong Temp rebound by the end of Week 1. Confidence in the forecast anomaly Pattern and Magnitude is above average with readings of ‘4’ on a Scale from 1 to 5.
Fig 9: The Week 2 Temperature ANOMALY forecast is based on the 12Z run of the GFS (60%) integrated with: the 12Z GFS Ensemble mean (10%), the 00Z EURO model Ensemble (10%) AND CLIMATOLOGY (20%) using the projected pattern along with explicit surface and 850mb (~5,000 FT) Temp forecasts. SOME Temps are adjusted for known or expected anomalous thermal patterns & projected storm system passages.The GFS forecast anomaly pattern and magnitude has been followed closely due to good consistency between all model suites and other longer range forecast tools. Actual anomalies are lower than those forecast by the ECMWF. Confidence in the anomaly Pattern is much above average for this time of year with a reading of ‘5’ on a scale of 1 to 5, while Confidence in actual anomaly magnitudes remains below average, with a reading of ‘2’ on a scale of 1 to 5.
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Quoting 1. wartsttocs: So I'll put this together for the kids. No snow week 2 in the mid atlantic CONFIDENCE LEVEL 5!! :-) ( admittedly stretched for bitter humor and that's not what Steve Gregory said, but I bet this does verify) |
7. georgevandenberghe
5:00 PM GMT on December 15, 2015|
Of the 12 calendar Months in DC , 5 have had record high monthly averages in the past decade. Oct 2007, June 2010 July 2011 March 2012 May 2015. December may well be added to the list in three weeks. 12/15 average to date 50.0. Warmest of record 1984 45.6. Also of the four boreal seasons, two of those four have had records set this decade Summer 2010 Spring 2012. No cold records for month or season although Feb 2015 was close Also of note summer 2010, summer 2011 and summer 2012 were all outlier warm summers far warmer than any others before (or since) |
6.
Steve Gregory
,
Sr. Forecaster/Risk Analysis
2:38 PM GMT on December 15, 2015
Quoting 4. Alan8156: From a subjective point of view - I've seen the GFS beat the ECMWF on several very recent storm system tracks - OTH, the ECMWF's forecast of warmth seems to be closer to reality than the GFS at the longer ranges - especially the ensembles. (The ECMWF has 51 members - the GFS Ensemble is still working with 21 members, though its physics and gridding was JUST recently upgraded big time - so this needs to be given a chance. for a few months to see how it does on average - but it's been in good agreement with the ECMWF this past week. ) Steve |
5.
Steve Gregory
,
Sr. Forecaster/Risk Analysis
2:32 PM GMT on December 15, 2015
Quoting 3. Humanities: The MJO, in a very indirect way - can impact storm tracks - but probably not in a long lasting way - and only when it is fairly strong and causing widespread, deep convection in the tropical Pacific basin - and more likely, if it is playing a role in tropical cyclone development which when they move into higher latitudes - can have a strong impact on the hemispheric pattern - at least for a while. Steve |
4. Alan8156
1:11 PM GMT on December 15, 2015|
Thanks, Steve. It seems to me that the ECMWF still outperforms the new GFS with respect to Atlantic tropical systems; I'm thinking in particular of how well it did with Joaquin's turn. How does the GFS do vis a vis the ECMWF in predicting temps and storms over the continental US? |
3. Humanities
2:19 AM GMT on December 15, 2015|
Hi Steve The warm anomalies in the Indian Ocean are very high this year. Is this effecting the MJO? Causing it to stay active in the Indian Ocean? Also the MJO over the Indian Ocean and the storm track into the Pacific Northwest/Northern California have both been in place for a while now. Does the storm track moving further south depend on the MJO changing? Or are these two things independent of each other? Thanks for the JASON animations - there are patterns but it is chaotic too. It's really interesting to see! |
2. Snacker2
11:48 PM GMT on December 14, 2015| I am loving this winter so far. Can't say I feel sorry for the west coast that cheated winter the last 2 years while we had full on winter. Plus, grass is still green in Wisconsin! Its going to be a green Christmas! Bleep the white Christmas nonsense. Its overrated. |
1. wartsttocs
9:55 PM GMT on December 14, 2015| I don't remember a '5' being used in a week 2 outlook before. I am thrilled! |
8. georgevandenberghe
9:20 PM GMT on December 15, 2015