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I’ve seen some long range outlooks issued in the private sector which seem to give the impression the rest of this summer will tend to be a write off. I think some of what I’m seeing is overstated and oversimplified. The MEAN for July, when tabulated, will probably show a tendency toward some troughing in the east and more ridging in the west. But the mean is a broad brush set of values which mask the details of our shorter term weather patterns. For example, the 32 day European 500 mb ensemble mean shows some periods during July in which heights rise in the east, and some warmer temperatures would be likely to return, particularly later in the month. The CFS has somewhat similar tendencies in the extended range. I’m not seeing signs of a return to a strong, lasting eastern ridge as we experienced for a large part of May, true. And so I have no reason to see a flip flop over to an extended period of hot weather in our region. (I will not speculate on August & September). That there are tendencies for a western ridge/eastern trough to rebuild over time is not to be denied at this stage. For example, the European mean shows a deep trough returning to the east in mid-July, toward the 17th. But it also shows rising 500mb heights starting to develop later in the month. As for precipitation, troughing in the east does favor more episodic short wave passages. But the location of the axis of that troughing and its amplitude will be key to how much rainfall occurs and how often. This last weekend was a truly unusual event for this time of the year, statistically…a rarity even with the western ridge/eastern trough tendency.
As for ENSO, moderate el nino conditions persist, with nino region 3.4 again showing a positive anomaly of 1.4 degrees…no intensification in the last 2 weeks. The MJO is active and expected to strengthen even more over the next 1-2 weeks. CPC feels the greatest impact from the MJO will be an increase in SW and NW Pacific tropical cyclone activity. The propagation to the east is likely to stop. The MJO is still considered to be interfering with the impact of el nino at this time, not that el nino would have a major impact in the summer in our region.
I suspect all but Rip Van Winkle have noticed we’ve been in a more active pattern with more frequent rounds of convection crossing parts of the region. There is more to come into at least this weekend, with less clarity showing for next week. The nature of the convective beast is uneven coverage, uncertain intensity, and different timing and pathways between the number of high resolution models in play. Global models have improved resolution from a few years back, but they are not a substitute for the high-res mesoscale/close-in models when you get closer to each event. Later this week, the moisture surging into SE TX and SW LA from a vigorous tropical disturbance (as of Monday evening) in the NW Gulf will curl around the warm SE ridge and move toward the Ohio Valley. Current indications point to this main surge staying south of our region, after producing potentially serious flooding in parts of the western Gulf states and Miss Valley. We can be grateful for that trajectory. In the mean over the next couple of weeks, the 500mb flow will be more zonal than not. Short waves embedded in that flow will be difficult to discern more than a few days in advance. There are signs that this week and coming weekend will be wetter than at least the first half of next week. There are no signs of any unusual cooling, but heights may lower over the Great Lakes for a few days early next week, bringing some cooling. Average high as of June 15 is 75 and the average low is 57. Lake Erie has slipped to 59, which is -2. June temps thus far are not far from average.
As for ENSO, el nino continues to be at moderate intensity currently. Key region 3.4 has a positive anomaly of 1.3 degrees having slipped to 1.2 degrees the previous week. More models are now pointing toward a potential Strong el nino, with 90% confidence of el nino continuing through the rest of the year, and 85% confidence it will continue through next winter. Duration is less uncertain than intensity, even with more models leaning toward moderate to strong, and more toward strong than in at any time in this recent cycle. In general, the amplitude/strength of el nino is expected to increase by mid and late summer from where it is now. A strong el nino is often associated with warmer than average temperatures across the northern tier of the lower 48. Precipitation is less certain. Some of memories of the destructive Pacific storms focus on the el ninos of 82-83 in CA, and again in 97-98. That part of the country desperately needs rain. The destructive aspects of a strong el nino are far from a given, as no 2 el ninos are the same…and no 2 Strong el ninos are the same. So, a moderate to strong el nino increases probabilities for a wetter and perhaps stormier winter in CA & the SW, but does not make such a pattern inevitable. An el nino as strong as the extremely anomalous 97-98 event would increase those odds. At this point, only one outlier model out of many is showing such an extreme solution.
What I can say at this early point is that if el nino remains at its current intensity or strengthens further (as is favored in many models), the probability of having extreme cold winters in our part of the country as per the last 2 winters goes down sharply. Snowfall projections are more difficult, and a warmer winter than the last 2, if realized, does not guarantee a big snow drought here or along the NE coast.
Finally, the el nino of moderate or greater intensity lessens the likelihood of a busy Atlantic hurricane season, while it increases activity in the eastern and central Pacific. As I pointed out in an earlier thread, however, killer Hurricane Andrew occurred during a vigorous el nino.
After Saturday morning (May 23) frost vanished, the warmth began to arrive on Sunday. It will hang around much of the time well into June, with only occasional interruptions. Looking at the overall distribution of atmospheric heights/pressure at the 500 mb level in ensemble means over the next 14-16 days, there are no signs of a fundamental, lasting pattern shift going back to a western ridge/eastern trough. The strength of ridging in the east will certainly weaken at times, and not measure up to mid-summer heights much of the time. However, we will have above average temperatures all this week, with a brief but very noticeable interruption later Saturday night into Sunday. With a prevailing SW flow much of the week, the metro area will be a little cooler than areas farther inland or closer to Lake Ontario (typical late spring climatology for a SW flow). A stronger cold front will cross the region Saturday into Saturday night, giving us our best opportunity for more widespread showers & tshowers. The models are not in very good agreement over how much drying will occur on Sunday or when the drying will occur. The ensembles point to some rebuilding of heights beginning all over again the following week.
Soil moisture is deficient north of the southern tier. As of Monday, May 25th, rainfall at the airport (which is fairly representative of the Niagara Frontier) was only .73″ with the average/normal being 2.01″. For the year, we are also more than 1/3 below average. Coverage for the work week’s convection looks spotty to me, and sparse at times. If we fail to pick up much in the way of widespread showers with the weekend cold front, conditions for growers will continue to deteriorate without irrigation.
As of this posting–Tuesday night, May 12–we are in the midst of a fairly sharp cooldown from the sultry conditions we had for several consecutive days, including the 88 degree record highs last Friday and Saturday. There will probably be some patchy inland frost and even some light freeze conditions Wednesday night, with the freeze confined to areas Well S & SE. But another gradual warmup will return by Friday into next Monday, followed by another cooldown (probably not quite as sharp as this cooldown). In other words, ups and downs. The downs will tend to be of shorter duration than the ups, and the next few ups do not currently appear to be quite so warm as what occurred late last week and this past weekend.
Until Tuesday of this week, May had been a Much Warmer than average month, with well below average rainfall. The extended range computer guidance suggests after another strong ridge develops Sunday into Monday ahead of the next cold front, the amplitude of the coming ups and downs will be a little flatter over the next couple of weeks. Part of that flatter tendency shows up because what we call ensembles of computer models (many runs of the same model, but each with slightly different initial conditions in each run because we can never “know” the precise initial condition of the atmosphere) tend to smooth the many individual runs of each model into a lower amplitude mean solution. (i.e., the European model ensemble–the most sophisticated of any global model–has 51 runs, compared to 21 runs for the American and Canadian model ensembles…much more supercomputer crunch power.)
Still, if I were a gambling man, I’d bet May will end up warmer than average, as was April. But we may not have as long a stretch of warm days as we had during the first 11 days of May.
El Nino conditions continue, currently showing characteristics of a Moderate el nino. One longer range US model and its ensemble projects a Strong el nino to develop by June-July and into the autumn and early winter. There are a number of meteorological pundits who have been trumpeting that a strong el nino tends to produce a cooler and wetter than average summer in the NE. Yet when I scour the data and climate records, I find only weaker evidence to support this–especially the wetter part. We do know that a moderate to strong el nino tends to disrupt the development of tropical cyclones in the Atlantic. Some experimental longer range models do suggest periods of cooler weather for parts of June and July, along with warmer periods. In other words, more ups and downs. El nino’s main effects are in the cold weather months, and not nearly so much in the warm weather months.
Bottom line, if you don’t want to wade through all the esoteric stuff below is this: After a chilly Monday April 27, temperatures will be more seasonable and occasionally warmer than average this week and next week. Cloud cover and precipitation chances are much more uncertain later this week and early next week. But the overall pattern seems to be evolving to one in which colder Canadian air will tend to stay farther north most of the time. Now the esoteric stuff for my fellow weather nerds, and for courageous folks who want to try wading into a semi-technical discussion with model acronyms and the like.
In general, a far from foolproof pattern is in the works for this week, especially later on in the week, as far as cloud cover and minor precipitation goes. Models show fairly poor agreement on seemingly minor features in our region. The operational GFS is hypersensitive to spotty light rainfall in recent runs, and is pessimistic to that extent. The ECMWF has its problematical periods as well, but is not as pessimistic overall as is the GFS, nor is the GEM.
All those smaller uncertainties aside, there is decent agreement of seasonable temperatures (average high is now 60 as of the 27th) and occasionally above average temperatures holding sway most of the time into next week. We’re not yet looking at a return to mid and upper 70s in the near future. But there should be highs of 60 or higher most days, once you get away from the cooler lakeshores. There may be some days where upper 60s could be reached. Cold fronts will usher in only Pacific air with the arctic connection now lost. Ensemble means are showing less persistent ridging in the Canadian west, and less troughing near the Great Lakes, out to 16 days.
In the longer term, the ECMWF 32 day ensemble mean still has some ups and downs, but fewer downs in today’s run than in last week’s runs. The CFS v2 also has more ups than downs.
El Nino showed more strengthening this past week. For the first time this year, key Nino region 3.4 reached a positive anomaly of 1.0 degrees. If the anomaly held at 1.0 over an extended period, what has been classified as weak el nino conditions would be considered moderate conditions. 6 of 24 dynamic and statistical ENSO models now project several months of strong el nino conditions later in the summer. The CFS is the most robust, keep a strong el nino through late summer into the winter, though some weakening increases late in the year. Based on SSTs and near sfc temps (0-300 meters), the structure of the warming does not seem tied so much to the downwelling/warm phase of a Kelvin wave. Wind anomalies seem to be playing more of a role, and Kelvin waves less at this particular time, although the feedback mechanisms into these directional wind anomalies is another topic for another day.
As many of you know, a moderate to strong el nino would increase wind shear over the Atlantic hurricane basin and lessen hurricane probabilities (while east Pacific conditions would be more favorable for hurricanes). A strong el nino has been associated with milder than average temperatures during the late fall and winter in our region, and would likely increase the chances for strong Pacific storms to move into California and the west at that time.
This continues to be VERY speculative on my part, since verification of ENSO phases that far out in time often does not work out well. Please keep that in mind.
After a 78 degree Monday and a 71 degree Thursday this week, the pattern which will be evolving by April 21 will be disappointing to most folks, and I say that with no empirical data to support the use of that word. A fairly deep upper level low will be crossing the northern Great Lakes and Ontario bringing progressively cooler temperatures from Tuesday through the remainder of next week. Daytime high temperatures will be running below average, though nighttime cloud cover should keep overnight lows from running too far below average. The W to NW flow will produce some instability showers most days next week behind a cold front, following more numerous showers & a few possible Tshowers ahead of that front Sunday night into Monday. Daytime heating with colder air aloft will make the most favored time for spotty showers during the afternoon Tuesday likely into Friday. We’re not heading into unprecedented chill. It’s more a matter of thermal backsliding with warming and drying redeveloping with a western ridge in the US and cooling over the Great Lakes with a trough redeveloping in the Great Lakes. The pattern will tend to relax somewhat by the end of April.
Still, the mechanisms which have led to the persistent redevelopment of this western ridge/eastern trough have not magically dissipated. Researcher Dr. Judah Cohen and his colleagues in Cambridge MA are somewhat pessimistic about the mid-spring period in much of eastern North America due to this persistence. I’m not quite so pessimistic as these learned scholars are. For the time being, though, the rebuilding of a warm eastern ridge is not showing in the extended range models over the period from April 19th into early May, so we’ll leave it at that and hold off on undue pessimism unless and until I see more evidence than just persistence.
On the matter of el nino, weak el nino conditions persist. A weak el nino in the mid spring and summer is not known by itself as a major contributor to weather patterns in our part of the country. Most models which predict ENSO/El Nino Southern Oscillation trends favor el nino lasting through most or all of the year. One US model, the Climate Forecast System, more aggressively is tending to show strengthening of el nino to moderate or possibly even strong amplitude by later this summer into the autumn, before weakening toward the tail end of the year and early next year. Depending on the future location of such a warm pool of tropical waters–central vs eastern Pacific equatorial waters–a strong el nino MAY bring a stormier pattern to the Pacific coast and the west, with desperately needed rains (although such storms can also be destructive in parts of CA). MAY is the key word here. And, a stronger el nino might also portend a milder winter in our part of the country than we’ve experienced during the last 2 winters. I want to make it clear that what I’ve written here is highly speculative at best. The prediction of ENSO state more than a few months in advance does not have the best track record even for experts in the field.
I’ll keep you updated, natch.
Spring is still unlikely to to produce a genuinely long string of sunny & warm days around here–it seldom does this early in the season. However, conditions will favor seasonable to occasionally above average temperatures much of the time over the next 14-16 days. At the time of this posting, though, a chilly couple of days will be setting up, but a deeper low pressure system will pump up some warmer temperatures Thursday and at least part of Friday along with some showers & possible Tstorms. The low may send some stronger storms toward parts of the Great Lakes after visiting the midwest by later Thursday into Friday AM. A cold front crossing our region late this week will usher in somewhat cooler but dry conditions for the weekend which will also mean abundant sunshine both weekend days. Later in the 8-14 day period, ensemble means are pointing to some troughing returning to the Great Lakes, allowing temps to drop a little below average. Some ridging over the SE will be flattened down for a while, which makes truly warm temps during that period unlikely to show up. On the whole, still undetermined tracks and intensities of short waves will have more to do with our weather than any high amplitude pattern.
El Nino remains weak, but has shown some modest strengthening in recent weeks. Nino region 3.4 now shows a +.7 degree anomaly and the eastern Pacific regions have warmed as well. Some of this has been due to a downwelling Kevin wave, but not all of it. The MJO had been very active and propagating eastward. It’s expected to weaken in week 2 and have less influence in general.
The long-advertised chillier pattern will be in place from Tuesday the 17th through that late part of the month. But there are going to be some ups and downs within the overall mean pattern, rather than a steady-state chilly pattern day after day. By late this week, high temps should be closer to average (low 40s) for a day or 2 and then take another sharp downward trend next weekend by later Saturday into Sunday. There will be several days in which even the high temperature stays below freezing. In the mean, there will be more days when the high temperature passes the 32 degree mark. With that in mind, a slow melt should continue on streams, creeks and in the shrinking snowpack. This kind of pattern may continue to reduce the risk of major ice jam flooding, but there can be “no guarantees” on that.
No major storms are currently indicated in the next week for our vicinity. No one should assume we are through with measurable or even significant snow. It is simply too soon for such expectations, and with a colder than average pattern odds of a true snow drought lasting through most of the month are not all that favorable. And on the other hand, on the day of this posting (Monday the 16th) nearby Cleveland and Pittsburgh both passed the 60 degree mark. So any low pressure system could be–albeit briefly–capable of pumping unseasonably mild air for a day. So, “all is not lost”.
As I mentioned last Friday the 6th, we are done with subzero readings, following a new record low and the 12th subzero low of the winter (the 3rd most subzero total days of any winter going back to 1871). Our temperatures will run a bit above average inland from Lake Erie for a few days this week, before cooler and more unsettled conditions arrive for the St Patty’s parade(s). This modest moderation will continue to shelter us from poor drainage flooding or any threat of ice jamming, unless we were to receive unexpectedly heavy rain this coming Saturday. Temperatures may be just cool enough to allow a bit of a mix to accompany the more widespread periods of rain on Saturday, and the occasional showers or drizzle on Sunday. Neither the First Ward nor the Delaware Avenue parades will be basking in sunshine and mild temperatures, but readings should be tolerably cool/chilly without raising the risk of frostbite which has occurred in some parades in the past. As of this posting, Saturday looks wetter than Sunday, but neither day will win any awards. Readings will again moderate on Monday.
However, by the 17th, there are signs a ridge of high pressure will redevelop over western North America, forcing the polar jet stream to go around it over NW Canada where this jet will tap into some modified arctic air, delivering it to the Great Lakes. This means temperatures will again be headed solidly below the average high closer to 40 or 41 at that time. Again, we won’t be returning to a true polar blast for our region but it does currently appear our temperatures will be running more than a couple of degrees below average. Even that colder trend will have some ups and downs within it. In the mean, though, it looks like our daytime highs will be below average most of the time from the 17th through at least the 24th or 25th. At least it can be said this type of pattern will keep the risk of ice jam flooding low.
The extreme pattern which dominated February isn’t going to be so extreme through March 12th or so. However, temperatures will still be below average for this time of the year most days (as of this posting, the average high is 37). The huge western ridge of warm high pressure over the west will slowly flatten out and the polar jet stream which has to go around it will lose its true polar connection. That will allow arctic air masses the chance to moderate a little before they drop down into the Great Lakes, rather than drop down our way staight from northern Siberia and the North Pole. This western ridge will retreat more into the NE Pacific, and the long dip in the polar jet stream over the east will lose some of its definition as well. Within this partial relaxation of the pattern, there will be ups and downs, with quick hits of arctic air (such as on Thursday the 5th), followed by partial recovery to near normal temperatures–but still a little below.
Right around the 14th and 15th, all 3 of the extended range tools we use to predict the overall North American temperature pattern agree the pattern will shift to a more West-to-East flow, instead of NW to SE. The kind of flow keep the true arctic air up in its “zone” to the north and allows milder Pacific air to cross the lower 48 more frequently. As you might imagine, a Pacific flow is considerably milder than a polar or arctic flow.
I’m not saying that at that point we’ll be done with winter and the threat of wintry weather. What I am saying is that the extremes in temperatures as far as truly bitter blasts will become much less likely. As in the previous thread, the more gradual this pattern change is, the better off we’ll be. There is thick ice on all streams and creeks and a huge amount of water stored in our deep snow cover. A sudden, strong thaw would virtually guarantee more serious flood potential, both from ice jams and from snowmelt. Nature will deal out what it deals out regardless of what we “wish” for. All we can do is hope the moderation is gentler than it’s been in years past.