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Category: EPO
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Jun 18
Long Range Update: Changes Afoot…
Looking at a simple snapshot of the latest sea surface temperature anomaly map would suggest a La Nina is brewing (image 1), BUT the latest SOI (Southern Oscillation Index, also knows as the SOI) suggests otherwise (images 2-3):
In fact, the SOI values noted would suggest an El Nino is coming on. The daily hit of more than 30 suggests some wild swings in the weather over the upcoming couple of weeks across the Lower 48. Now, we still anticipate this to transition more towards a positive direction and a subsequent La Nina to, indeed, develop by fall and winter, but this is worth continuing to pay attention to and we’ll do just that.
As we look at June to-date across central Indiana, temperatures are running a little more than 2° above normal and precipitation is just over 1″ below normal. Given the pattern ahead, we continue to like where we stand with our June forecast overall: near-average precipitation and temperatures. This will, obviously take a wetter, cooler shift in the regime as we move through the next 10-12 days. Overall, that’s where we continue to believe we’re heading.
The latest JMA Weeklies hot off the press shows this big cool, wet change across our region. A series of troughs are shown to descend into the Ohio Valley during the next 10-16 days. As the individual cold fronts sweep through the region, better chances of rain will result and temperatures will run cooler than normal, overall.
Week 1
Week 2
The latest GEFS data is very similar in this wet, cool shift.
There’s support for this pattern in looking at the latest East Pacific Oscillation, as well. Negative values support central/ eastern cool and periods of transition from positive to negative (and vice-versa) also can help promote wet/ more active periods.
The MJO (Madden Julian Oscillation) is a “sneaky” wild card in all of this. Note how the MJO is currently shown to slowly move through Phase 2 before going into the wheelhouse and emerging into Phase 8 by month’s end. While certainly not highly amplified, this is enough to have impacts. Note that Phases 2 and 8 this time of year maintain a cooler look, locally.
In summary, though it’s certainly been dry over the past couple of weeks, we think there’s more than enough reason not to fret. Not only are we looking at a pattern that should keep the heat (at least in a prolonged sense) west of our region, but the pattern drivers above should also result in a much more active regime with frontal passages and associated areas of low pressure moving through the region. This will begin in earnest early next week and continue through Week 2.
Permanent link to this article: https://indywx.com/long-range-update-changes-afoot/
Jun 12
Long Range Update: Timing Out When The Dry Pattern Breaks Down; 2nd Half Of Summer Chatter…
The balance of the upcoming 7-10 days will feature bone dry conditions across central Indiana. A fast moving disturbance will drop southeast Saturday and could spawn a scattered shower across central Indiana, but we believe the more concentrated rain activity will remain to our east and southwest. If you do see a Saturday shower, count yourself lucky! This disturbance and associated cold front will serve to reinforce the dry airmass currently in place, along with bring temperatures down another couple of “notches” for the weekend (wouldn’t be surprised if some outlying areas get into the 40s Sunday or Monday mornings).
As we look ahead, a ridge of high pressure will dominate next week’s weather pattern. An extended stretch of dry (pleasant humidity levels), sunny days can be expected with a slow warming trend.
Things begin to get a little more “murky” late next week as forecast model solutions differ significantly. The new GFS forecast model drives a cold front into the Ohio Valley before stalling out as multiple disturbances ride along the boundary. This would lead to needed rain (and potentially heavy rain at that) late next week into next weekend. Meanwhile, the European model isn’t nearly as excited about this wet weather potential. The reality likely lies somewhere in between and we’ll trend our forecast wetter late week, but hold on the heavy rain threat for now. Stay tuned.
With that said, we do believe (given the pattern drivers discussed below) that the wetter trends shown on the GFS ensemble data in the Week 2 (and beyond) time frame has validity.
The latest JMA Weekly data also shows a similar wet idea during this time period.
As we look at the PNA and EPO, the transition in both teleconnections next week do give credence to the wetter them shown above during the said period.
Additionally, the positive PNA (image 1 above) and negative EPO (image 2 above) argue for the possibility of another period of cool weather to wrap up the month. This would come after transitional heat late next week.
The GEFS is cooler than the European during this time frame. Given the above, it wouldn’t surprise us if the Euro is forced to cool as we get closer to this period.
We’re undoubtedly entering into a critical time frame for the remainder of the summer. The upcoming couple of weeks will go a long way in determining the balance of the rest of this season. Despite the short-term dry pattern, we do believe (at least locally), rain will return before things get out of hand. The same may not be able to be said just to our west. It’s there (more from the Rockies into the Plains) where we think July heat will build in more significant fashion with the drier soils.
Permanent link to this article: https://indywx.com/long-range-update-timing-out-when-the-dry-pattern-breaks-down-2nd-half-of-summer-chatter/
May 22
Long Range Update: Warmth Once Again Takes A Back Seat To Cooler Times; Drier Open To June?
With meteorological summer looming around the corner, will the pattern follow suit? At least in the short-term, warmth and humidity will have things feeling very much like summer, but this warmer regime likely won’t hold. The culprit? You guessed it- developing negative EPO, strongly positive PNA, and the MJO re-amplifying with eyes sets on the cooler phases to open June.
After a chilly May (month-to-date), most will welcome this weekend’s heat and humidity with open arms! This is courtesy of finally kicking the “cut off” low to the curb and replacing its’ influence with an upper level ridge. Scattered shower and thunderstorm activity is possible through the short-term, but coverage will be of the “splash and dash” variety- very typical of summer-time!
This warmer regime will be fleeting as a combination of ingredients align in a manner to drive cooler, more refreshing air back into the region as we close May and open June. Most notably this is being driven by a negative EPO, strongly positive PNA, and the MJO set to roll through Phases 7 and 8 during said period.
Accordingly, we note the models shifting things up quite significantly as we go into the Week 2 time period (May 29th-June 4th).
The cooler regime will likely also come with a drier overall pattern to open June, at least compared to average.
Permanent link to this article: https://indywx.com/long-range-update-warmth-once-again-takes-a-back-seat-to-cooler-times-drier-open-to-june/
May 20
VIDEO: Warming Up For Memorial Day Weekend, But The Pattern Once Again Trends Cooler To Close May…
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Permanent link to this article: https://indywx.com/video-warming-up-for-memorial-day-weekend-but-the-pattern-once-again-trends-cooler-to-close-may/