Andy Dressler says:

“UKMET has abruptly shifted to showing an unfavorable setup for the Atlantic hurricane season, along with the CFS”….

Levi, I think you also made additional Twitter reference to how all models were now suddenly switching around and no longer are “bullish” on an active Atlantic Hurricane season. While there is no evidence to anticipate a late summer/early fall El Nino to take place, I do think there is something else at play here and can’t quite put my finger on it. I realize that the month to month MDR upper level winds have shown to be near (or even below average), I still nonetheless have 2 points of contention with that data. 1) If I am correct, this is based on a “deep layer mean” which consist of 250mb levels down to the 850mb levels and thus believe that the persistent strength of upper level 200mb winds which have been nearly consistent through most of the Atlantic basin, have been slightly “muted” by some of the lower level winds used to determine deep layer mean. Thus perhaps suggesting a “less than hostile” upper level environment than what one can more plainly see if simply looking at present 200mb data and recent historical 200mb flow. 2) I think that many in the meteorological society (and nearly everyone in the media or general public) have tended to over amplify the El Nino/La Nina topic to the point where every week data is analyzed to determine if we are soon to experience one or the other. Moderate or strong events are obvious global level weather players. Throw in Kelvin Waves, MDR’s, Long Wave patterns, and just when we think we’re starting to figure much of it out, Mother Nature throws a new curve ball at us (cosmic radiation, etc. – who knows? LOL). All I know is that you indicated that Analogue data maps as compared to this year, might now suggest that the summer months “could show” lower heights (less ridging), yet might that aid to the present increased Atlantic instability? On the flip side, indications now might be that there will be “higher” surface pressures through much of the Atlantic (though lower in the Caribbean during Sept. I think), and finally indications of present upper level shear conditions to likely to continue to be persistent through at least the remainder of the month. It is this one sole persistent condition that continues to trouble me, at least from a perspective of quite grasping its origin along with potential evolution. A few weeks ago, I sent an email to you regarding a point that I’ve recently posted on and was curious as to your thoughts on it. Though less intense through the MDR, there has been an oddly strong and persistent band of strong westerlies which has continued to traverse the Gulf, across Florida and continuing Eastward to Africa. It’s appearance would seem more “sub tropical jet like”, in that this band has existed south of decent upper level ridging that seemed to be holding on over the Northeast Conus and parts of the North Atlantic. Regarding Hurricane season, El Nino is most typically regarded as a buffer to development due the the stronger westerly shear conditions over much of the lower latitudes of the Caribbean and Central Atlantic MDR. I seem to recollect that here in S. Florida this flow would indeed cause a sub tropical “split flow” under the main Westerlies that would cause warmer than normal S. Florida winters. While Pacific SST’s would indicate that no El Nino is presently in play, I can’t help but notice the never ending flow of strong Upper level winds that have continued to blow in from the west and extending over much of the Atlantic sub tropical regions and actually throughout much of the Atlantic MDR as well. Some i’ve talked to have been quick to simply state, “well, its June”. I think this significantly underscores the point, the prior 60 days persistence of this UL flow, and that this feature seems far more prominent than perhaps a small band of westerlies being funneled into some pole-ward East Coast TUTT. In fact, I would almost characterize this feature to appear more like a “trans-Atlantic” which runs east/west contrary to how such East Coast TUTT features are normally oriented.

Providing greater than recent year average atmospheric instability and minimal SAL conditions, coupled with average or slightly above average SST’s a heightened quantitative number of tropical cyclones might well still occur. But assuming the persistent (not El Nino, but like El Nino) upper level conditions, would likely temper a little, the prior anticipated overall number of developing storms for the upcoming season. I now would anticipate fewer (or no?) Cape Verde “long tracks”. Assume that most of the tropical cyclone development will occur in the farther south latitudes where upper level shear is less impacting, along with another zone of development to occur north of 35N, developing north of this split layer of strong upper level winds. Finally, I would guess that we might see faster “spin ups” such as Andrea to occur and depending on the location of the less dominant but likely enhanced height & smaller upper level anticyclones….still see a couple of quick developing major hurricanes which may well impact the Greater Antilles, Central America, and Gulf regions.