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.