The Map Gets “Flatter,” the Confidence Grows LowerJune 2nd, 2014 at 9:50 pm by Don Paul under 4 Warn Weather
As we’re now into the warm weather season, the surface features on the weather map tend to be flatter and weaker, as do many of the mid-level features aloft. In other words, timing weaker more subtle systems makes for some challenging forecasting. That doesn’t mean ALL systems are weak and poorly defined. In fact, as I type this post conditions look favorable for a rather major Severe Weather Outbreak on Tuesday the 3rd over portions of Iowa, Minnesota, Nebraska, NE Kansas and west central Illinois. But in the mean, defining troughs and ridges in the 500 mb flow, properly placing them, and properly determining their strength/amplitude becomes tougher. That’s because the mean tends to produce more of a zonal look. That’s in contrast to the blocky, high amplitude pattern we had so often until recently.
And remember, this mean is often the smoothed mean of many ensemble members in the global models which have a lot of spread between one another. The mean can be a best choice by default. But it is not necessarily the most reliable choice.
There will be a cooldown with reduced humidity returning toward Wednesday morning. Almost immediately afterward, there is already low confidence as to when any showers associated with an area of low pressure going by to our south might arrive in parts of WNY, with 2 operational models bringing those showers back in by mid or late Wednesday afternoon. Odds do favor much of the rain with that system staying farther south. The GFS is blindingly fast with onset and exit times, and viewed with suspicion on that speed. After lovely and dry days on Friday and Saturday, during Sunday another area of low pressure will be approaching, probably bringing some convection in by later in the day, with a few more rounds into Monday AM. There are no signs of prolonged heat and humidity, nor are there signs of prolonged cool weather. So, at this point, much of this next weekend looks pleasant. But unlike the last 2 weekends, the finish to the weekend is in doubt.
There are no changes to the ENSO forecast this week. The so-called key Nino Region 3.4 has a +.6 degree positive SST anomaly. Generally, an el nino is not considered as such unless there are 3 consecutive months of el nino conditions. A couple of weeks doesn’t cut it, partially due to the rising and ebbing warming/cooling caused by Kelvin waves traversing the Pacific. I’m still seeing only a handful of ENSO models projecting a truly strong el nino. Many, including the mean of the CFSv2, lean toward a moderate el nino.