Weather It Is (A Dramatic Entrance)

Good Afternoon:

Today's rain is a fond reminder of the rains I remember growing up (in the eastern US).  We've had about 10 mm of rain (here in Efrat) since last night.  Last year, we also had a number of small rain events before January brought its unusual cold.

A weak storm will approach on Wednesday and then the bottom will fall out on the temperature scale.

We already mentioned that this El-Nino year is bringing instability to the global forecast pattern (as seen in some members of the global ensemble).  What do we mean by this? It means that the surface energy flux (associated with the warm Pacific waters) is creating strong convection that is feeding upscale into the global circulation pattern.  Because these convective systems are hard to predict, the ensemble forecast shows a lot of dispersion (as a realistic reflection of the "unknown" influences of this convection).

Well, one of those members has "decided" to "express" itself in a big way and right now it's dragging almost 60% of the global ensemble members with it -- to possibly the coldest weather this early in the winter season in years.

The chill should begin to move in after the storm on Thursday  (a light rain event) and then bone-chilling cold should arrive Erev Shabat and continue its grip into Sunday morning.

This is a rapidly evolving system and at the moment there is a greater than 50% chance that there will be snow showers (some of them briefly heavy) at the higher elevations.  However, at 700 mb and especially at 500 mb the upper level trough still remains ill-defined, so we wouldn't expect any more than a "wipe-away" accumulation (if that).

Yet, we expect this to change as "baroclinic" (temperature) feedbacks between the developing surface/lower atmospheric become better resolved by the ensemble.  When it does, we'll be able to tell whether this will be a showery or more significant rain/snow event.

We're just a few days away -- so there isn't much time for the circulation pattern to sort itself out -- but it will. You can count on it.

The unusually cold weather should be followed by normal winter cold next week.

Barry Lynn