An Omega Block for the U.K. (H. Michael Mogil, CCM, CBM, NWA-DS*)
The other day, Fred Mills, a colleague in the U.K., penned me a note concerning his weather observations. First, he noted that promised snowstorms were missing the U.K. (by passing well to the north) and that the weather south of London was actually quite nice for winter. Then, Mills commented on the contrails that he observed, “…the upper winds (as indicated by overflying aircraft at about 35 thousand feet) are very, very fast indeed, and from due north.”
His e-mail message prompted me to check on the upper level maps for the U.K. region. And, I’m pleased to report that Mills was “spot on!”
A large, closed, upper-level high-pressure system covered the region. But even more importantly, the wind flow around the high was in the shape of the Greek letter – Omega. Here, winds approach the high from the west and are re-directed northward. Eventually, the winds stop their northward trek and recurve toward the south. This “Omega” flow pattern is easily seen on the two upper-level wind flow maps for early on January 24, 2019 (Fig.1).
Omega highs tend to be very recalcitrant and hang around for long periods. This high, however, is already out of the picture. A more progressive (west-to-east) flow is now in place, bringing some light snow, but also even warmer temperatures, to the U.K.
Finally, Mills’ comments concerning “very fast” contrail movement were on target as well. The jet stream over the U.K. around the time of his observation contained winds above 110 miles per hour (see purple shading in Fig. 1).
© 2019 H. Michael Mogil
Originally posted 1/26/19
* The National Weather Association Digital Seal (NWA-DS) is awarded to individuals who pass stringent meteorological testing and evaluation of written weather content. H. Michael Mogil was awarded the second such seal and is a strong advocate for its use by weather bloggers.