A Blustery Month - Sometimes...

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We've gotten a number of questions about how windy it seems to be this month, and there have indeed been some very gusty days, including three so far with winds reaching or exceeding 40 mph at the Raleigh-Durham airport (17, 18 and 29 Jan). However, when it comes to how windy we've been on average, it really hasn't been a standout month, and in fact we're running a little below the "normal" wind speed for January, with this month's mean so far standing at 7.4 mph, versus an average for the years 1971-2000 (defined as the current "normal") of an even 8 mph. So, while we've seen some quite blustery periods, winds haven't been as strong as frequently or over as sustained a period as they have many times in the past.

On the subject of normals and departures, while it has kind of snuck up on us a bit, we've gotten rather dry across the area once again in the past few weeks, with rainfall at the airport running at less than half of the normal amount for January to this point, a deficit for the month of -2.02". Looking back over longer time scales, we're still in pretty good shape over a three-month period, with a 90-day surplus of .3", but the year-long trend still reflects last year's summer and fall drought, with the 365-day period showing a shortfall of -4.4". There's a deepening upper level trough swinging our way from the west tonight that could help a little, but models have been rather inconsistent over time on how this system will play out, with a complex multi-center low pressure area forming in our vicinity at the surface. On some runs, these collapse into a single intense low over eastern Carolina that concentrates moisture and maximizes lift, for what appears to be a good shot at one to three quarters of an inch of rain, while other runs keep the lows more diffuse and the upper a little weaker and faster, leaving us with more fragmented coverage and totals that look more like one or 2 tenths of an inch instead. We'll know by this time tomorrow (Tuesday) how things turned out!

Finally, we got a reminder note from one of our colleagues at the National Weather Service office that the NWS is planning to implement an updated and improved version of the Fujita tornado intensity scale, probably in 2007. This is intended to remedy some of the limitations inherent in the scale as it has existed since the early 70s. The new "Enhanced Fujita Scale" and its relationship to the existing one is described in detail in this report. Interesting to note that the while the current F5 rating is listed as winds 261-318 mph, the new one uses a revised wind scale with EF5 given as >200 mph. No upper limit is included with EF5 in order to discourage people (and media members) from focusing on the wind speed at the top of the range.