For the past few years, there has been a lot of talk in the news about El Niño. Now, it's time for the opposite pattern to appear: La Niña. The change it causes to Sea Surface Temperatures (SST) will influence our winter weather.Topics: Cross Enterprise | Frontier |
The QBO, or Quasi-Biennial Oscillation, is an oscillation in the wind direction in the stratosphere within about 15 degrees of the equator. Over a roughly two-year period, winds tend to oscillate between westward and eastward, with the switch between west and east winds starting high in the stratosphere and then shifting lower in altitude with time. The QBO is the result of waves propagating vertically in the atmosphere that then interact with the mean flow to slowly change wind speeds and direction. These changes influence the overall global circulation patterns, which in turn influence winter weather patterns across North America. The following plot shows the regular cycle in the QBO. Interestingly, the QBO has been positive for the last two winters, a highly unusual event. Since last winter, the QBO has turned sharply negative though, and that negative trend should continue into the upcoming winter.
With the pattern turning cold enough at the end of October to produce widespread frosts and freezes, it is an excellent time to look at when the average first freeze occurs across the country. Once frost begins to show up, the first snowfall will soon follow.
As of early October, the 2017 Atlantic hurricane season has produced 14 named storms, 8 of which have reached hurricane strength, and 5 of those major hurricane status (Category 3 or higher). Regarding storm numbers, this year is still below the average (since 1995) of 16 named storms for both neutral ENSO years and La Niña years (a La Niña is developing this year), but already at the average for hurricanes and one storm ahead of the average for major hurricanes.Topics: Tropical | Frontier | Hurricane |
Summer 2017 was hotter than normal for the U.S., ranking 15th hottest on record out of the last 123 years. However, unlike summer 2016, the heat this year was focused on the western half of the country, with the eastern US much more seasonal overall. The plots below show the monthly temperature anomalies for each month of the summer, along with the summer composite.Topics: Frontier |
September 1 marked the halfway point in the Atlantic hurricane season – at least according to the calendar. That means we still have three more months to go. Typically, activity is low in June and July and by the time August arrives we’ve had just a few named storms and maybe one hurricane. It is often during the last half of August that activity quickly ramps up toward the peak in mid-September, and then the Atlantic usually stays busy into October before settling down for the concluding month of November.Topics: Frontier | Hurricane |
While some extreme heat has been seen this summer across portions of the country, most recently across the Pacific Northwest, the entire June-August summer period is running much cooler than last year for the country on a population weighted basis.Topics: Frontier |
The developing pattern across North America features a strong upper level ridge along the West Coast and a central and eastern US trough. The West Coast ridge is sending temperatures to near all-time record highs across the Pacific Northwest while directing cooler air southward out of Canada into the Plains and Midwest where temperatures are falling to much below normal levels. We thought it would be worthwhile to look at past August patterns and find those that were similar to this year.Topics: Frontier |