Tornadoes require clashes of air masses to form generally to include cold, dry air in the upper atmosphere and very warm and humid air in the lower atmosphere. For much of the spring, the missing ingredient for this scenario in the US was the influx of very warm and humid air from the Gulf of Mexico thanks in large part to the persistent cold pattern in the central and eastern US that acted to inhibit Gulf of Mexico air from advancing northward. The cold air masses, however, began to retreat a couple of weeks ago and subsequently, dew points, which are a true measure of moisture content in the air, have consistently climbed in the central and eastern US and this increased dramatically the prospects for severe weather.
Indeed, the combination of very warm and humid low-level air with a vigorous cold upper-level low pressure trough on Monday helped to spawn the powerful tornado that struck portions of Oklahoma with a major impact on Moore, a heavily populated (50,000 residents) suburb of Oklahoma City some twenty miles to its south. The preliminary estimate is that the one-to-two mile wide tornado that struck the town of Moore reached EF-4 status on the “Enhanced Fugita” scale (5 being the most intense) with winds of nearly 200 mph, but these estimates will be re-evaluated over the next several days/weeks as tornado experts on the ground closely assess the damage and I think it may very well end up being classified as an EF-5. The tornado lasted for about 40 minutes causing destruction over a 20 mile swath.
The overall weather pattern that helped to produce the severe weather yesterday (i.e., warm, humid low level air, strong cold upper-level low with a powerful jet streak, strong surface cold front) will continue for the next couple of days with the severe weather threat zone slowly shifting eastward. There is a threat today for severe weather from the southern Plains to the Upper Midwest, and then likely in the Ohio Valley on Wednesday, and then perhaps in the Mid-Atlantic and Northeast US late Thursday as a strong cold front approaches the east coast. Strong-to-severe thunderstorms are possible later Thursday in the region from the Carolinas to New England as all the atmospheric dynamics shifts towards the east coast. This afternoon’s video includes some time-lapse video of yesterday’s tornado and a detailed discussion as to why the previously quiet tornado season has ended.
7:00 AM | Still a bit on the cool side today, but mid-week gets milder, although somewhat unsettled and the upcoming weekend looks warm
Mostly cloudy early with scattered showers possible, some sun late, cool, highs in the mid 60’s
Partly cloudy, chilly, lows in the low-to-mid 40’s
Partly sunny, milder, maybe a shower or thunderstorm, mid 70’s
Mostly cloudy, cool, a shower or thunderstorm possible, upper 40’s
Mostly sunny, breezy, mild, chance for a shower or thunderstorm, low 70’s
Partly sunny, warm, near 80
Mostly sunny, warm, low 80’s
Partly sunny, warm, low 80’s
Cooler weather began the new week and will continue today as high temperatures hold at below normal levels in the middle 60’s. An upper level ridge will move across the state on Wednesday and this will allow for some warmer conditions although a shower or thunderstorms cannot be ruled out in the mid-week time frame. Drier and warmer conditions are likely in the southern Rockies this weekend.
Mostly cloudy, cool, showers likely and possibly a thunderstorm, highs in the low 60’s
Mostly cloudy, colder, chance for showers and thunderstorms, lows in the low-to-mid 40’s
Mostly sunny, a bit milder, upper 60’s
Partly cloudy, cool, mid 40’s
Partly sunny, warmer, maybe a shower or thunderstorm, low-to-mid 70’s
Partly sunny, pleasant, breezy, mid 70’s
Partly sunny, warm, slight chance for a shower or thunderstorm, mid-to-upper 70’s
Partly sunny, warm, low 80's
Cooler weather will begin the new work week as high temperatures hold at below normal levels in the lower 60’s. The upper level trough causing today’s cooler conditions will move away to our east on Tuesday and this will allow for warmer conditions here by mid-week with high temperatures getting back to the 70’s.
2:30 PM | Sunspot region unleashes another solar flare (M-class) early Friday; possible northern lights tonight from X-flare that occurred earlier this week
The active sunspot region called AR1748 unleashed an M-class solar flare at 0858 UT on Friday, May 17th. While this is not the strongest flare that we’ve seen from AR1748, it actually may be the most geoeffective as this sunspot is now facing the Earth more directly than before, and the explosion might have hurled a coronal mass ejection (CME) towards the Earth.
Another CME that was sent into space earlier this week by an X1-flare from the same sunspot region might deliver a glancing blow to the Earth’s magnetic field later tonight. NOAA forecasters estimate a 40% chance of polar geomagnetic storms when the cloud arrives. High-latitude sky watchers should be on alert for northern lights later tonight.