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Category 6 has moved! See the latest from Dr. Jeff Masters and Bob Henson here.A Quiet Tornado Season Revs Up; Tropics Calm Down
After making landfall at 6:15 am EDT Sunday on the coast of South Carolina just south of the North Carolina border as the strongest tropical storm ever recorded to hit the U.S. so early in the year, Tropical Storm Ana dissipated on Sunday evening over North Carolina. The storm brought a number of wind gusts of 50 - 60 mph to the coast, but no significant flooding or damage was reported. Before Ana, only six tropical cyclones tracked over the Gulf Coast or East Coast before June 1. Ana was the earliest. (Tropical cyclones include tropical depressions, tropical storms and hurricanes.)
Figure 1. Infrared VIIRS image of Super Typhoon Noul as seen by Suomi satellite at 05:25 UTC May 10, 2015. At the time, Noul was nearing landfall on the northeastern tip of the Philippines' Luzon Island a Category 5 storm with 160 mph winds. Image credit: Lan Lindsey, NOAA/NASA RAMMB/CIRA.
Typhoon Noul (called Dodong in the Philippines) weakened to a Category 1 storm with top winds of 90 mph Monday morning after belting the extreme northeastern tip of the Philippines' Luzon Island as a Category 5 storm with 160 mph winds on Sunday morning. Two deaths are being blamed on the storm, but damage was limited by the fact that the northeastern Luzon is relatively sparsely populated. Satellite loops on Monday morning showed that Noul was barely recognizable as a typhoon, looking like a large misshapen blob of heavy thunderstorms. Noul is caught in a trough of low pressure that will swing the storm to the north and northeast, out to sea, skirting the Ryukyu Islands and the coast of Japan. The Yaeyama island chain of far southern Japan received some powerful winds from Noul on Monday morning; the Ishigaki-jima observation site--with records since 1897--set an all-time sustained wind record for the month of May, with 28.8 m/s (64.4 mph). Gusts up to 44.1 m/s (98.6 mph) also occurred. Farther east, Shimoji clocked a sustained wind of 36.4 m/s (81.4 mph) and a gust to 47.8 m/s (106.9 mph) around 1 a.m. JST (noon U.S. EDT). Thanks go to TWC's Nick Wiltgen for these wind stats.
Next up is Tropical Storm Dolphin, which formed over Micronesia on May 9, breaking the record set on May 19, 1971 for the earliest formation of the Northwest Pacific's seventh named storm of the year, according to statistics from the Japan Meteorological Agency's database from 1951 - 2015 maintained by Digital Typhoon. Dolphin is not yet well-organized, as seen on satellite loops, due to high wind shear. However, wind shear will relax to the low range by Wednesday, which should allow the storm to intensify into a typhoon when it makes its closest approach to Guam on Thursday and Friday. Guam will likely be the last land area Dolphin will affect, as a strong trough of low pressure should recurve the storm to the north out to sea late this week.
Tornadoes strike eastern South Dakota, east Texas
What began as one of the least active tornado seasons on record kicked into high gear over the weekend. Sunday produced a total of 26 tornado reports, following 53 reports on Saturday, according to preliminary data from NOAA's Storm Prediction Center. The worst strikes were early and late on Sunday. From around 10:30 to 11:00 am CDT, a tornado with a preliminary EF2 rating carved a quarter-mile-wide, 17-mile-long path across eastern South Dakota, causing 9 injuries and damaging more than 20 buildings in the town of Delmont. Another tornado struck Van, TX (about 100 miles east of Dallas) at around 8:45 pm CDT. The town's emergency management coordinator, Chuck Allen, estimated early on Monday morning that about 30 percent of the town of Van had been damaged, with some homes destroyed. At least 26 people were injured, with search and recovery operations continuing today.
Figure 2. Rev. David Otten, from Immanuel Lutheran Church in Dimock, SD, walks down Main Street in Delmont, SD, in front of Zion Lutheran Church after a tornado heavily damaged the structure on Sunday, May 10. Otten was filling in for Rev. Brian Bucklew but wasn't in the church when the tornado hit. Image credit: Joe Ahlquist/The Argus Leader, via AP.
The severe weather outbreak that began on Wednesday in Texas and Oklahoma will be winding down on Monday, as the upper-level low and associated cold front move into the Great Lakes and lower Mississippi Valley. Instability and wind shear have both decreased, but tornadic supercells are still possible, particularly in eastern Indiana, Ohio, and southeast Michigan. Heavy rain, wind, and hail can be expected along the length of the front, especially in Mississippi, Louisiana, and south Texas.
Figure 3. Preliminary severe weather reports for Saturday, May 9 (top) and Sunday, May 10 (bottom) show the bifurcated nature of the weekend outbreak, with one focal point near the surface low, which shifted from Colorado and Kansas to South Dakota and Iowa. Another focal point, along the trailing cold front, remained in Texas and Oklahoma. Image credit: NOAA/SPC.
After today's storms, the nation will see a brief respite, but forecast models strongly suggest that another multiday outbreak will unfold over the coming weekend, likely starting in Colorado and Kansas on Friday and expanding further into the Great Plains on Saturday. Thus far we've seen about 150 preliminary tornado reports for May, compared to an average for the entire month of 173 during the last three years (2012 - 2014). After Sunday's tornadoes, our preliminary total for the year is now around 400, just below the "inflation-adjusted" average for this point in the year. The average year-to-date total in that database climbs to around 600 by May 31. It would take a very busy last half of May to reach that point, but given the model indications for this coming weekend, and the longer-range suggestions of continued upper-level troughiness in the West, I wouldn't rule it out.
The good news is that tornado deaths and injuries have been remarkably low to date. Only three tornado-related fatalities appear in the SPC database through May 7. The years 2012 through 2014 averaged 34 deaths by the end of May, and the year before that--2011--saw more than 500 deaths by that point. The relatively light human toll is partially due to luck (this year's tornadoes have been missing large population centers) and partially due to the very small number of stronger tornadoes. Only one EF4 tornado and three EF3 tornadoes had been confirmed in unofficial totals through May 6. Over the last several decades, the total number of EF3/EF4/EF5 tornadoes has ranged between about 20 and 60, with 2011 a notable exception (more than 80 were observed that year). Most of these are rated EF3; only a handful of EF4 tornadoes occur in a typical year, and only about a dozen EF5s can be expected per decade.
Figure 4. This tornado northeast of Eads, CO, on Saturday, May 9 is approaching the end of its life cycle. Image credit: Bob Henson.
Snow and tornadoes in the same state--on the same day?
Old-timers from Colorado to South Dakota were impressed but not shocked by the wind-driven, late-season snowfall that wrapped around the back side of this weekend's strong low-pressure system over the Plains. Rapid City has recorded measurable snow as late as June 13, 1969, and Denver averages 1.7" in May (albeit with large year-to-year variability). Ground temperatures are warming up quickly, so to get much accumulation, the snow has to be falling heavily. Likewise, in order to cool down an already-chilly airmass enough to make it snow this late in the spring, heavy precipitation is usually needed. The Rapid City NWS office reported 13.6" on Saturday and Sunday, its second heaviest May snowstorm and the heaviest ever recorded so late in the season. Denver's totals of 3.5" on Saturday and 0.5" on Sunday were both enough to set daily records, but the month's all-time record of 11.5" on May 5, 1917, remains untouched.
Just as impressive as the snow itself was the juxtaposition of winter weather and severe weather within the same state. Snow and tornadoes were being observed at the same time (in different locations) in Colorado on Saturday afternoon and South Dakota on Sunday morning. I experienced this contrast first-hand while driving back to the Boulder, CO, area on Saturday from my visit to the NOAA Hazardous Weather Testbed in Norman, OK. Our route through far eastern Colorado took us just east of a long-lived, northward-moving supercell that produced several highly visible tornadoes north of the town of Eads. I once spent an entire summer storm-chasing in Colorado for NOAA as part of a validation program for the prototype NEXRAD radar, but this was the most spectacular sequence of tornadoes I've ever seen here. The last part of the drive was the most stressful, as howling winds and heavy snow struck the Denver area just before we arrived. This was the first time I've gone from a tornado warning to a winter storm warning in the space of six hours!
Bob Henson (severe); Jeff Masters (tropical)
Figure 5. Another tornado from the supercell that produced the twister in Figure 4 above, photographed from near Cheyenne Wells, CO, on Saturday, May 9. Image credit: wunderphotographer adkinsadam1.
Figure 6. A snow-covered scene from the Denver suburb of Arvada on Sunday, May 10. Image credit: wunderphotographer NapalmSnowcone.
Figure 1. Infrared VIIRS image of Super Typhoon Noul as seen by Suomi satellite at 05:25 UTC May 10, 2015. At the time, Noul was nearing landfall on the northeastern tip of the Philippines' Luzon Island a Category 5 storm with 160 mph winds. Image credit: Lan Lindsey, NOAA/NASA RAMMB/CIRA.
Typhoon Noul (called Dodong in the Philippines) weakened to a Category 1 storm with top winds of 90 mph Monday morning after belting the extreme northeastern tip of the Philippines' Luzon Island as a Category 5 storm with 160 mph winds on Sunday morning. Two deaths are being blamed on the storm, but damage was limited by the fact that the northeastern Luzon is relatively sparsely populated. Satellite loops on Monday morning showed that Noul was barely recognizable as a typhoon, looking like a large misshapen blob of heavy thunderstorms. Noul is caught in a trough of low pressure that will swing the storm to the north and northeast, out to sea, skirting the Ryukyu Islands and the coast of Japan. The Yaeyama island chain of far southern Japan received some powerful winds from Noul on Monday morning; the Ishigaki-jima observation site--with records since 1897--set an all-time sustained wind record for the month of May, with 28.8 m/s (64.4 mph). Gusts up to 44.1 m/s (98.6 mph) also occurred. Farther east, Shimoji clocked a sustained wind of 36.4 m/s (81.4 mph) and a gust to 47.8 m/s (106.9 mph) around 1 a.m. JST (noon U.S. EDT). Thanks go to TWC's Nick Wiltgen for these wind stats.
Next up is Tropical Storm Dolphin, which formed over Micronesia on May 9, breaking the record set on May 19, 1971 for the earliest formation of the Northwest Pacific's seventh named storm of the year, according to statistics from the Japan Meteorological Agency's database from 1951 - 2015 maintained by Digital Typhoon. Dolphin is not yet well-organized, as seen on satellite loops, due to high wind shear. However, wind shear will relax to the low range by Wednesday, which should allow the storm to intensify into a typhoon when it makes its closest approach to Guam on Thursday and Friday. Guam will likely be the last land area Dolphin will affect, as a strong trough of low pressure should recurve the storm to the north out to sea late this week.
Tornadoes strike eastern South Dakota, east Texas
What began as one of the least active tornado seasons on record kicked into high gear over the weekend. Sunday produced a total of 26 tornado reports, following 53 reports on Saturday, according to preliminary data from NOAA's Storm Prediction Center. The worst strikes were early and late on Sunday. From around 10:30 to 11:00 am CDT, a tornado with a preliminary EF2 rating carved a quarter-mile-wide, 17-mile-long path across eastern South Dakota, causing 9 injuries and damaging more than 20 buildings in the town of Delmont. Another tornado struck Van, TX (about 100 miles east of Dallas) at around 8:45 pm CDT. The town's emergency management coordinator, Chuck Allen, estimated early on Monday morning that about 30 percent of the town of Van had been damaged, with some homes destroyed. At least 26 people were injured, with search and recovery operations continuing today.
Figure 2. Rev. David Otten, from Immanuel Lutheran Church in Dimock, SD, walks down Main Street in Delmont, SD, in front of Zion Lutheran Church after a tornado heavily damaged the structure on Sunday, May 10. Otten was filling in for Rev. Brian Bucklew but wasn't in the church when the tornado hit. Image credit: Joe Ahlquist/The Argus Leader, via AP.
The severe weather outbreak that began on Wednesday in Texas and Oklahoma will be winding down on Monday, as the upper-level low and associated cold front move into the Great Lakes and lower Mississippi Valley. Instability and wind shear have both decreased, but tornadic supercells are still possible, particularly in eastern Indiana, Ohio, and southeast Michigan. Heavy rain, wind, and hail can be expected along the length of the front, especially in Mississippi, Louisiana, and south Texas.
Figure 3. Preliminary severe weather reports for Saturday, May 9 (top) and Sunday, May 10 (bottom) show the bifurcated nature of the weekend outbreak, with one focal point near the surface low, which shifted from Colorado and Kansas to South Dakota and Iowa. Another focal point, along the trailing cold front, remained in Texas and Oklahoma. Image credit: NOAA/SPC.
After today's storms, the nation will see a brief respite, but forecast models strongly suggest that another multiday outbreak will unfold over the coming weekend, likely starting in Colorado and Kansas on Friday and expanding further into the Great Plains on Saturday. Thus far we've seen about 150 preliminary tornado reports for May, compared to an average for the entire month of 173 during the last three years (2012 - 2014). After Sunday's tornadoes, our preliminary total for the year is now around 400, just below the "inflation-adjusted" average for this point in the year. The average year-to-date total in that database climbs to around 600 by May 31. It would take a very busy last half of May to reach that point, but given the model indications for this coming weekend, and the longer-range suggestions of continued upper-level troughiness in the West, I wouldn't rule it out.
The good news is that tornado deaths and injuries have been remarkably low to date. Only three tornado-related fatalities appear in the SPC database through May 7. The years 2012 through 2014 averaged 34 deaths by the end of May, and the year before that--2011--saw more than 500 deaths by that point. The relatively light human toll is partially due to luck (this year's tornadoes have been missing large population centers) and partially due to the very small number of stronger tornadoes. Only one EF4 tornado and three EF3 tornadoes had been confirmed in unofficial totals through May 6. Over the last several decades, the total number of EF3/EF4/EF5 tornadoes has ranged between about 20 and 60, with 2011 a notable exception (more than 80 were observed that year). Most of these are rated EF3; only a handful of EF4 tornadoes occur in a typical year, and only about a dozen EF5s can be expected per decade.
Figure 4. This tornado northeast of Eads, CO, on Saturday, May 9 is approaching the end of its life cycle. Image credit: Bob Henson.
Snow and tornadoes in the same state--on the same day?
Old-timers from Colorado to South Dakota were impressed but not shocked by the wind-driven, late-season snowfall that wrapped around the back side of this weekend's strong low-pressure system over the Plains. Rapid City has recorded measurable snow as late as June 13, 1969, and Denver averages 1.7" in May (albeit with large year-to-year variability). Ground temperatures are warming up quickly, so to get much accumulation, the snow has to be falling heavily. Likewise, in order to cool down an already-chilly airmass enough to make it snow this late in the spring, heavy precipitation is usually needed. The Rapid City NWS office reported 13.6" on Saturday and Sunday, its second heaviest May snowstorm and the heaviest ever recorded so late in the season. Denver's totals of 3.5" on Saturday and 0.5" on Sunday were both enough to set daily records, but the month's all-time record of 11.5" on May 5, 1917, remains untouched.
Just as impressive as the snow itself was the juxtaposition of winter weather and severe weather within the same state. Snow and tornadoes were being observed at the same time (in different locations) in Colorado on Saturday afternoon and South Dakota on Sunday morning. I experienced this contrast first-hand while driving back to the Boulder, CO, area on Saturday from my visit to the NOAA Hazardous Weather Testbed in Norman, OK. Our route through far eastern Colorado took us just east of a long-lived, northward-moving supercell that produced several highly visible tornadoes north of the town of Eads. I once spent an entire summer storm-chasing in Colorado for NOAA as part of a validation program for the prototype NEXRAD radar, but this was the most spectacular sequence of tornadoes I've ever seen here. The last part of the drive was the most stressful, as howling winds and heavy snow struck the Denver area just before we arrived. This was the first time I've gone from a tornado warning to a winter storm warning in the space of six hours!
Bob Henson (severe); Jeff Masters (tropical)
Figure 5. Another tornado from the supercell that produced the twister in Figure 4 above, photographed from near Cheyenne Wells, CO, on Saturday, May 9. Image credit: wunderphotographer adkinsadam1.
Figure 6. A snow-covered scene from the Denver suburb of Arvada on Sunday, May 10. Image credit: wunderphotographer NapalmSnowcone.
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