Quiet Start to the 2015 Severe Weather Season
Thanks to colder than average weather in the eastern half of the country, severe weather has been fairly limited/non-existent so far this year.
(Image courtesy: NSSL)
2015 PRELIMINARY Tornado Count
WOW! Take a look at how few tornadoes we’ve seen across the nation so far this year (through March 17th). In fact, through the data listed (2005), this is the lowest number of tornadoes through March 17th; the closest was 56 in 2005. Interestingly, the 2005-2014 average is 173!
Cooler Than Average So Far in 2015
Take a look at the year temperature departure from average across North America and note how the continent looks to be divided with cooler than average temps to the east, while warmer than average temperatures are found to the west. We’ve been in a fairly persistent pattern over the past couple/few months, which has kept the severe weather threat pretty low in the heart of the severe country, which typically sits east of the Rockies, closer to the Gulf Coast Region.
(Image courtesy: WeatherBell)
Severe Watches So Far This March
Here’s some interesting info from NOAA’s SPC about the lack of severe weather this year so far. Interestingly, in a month that averages nearly 80 tornadoes nationally, we have yet to see even a tornado watch this March!
Latest from the SPC WCM page.
NORMAN, Okla. During a month when severe weather typically strikes, this March has been unusually quiet, with no tornado or severe thunderstorm watches issued by NOAA’s Storm Prediction Center so far. And, National Weather Service forecasters see no sign of dramatic change for the next week at least.
“We are in uncharted territory with respect to lack of severe weather”, said Greg Carbin, SPC’s warning coordination meteorologist. “This has never happened in the record of SPC watches dating back to 1970.”
Since the beginning of 2015, the SPC has issued only four tornado watches and no severe thunderstorm watches, which is less than 10 percent of the typical number of 52 tornado watches issued by mid-March. The approximately 20 tornadoes reported since January 1 is well below the 10-year average of 130 for that time period.
There is no one clear reason to explain the lack of tornadoes, Carbin said. “We’re in a persistent pattern that suppresses severe weather, and the right ingredients — moisture, instability, and lift — have not been brought together in any consistent way so far this year.”
Forecasters expect a change soon, however. April and May are typically the busiest months for severe weather and tornadoes. Patterns can change in a few days, Carbin said, and it’s important to be prepared for severe weather when it occurs.
Analysis of the ten lowest and ten highest watch count years through the middle of March reveals little correlation to the subsequent number of tornadoes through the end of June. For example, early 2012 was particularly active with 77 watches issued through mid-March. The subsequent period through the end of June was unusually quiet for tornadoes with about 130 fewer EF1 and stronger tornadoes occurring than what would normally be expected. On the other hand, 1984, with a relatively low watch count of 28 through mid-March, became more active and by late June had about 100 EF1 and stronger tornadoes above the long-term mean of 285.
Average Tornadoes In March
According to NOAA’s SPC, the 1989-2013 national average tornado county is around 80 for the month of March. As you can see, the biggest tornado producing states (on average for March) are located in the Southern Plains and the Gulf Coast States with Texas at the top with an average of 11.
Last Active March?
If you can recall back to March 2012, it was a VERY warm month. Most of the eastern half of the country was WELL above average in the temperature department. The weather pattern was very active too, which allowed for nearly 2,000 severe weather reports; 225 of which were tornado reports!
Upcoming Severe Threat
According to NOAA’s SPC, there is a MARGINAL SEVERE THREAT on Thursday across parts of the Southern Plains. Here’s more from the SPC:
…SWRN OK THROUGH NWRN TX…
EAST OF A LEE LOW OVER WRN TX…A WARM FRONT WILL LIFT NWD INTO SRN
OK THURSDAY AFTERNOON. SOUTH OF THIS BOUNDARY…PARTIALLY MODIFIED
GULF AIR /LOW 60S F NEAR-SFC DEWPOINTS/ WILL ADVECT THROUGH THE WARM
SECTOR. STEEPER /6.5 C/KM 850-500 MB/ LAPSE RATES WILL SPREAD EWD
ABOVE WRN FRINGE OF MOIST AXIS WHERE AT LEAST MODEST DIABATIC
WARMING SHOULD CONTRIBUTE TO AN AXIS OF 400-800 J/KG MLCAPE. WEAK
SHORTWAVE RIDGING WILL PERSIST OVER THIS REGION DURING THE DAY WHICH
/ALONG WITH A MODEST CAPPING INVERSION ALOFT/ SHOULD LIMIT
THUNDERSTORM DEVELOPMENT IN WARM SECTOR. HOWEVER…ASCENT ALONG THE
ADVANCING COLD FRONT MAY BE SUFFICIENT TO INITIATE THUNDERSTORMS AS
IT INTERCEPTS THE MOIST AXIS. DEEP-LAYER SHEAR FROM 35-45 KT WILL
SUPPORT POTENTIAL FOR A FEW ORGANIZED STORMS…BUT THERE MAY BE A
TENDENCY FOR ACTIVITY TO BE UNDERCUT BY THE SWD MOVING FRONT. A FEW
OF THE STRONGER STORMS MIGHT BECOME CAPABLE OF PRODUCING HAIL AND
GUSTY WINDS THROUGH EARLY EVENING.
National Weather Outlook
While temperatures have cooled rather dramatically across the northern half of the country since earlier this week, weather across the southern half of the country remains quite active. The loop below shows wet conditions unfolding from the Four Corners Region to the Mid-Atlantic/Northeast through AM Friday. Note that some of this precipitation looks to turn into more of a wintry mess in the Northeast by late week.
Heavy Precipitation Potential
According to NOAA’s HPC, the 5 day precipitation outlook shows nearly 2″ to 3″+ rain possible from parts of Texas to Georgia/South Carolina. Some of this heavy rain could lead to additional flooding through the end of the week.
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