Through Monday, the preliminary number of U.S. tornado reports is running above average and is the most at this point in five years.

NOAA's Storm Prediction Center (SPC) has logged 299 preliminary reports of tornadoes, more than double the 2005-2015 average of 133 reports typically received by March 6.

The last time the nation had this many tornado reports through the first week of March was in 2012, when there were 304 preliminary reports.

Interestingly, despite the active start to 2012, the total number of tornado reports over that entire year (1,116) ended up below the 2005-2015 average of 1,402.

That active year continued into April before dipping below average in the typical peak months of May and June, and the number of tornado reports trended even further below average as the year continued.

(MORE: Tornado Central )

Four years prior to that, 2008 also got off to a fast start.

By March 6, 2008, there were 398 reports of tornadoes – more than both 2012 and 2017. This included a January 7-8 outbreak with 54 confirmed tornadoes in the Midwest, making it the second-largest January tornado outbreak on record, at the time.

The following month featured the infamous "Super Tuesday Outbreak" on February 5. While 24 states held primary elections, 87 confirmed tornadoes were responsible for 57 deaths in the Southeast . The number of tornado-related fatalities (58) reported in February 2008 was the second-highest on record for any February in the U.S.

In all, 2008 ran well above average in tornado reports for nearly the entire year, finishing with 2,194 total reports – almost 800 reports above average. The third-most-active May on record, which included 460 confirmed tornadoes , contributed to over 20 percent of 2008's tornado reports.

(MORE: Tornadoes in March: The Start of Spring's Notorious Reputation )

One reason for the far-above-average first two-plus months of 2017 is the persistent warmth of the Gulf of Mexico and Caribbean Sea. This helps to generate plenty of warm, moist air into which low-pressure systems can tap, providing fuel for severe thunderstorms to develop.

In records dating to 1891, this is the first year Gulf of Mexico sea-surface temperatures never dropped below 73 degrees , when averaged across the entire Gulf. As of March 6 , sea-surface temperatures over the western Gulf were above average by 1 to 2 degrees Celsius (1.8 to 3.6 degrees Fahrenheit).

(MORE: Gulf of Mexico Warmth Could Lead to More Intense Severe Season, But Not More Hurricanes )

A more fundamental reason for the uptick in tornadoes so far in 2017 is the overall jet stream pattern.

Unlike some past winters, a persistent southward plunge of the jet stream has been in the West, rather than the East, so far.

This pattern allows warm, even somewhat humid air to fester in the South, and race northward into parts of the Midwest and up the Eastern Seaboard when these jet stream disturbances pivot out of the West.

The result, severe thunderstorms have occurred as far north as far upstate New York, and tornadoes have been reported as far north as central Minnesota .

MORE ON WEATHER.COM: Midwest Severe Weather Outbreak (Mar. 6, 2017)