Hurricane Season

Forecasters from the National Oceanic and Atmospheric Administration (NOAA) released their outlook for hurricane development in the Atlantic basin last week. They are calling for a near average hurricane season with around 14 named systems developing this hurricane season which runs from June 1 through November 30.

There are two principle factors that may lessen the number of hurricanes that form this year. First is the average oceanic temperatures in the Atlantic basin are cooler than they have been in recent years. Warmer ocean temperatures are generally more conducive to tropical development. The other factor will be wind shear. It appears a very weak El Nino may develop in the Pacific Ocean this summer into early autumn. El Ninos tend to induce a westerly wind component into the Gulf of Mexico and Caribbean Sea. This westerly wind counters the easterly trade wind that dominates the tropical areas of the Atlantic Ocean inhibiting the development of tropical systems.

Positive and Negative Summer Forecast

I have had numerous conversations in recent weeks with people all asking the same basic question, “will the cool weather last through the summer?” Most of the last 18 months have been cooler than average including our current spring season.

One positive factor that may help end this stretch of cool weather has been our lack of rain recently. Since April 1 most of the area has received slightly below average rainfall even when we factor in the rain from Memorial Day. This has allowed the top soil to become slightly drier which helps increase the air temperature. Plus, historically the summers following two consecutive La Nina winters tended to be finish near or slightly above normal for temperatures with slightly below average precipitation.

Two negative factors influencing our summer temperatures will be this persistent cool and wet phase we have been in and the Sun being in a long solar minimum.

Thermal Contrasts

Last week brought some strong temperatures boundaries to the region. Last Monday, May 18, a strong cold front moved through our area. At one point that afternoon, Langdon, ND was reporting a temperature of 46 degrees behind the front and in Wheaton, MN where the front had not yet passed it was 88 degrees. Both cities are in our TV coverage area.

That same front on Tuesday, May 19 surged north as a warm front and by early evening Wheaton, MN had soared to 95 degrees, whereas Fargo Moorhead only managed a high of 69 degrees and Langdon, ND remained in the upper 50s. But the temperature range that day was much more pronounced within Minnesota. Granite Falls on that day hit 100 degrees at 4:00 PM, yet at the same time it was only 34 degrees in Grand Marais, a difference of 66 degrees. Temperatures ranges of that magnitude within Minnesota are quite rare.

Empire Builder Tornado

Courtesy of "The Weather Doctor".  Full link:  http://www.islandnet.com/~see/weather/history/tornadotrains.htm

 

On 27 May 1931, the Great Northern Railway’s crack transcontinental passenger train The Empire Builder was heading eastbound from Seattle to Chicago. Less than an hour out of Fargo, North Dakota, disaster would strike. Late that afternoon an area of severe thunderstorms raged through Clay County, Minnesota. Suddenly, a funnel cloud formed, first observed by farmers in northern Kurtz township about 10 miles (16 km) south of Moorhead heading on an east-northeasterly course. At approximately 4:30 PM, The Empire Builder, eight miles (12.8 km) past Moorhead near the community of Sabin, encountered the heavy weather. Engineer B.E. McKee drove the great locomotive pulling twelve cars including five Pullman cars behind it into the storm.

Neither he nor fireman Klinfihn saw the funnel cloud approaching, though both observed the advancing storm. As the train sped southeast across the Minnesota prairie at 60 mph (96 km/h), the tornado (later rated an F3) struck it nearly broadside, and its force lifted five of the 70-ton passenger coaches from the rails. It carried one car through the air and deposited it in a ditch eighty feet (24.4 m) off the track bed. The remaining passenger cars were derailed. Only the 136-ton locomotive and 94-ton tender remained on the track. Interestingly, the coupling between the tender and the mail car was found to be closed after the impact. This suggests that the mail car was lifted vertically out of the coupling, at least a few inches before being blown from the tracks. All the cars remained coupled to each other, though some couplings were badly twisted by the derailment. All but one of the cars fell on their side, the lone exception was a car caught between two coaches which could not fall over.

 

Tornado meet The Empire Builder May 1931 The Empire Builder, bound from Seattle to Chicago, was struck by a tornado, May 27, 1931. Only the 136-ton locomotive remained on the track. Courtesy, Historic NWS Collection, NOAA

 

 

McKee saw the tornado moments before it struck and thought the locomotive took the brunt of the strike. The force of the wind blew out the cab windows and tore the engineer’s goggles off his face and out of the cab by a force that he described as "a suction at his body." Fifty-seven of the 117 passengers were injured by the impact and flying glass, and one was killed when he was hurled (or perhaps jumped in fear (?) according to a Pullman spokesman) through a day coach window and crushed in the wreckage. The railroad quickly sent a rescue train from Fargo to the wreck site. After loading the passengers, this train took them back to Fargo where the injured were taken to the hospitals. Stan Cowan, a reporter with the Moorhead Daily News recalled: "this tornado actually tipped this train over on its side which was, of course, going ahead full speed."

 

Tornado meet The Empire Builder May 1931 The Empire Builder was struck by a tornado east of Moorhead, Minnesota while traveling nearly 60 miles an hour. Courtesy, Historic NWS Collection, NOAA

 

The tornado tore a path forty miles (66 km) long across the Minnesota countryside. A additional death was recorded apart from the Empire Builder accident; however, damage to local farms was estimated at $200,000.

 

Memorial Day Weather

Memorial Day was traditionally observed on May 30 until 1971, but since has been designated to the last Monday in May. Since records have been taken in Fargo Moorhead the average high on Memorial Day has been 72 degrees with an average low of 49 degrees. 63 percent of the time this day has had no measurable precipitation. The wettest Memorial Day was back in 1977 when 1.13 inches fell. Not far behind and probably a day many of you remember was the 1.01 inches that fell in 2004. It rained steadily all three days of the Memorial Day weekend that year. The warmest Memorial Day was a 104 degree high in 1934 and the coolest was a high of 51 degrees in 1887. 2008 was one of the coolest with a high of only 62. 

Yesterday we recorded 0.34 inches officially at Hector Int’l with a High of 77° so approximately one-third of the day was reasonably nice.

 

 

So Far this May…

Through Thursday, May 21.  Fargo Moorhead is running 3.9 degrees below average (statistically significant) with 1.26 inches of rain (dry, but not extremely so).  Seems very likely May will once again finsish below average for temperatures.  A trend that has been persistant for most of the past 18 months.  Without another significant rain system (which is possible), this would be our second month with below average rainfall, which would buck a trend of extremely wet conditions the past 12 months.

 

Cool Springs

I was asked if there is a correlation between cold and snowy winters and a delayed spring. As with all such analysis, you will always find exceptions, but as a general rule there is an association for two principle reasons. The first may be the more obvious; a deep snow pack takes more time to melt therefore reducing the air temperature for a longer stretch of the spring as some of the sun’s energy is reflected back into space. Plus, melting snow cools the lower atmosphere through the process of evaporative cooling.

The second reason to this correlation can be attributed to La Ninas. Cold and snowy winters often occur when a La Nina is active in the Pacific Ocean. A high percentage of springs following a La Nina winter or having a La Nina active during the spring tend to be cooler and wetter than normal, just like this year.

Vortex

I rarely go through a public speaking engagement without someone asking me about how tornadoes form. My response is “we don’t know for sure” and then go through a brief description on what we do know. It is a basic question, without a definitive answer. There are many other aspects of tornadoes we still do not understand. In an attempt to find the answers to these questions, the largest and most ambitious research effort to understand tornadoes is currently underway.

Called VORTEX2, the research will be conducted over the course of the next several weeks throughout tornado alley. Over one-hundred scientists and crew utilizing ten mobile doppler radar trucks and an array of other research vehicles will be analyzing severe storms trying to understand the many mechanisms involved with tornadic development. If you would like to follow along with the research and see many of the dramatic photos taken you can go to their homepage at http://www.vortex2.org.

Slow Ice Out

The warm and windy conditions back on April 23 and 24 opened most of the lakes in Otter Tail and Becker counties. In extreme northern Minnesota the cold weather that followed those two days kept the ice on many lakes near the Canadian border until very recently. Lake of the Woods was not considered to be ice-free until May 8 and several lakes around Ely, Minnesota did not open completely until May 10 or 11. Most of the lakes in Minnesota became ice-free about ten days later than average. This is not surprising considering the cold winter and the cool spring that this region has experienced.

Phenology is the study of the timing of natural events and many residents in Minnesota will track the ice in and out days every year. For me, I keep track of when my ornamental crab apple trees flower each spring and they will be blooming very late this year.

Cold Mays

This decade has not been kind to those who want mild and pleasant May weather. Only three Mays this decade ended with above average temperatures and two of those three finished just slightly above normal. Including the first half of our current month, the other six Mays have finished below average, many well below.

May 2002 was the coldest of all with temperatures that month finishing more than six degrees below average. May 2004 was not far behind finishing more than 5 degrees below the average. As a reference, this month so far has been averaging around four degrees below normal to this point. Not only has this month been cool in recent years, but also wet.

The average rain in the 2000s has been 3.42 inches in comparison to the long-term average of 2.61 inches. The wettest year was in 2004 when 6.22 inches measured and ranked as the 4th wettest since 1881.