flooding in Pocahontas
© Caitlin Sullinger
The photo above shows an aerial view of the flooding in Pocahontas, Arkansas, on May 2, 2017.
Spring 2017 has produced interesting out-of-season weather conditions and in some cases new records have been set.

Below we take a look at several of these recent unusual occurrences.

1) Eastern Pacific Hurricane Season Off to Record Early Start

Tropical Storm Adrian formed May 9, setting a new record for earliest tropical cyclone formation in the northeast Pacific in the satellite era. The previous record was held by Hurricane Alma in 1990, which developed May 12 and became a named storm May 14.

Satellite image of Tropical Storm Adrian
© The Weather Channel
Satellite image of Tropical Storm Adrian on May 10, 2017.
Adrian formed off the coast of southern Mexico and impacts will depend on its track, which is uncertain given that Adrian is expected to be in an area of weak steering currents by this weekend.

Heavy rain, however is likely in portions of southern Mexico and the mountains of Guatemala, which could lead to flash flooding and mudslides. If Adrian stalls off the coast, then rain may persist in the region over several days, increasing the risk of flooding.

2) New Record Set for Strongest May Southern Hemisphere Tropical Cyclone

Tropical Cyclone Donna became the strongest May Southern Hemisphere tropical cyclone on record May 7 when it rapidly intensified and reached the equivalent of a Category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale, according to Colorado State University meteorologist and tropical scientist Dr. Phil Klotzbach.

Satellite image of Tropical Cyclone Donna
© The Weather Channel
Satellite image of Tropical Cyclone Donna on May 7.
Donna impacted areas of Vanuatu and New Caledonia in the South Pacific with gusty winds and locally heavy rain. Fortunately, the core of the strongest winds and heaviest rain stayed far enough away from land that the worst conditions remained over the ocean.

Tropical season runs from November to April in the Southern Hemisphere, technically making Donna an out-of-season system. However, tropical cyclones can form in any month of the year.

3) Tropical Storm Formed in the Atlantic in April

The Atlantic hasn't been left out of the tropical oddities this spring. In April, Tropical Storm Arlene developed, becoming only the second tropical storm in the Atlantic in the satellite era.

The other April Atlantic tropical storm was Ana in 2003.

Arlene formed in the central Atlantic and did not impact land. Before satellites, both Ana and Arlene would have been nearly impossible to detect, so it's possible that others occurred prior to the satellite era.

This was also the third consecutive year that a tropical system formed in the Atlantic before the official June 1 start date of hurricane season.

This first named storm of the Atlantic hurricane season was first designated Subtropical Depression One on April 19 and then enough convection developed near the center that it was named Tropical Storm Arlene on April 20.

4) Snow In The East In May

An omega block set up over the U.S. in early May, resulting in some noticeable changes, especially in the East.

A southward dip in the jet stream, or upper-level trough, took hold of the Eastern U.S. for the first weekend of May. A slow-moving low-pressure system remained over the Northeast during the weekend and into Monday resulting in a prolonged period of cool, showery weather.

The colder-than-average temperatures allowed some of the precipitation to fall as snow. On Saturday, May 6, snow was reported in the higher elevations of North Carolina and Tennessee.

Sunday into Monday morning this chilly and wet pattern persisted and snow was reported in parts of upstate New York and northwestern Connecticut.

Snow can fall in these areas in May, but is not a common occurrence and not what most expect or desire.

5) Late-Season Rain in Southern California

The omega block also allowed a slow-moving area of low pressure to impact the West. This low-pressure system brought a late-season rain into southern California, possibly the last decent rain of the wet season.

On Sunday, downtown Los Angeles received 0.30 inches of rain, which is more than the average precipitation of 0.26 inches expected in May. Downtown Los Angeles has received more than 4.5 inches of rain above average for the wet season, which began on Oct. 1.

San Diego measured 0.89 inches over the weekend, more than 7 times the average of 0.12 inches for May.

In addition, snow fell in some of the mountains of southern California.

Southern California is not the only area of the West to experience unusual weather. A supercell, or rotating thunderstorm, was noted in southern Oregon, southeast of Crater Lake on May 4.

A tornado warning was issued for this storm and for the first time, the National Weather Service in Medford performed an aerial survey for evidence of tornado damage, but none was found.

6) A Nor'easter Is Possible For Mother's Day Weekend

The Northeast remains stuck in a cool, wet pattern and this will continue through Mother's Day. In fact, there are indications that a late-season nor'easter may be in store for the region this weekend.

Possible nor'easter setup
© The Weather Channel
Possible nor'easter setup.
This possible nor'easter will bring rain and wind to the Northeast. While many think of snow with nor'easters, snow is not necessary as the term refers to stronger areas of low pressure along the East coast with winds typically from the northeast.

Nor'easters are most common September through April.

There are still uncertainties in the forecast, but rain is likely to develop in the mid-Atlantic Friday and then spread into the Northeast over the weekend. Some coastal flooding is also possible with this system.

Honorable Mentions

While not out-of-season, there have also been a couple of other notable events that we've seen this spring related to heavy rain and flooding.

Buffalo, New York, has already set a record for the most precipitation in the spring, incredibly with several weeks left in the season.

From March 1-May 9, Buffalo has measured 14.21 inches of precipitation, more than double the average amount of 6.80 inches expected during this time period. The previous record was 12.03 inches set in 1991.

The rainfall, combined with snowmelt, has also resulted in record high water levels on Lake Ontario for this time of year. On May 7, the average lake level was 248.50 feet, which broke the record for mid-May of 248.46 feet set in 1973. Levels have continued to rise through May 9.

Consequently, flooding and erosion have been reported along the lakeshore.

The combination of higher water levels, above-average rainfall and saturated soil from snowmelt has also caused flooding and evacuations in Montreal. Neighborhoods are underwater in some areas and two people are missing.

Record flooding also occurred in Missouri, Arkansas and Oklahoma at the end of April and beginning of May. Record river flooding was observed in 14 gauge locations. Levee breaches were experienced along the Black River, resulting in massive flooding in Pocahontas, Arkansas.