Archive for May, 2014

A little more about El Nino’s global impacts
May 24, 2014

By Meteorologist Mike Skurko

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NOAA recently announced it’s prediction for the 2014 Atlantic hurricane season.  At the top of the list of influences on this year’s forecast was the presence of El Nino.  How is it that the warming of waters in the Pacific can lead to a quiet hurricane season in the Atlantic?  Further, how does it influence a wide variety of dramatic weather changes around the world?

An article published this week by NOAA’s climate.gov website explains this phenomenon.  A lot of it is a cause-effect chain that continues influencing the next event.  Here is a summary:

El Nino develops when the ocean waters in the Pacific near the equator become warmer than normal (when they are cooler than normal, it’s referred to as La Nina).  These warmer waters promote more thunderstorm activity in this region with more of this warm air available.  This rising warm air also warms the upper-levels of the atmosphere more than normal, not just the sea surface temperatures.

This warmer air in the upper atmosphere gets carried away from the tropics by the Hadley Circulation.  With an abundance of warmer air available to be carried away, the Hadley Circulation intensifies, which causes changes in large-scale jet stream and other climate patterns.

For some areas, these changing patterns cause much drier weather.  For others, it’s a rainy season.  For the Atlantic tropics, it’s a quieter hurricane season.  Etc. Etc.

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Click here for the full NOAA article regarding El Nino’s global impacts: http://www.climate.gov/news-features/blogs/enso/how-enso-leads-cascade-global-impacts

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NOAA predicts less-active 2014 hurricane season
May 23, 2014

By Meteorologist Mike Skurko

NOAA predicts a slightly less-active 2014 Atlantic hurricane season, with the following number of named storms, hurricanes, and major hurricanes expected to develop (note, this does not mean “make landfall”):

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NOAA cited two main factors in their below-average forecast for this season: the return of El Nino in the Pacific and cooler ocean waters in the Atlantic.  Here is a brief breakdown of why each of those factors would prohibit the development of many hurricanes.

El Nino

Many long-range guidance expects El Nino to develop this summer.  In fact, there are signs it is already brewing.  Among El Nino’s global weather impacts, it has been linked to stronger wind shear in the Atlantic. Wind shear is the differences in wind speed and direction with height. Strong wind shear can effectively tear apart the top of developing storms before they can mature into tropical systems. Therefore, the presence of El Nino, and more wind shear, is less favorable for hurricane development.

Secondly, hurricanes begin as weak storm systems/disturbances that move off the African continent and enter the tropical Atlantic waters, as shown below.  These systems are carried by the tropical trade winds.  El Nino has also been linked to stronger trade winds in this region, which is also unfavorable for hurricane development.
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Cooler Atlantic waters
Second, something that most people are familiar with, hurricanes need warm waters to grow and sustain themselves.  NOAA forecasters expect sea-surface temperatures to be cooler than normal, which would also be unfavorable for an active hurricane season.  Waters above 80 degrees Fahrenheit are best for hurricane development, which you can see on the graphic below means that hurricanes do not frequently make it northward into New England (despite Irene and Sandy over the last few years).
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The Atlantic hurricane season runs from June 1 to November 30, and typically peaks from mid-August to mid-September.

Friday night’s rainfall totals
May 17, 2014

By Meteorologist Mike Skurko

Here are the rainfall reports for Friday, May 16 into early Saturday morning.  The heaviest rain occurred in the Springfield area between 2 and 4 a.m. according to automated hourly reports from Barnes, Westover, and Bradley Int’l.  Most of these reports are courtesy of the National Weather Service’s SKYWARN program.

Hampden County
Granville, MA: 2.18″
East Longmeadow, MA: 2.13″
Springfield, MA: 1.93″
Agawam, MA: 1.85″
Chicopee, MA: 1.69″
Palmer, MA: 1.65″
Westfield, MA: 1.54″
West Springfield, MA: 1.36″
Brimfield, MA: 1.04″

Hampshire County
Westhampton, MA: 2.04″
Wiliamsburg, MA: 1.80″
Northampton, MA: 1.70″
Easthampton, MA: 1.60″

Franklin County
Shelburne, MA: 1.82″
Deerfield, MA: 1.71″
Greenfield, MA: 1.71″
Colrain, MA: 1.70″
Charlemont, MA: 1.50″

El Nino starting to brew
May 10, 2014

By Meteorologist Mike Skurko

El Nino, the warming of ocean waters in the equatorial Pacific, is starting to, well … warm up.  NOAA made the recent announcement which shouldn’t come as much of a surprise.  Long-range computer models were indicating the potential return of El Nino later this year.

Now, observations are starting to show that warm up starting to occur.  The image below is a cross section of the Pacific Ocean for mid-February and mid-April.  It shows a pool of warmer-than-normal water (shown in red) starting to migrate across the deep waters of the central Pacific to the surface just off the coast of South America.

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Above-normal sea surface temperatures are not common off the South America coast.  In this region near the equator, winds blow from west to east (think about tropical storms and hurricanes in the Atlantic moving west to east towards us in the Atlantic).  The easterly winds pile up sun-warmed surface waters in the western Pacific towards Indonesia.  If those winds ease up or reverse direction, the warm pool of water begins a slow slosh back towards South America.

NOAA officially declares El Nino underway when the monthly average temperature in the eastern Pacific is 0.5° Celsius or more above average.

El Nino has been linked to global weather pattern changes.  One of the most notable impacts to the eastern U.S. is a quieter Atlantic hurricane season.

April 2014 recap
May 4, 2014

By Meteorologist Mike Skurko

Our cold, snowy winter may lead people to believe that it has been a slow start to spring.  Believe it or not, our high temperatures last month would disagree.  Our average high was 60.6 degrees, almost right on the average mark.  A brief dusting of snow in the middle of the month is also nothing out of the ordinary.

While our total precipitation was well above normal, that number is a little misleading.  Through the first 29 days of April, precipitation was within a tenth of an inch to the monthly average.  However, on April 30th the Pioneer Valley recorded 1.94 inches of rain, breaking the previous record 1.03 inches set in 1991.

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