Archive for July, 2013

Warmest July on record for Pioneer Valley
July 31, 2013

By Meteorologist Mike Skurko

July 2013 is the warmest July on record at Bradley International Airport, the official NOAA climate station for the Pioneer Valley.  The average high temperature was 87.2 degrees, and the average low was 68.6.  Therefore the average mean temperature (averaging the highs and lows together) was 77.9 degrees.  The previous record was 77.1 degrees set in 2010 and 1994.

It is not a far stretch to say that we shattered this record.  This new record beat the previous record by 0.8 degrees, but consider that the top-10 list of the warmest Julys are separated by only 0.9 degrees from 2nd place (77.1 degrees) to 10th place (76.2 degrees).  Providence also set a new record for the warmest July, while Worcester cracks their top-5 and Boston reaches their top-10.

wx blog

NOAA, National Weather Service doubling computing power
July 30, 2013

By Meteorologist Mike Skurko

One of the common questions asked to meteorologists, unfortunately, is “why are the forecasts wrong?”  Some people ask it humorously, a few ask it a little more sincerely.  For those who are actually curious, a large part of forecasting errors can be attributed to the limited computer power that is available.  On Monday, NOAA booted up a new computer system that will more than double it’s computing power used to sort through and forecast weather information.

Named “Tide”, the new supercomputer operates at 213 teraflops (213 trillion calculations per second), up from the 90-teraflop supercomputers that NOAA previously used.  This will allow forecast models to ingest more weather data and perform more complex calculations/equations.  The end result should be more detailed, more accurate atmospheric models for meteorologists to interpret, and thus make more accurate forecasts.

While our 7-day forecast for western Massachusetts may not see any noticeable changes, NOAA said the biggest improvement will come to hurricane forecasters.  A new Hurricane Weather Research and Forecasting (HWRF) model will be implemented with the new computer upgrade.  Research with this newer HWRF model has shown a 15 percent improvement in hurricane track and intensity forecasts.

wx blog

A brief history of why/how faster computers will lead to more accurate forecasts: In 1904, Norwegian physicist Vilhelm Bjerknes stated that weather forecasting should be considered as a mathematical problem … with an initial set of data and an end number that can be calculated.  This is the basis of Numerical Weather Prediction, a concept that is fundamental to meteorology today.

Theoretically, the exact weather could be accurately calculated for an exact location and an exact moment in time if using the correct set of initial data and correct equations that influence the weather.  However, the problem is that the amount of data and all of the calculations needed are way too complex for even the most sophisticated supercomputers in the world to handle.  By time a forecast could be accurately solved, it could be days or weeks later and completely irrelevant!

Therefore, today’s supercomputers cut corners in the data and equations used.  Some quantities are estimated.  Some equations use “close-enough” approximations.  It is also impossible to collect every single weather variable in every single tiny section of the world, so computers must use estimations for the data that is missing.  The correct solving of one equation or variable at one location is needed to solve the next equation.  Rounding off numbers and these estimations and approximations can quickly snowball from one equation to the next and lead to inaccuracies.

With these faster supercomputers at NOAA, a few of those corners may not need to be cut … as equations can be solved faster and in a more detailed manner.  This should continue to help forecasters get more accurate and higher resolution models of hurricanes, severe weather outbreaks, and snowstorms in the years to come.

Meteorology 101: Cold fronts bring in drier air too
July 28, 2013

By Meteorologist Mike Skurko

Our forecast for western Massachusetts calls for an approaching cold front to deliver scattered showers Sunday evening through Monday morning.  After the cold front passes Monday, skies will clear out nicely through the second-half of the day.  However, you may have noticed that Sunday’s high temperature was 82 degrees in Springfield, while Monday’s forecast expects a high of 83 degrees.

How can this be? If a cold front is expected to cross the region, why does tomorrow’s high temperature go up a degree? Why does Tuesday and Wednesday’s high temperature stay in the lower-80s as well? Shouldn’t a cool down be coming behind a cold front?

Yes, usually cold fronts deliver cool temperatures, but they have other characteristics as well.  A front is defined as the boundary of two different types of airmasses.  For example, if a dry, Candian airmass from the north is moving in and undercutting the warmer, moist airmass in place, a front is put on the map where these two airmasses meet.  Sunday was cloudy, a little muggy, and had scattered showers (the warmer airmass).  After the front passes, we will have sunny skies and much lower humidity (the Canadian airmass).

Winds ahead of a westward moving cold front typically come up from the south ahead of the front, and switch to a refreshing north or west direction behind the front.  The computer model for Sunday evening also illustrates that below.  You can easily see how the location of the front cuts through central Pennsylvania … winds are from the south ahead of the front, and westerly behind the front.

wx blog

These Canadian airmasses are also much drier behind the cold front.  The same computer model below shows dewpoints instead of winds.  You can easily see where the boundary of the humid air and dry air is located.  That boundary is also right across central Pennsylvania.

wx blog2

The reason our high temperatures will hold in the lower-80s is most likely because of the abundance of sunshine expected through the middle of the week.  Perhaps the more noticeable cool down behind the cold front will be at night.  These two models below show the expected overnight lows for Sunday night and Monday night.  You can see the cooler airmass behind the front.  Western Mass doesn’t quite get it on Sunday night (the green shading represents temperatures in the 50s), as the front has yet to move through.  By Monday night, the front passes and we enjoy a refreshingly cool night with the rest of the Northeast.

wx blog3

wx blog4

Images courtesy Dept. of Meteorology, The Pennsylvania State University

Peak hurricane season not here yet
July 27, 2013

By Meteorologist Mike Skurko

I couldn’t help but notice how #Dorian was trending on twitter over the last few days.  It was just a harmless tropical storm that formed well out in the eastern Atlantic earlier this week.  However, it’s track was consistently heading towards the Caribbean, and headlines on some weather websites brought up some hype about it’s potential impacts on the United States.

Thankfully, Dorian dissipated at 5 p.m. Saturday and will just be a minor footnote as a named storm this season.  While there are exceptions, the Atlantic and Gulf Coasts usually do not have to be on high alert for tropical storms and hurricanes until later next month.  The peak of the Atlantic hurricane season is from late-August through late-September, as illustrated on the NOAA graphic below:

wx blog

There are two main reasons why hurricane seasons peak at this time.  First, the ocean temperatures become warmest at this time.  Water has a high heat capacity, meaning it takes more energy to warm a body of water than, say, the land.  Anyone who has visited a New England beach in the late Spring knows this.  While the land temperatures are warming up, the ocean still remains chilly from the winter.  In late-August, the ocean is just getting to it’s warmest point, even though we’ve already gone through an entire summer of high heat.  Warm oceans are a prime ingredient for tropical development.

The second reason deals with the African easterly jet.  In North America, the jet stream divides the cold, dry Canadian air from the warm, moist tropical air.  In Africa, a similar division of temperature and moisture occurs in between the Sahara Desert and the Gulf of Guinea.  This African jet will generate waves of energy westward off the African continent and into the Atlantic … this is one of the prime catalysts for tropical storms.  This jet and it’s disturbances becomes most prominent in late-August as well.

Together, the two “peaks” of these environmental conditions help create the peak of hurricane season.

Recapping the heat wave
July 21, 2013

By Meteorologist Mike Skurko

Surprisingly, no new records were set during this 7-day heat wave at Bradley International.  The record highs were 96 degrees for Tuesday, 97 degrees for Wednesday, and 100 degrees for each of the other 5 days (and FYI today’s record high is 101).

The longest heat wave on record is 10 days, set back in 1995.  The most heat waves in one year is seven, set in 1949.  This is our fourth heat wave of the year at Bradley.

This is also the 13th heat wave in the last 65 years that lasted seven days … which averages out to about once every five years.  Hopefully, we do not have to face another stretch of hot weather like this until 2018!

wx blog

Storm Prediction Center outlooks
July 20, 2013

By Meteorologist Mike Skurko

Saturday had a high anticipation of severe weather across western Massachusetts.  For the last several days, it was known that on Saturday a sharp cold front would be slicing into the hot, humid airmass we’ve had in place all week.  NOAA’s Storm Predicition Center (SPC) in Oklahoma also recognized this by putting western Massachusetts in the “Slight Risk” category for severe thunderstorms today.

So what happened? Why did we not see a severe weather outbreak in western Massachusetts?  Well, we were not guaranteed to have one to begin with.

I often see the SPC outlook making the rounds across social media on days like this.  The SPC is responsible for issuing all severe thunderstorm and tornado watch boxes across the country (it is up to the local offices to issue the actual warnings).  Along with their watches, the SPC also issues severe thunderstorm outlook maps for the next three days using a Slight/Moderate/High risk classification system.  The following is Saturday’s map:

wx blog

These outlooks are based on the risk of three individual hazards: tornadoes, wind damage, and lightning.  Those outlooks, also issued by the SPC, are listed below for Saturday:

wx blog2

As you can see, the only hazard the SPC expected us to face on Saturday was a 15% threat of wind damage (15% shaded in gold, 5% shaded in brown, 2% shaded in green).  Using the SPC table below, the most significant severe threat needed to accommodate the 15% threat of wind damage would be the “Slight Risk” category.  You can also see how the tornado, wind damage, and hail expectancies also line up with a “Slight Risk” for Nebraska/South Dakota.

wx blog3

Yes, that does seem daunting…Springfield being under a 15% category for wind damage.  However, there is a HUGE difference between these percentages from the SPC and the percentages we are used to seeing with weather forecasts (such as “30% chance of rain”).  The definition of these percentages issued by the SPC is the “probability of [hazard] within 25 miles of a point.”  That is much different than simply saying a 15% chance of wind damage, or that 15% of the population within the circled area will get experience wind damage.

Lets think about that area…within 25 miles of a point.  Remember elementary math…the surface area of a circle is pi times the radius squared.  As shown below, all of the surrounding area in a 25-mile radius from a point would encompass a surface area of 1963 square miles.  To put that in perspective, the combined surface area of Hampden, Hampshire, and Franklin Counties is 1904 square miles.

This means that the SPC’s 15% outlook for wind damage would equate to just a 15% chance (about a 1-in-7 chance) of a wind damage report in an area roughly the size of our entire viewing area, minus the Berkshires.  To further put this in perspective, if Franklin, Hampden, and Hampshire Counties were all under the SPC’s 15% risk of wind damage every day of the week, it is possible that only one day out of those seven in western Massachusetts actually has wind damage reported.

So, statistically speaking, even this slight risk category is not a guarantee that severe weather will pop up somewhere in the region.  While these outlooks must be monitored closely and taken seriously, these outlooks from the SPC still incorporate the very real possibility that no severe weather happens at all.

Heat wave records for the Pioneer Valley
July 16, 2013

By Meteorologist Mike Skurko

Our high temperature reached the lower-90s for the third consecutive day in Springfield, giving us our 3rd official heat wave of the year.  Bradley International Airport, the official climate station of the Pioneer Valley, has now recorded its 4th heat wave of the year (June 23rd reached 91 degrees at Bradley, but only hit 89 in Springfield and prevented a heat wave for the city during that stretch).

The Northeast Regional Climate Center recently compiled a list of all the recorded heat waves at the official climate stations across southern New England.  Having four or more heat waves in one year happens about 23% of the time, or roughly once in every four years.  Dating back to 1949, the average number of heat waves per year is 2.2 at Bradley.  The most ever recorded in one year was 7 in 1949.  The last year without a heat wave was 2004.

The longest heat wave on record is 10 days from July 24 to August 2, 1995.  Current forecasts call for this heat wave to last through Friday in Springfield, but may persist through Saturday at Bradley (Springfield’s forecasted high temperature for Saturday is 88, with Bradley Int’l typically about 1 or 2 degrees warmer than Springfield).  If it does last through Saturday, that would be a 7-day heat wave, which has only been recorded 13 times … or about once every 5 years.

Heat wave grips western Mass this week
July 14, 2013

By Meteorologist Mike Skurko

High temperatures reached 91 degrees in Springfield on Sunday afternoon, and will continue to stay in the low and mid-90s through the entire workweek.  A large area of high pressure will remain stationary over the eastern U.S. for the next several days.  This is rerouting the jet stream way up to the north in Canada, and allowing tropical-like heat and humidity to surge into western Massachusetts this week.

The three images below represent forecast models for Monday, Wednesday, and Saturday afternoon.  The area shaded in blue represents the fastest winds approximately 12,000 meters (40,000 feet) above the surface.  This is the expected location of the jetstream this week.  Notice how far north it stays.

wx blog

wx blog2

wx blog3

By Saturday, a trough will start to dig into the Northeast.  High pressure shifts offshore, and the jet stream returns closer to New England, which will break the heat wave by the weekend.  However, the more seasonal air coming back to town will clash with the hot and humid air in place, potentially triggering strong thunderstorms in the region on Saturday.

This map is the NOAA Storms Prediction Center’s severe weather outlook for the week.  Notice how the risk of severe thunderstorms continues to push east, with western Massachusetts in the target area by Saturday (Day 7).

wx blog4

Tolland County tornado
July 13, 2013

By Meteorologist Mike Skurko

Here is the official statement from the National Weather Service regarding the June 10th tornado near Andover, Coventry, and Mansfield, CT.  The tornado skipped across 11.2 miles, and was rated an EF-1 for estimated winds of 90 mph.  Meanwhile, the town of Tolland was hit by a microburst about an hour earlier, with wind gusts estimated at 80 mph.

wx blog

...TORNADO CONFIRMED NEAR ANDOVER...COVENTRY AND MANSFIELD IN
TOLLAND COUNTY CT...

LOCATION...ANDOVER...COVENTRY AND MANSFIELD IN TOLLAND COUNTY CT
DATE...JULY 10 2013
ESTIMATED TIME...520 PM EDT
MAXIMUM EF-SCALE
RATING...EF-1
ESTIMATED MAXIMUM WIND SPEED...90 MPH
MAXIMUM PATH WIDTH...100 YARDS
PATH LENGTH...11.2 MILES
BEGINNING LAT/LON...41.72N / 72.41W
ENDING LAT/LON...41.77N / 72.21W
* FATALITIES...0
* INJURIES...0

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT
  TO CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION
  IN NWS STORM DATA.

...SUMMARY...
THE NATIONAL WEATHER SERVICE IN TAUNTON MA HAS CONFIRMED A
TORNADO NEAR ANDOVER...COVENTRY AND MANSFIELD IN TOLLAND COUNTY CT
ON JULY 10 2013.

THE SURVEY TEAM FOUND A DISCONTINUOUS DAMAGE PATH OF 11.2 MILES
LONG AND 100 YARDS WIDE FROM ANDOVER TO MANSFIELD CT. THE TORNADO
FIRST TOUCHED DOWN IN ANDOVER AROUND 520 PM EDT AND FINALLY LIFTED
IN MANSFIELD AROUND 551 PM EDT.

ALONG THE DAMAGE PATH THERE WERE NUMEROUS TREES UPROOTED. TREE
TOPS WERE ALSO SNAPPED OFF. THE ONLY STRUCTURAL DAMAGE OBSERVED
WAS TO A SHEET METAL BARN. NO INJURIES WERE REPORTED.

BASED UPON THE OBSERVED  DAMAGE THE TORNADO HAD MAXIMUM WIND
SPEEDS AROUND 90 MPH. THIS IS CLASSIFIED AS EF-1 ON THE ENHANCED
FUJITA SCALE.

THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT
WEATHER.GOV/BOX.

FOR REFERENCE...THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES
INTO THE FOLLOWING CATEGORIES:

EF0...WIND SPEEDS 65 TO 85 MPH.
EF1...WIND SPEEDS 86 TO 110 MPH.
EF2...WIND SPEEDS 111 TO 135 MPH.
EF3...WIND SPEEDS 136 TO 165 MPH.
EF4...WIND SPEEDS 166 TO 200 MPH.
EF5...WIND SPEEDS GREATER THAN 200 MPH.

June 2013 review
July 3, 2013

By Meteorologist Mike Skurko

This June was rainy across western Massachusetts and southern New England.  Not only did the Pioneer Valley have its second-rainiest June on record, the other three official climate sites in the region also made their top-3 for total rainfall in June.

Bradley International Airport totaled 10.79 inches this June (day-by-day rainfall shown on the graph below).  Providence and Worcester each recorded 10.1 inches of rainfall for their second-rainiest June as well.  Boston recorded 10.5 inches for its third rainiest June on record.  The all-time record year at all four locations is 1982.  Bradley had 13.6 inches of rain that June.

wx blog2

High temperatures were just a touch above normal.  A heat wave on the 23rd, 24th, and 25th helped push those numbers above normal.  Our average high this past month was 80.1 degrees, while the normal average for June is 79.6 degrees.

wx blog