Category Archives: tropics

Hurricane Season 2013

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Today marks the beginning of the Atlantic Hurricane season.  The tropical season in the northern Atlantic runs from June 1 through November 30.  Although tropical systems have and can develop outside of that time period, a vast majority of tropical systems do develop during those six months.  Hurricane Sandy continues to make news to this day as coastal residents in New Jersey and New York continue to recover, but overall, the United States have been in a hurricane drought for the past several years. 

Florida for instance has gone seven years without a land falling hurricane and the United States as a whole has not had a major Hurricane (Category 3 or higher) come on shore since 2005.  Both of those are the longest such periods since at least the Civil War.  This upcoming tropical season has potential to be a busy with many factors coming into play favorable for hurricane development, meaning, those streaks could unfortunately come to an end this year.

Evan

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In the Atlantic Ocean they are called hurricanes.   In the western Pacific they are referred to as typhoons.  In the southern Pacific and in the Indian Ocean they are referenced as tropical cyclones.  The tropical cyclone season is just beginning and already one has brought devastation.

Somoa and neighboring American Somoa were hit last week by Tropical Cyclone Evan.   Evan was a Category 2 Tropical Cyclone when it made a direct hit on Upolu, the eastern of the two principle islands of Somoa.  It then moved northeast with the eye wall just missing American Somoa and then it stalled and moved back toward Somoa with the eye wall barely missing them again.  That track kept high wind and torrential rainfall over the area for a few days. Tragically at least three deaths were attributed to Evan with two of those deaths being young children.

The storm then intensified into a Category 4 storm and headed southwest and had major impacts on Fiji on Monday.

The Static Illusion

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There is no denying that Sandy caused horrific damage to the east coast.  Although many people were surprised that such an event hit where it did, most meteorologists on the other hand were instead surprised that area was not hit again sooner.  In this space and during many of my public talks I have mentioned that our weather patterns in recent years have transitioned to what occurred in the 1950s and 1960s.

The 1950s recorded several hurricane strikes along the east coast with many causing devastation on par with Sandy.  With a much higher population base in combination with increased land use changes along the coast, although exceptionally heart breaking to see, the amount of damage was not unexpected.

Until humans realize that the boundary between land and ocean (or lake and rivers) is not static we are going to continue to experience such destruction in the future, as if we want to admit it or not, the forces of nature can not be controlled.

The Typhoon Did It

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When Hurricane Isaac was moving toward the United States, several individuals emailed and asked if it would have any impact on us locally. Historically, it has been rare for the remnants of a hurricane or tropical system to bring rainfall into this area.  Instead of getting rain from a tropical system, a hurricane may help alter the upper level wind flow to temporarily adjust the pattern that would influence our weather in that manner.

That is particularly true with western Pacific typhoons.  Powerful typhoons in particular often help form a large ridge of high pressure to their east, which induces the formation of an area of low pressure and a corresponding trough east of that ridge in the Aleutian Islands.  That storm in turn tends to advect warmer Pacific air into Alaska.   The colder air over Alaska is then forced south into the lower 48 states impacting areas east of the Rocky Mountains in particular.

In some ways, typhoons in the Pacific can alter our weather more than their hurricane cousins in the Atlantic.

The I’s Have it

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In the past decade Apple has able to name things with the letter “i” that resonated into the common vernacular of our culture.    In the weather world, the past decade has also brought about a plethora of “i” named hurricanes that have become equally well-known.  Hurricanes names are cycled over a period of 6 years, which means the same list of names used in 2012, will be used again in 2018, unless a hurricane name becomes retired.

Hurricane names are retired when the storm produces devastating damage, or has high impacts in many areas.  The letter of the alphabet with the most retired names is the letter “i”.  In fact, 7 of the last 11 hurricanes that started with the letter “i” have been retired.

Since the advent of using satellites to detect hurricanes, it is often during the peak of the hurricane season that we reach the 9th named storm which is one reason, besides just coincidence,  that so many “i” storms have been retired in recent years.

2012 Hurricane Season

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Although very few tropical storms or hurricanes have struck the United States n recent years, the overall number of systems in the Atlantic Ocean has been well above the long-term means during this time period.   A combination of warmer than normal sea surface temperatures in conjunction with favorable upper-level winds has been the attributing factors to these increased numbers.

There are some indications that the 2012 hurricane season may be quieter than in recent years.  The Atlantic Ocean, like the Pacific, goes through a slow oscillation between warmer and cooler water temperatures.  Sea surface temperatures this year are expected to be near or even slowly below normal, a significant departure from recent years.  Plus, a weak El Nino may develop by the end of the summer, which tends to produce unfavorable winds for hurricane development in the Atlantic.

All of this is conjecture at this point, but most hurricane experts expect fewer storms this year than in the recent past.  Yet, as we learned in 1992 with Hurricane Andrew, it only takes one storm.

 

The End Has Come

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With the beginning of December comes the official end of the Atlantic Hurricane season.  Historically, it has been rare for tropical seasons to form after November, so it is likely that no more named systems will develop until next summer.

In total, 19 tropical systems formed this year which is tied for the third-highest total since records began in 1851. That is well above the average of 11 named system, although, there were several small, short-lived systems this year that would have not been detected before the satellite era. Although the average number of named systems during the hurricane season is 11, the average number that reach hurricane strength is 6 and this year only 7 of those 19 named systems reached that status which is right near the historic average.

For the first time in 3 years a hurricane, Irene, hit the United States. That ended the longest period between land falling hurricanes in the country since the Civil War.

Quiet or Busy?

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Although another tropical system or two could easily form in the coming days and weeks, the hurricane season in the Atlantic Ocean is beginning to wind down.  If you ask most Americans if it was a busy or quiet season, for the 3rd straight year, most people would say it was a quiet year.  Only one hurricane, Irene struck the coast of the United States this year.  That was the first land falling hurricane in nearly three years ending the longest such stretch since the Civil War.

Another positive factor of the season so far is that no major hurricane (Category 3 or higher) made landfall in the country.  The last time that occurred was Hurricane Wilma back in 2005.  It is these reasons that this hurricane season will likely be remembered as a quiet one, although, by the numbers, 17 storms formed, which is above average.  But with tropical systems it is where they go, rather than the actual number that is far more important.

Hurricane Hunters

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As the tropical season becomes more active, the hurricane hunter aircraft will become increasingly important to gather critical information about the structure and intensity of storms as they approach land.  The development of satellite technology in the 1960s was a revolution in the detection and tracking of tropical systems around the globe, yet, it is the detailed information gathered first hand by aircraft penetrating the hurricanes that still brings in some of the most critical information for meteorologist as they try to forecast the track and evolution of these systems.

Although we take for granted these critical missions, in many ways, the concept of flying airplanes into a hurricane to gather information came about somewhat by chance.  In was in late July, 1943, that Lieutenant Ralph O’Hair and Colonel Joseph Duckworth, flying a single engine AT-6, decided “just for fun” to fly into a hurricane.

It was this precedent that started regular Air Force flights into hurricanes and these flights were credited for saving countless lives just a year later.

1000 Days and Counting

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It has now been over 1,000 days since a hurricane has made landfall on the United States.  The last time a hurricane impacted the country was on September 13, 2008 when Hurricane Ike moved over the Houston area as a Category 2 storm.  This current stretch without a hurricane is the longest since the Civil War, so historically it has been a very unique and fortunate quiet period for the country.

Although the United States may have been missed, our neighbors to the north, Canada, have not been so lucky.  Hurricane Kyle made landfall in Nova Scotia on September 29, 2008, Hurricane Bill stuck Newfoundland on August 23, 2009 and finally, Hurricane Earl after narrowly missing the outer banks of North Carolina by roughly 85 miles hit Nova Scotia on September 4, 2010.

The odds are low that another tropical season will pass without a land-falling hurricane, but considering the other weather disasters this year, it would be great to beat the odds once again.