Masters: The Atlantic Hurricane Season Is Getting Longer

The East coast was drenched by record-smashing tropical storm Andrea this week.

Predicted rainfall for the 48-hour period from 8 am EDT Friday, June 7, to 8 am EDT Sunday, June 8, 2013. Image credit: NOAA.

The L.A. Times reported a few of the records demolished by this early-season tropical storm:

In some places, rainfall measurements smashed century-old totals as flash flooding occurred. Central Park saw 4.16 inches of rain, more than double the record set in 1918. No major damage was reported.

Philadelphia International Airport measured 3.5 inches of rain, compared to the 1.79-inch mark set in 1904. In Newark, N.J., 3.71 inches of rain broke a 1931 measurement of 1.11 inches.

Meteorologist and former hurricane Hunter Dr. Jeff Masters discusses the long-term trend:

Andrea’s formation in June continues a pattern of an unusually large number of early-season Atlantic named storms we’ve seen in recent years. Climatologically, June is the second quietest month of the Atlantic hurricane season, behind November. During the period 1870 – 2012, we averaged one named storm every two years in June, and 0.7 named storms per year during May and June. In the nineteen years since the current active hurricane period began in 1995, there have been fifteen June named storms (if we include 2013’s Tropical Storm Andrea.) June activity has nearly doubled since 1995, and May activity has more than doubled (there were seventeen May storms in the 75-year period 1870 – 1994, compared to 6 in the 19-year period 1995 – 2013.) Some of this difference can be attributed to observation gaps, due to the lack of satellite data before 1966.

However, even during the satellite era, we have seen an increase in both early season (May – June) and late season (November – December) Atlantic tropical storms. Dr. Jim Kossin of the University of Wisconsin looked at the reasons for this in a 2008 paper titled, “Is the North Atlantic hurricane season getting longer?” He concluded that there is a “apparent tendency toward more common early- and late-season storms that correlates with warming Sea Surface Temperature but the uncertainty in these relationships is high.” He found that hurricane season for both the period 1950-2007 and 1980-2007 got longer by 5 to 10 days per decade (see my blog post on the paper.)

This post has been updated.

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5 Responses to Masters: The Atlantic Hurricane Season Is Getting Longer

  1. prokaryotes says:

    Was the 2010 Haiti Earthquake triggered by deforestation and the 2008 hurricanes?

    Wdowinsky gave two other examples in Taiwan where earthquakes followed several months after the passage of tropical cyclones that dumped heavy rains over mountainous regions. His theory of tropical cyclone-triggered quakes deserves consideration

  2. ClimateAce says:

    Joe they don’t have a clue
    when I turn on the news I hear nothing about climate change
    nobodies calling out John McCain for his flip-flop
    but boy does it get hot
    last year was the hottest ever
    since it began being measured
    our natural resources are our most precious treasure
    we gotta live sustainable so they’ll be around forever

  3. Merrelyn Emery says:

    I wonder how long it will be before you have one in March, ME

  4. FrankD says:

    Actually, that has happened once before ME, in 1908. A Category 2 hurricane ran through the Lesser Antilles from March 6 – 9 (passed out of shipping lanes at that point, might have lasted a bit longer unobserved).

    One thing to keep in mind when talking about hurricane frequency is the (apparent) ~60 cycle of high and low seasons – we are currently at the higher end of the scale, so we would expect a relatively large number of off-season storms, even without AGW. The satellite record is not long enough to be used to measure this without being confounded by other factors.

    The last peak saw 7 off-season (outside June – November) storms between 1948 and 1959, and the period before that saw 7 in a burst between 1887 and 1890. Our current run of 11 in the last decade looks a little higher, but not enough to show a clear signal, given better observation.

    I hasten to add I’m not saying the season isn’t getting longer – I would expect it would, given our concerted effort to jack up sea surface temperatures. Only that the data is not conclusive on that point. Early-season (June) data might show more clearly (as the cited paper suggests, but I’ve not reviewed those numbers personally.