Hurricane Isaac: An Ill Wind that Blows some Good

Hurricane Isaac just slammed the New Orleans area, causing a great deal of flooding to Plaquemines Parish to its south.  It also killed quite a few people in Haiti.  While it never got beyond Category 1, it was a very large, wet, and slow-miving storm, and dropped as much as 20 inches of rain in New Orleans!  (in comparison, the disastrous rains of Irene in Vermont last year were mostly under 10 inches).

A wet storm wasn't welcome in New Orleans, but it sure was to the north as it moved up the Mississippi River Valley.  That area is experiencing very severe drought, and the deluge that just passed through the area helped reduce the drought quite a bit.  Unfortunately, it was too late for many farmers.


Above: NOAA map of drought conditions.

Jeff Masters' blog has a lot of great info about this hurricane and its positive and negative effects.  The expression "it's an ill wind that blows no good" seems to apply here.  Many natural disasters have upsides to some, even as they harm others.  Irene pulled Vermont together in a tremendous way, though I would definitely say Irene blew much more ill than good for Vermont.  Isaac, on the other hand, may actually be remembered as much for its benefits as its harm, at least in the US.  (Haiti, on the other hand, has horrific flooding in almost any storm, because its extreme poverty has caused people to remove all of the trees from their slopes, resulting in extreme watershed degradation.  The deaths in Haiti are tragic but seem more related to social and environmental factors than the severity of Isaac per se).  Isaac will even probably kick some moisture into a front crossing Vermont early next week.  We could certainly use the rain here, though we haven't had as severe drought as most of the US.

Tropical systems may cause a lot of devastation, but they are part of our climate and if they were to stop happening (which is admittedly not going to happen), precipitation would be greatly decreased in some areas.  Here's a very neat map of the highest recorded precipitation dropped on each state by tropical system, again from NOAA:



Hawaii wasn't included but of course is affected by tropical systems, heavily at times.  Alaska has never been hit by a tropical system... moisture from their remnants has affected Alaska, but by then it has often merged with other storm systems so it's hard to say how much the hurricane or typhoon caused.  Here's a very neat Wikipidia page with detailed numbers.  It appears Floyd beat out Irene in terms of highest precipitation, though it caused less damage, probably because last summer was so wet even before Irene hit.  It's incredible that the entire US is affected by tropical storm and hurricane precipitation, including Wyoming (!) and Washington State.  If you dig into old records, you will also learn that southern California is vulnerable to rare tropical systems  - notable not only due to their ability to cause severe flooding but that they usually occur at the end of the dry season, when coastal California usually receives little to no precipitation for months at a time (a complete lack of rainfall from June through September is common and heavy summer rain is nearly unheard of)

Speaking of ill winds, it's worth keeping an eye on Tropical Storm Leslie.  It may be far from land, but some computer models have showed it possibly impacting the east coast of US or Canada.  It's far too far away to be concerned about yet, especially since many computer models show it dissipating harmlessly at sea.  But, it's good to be prepared.

On a side note, I have to apologize for the lack of photos in my blog.  My iPhone died, and I won't have a new phone for a few weeks as I've opted to try out the new iPhone 5 rather than buying an older one.  We'll see how that goes!