Thoughts on a Cold April, Hurricane Season

So far through nearly 2 weeks of April the average US temperature is -0.7 C below average.
NCEP April to date temperature anomaly (image weatherbell)
Its been about average or a few tenths of a degree below average in Southern New England.  Europe has also been very cold so far in April
NCEP April to date temperature anomaly (image weatherbell)
Global we are a few hundredths of a degree warmer than the 1981-2010 average so far this year
NCEP year to date temp anomaly (image weatherbell)
Much of the Northern Hemisphere mid latitudes have been colder than average and the cause of this is strong blocking near Greenland.  When meteorologists talk of a "block" its often high pressure redirecting the storm track.  We track blocking through the Arctic Oscillation (AO) and North Atlantic Oscillation (NAO).  Since February both have been strongly negative
NAO, AO 2012-13 (image weatherbell)
The recent trend to neutral has allowed temperatures in the Eastern US to rebound last week.  Here is the 7 day temperature anomaly
Last 7 day anomaly, NCEP (image weatherbell)
Notice the cold in Alaska.  That will likely try to invade the lower 48 in the second half of April.  The Climate Prediction Center is on board, as here is their 8-14 day forecast
CPC 8-14 day temperature outlook
The average high in Boston this time of year is 55 degrees.  In a week the average high is 57, and in two weeks the average high is 60.  By the looks of it we will be in the 50's and low 60's for the rest of the month.  
(Note- there may be a few days in the 40's and a few days in the 70's).  With cool air like this in the east one would expect a trough and above average precipitation.  The CPC agrees with this as well
8-14 day precipitation forecast CPC
For those of us in the Blackstone Valley the river forecast looks good even with a wet April and May.  
Blackstone River at Northbridge flood outlook (NWS Boston)
Of course with a few tropical systems this summer this could change.  Speaking of tropical weather...

2013 Atlantic Hurricane Season
I posted 3 weeks ago with my initial thoughts on the 2013 North Atlantic Hurricane Season.  This week several major Hurricane forecasting outlets posted their outlooks for the season.  Here is a quick summary
  • Colorado State- 18 TS, 9 Hurricanes, 4 Major Hurricanes
  • Tropical Storm Risk- 15 TS, 8 Hurricanes, 3 Major Hurricanes
  • Weather Service International- 16 TS, 9 Hurricanes, 5 Major Hurricanes
  • Weatherbell Analytic's- 16 TS, 12 Hurricanes, 5 Major Hurricanes, ACE 165
  • ZG WX- 23 TS, 11 Hurricanes, 6 Major Hurricanes, ACE 190
I am higher with my totals pretty much across the board.  I use a blended technique of averages, analogs  and observational evidence to make my forecast. Here is my 2011 Hurricane Season forecast in which I predicted increased east coast Hurricane activity.  Since then the Northeast has been hit by Hurricanes Irene and Sandy.  So first and foremost lets look at Atlantic Sea Surface Temperature Anomalies (SSTA)
 Sea Surface Temperature Anomalies, 4-11-13 (NOAA OSPO)
The set up in the Atlantic is called a tripole.  Warm over cold over warm.  This will allow for explosive development in the deep tropics, something that was missing last year.  Last year most of the action was north of 30 latitude.
2012 NAHS tracks (NHC)
Here is what the sea surface temperatures looked like in April 2012
Sea Surface Temperature Anomaly 4-12-12 (NOAA OSPO)
Major differences I see immediately is the El Nino signal developing.  The cold South Atlantic water is all the way to the equator, no Atlantic tripole, and a much more defined cold PDO signal.  Here is what the surface temperature anomaly looked like in April 2012
Global Temperature Anomaly April 2012 (image weatherbell)
And globally April 2013 (to date)
Global Temperature Anomaly April 2013 to date (image weatherbell)
See the cold air in April 2012 off the coast of Africa? That really hampered the Cape Verde season last year.  It is already much warmer in 2013.  Here is a look at the SSTA for 2005, the year of the Hurricane.
Sea Surface Temperature Anomaly 4-12-2005 (NOAA OSPO)
Classic tripole, up-welling cold water off the Pacific South American Coast and a weak cold PDO look.  My analogs are 1957, 1960, 1969, 2003, and 2005.  2010 and 2004 are being used by some forecasters and I have no problem with that as they are similar.  Why these years?  1957 wass coming off a long strong La Nina from 1954-56.  El Nino conditions actually developed in 1957 which I do not expect, but overall the pattern was similar to what I see in 2013.  1957 is the weakest analog of all which would be good news for the coast (sort of).  
Hurricane Audrey 1957 (Wikipedia)
Until Hurricane Katrina in 2005 Audrey was the deadliest Hurricane since the Great New England Hurricane of 1938.  Another weak El Nino developed in the late 1950's but had weakened to neutral by 1960.  The big storm in 1960 was Hurricane Donna
Hurricane Donna 1960 (Wikipedia)
Donna remains the only Hurricane in modern times to bring Hurricane conditions to every state along the East Coast.  See where Donna formed?  That is something I am worried about in 2013.  1969 was another year with a weak El Nino.  However winter of 1968-69 behaved much like winter 2012-13. It was a warm start but it finished with multiple major snowstorms, just like this year.  The biggest storm of 1969 was Hurricane Camille, a top 5 most notable storm in US history with Katrina, 1938, 1935 Labor Day, and 1900 Galveston.  
Hurricane Camille 1969 (Wikipedia)
Camille is one of 3 cat 5's to strike the coast in the 20th century along with Andrew 92 and Labor Day 1935 in South Florida.  Now 2003 and 2005 are the two years I really like for my analog's.  2002 was an El Nino that ended early, much like 2012.  Winter 2002-03 was a top 5 snowiest winter in Southern New England like 2012-13.  Why does that matter?  The late winter patterns often set up again in late summer.  2003's biggest storm was Hurricane Isabel which slammed into North Carolina
Hurricane Isabel 2003 (Wikipedia)
Isabel rode along the Southwest edge of a strong subtropical ridge (Bermuda High) and a trough approached the east coast, capturing Isabel.   The more I look at 2004, the more I like that season as an analog.  But what Hurricane do I pick to show you?  Ah here is the map
2004 Atlantic Hurricane Season tracks (NHC)
Four hurricanes directly struck the Florida coast.  Hurricane Charley was a category 4 hurricane and to this day there has not been a stronger hurricane to hit the US since then (in terms of winds).  
Hurricane Charley 2004 (Wikipedia)
I don't really like saying this, but 2005 is the top analog.  SSTA, ocean cycles, ENSO phase all line up.  Here is Hurricane Katrina's track
Hurricane Katrina 2005 (Wikipedia)
I am higher on the amount of total storms simply due to technology.  We have great satellite and radar observation so storms in the North Atlantic that use to go undetected are easy to see.  So I like the second most active season on record (really the 3rd after 1933, but I won't go there).  The season should start fast so be prepared EVERYWHERE from Brownsville, TX to Bar Harbor, ME.  Cheers, talk to you all tomorrow.


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