Weekend Forecast and General Weather Thoughts

The upper level disturbance that brought a round of severe weather to New England yesterday has moved offshore and it has taken the humidity with it.  It left a mark in Methuen as a microburst (a real confirmed one) with 70 mph wind gusts  uprooted 20-30 trees.
Tree, Utility damage in Methuen, MA (image credit Boston Globe)
Emery Street, Methuen, MA (image credit Morgan Murphy/CBS Boston)
Overall there were many wind reports in New England and even a few hail reports.
5/28/2015 SPC preliminary storm reports
Temperatures this morning are in the 70's, on the way to low 80's inland and mid 70's near the coast.
2 m temps 10 am (image weatherbell)
Here is the surface chart as of 8 am.  Notice the cold front to the south of the region and also the front in the upper Midwest.  High pressure is in control over the interior northeast.  This is temporary
WPC Surface analysis 8 am
 At 500 mb
12z NAM 500 mb vorticity 8 am (image NCEP)

 By later this evening the high will slide offshore and the front from the Midwest will slowly move east.  Dew points will rise into the 60's again tomorrow, but not before a nice evening in which temperatures will not drop out of the 60's in Southern New England.  Up north temperatures will fall into the 50's.
WPC surface forecast 8 PM tonight
As the high moves offshore Southwesterly flow will resume so tomorrow will easily reach the mid 80s.  The atmosphere will be unstable tomorrow but with the front well to the west and temperatures warm aloft (mid levels) it will be difficult to get thunderstorm formation.  A few pop up storms are possible especially in the Northwestern half of New England (if we slice from Caribou to Stamford).  Therefore if you are in the Lakes region keep an eye to the sky especially late afternoon.
SPC Day 2 (Saturday) Thunderstorm outlook

Saturday night is fine as any convection should die down as we lose the heating of the day.  Sunday looks to be unsettled region wide.  While not anticipating a total washout the threat of rain will linger all day and into Sunday night.  Temperatures are around 70 (will get warmer with any breaks of sun) and dew points in upper 50's/low 60's.

As you may have noticed much of Southern New England is experiencing a moderate drought.  Some have asked how is this possible after all the snow this winter?! The answer is that we didn't receive as much precipitation as you might think.  Since it was so cold the snowfall ratio's were on the order of 20-25-1.  That means for every 1 inch of precipitation we got 20-25 inches of snow.  Normally we see a 10-1 ratio.
US Drought monitor, released 5/28/2015 (NOAA)
Yesterday's storms really didn't help much
24 hour observed rainfall (AHPS precipitation analysis)
While a soaking rain is possible on Monday the long term outlook is not positive.  The Climate Prediction Center is forecasting these conditions to continue through August.  Hurricane season begins on Monday so we may have to hope for a tropical system to replenish our water supply.

CPC seasonal drought outlook (NOAA)
Speaking of hurricanes the seasonal forecasts are out and by all reputable accounts we are in for a "down" season.
NOAA, Colorado State, and Weather Channel predictions (image Weather Channel twitter)
 While this appears to be good news the truth is it does not mean much unless you are someone like me who gets excited to track a tropical storm near the Canary Islands.  Given that our already quite low to impacted by a tropical system a down season does not do much to decrease ours odds.  In fact in 1991 which was a down year Hurricane Bob blasted SE New England and the perfect storm battered the coast late in the season.    The reason for the down forecasts? Perhaps you have heard of El Nino.
OSPO Sea Surface Temperature Anomaly 5.28.15
This is a sea surface anomaly chart.  Please notice the red/orange along the equator in the Pacific Ocean near Central and South America.  This is abnormal as usually the warmest water relative to average in the pacific is in the Western Pacific.  Basically trade winds blow east to west across the Pacific.  There are two ocean currents, one on each side of the equator that also flow east to west.  As these currents move west they are heated by the sun and tend to pool water in the West Pacific.   For comparison here is 2013, a "neutral" year
OSPO Sea Surface Temperature Anomaly 5.30.2013
Along the equator there is a weaker current that moves west to east.  At times this current becomes stronger as the trade winds weaken.  The warm water sloshes back east and thus we have an El Nino.  Due to this constant wind the Western Pacific sea surface sits a few meters higher than the east.  This evens out during warm events.  But why does this cause a disruption to the Atlantic Hurricane season?  All the warm water in the eastern Pacific allows for favorable thunderstorm growth in that region.  With all the rising air there it creates a ripple effect of stronger than normal winds in the eastern Atlantic and higher pressures than normal in the Caribbean Sea.  Those factors suppress thunderstorm development.

It means that we are looking at a warm dry summer!  That's what the odds say.  Every El Nino behaves differently.  A particular interest of mine in college was how El Nino and La Nina's behave.  In 2009
the Pacific was also bringing on an El Nino event.  The summer of 09 was horrible in New England; rain and cool.   The oceans and atmosphere are different this time around so if you work in an industry that is dependent on water be aware that this will likely get worse before it gets better.

Have a good weekend and thanks for reading



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