Tuesday, May 6, 2014

Mother's Day Weekend Forecast

It looks like a brief warm up is on the way for the weekend.  Enjoy it!  Here is the forecast for the rest of the week/weekend.

Short Term Forecast
Temperatures this afternoon are generally in the upper 50's.  However when there are breaks of sun and the wind relaxes temperatures jump into the mid 60's
3 PM 2 m temperatures (image Weatherbell)
Here is the current regional radar loop
NWS Northeast Regional Radar 428 PM
Here is the visible satellite
GOES_East Visible Satellite 430 PM (image NOAA)
These clouds and showers are driven by differences in ground temperature and cold air aloft.  Check the surface chart and notice flow is out of Northwest around high pressure in Ontario/Quebec
WPC Surface Analysis 2 PM
Also notice the front draped horizontally across the US.  This front will slowly push north and east as a trough in the west digs.  This will allow for some severe weather in the Central US over the next several days.  In the meantime tonight clouds will dissipate tonight so temperatures will fall into the upper 30's/low 40's.  

High pressure will remain in control tomorrow.  Winds will be lighter (except near coast).  Expect mid 60's in general with a few locations near 70.  It will be cooler at the coast.

Rain breaks out in SW New England but will struggle to reach SE New England.  Temperatures in mid 60s with partly cloudy skies

Slight chance of showers in Western/Central MA/CT but SE MA and RI looks mostly dry.  Temps in the low 60s

Weekend Forecast
Warm front will finally move through Southern New England Friday night.  Some left over precipitation likely Saturday AM but it will clear and the sun will break out in the PM.  Temperatures rise into mid 70s.  
WPC Saturday 8 am Surface Forecast
The cold front trailing through the Ohio Valley will set off some showers/thunderstorms Saturday night into Sunday morning.  However I do not expect this to be widespread in Southern New England.  Looks heavier in Central/Northern New England.  Temperatures will rise into the low 70's.  There could be a light shower in the PM.

I teased the potential for 80 on Monday.  Its 6 days away so this could change, but I do like another warm day Monday.  

Enjoy it, temperatures look to return to below normal next week with more rain.
CPC 8-14 day temp outlook
I will fine tune the weekend forecast Thursday.  Have a great night.

-Zack Green

Saturday, May 3, 2014

Hurricane Season A Month Away

In my opinion the worst forecast I have ever made was for the 2013 Atlantic Hurricane Season (some of you may debate that).  I looked at the Sea Surface Temperature Anomalies of March and April, the persistent cold of March 2013 and saw similarities to 1954 and 2005.  I tossed out 1993 as an analog which was probably the best match in hindsight.  Here is my post from March 2013.  Lessons were learned on my part namely trust the data and do not rush a forecast just to be first.
NHC 2013 Atlantic Tropical Cyclone Tracks
2013 forecast
20-25 named storms
8-12 hurricanes
4-6 major with 1 cat 5

Actual 2013
13 named storms
2 Hurricanes
0 Major Hurricanes

I am glad the United States was sparred and everyone got a year to relax.  I am also disappointed in myself for ignoring the data I've been collecting since my Sr year at Umass-Lowell.  Instead of going big with a 20-25 year I would have pulled back to 11-15 named storms, 4-8 hurricanes, and 2-4 major.  I still would have been wrong but I would have been closer.  With that said here are my thoughts for 2014

2014 Atlantic Hurricane Season
By most model and observational accounts an El Nino will develop during the summer.  See the model plume graph
Intermational Research Institute/CPC/Columbia U ENSO model plume 
The El Nino threshold is 0.5.  Here is the observational evidence of an oncoming warm event
NOAA/OSPO Sea Surface Temperature Anomaly 5/1/2014
For comparison lets look at this time a year ago, with no El Nino/La Nina coming on
NOAA/OSPO Sea Surface Temperature Anomaly 5/2/2013
Notice the colder blues off of NW South America in 2013.  That shows up welling of nutrient rich water which indicates stronger trade winds.  That does not allow the warm water of the Western Pacific warm pool to slosh east.  In 2014 the trade winds are weaker and the warm water is moving eastward along the equator.  The warm pool south of Alaska in 2013 is also what helped cause the record cold May of 2013 in the Midwest as it helped build a ridge in the Northeast Pacific.  That in turn led to a trough downstream that had an Arctic connection.  

Now that we have solid evidence that a warm event will occur, its time to find similar years.  There was a lot of hysteria over the past few months about a Super El Nino this year.  That of course is possible; never rule anything completely out in meteorology.  However it was questionable to those who study Pacific Ocean dynamics for two main reasons.  First of all El Nino prediction is weakest in late winter/early spring.  The model cannot handle the equinox for some reason and forecasts tend to be wild.  That didn't stop many people from comparing this event to the infamous 1997/98 Super El Nino.  Secondly the Pacific is in an overall cool phase.  Nearly all Super Nino's have occurred during the warm phase.  
El Nino AMO/PDO averages North Atlantic Hurricane Season (personal research)
The Atlantic warm phase is at its weakest point in about 20 years.  It remains to be seen if this is the midpoint of this cycle or if the downward turn has begun.  There was a similar dip in the late 40's before the AMO rebounded for another 15-20 years.  The PDO flipped for good around 2007, but it was cool from 98-02 following the 97/98 Super Nino event.  So my best two matches are 2002 and 2009.

Here is 2002 Sea Surface Anomaly
NOAA/OSPO Sea Surface Temperature Anomaly 5/3/2002 
Here is the 2002 tracks
NHC 2002 Atlantic Tropical Cyclone Tracks
Here is 2009 SSTA
NOAA/OSPO Sea Surface Temperature Anomaly 5/4/2009
And here are the 2009 tropical cyclone tracks
NHC 2009 Atlantic Tropical Cyclone Tracks
2002 at the moment looks like a better blend.  Statistically speaking we should expect 10 TS, 6 H, and 3 MH in 2014 with an ACE of around 100.  Looking closer to 2002

12 TS
4 H
2 MH
65 ACE

and 2009
9 TS
3 H
2 MH
51 ACE

Blending the stats & analogs my forecast is

11-13 TS
3-5 H
2-3 MH
60-80 ACE

It only takes one storm to make a hurricane season memorable.  With the far east Atlantic looking unfavorable for development everyone needs to watch closely for systems developing near the United States.  Don't let 2013 or the oncoming El Nino lull you into a false sense of security.  Irene was a weakening Tropical Storm and I was without power for 4.5 days.  Imagine a Category 2 Hurricane Southern New England?  

Have a good day
Zack Green

Thursday, May 1, 2014

Decent Weekend, Long Range Thoughts

The cold that has been bottled up in Canada surged into the United States as April ended and May began.  Here is the temperature anomaly for the last two weeks (departure from average)
NCEP CFSv2 2 week temperature anomaly (Image Weatherbell)
Here is the temperature anomaly from 8 am this morning off the GFS
12z GFS 8 am 2 m temp anomaly (Image Weatherbell)
Unfortunately mother nature brought this cool air mass into the US in violent fashion.  It snowed heavily in the Dakota's, rained heavily in Florida, and most notably tornadoes claimed the lives of dozens of people from Kansas to North Carolina.  Tornado season had gotten off to a record quiet start in 2014.  It is a reminder that all it takes is one severe outbreak to cause untold devastation.  On a lighter note, the weekend forecast

Short Term Forecast
Temps tonight are in the upper 50's in general and will not fall much due to cloud cover.  After midnight the clouds will erode away and temps will fall to around 50.  Tomorrow will be Partly Cloudy with a chance of isolated showers/thunderstorms due to some cold air aloft.  Temps will be in the low 60's west of 495 and mid 60's closer to Boston.  Expect similar weather on Saturday albeit warmer inland.

Sunday looks to be showery with temperatures in the mid 50s to near 60.  The culprit will be an Upper Level Low Pressure system moving out of the Great Lakes
12z NAM 500 mb vort 2 PM Sunday (Image NCEP)
Next Week
Early next week will be cooler than average due to the upper level system passing slowly offshore.  It should be mainly dry with only isolated showers Monday-Tuesday-Wednesday.  By Thursday another disturbance will be approaching Southern New England.  A warm front will try to move across the region but it will be fought by a northeast wind off the Gulf of Maine.  This fight could go on for several days.  But it is in the longer range so nothing to worry about as of now. Cool air looks to reload in Canada in the 6-10 day, especially Eastern Canada.  Sorry for those looking for Sunny and 75...try listening to some Joe Nichols.

Go Bruins

-Zack Green

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