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.  

Wednesday

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.

Thursday

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

Friday

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

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

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

Moderate Rainfall Friday Night-Saturday

Hopefully everyone has a chance to enjoy the great weather today.  Rain will move into the region overnight leaving Saturday unsettled.  Sunday will be overcast with isolated showers.  Skies will begin to clear Sunday afternoon/evening and high pressure builds in for early next week.  I posted the other day about the potential for a rainy pattern to set up.  I still like that set up for the end of next week/next weekend.

Current Conditions 
Temperatures have climbed into the low 60s this afternoon away from the coast. The winds have also relaxed which is very welcome after yesterday

2 PM 2 m temperatures (image Weatherbell)

High pressure has slid offshore and will continue to move east this afternoon.  Tonight/tomorrows rain is driven by low pressure in the Great Lakes

WPC Surface Analysis 2 PM EST

Here is the upper level support for the systems

18z NAM 500 mb vorticity 2 PM Fri (image NCEP)

The Northeast radar shows this progressing nicely to the northeast

NWS Northeast Regional Radar 328 PM

There is a tornado watch for North Carolina and Virginia.  Southern New England will stay out of the severe weather but a few embedded thunderstorms are possible tonight and tomorrow.

Forecast

Light rain reaches SW New England by Midnight.  Steady rain overspreads Southern New England between 2-4 am.  Temperatures drop into the 40s tonight and will stay in the 40s tomorrow.  Warmer air will try to work into SW New England tomorrow afternoon and it could reach the CT River.  

Total rainfall?  Looks like generally 0.75-1.25" with locally higher/lesser amounts.  

WPC day 1-2 precipitation totals

Saturday night is cool, with temperatures falling into the 30s.  On Sunday there will be leftover showers.  Temperatures climb into the low 50s.  Strong Canadian high pressure will protect the region from storms for the beginning of next week.  Have a good weekend.

-Zack Green

Looking Ahead; End of April and Early May

It has turned out to be a fairly decent April in Southern New England.  Temperatures have averaged slightly above normal through the 22nd

NCEP CFSv2 Month to Date Temp Anomaly April 2014 (image Weatherbell)

The last seven days are below normal, thanks in large part to last Wednesday-Friday.  Even the warmth of the weekend and past few days couldn't overcome the negative anomaly

NCEP CFSv2 Last 7 days Temp Anomaly 4-15 4-22 (image Weatherbell)

There are several things to note from the two images.  First is strength of the cold anomaly in South Central Canada.  Second is the warmth in the last seven days in Alaska and the NW Territories of Canada. Third is the cool anomalies in Atlantic Canada and Greenland.   Why are these features important?

1. According to a 1950 report by Jerome Namias found here April and May tend to be the opposite it terms of weather; in fact the difference is second to only October and November.  He also concluded that the strength of the reversal can be tied to the strength of the Canadian cold pool.  This makes sense; if April is warm and May is cold then there must be cold air lurking to the North.  Therefore seeing the cold pool in Canada gives weight to a cool May.
2. The recent warmth in Alaska is a result of a moving block.  Rossby in 1939 found a general 3-8 week weather pattern shift that often occurs in late winter or early spring.  Seeing Alaska and NW Canada move from cool to warm (relative to average) signals a shift of this block in the Pacific.
3. According to Namias and Rossby the best place to watch for this reversal is in the Atlantic.  So far we have seen lower heights across Greenland in April.  The long range EURO Ensemble mean/control both forecast upper level heights to rise across Greenland over the next 1-2 weeks.  This will allow the jet stream to weaken and buckle into the United States

You may ask why would I put faith in a 1939/1950 report and that is fair to ask.  First of all the past 15-20 years have been similar to the 1930s-1950s period due to similar ocean conditions (Atlantic warm, Pacific warm to cool).  These guys were bad ass.  They did not have computer models to solve complicated formula's.  They had to figure out why thing happened through observation and analysis.  There is a ton of meteorology to be learned from reading accounts of meteorologists from the 1930-1960.  A good place to start is here, the Monthly Weather Review.  Much was learned during World War II.  

So what does this mean for Southern New England?  Here is the Climate Prediction Centers 8-14 day analogs.

CPC 8-14 Upper Air Analog Chart (4/23/14, valid 5/4/14)

The dates jump out.  Here is May 9, 1954 at 8 PM EST

Plymouth State Reanalysis May 10, 1954 0 UTC 500 mb height

Here is this mornings EURO, 500 mb heights valid 8 days from now, Thursday at 8 am

12z EURO 500 mb heights 5/1 8 am (image Weatherbell)

Its not a perfect match as the trough is hung back a bit further in the Great Lakes and the Ridge in the west is more over California.  I expect this to slowly continue to push east as early May progresses.  The case from 2005 looks more similar to the CPC outlook, and it looks more similar to the day 10 EURO forecast.

Plymouth State Reanalysis April 26, 2005 0 UTC 500 mb heights

Here is the EURO next Saturday (keep in mind EURO will change slightly over next few days)

12z EURO 500 mb heights 5/3 (image Weatherbell)

The 2005 event stretch from late April in early May which is what I expect this year  The 1954 event was a May event.  Precipitation will be above average

May 1954 Precipitation Anomalies (ERSL)

April-May 05

April-May 05 precipitation anomalies (ERSL)

Temperatures should be below average for the Eastern 1/2 of the country

May 1954 temp anomaly (ERSL)

April-May 05

April-May 05 Temp Anomaly (ERSL)

As you can see there will be regional differences compared to the two years.  I expect the temperatures to be closer to 1954 given the cold pool available in Canada.  Next week looks rainy.  This could be one of those mid spring stretches where in rains for 7-8 days off/on and the sun goes into the witness protection for awhile.

It also looks like an El Nino is coming this year.  Its not likely to be a Super El Nino given the overall cool state of the Pacific Ocean.  However a moderate-strong event like 02-03 or 09-10 is certainly possible.  Questions/comments/complaints can be left on facebook or tweeted to me @zgreenwx .  Thanks for reading.  Sorry to bring bad news and I hope I am wrong.

Zack Green

Tuesday Weather Forecast

Low pressure in the Great Lakes will continue to push towards the Atlantic coast this morning.  An associated warm front will push temperatures into the mid 60's as the sun pops out this afternoon.  

Current Conditions

The Northeast regional radar as of 5 am 

NWS Northeast Regional Radar 458 am

There are some heavier downpours embedded within this rain.  That will slow the morning commute so give yourself some extra time.  The 2 am surface chart shows the warm front ready to surge north as the low lifts through Central New England later today

WPC Northeast Surface Analysis 2 am

Temperatures are generally in the mid 40's, although temps are near 50 in SE MA

4 am 2 m temps (Image Weatherbell)

Rainfall will end west to east between 9-11 am.  Winds will increase out of the Southwest with gusts as high as 25-30 mph.  Temperatures soar into the low to mid 60's.  

06z NAM hires 2 m temps 3 PM (image Weatherbell)

Temperatures tonight drop into the low 40's/upper 30's.  Wednesday is dry and cooler.  Next chance of rain appears to be Saturday.  Have a good one

-Zack Green

Rainfall Enables River Rises

Heavy rain overnight enabled local rivers and streams to rise and the result is minor to moderate flooding across Southern New England.  Here is a map of the rainfall totals from this system

NWS Boston Rainfall Reports

5.22" have fallen in Hope Valley, RI which is the highest amount I have found so far. See reports here.  Not surprisingly several rivers are near or above flood stage.  Yellow is near flood stage, orange is minor flooding, and red is moderate flooding.

Northeast River Forecast Center Current River Conditions

You can view river forecasts here .  The Yantic River in SE CT is the only river in moderate flood stage at the moment

NERFC Yantic River forecast 

The forecasts call for only minor flooding from here on out.  I did notice the rivers rose faster and higher than most of the forecast.  For example the Blackstone was forecast to rise to 6.6 ft yesterday afternoon, yet it is already at 8.3 feet.

NERFC Blackstone River forecast

The question now becomes how much more rain?  First of all let's look at the local surface chart

WPC Surface Analysis 11 am

A stalled boundary over the Cape separates raw temperatures from more spring like weather.  Here are the 1 PM temperatures (click to enlarge)

1 PM 2 m temperatures (image Weatherbell)

The precipitation has split in two batches.  One is just offshore MA up through Eastern Maine.  Another is pouring on the Mid Atlantic states

NWS Northeast Regional Radar 148 PM

The precip in the Mid Atlantic is driven by an impressive upper level system

12z NAM 500 mb vort valid 2 PM (image NCEP)

This shows up nicely on the water vapor satellite loop

GOES_East Water Vapor Satellite Loop 115 (NOAA)

This is not in a hurry to move so expect dry conditions throughout the afternoon.  Rain looks to move back in tonight and it could be heavy.  Here is 10 PM simulated radar

16z HRRR simulated radar 10 PM (image Weatherbell)

Due to the nature of the system it may be cold enough North and West of Worcester for freezing rain tomorrow AM.  For that reason a Winter Weather Advisory has been issued

03/30/14 NWS Headlines

That includes Northern Worcester Co, but the Flood Warning for the Assabet River takes precedent.  Monday looks miserable with temperatures in the upper 30's/low 40's.  That's all for now, another update tonight or tomorrow AM.

-Zack Green