Wednesday, March 14, 2012

Temporary "Cool Down" Tomorrow

A back door cold front (BDCF) is currently stalled out in Eastern Massachusetts creating a sharp temperature divide in New England.  A BDCF moves from the east to west instead of the typical west to east motion.  These are notoriously difficult to forecast; my professor of meteorology at Umass-Lowell, Dr. Frank Colby, gave a great presentation on the topic my freshman year.  He showed the differences between what the computer models were forecasting to happen and what actually happened.  That is why some of our weather has been "unexpected" this week.  Take last night...severe thunderstorms ripped across Southern NH and Northern MA.  Click here to read storm reports.  Severe hail ( > 1 inch diameter) was reported for the first time in the month of March since at least 1950, when record keeping began (h/t to Climate Data Center).  Some asked me if that was really lightning that was occurring last night when there were clear skies.  The answer is yes and that is an indication of the strength of these thunderstorms.  In fact the storms exhibited a tornado signature for a time, although due to a temperature of 53 one did not form.  Thankfully I see none of that in the next 5 days or so.

NOAA-NCEP real time temperatures, click to enlarge (will not be blurry)
10 Meter Wind (~30 ft to eliminate friction effects)
Notice the way the contours sharply cut as one nears the coast in the temperature chart and notice the wind barbs are moving in two different directions in western and eastern MA.  That shows where the cold front is right now.  It will make its way into Central MA, RI and eastern CT tonight.  This will drop temperatures into the upper 40's for awhile before rebounding into the lower 50's tomorrow afternoon when the sky is less cloudy.  On Friday a typical cold front will push across the region and this will have two effects.  First temperatures will be raw and showers and even a thunderstorm or two will develop as the energy moves past.  Secondly, it will help move an area of high pressure offshore and flip winds back to the west and southwest.  That means warm temperatures will return this weekend and downright HOT temperatures early next week.  It hit 80 degrees today in Chicago and that will be moving east.

Quick Forecast...
Tonight-             Clouds Increasing lows upper 30's
Tomorrow-        Cloudy start gradually clearing, highs in low 50's
Thursday Night- Increasing Clounds, chance of shower, lows upper 30's
Friday-              Scattered showers, possible thunder, highs in low 50's inland, 40's coast
Friday Night-     Isolated showers, low around 40
Saturday-          Clearing skies, Highs upper 60's
Sunday-            Sunny, Highs lower 70's

Finally I do think we will approach 80 on either Tuesday or Wednesday next week (some towns both).  It also appears another back door cold front wants to develop at that time frame.  This is a long way out and subject to change however a repeat of last nights severe weather outbreak cannot be ruled out.  Despite the record warm winter and lack of snowfall in the United States snow cover in the Northern Hemisphere is still running above average.  With the cold air still locked to the north, any intrusion south into these warm temperatures is bound to fire more severe weather.  Thunderstorms ahead of regular cold fronts will need to be monitored as well. This is something to keep in mind as we enjoy the warm March.  Thanks for reading!

Saturday, March 10, 2012

Warm Weather on the Way

500 mb vorticity  map (mid level of atmosphere) shows cut off low in SW, trough exiting  NE

The unseasonably warm weather will continue into middle to late March.  After approaching 70 on Thursday we cooled down yesterday and today.  I was expecting a quick burst of snow yesterday but I did not expect 3-6 inches north of Boston.  Here you can see the totals from last nights snow event.  That is behind us now as the energy is moving offshore of Cape Cod.  High pressure will build into the region and the warming trend will begin.  We have to get through today first as temperatures will only reach 40 or so.  Temperatures tonight will drop into the upper 20's before climbing into the upper 50's tomorrow.  The south coast will be held to the upper 40's due to  a southerly wind off the water.

The energy in Arizona and New Mexico has cut off from the general flow.  This will slowly move northeastward toward the Great Lakes.  Areas in the path of this low will see some heavy rainfall over the next several days.  This will help pull warm air into the Northeast.  High pressure will move offshore locking in a Southwesterly flow and setting up some of the warmest March weather in the last 100-125 years (that is how long records go back in the Northeast).  The lack of snow cover across the United States is not cooling off these air masses as they move across the country so we have more potential for higher temperatures.  (Hat tip to Eric Fisher of The Weather Channel).

Sunday- Highs Upper 50's inland, upper 40's coast DRY
Monday- Highs middle to upper 60's DRY Some exceed 70
Tuesday- Highs middle 60's, clouds increasing Rain likely (from the cut off)
Wednesday-Highs upper 50's windy

This looks to continue for the foreseeable meteorological future...(~2 weeks).  Enjoy it while we have it.

Friday, March 2, 2012

Wintry Precip Overnight, Heavy Rain Tomorrow

National NWS radar image
A powerful storm system sweeping across the United States will impact New England overnight.  This is the same system responsible for producing 53 tornadoes (and counting) across the Ohio Valley and the Deep South.  The storm will be weaker but there will still be some impacts around the region.  First off, a Winter Weather Advisory has been issued by the National Weather Service in the areas shaded below.  Image courtesy of NOAA
WWA txt here

Areas south of the Mass Pike will see very little snow and mainly a mixture of rain and sleet.  A warm front is surging north which will turn all precip over to rain by 3 am in the lower elevations.  Higher elevations will also turn over by 6 am.  The roads will be slick overnight so be careful on your way home.   Saturday will be warm, with highs near 50.  There will be a chance of a thunderstorm with this system as it moves through.  There will be no severe weather or tornadoes, but it will not be surprising to hear a few rumbles of thunder.  Most of the rain will be gone by 3-5 PM and skies will begin to clear for tomorrow night.
NOAA rainfall forecast for next 24 hrs

Next week is half winter/half spring.  On Sunday, Monday, and Tuesday it will feel more like winter, especially Monday and Tuesday when high temperatures will only be in the 30's.  The sun will be out from time to time.  One will notice a dramatic difference from Tuesday to Wednesday.  A subtropical ridge is looking to build in the Southwest Atlantic and funnel warm spring like weather into the northeast.  Highs right now look to climb in the upper 50's-low 60's.    This is the extended range of the forecast, but things are looking good.  Remember, if the pattern of the last few months remains in place, the nice long stretches of good weather will get progressively warmer and warmer as the sun continues to trek northward. 

Storm Prediction Center daily storm reports (so far)
Finally, thoughts and prayers to all those affected by the tornadoes this week.  Spring time is the beginning of tornado season due to the mixing of warm tropical air with cold arctic air.  This is a tornado outbreak to remember and its going to continue into the night.  Let us hope no more lives will be lost and all warnings are heeded.   Here you can view damage from today's storms.

Winter Storm Warning Now Issued For Worcester County

CLICK TO ENLARGE CLICK TO ENLARGE