Our amazing atmosphere

We observed a pretty interesting phenomenon at the weather center yesterday afternoon. I noticed that the dew points locally had crashed into the single digits as our frontal system was beginning to approach from the west. We knew going into yesterday that it was quite dry in the lowest levels of the atmosphere, but I noticed a sharp drop in the dew point just before 6:00 PM on our weather station. It dropped nearly 10ºF in about a half hour, which is very common when a cold front is moving through – but what seemed like an otherwise pretty ordinary day this was a notable observation.

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Obviously, when you see something that significant you often want to check to see what surrounding stations are reporting – So I pulled the Danbury Airport Observations (western side of town)… and the drop was just as dramatic – occurring right around 5:00 PM

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and the same for Oxford Airport. They are a little east so they reached their driest dew point just before 7:00 PM.

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Note that while this was going on the temperature (in blue) was steadily falling, but not at a particularly rapid rate, and the winds were light, and remained consistently out of the south. So it’s clear the answer to the question really had to do with what was going on above the surface.

It turns out some of our high resolution guidance actually had this drop modeled quite well. This is taken from the 18Z 3 KM NAM run yesterday:

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This is a diagram of temperature (red) and dew point (green) in western Connecticut from yesterday after as forecast in this model run. (where the lines are really far apart -that represents a DRY airmass, where the lines are close together it means the airmass has just about all the moisture it can hold!)

The chart reveals that there was a corridor of localized subsidence or “sinking air” that was causing the dew points in this near surface layer to briefly crash. This was coincident with some gusty southwest winds that picked up just above the dry layer. They were transporting a decent amount of moisture in, but it was arid near the ground around here during the dinner hour yesterday! **Update** The current thinking is that this was likely some sort of gravity wave along the moist/dry boundary layer.

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The gray shades indicate the sinking air in response to the wave moving through above the boundary layer (indicated by the pink frontogenesis contours).

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This dry air pocket did erode away as precipitation began to move into our area last night, but as you may imagine – the little rain that tried to move in struggled to reach the ground. Overnight rainfall was less that 0.01″ – what we meteorologists commonly report as “trace”!

Weather is awesome!

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Complicated weekend pattern

High pressure is analyzed to the east of New England and just south of the Canadian maritimes, while a warm front has stalled across central Pennsylvania. The ridging has been slow to break which has suppressed the onset and even allowed some sunshine to begin the day for part of the state. Southeasterly winds between these two features continues to advect in a plume of low level moisture in and the column will begin to saturate this afternoon.  Continue reading

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Winter 2016-2017

Westbrook, CT Total snowfall: 47.6″ – Trace snowfalls not included

  1. December 12, 2016:   0.3″
  2. December 16, 2016:   0.1″
  3. December 17, 2016:   5.6″
  4. January 6, 2017:         2.5″
  5. January 8, 2017:         7.8″
  6. January 15, 2017:       1.3″
  7. February 1, 2017:       3.8″
  8. February 9, 2017:       0.8″
  9. February 10, 2017:    12.2″
  10. February 11, 2017:     0.5″
  11. February 13, 2017:     2.5″
  12. February 16, 2017:     0.2″
  13. March 11, 2017:          4.8″
  14. March 14, 2017:          1.0″
  15. March 15, 2017:          4.2″
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New Milford, CT’s close call with a Supercell (5/31)

A Severe Thunderstorm impacted New Milford, CT between 7:36 and 7:55 PM last night (May 31, 2017). The storm strengthened into a possible tornado producing supercell over Dutchess county, NY with a very large hail signature east of Poughkeepsie shortly before 7:00 PM.

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Significant Damage was reported with this storm in Wappingers Falls around this time: “Tree tops snapped off. House impaled by branches. Shed blown down and partial collapse of house. Event occured on Maloney Road near Rt. 376” 1 inch diameter hail was observed in Arlington, and golf ball sized hail in Poughkeepsie around this time also.

The storm began to develop a hook echo signature as it approached an area just northeast of Hopewell Junction.

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Additional wind damage was reported:

Hopewell Junction: “Trees Down”

East Fishkill: “Trees down”

The storm maintained moderate to strong rotation all the way to the Sherman, CT, New York state border – the rotation at this time prompted a tornado warning from the national weather service.

Additional wind damage reports came in just west of the state line:

Hurd Corners: “Multiple maple trees downed”

 

The rotation began to rapidly weaken over Sherman, while areas of New Milford along Route 7, north of the Route 202 split reported 1″ hail.

No wind damage was observed, torrential rain, frequent lightning and locally severe hail occurred at the height of the storm.

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Thursday June 1, 2017 Forecast Discussion

Across Connecticut temperatures range from 58ºF to 61ºF this morning with skies becoming mostly sunny. Winds along the coast are southwesterly from 5 to 10 mph with a few higher gusts. Further inland it’s lighter and more variable around 5 mph and anywhere from south to southeasterly. A stationary front boundary is analyzed just inland of the immediate coast with a cold front beginning to slide towards the Hudson Valley. The front will cross the state today, behind which an axis of high pressure will begin to work into the area for tonight into Friday. Continue reading

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Wet weather and a Warming trend

As off 11 am, temperatures across the state remain in the upper 50s and lower 60s, with winds generally between 3 and 7 mph out of the south east. As an axis of high pressure shifts east, Mid and high level clouds will continue to spread in from the south and west from a broad but weak area of low pressure near the South Carolina coast.

An associated upper level cut off low will begin to slide eastward across north Georgia as a broad western trough moves in over the rockies. The closed low, vertically stacked with the surface low, will gradually propagate towards eastern North Carolina through Tuesday afternoon.

A moist southeasterly flow ahead of the low center lifting over a warm front will cause a broad, but light area of rain to develop during the evening hours Monday and continue through the day on Tuesday. Low level jet energy arrives by Tuesday evening which will help fuel periods of heavier rain during the evening and overnight hours – Favoring southern and eastern Connecticut.  The low level jet forcing will shift east of the region by Wednesday morning. Lingering low level moisture will cause light rain and drizzle to persist well after the steadiest precipitation shifts away from the area Wednesday morning.

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Winter’s early spring wrath

Despite the calendar, another round of March winter weather is on the way for some in Southern New England. A large wrapped up area of low pressure in the central US will bring stormy weather into the region tomorrow through the first part of the weekend.  Continue reading

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Winter 2016/17 Snowfall

10/28/2016: T
11/21/2016:  T

12-Dec-16 0.3″
16-Dec-16 0.1″
17-Dec-16 5.6″
6-Jan-17 2.5″
8-Jan-17 7.8″
15-Jan-17 1.3″
1-Feb-17 3.8″
9-Feb-17 0.8″
10-Feb-17 12.2″
11-Feb-17 0.5″
13-Feb-17 2.5″
16-Feb-17 0.2″
11-Mar-17 4.8″
 Seasonal Total: 42.4″
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Light snow Friday, a more significant storm next week?

A cold front passage early this morning has begun to bring drier air into the region. Dew point depressions are 5 to 10ºF state wide with air temperatures still hanging around in the upper 40s to near 50. The visible Satellite picture reveals some clearing skies beginning to work their way towards us – already into parts of the Hudson valley and western New Jersey as of 9:00 AM. This will move into the state through midday. Continue reading

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Mild through mid week with late week cold

Well congratulations! Today is the first stereotypical March day across Connecticut with occasional rain showers and temperatures that will crawl through the 40s up to around 50ºF by later this afternoon and early evening. This is not a washout but you are going to want the jacket if you are venturing out today. Despite near or above normal temperatures it will feel cold.  Continue reading

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