January Discobs 2025

[WEATHER53]

1 hour ago, WEATHER53 said:

Just hit 28 and I think that’s it 

Down to 27.8 after peaking at 28.2 and maximum in the direct sun just 33.3 so very little melting and little oomph to the sun 

[RIC_WX]

54 minutes ago, katabatic said:

I hit -15.2 yesterday and -8.9 this morning. Definitely the coldest since I've been here (but that's only 3 winters). I have no idea how unusual -15 is. My guess is lately (of course) it's extremely rare but prior to say 2015?

I think all of this is microclimate specific.  There is probably a reason why I consistently bottom out around -12 under the most ideal conditions.  Now that the lake is frozen, I have noticed the stations lower than me (at 2595', I am 160' or so above the lake) seem to be bottoming out a bit lower as the cold air settles.  This is not typical when the ice is out, I will radiate much faster after sunset and typically the lakefront stations will be 2-3*F warmer.  Your microclimate is inevitably different and influenced by the toppgraphy closer by.

[WEATHER53]

27.6 at 4pm after a high of 28.2 in Kemp Mill and 25 in Frederick 

Let the plunging begin 

[CAPE]

High of 27 after a low of 1.

Didn't think it would make it to the forecast high of 31 today.

 

[stormy]

33.3 degrees at 4:15. This is the first time above freezing in 4 days.

Going back to the 60's which I lived through, this is insane. 

Ice on ponds is 6 inches thick which has not been achieved in many years.

 

[WEATHER53]

5 minutes ago, stormy said:

33.3 degrees at 4:15. This is the first time above freezing in 4 days.

Going back to the 60's which I lived through, this is insane. 

Ice on ponds is 6 inches thick which has not been achieved in many years.

 

Back then this is the way it was for about 12 of the 15 winters between  1957 to 1972 

[T. August]

28.7°. It’s been below freezing since Sunday afternoon/evening. Wish I would have gotten to test out the ice on the inlet before the thaw. Last time I walked across was 2018.

[TSG]

5 hours ago, WEATHER53 said:

More of a defect than UHI

Im presuming they have absolutely zero snow, none, within 100 yards of the station?

Nope. There's no defect, it's a combination of factors and this has been explained many times. Here it is again:

 

Early in the season the Potomac is contributing significant warmth. This is obviously not a factor at this point as the river has frozen over.

DCA radiates horribly due to being in a relative "bowl" within it's landscape. See the images below. BWI is on a high point within in it's environment, basically the exact opposite of DCA, and IAD is in an open plain. Neither location has a significant portion of it's upward view obstructed by urban environments. Portions of the sky or treelines at ambient temp that are visible at BWI and Dulles to the measurement location are replaced with city skyline radiating heat back towards the airport.

This environment also contributes to localized downsloping effects. IAD is at ~325ft above sea level, where I grew up in Falls Church it was basically the exact same elevation with a few hilltops closer to 400ft nearby. That's 17 miles as the crow flies with basically zero elevation change. You then lose those 300-400ft in the next ~6 miles which will net over a degree F in temperature increase.

You also get an enhanced UHI effect when wind is coming in from the West/Northwest, which it often is when this "issue" comes up. That entire strip west of the GW parkway is ~250-300ft tall buildings built primarily in the 70s and 80s that have next to no insulation and constantly belch wasted heat into the environment during the winter. It's a one mile long, quarter mile wide heat exchanger that's less than a mile away from the measurement site. Nothing like that exists for either of the other locations. Although I could imagine IAD may be seeing similar effects on a North wind from the massive amount of data centers that have gone up the last 10 years, but they are much further from the sensor location.

The overall UHI effect across a metro region is not anywhere close to homogenized or a standard gradient extending out from the cities. It's highly dependent on the local environment. Show up with some actual data if you legitimately think this needs to be looked at. Otherwise you're probably going to get this response from me every time you bring it up.

The horse is a finely minced pulp at this point, let it go. 

[blizzardmeiser]

25.6.  Might not go above freezing till Sunday.  Days are definitely getting longer- leaving in daylight!

[stormy]

30 minutes ago, WEATHER53 said:

Back then this is the way it was for about 12 of the 15 winters between  1957 to 1972 

In the 60's this was expected. But in the past 15 years we have been spoiled until this year.

From March 1958 thru the 60's it was tough from November thru March.   Young folks cannot relate because they didn't live through it.

[wxdude64]

High of 31.6, almost freezing, but not quite. Did get a bit of melting from full sun between 2-4 pm, especially south facing, when temp went from 22-31 in about 10 minutes once we broke out of the clouds. Already down to 28.9/13.0 at 5:30. 

[WEATHER53]

37 minutes ago, TSG said:

Nope. There's no defect, it's a combination of factors and this has been explained many times. Here it is again:

 

Early in the season the Potomac is contributing significant warmth. This is obviously not a factor at this point as the river has frozen over.

DCA radiates horribly due to being in a relative "bowl" within it's landscape. See the images below. BWI is on a high point within in it's environment, basically the exact opposite of DCA, and IAD is in an open plain. Neither location has a significant portion of it's upward view obstructed by urban environments. Portions of the sky or treelines at ambient temp that are visible at BWI and Dulles to the measurement location are replaced with city skyline radiating heat back towards the airport.

This environment also contributes to localized downsloping effects. IAD is at ~325ft above sea level, where I grew up in Falls Church it was basically the exact same elevation with a few hilltops closer to 400ft nearby. That's 17 miles as the crow flies with basically zero elevation change. You then lose those 300-400ft in the next ~6 miles which will net over a degree F in temperature increase.

You also get an enhanced UHI effect when wind is coming in from the West/Northwest, which it often is when this "issue" comes up. That entire strip west of the GW parkway is ~250-300ft tall buildings built primarily in the 70s and 80s that have next to no insulation and constantly belch wasted heat into the environment during the winter. It's a one mile long, quarter mile wide heat exchanger that's less than a mile away from the measurement site. Nothing like that exists for either of the other locations. Although I could imagine IAD may be seeing similar effects on a North wind from the massive amount of data centers that have gone up the last 10 years, but they are much further from the sensor location.

The overall UHI effect across a metro region is not anywhere close to homogenized or a standard gradient extending out from the cities. It's highly dependent on the local environment. Show up with some actual data if you legitimately think this needs to be looked at. Otherwise you're probably going to get this response from me every time you bring it up.

The horse is a finely minced pulp at this point, let it go. 

It has many stations within 10 miles  of it  that do not support your assessment.

DCA is not over by the Williard  which is all buildings all close together, streets, no green space 

DCA has a tree lined parkway running next to it and water surrounding most  sides of it.  Annapolis is further east  at same c elevation and close to a much bigger body of water yet is generally 3+ degrees colder  it should actually be warmer but DCA us flawed, . Camp Springs/Andrews  further east and developed and always colder.

DCA does ok when winds mix things up and homogenize. When its clear and calm , DCA has impediments to radiation to such an extreme that something artificial is prohibitory 

[WEATHER53]

43 minutes ago, stormy said:

In the 60's this was expected. But in the past 15 years we have been spoiled until this year.

From March 1958 thru the 60's it was tough from November thru March.   Young folks cannot relate because they didn't live through it.

We ice skated and sledded many times every year, it was rare when we could not 

[stormy]

The GFS says the next 15 days will be controlled by the continuing drought:

[TSG]

2 minutes ago, WEATHER53 said:

It has many stations within 10 miles  of it  that do not support your assessment.

DCA is not over by the Williard  which is all buildings all close together, streets, no green space 

DCA has a tree lined parkway running next to it and water surrounding most  sides of it.  Annapolis is further east  at same c elevation and close to a much bigger body of water yet is generally 3+ degrees colder  it should actually be warmer but DCA us flawed, . Camp Springs/Andrews  further east and developed and always colder.

DCA does ok when winds mix things up and homogenize. When its clear and calm , DCA has impediments to radiation to such an extreme that something artificial is prohibitory 

Oh ok. If there's so many stations that support your assessment how about you actually put that analysis together for us. It must be an easy job if there's so much supporting data around.

[TSG]

47 minutes ago, WEATHER53 said:

It has many stations within 10 miles  of it  that do not support your assessment.

DCA is not over by the Williard  which is all buildings all close together, streets, no green space 

DCA has a tree lined parkway running next to it and water surrounding most  sides of it.  Annapolis is further east  at same c elevation and close to a much bigger body of water yet is generally 3+ degrees colder  it should actually be warmer but DCA us flawed, . Camp Springs/Andrews  further east and developed and always colder.

DCA does ok when winds mix things up and homogenize. When its clear and calm , DCA has impediments to radiation to such an extreme that something artificial is prohibitory 

Also not quite sure how you expect the ~300ft of trees that are stuck between a small city and over 400 acres of paved parking lot and tarmac to be the primary driver of temperature there lol

You do realize there are 100000000x more trees around IAD and BWI, right?

[aldie 22]

18.7 zero noticeable melting today 

[pazzo83]

2 hours ago, WEATHER53 said:

It has many stations within 10 miles  of it  that do not support your assessment.

DCA is not over by the Williard  which is all buildings all close together, streets, no green space 

DCA has a tree lined parkway running next to it and water surrounding most  sides of it.  Annapolis is further east  at same c elevation and close to a much bigger body of water yet is generally 3+ degrees colder  it should actually be warmer but DCA us flawed, . Camp Springs/Andrews  further east and developed and always colder.

DCA does ok when winds mix things up and homogenize. When its clear and calm , DCA has impediments to radiation to such an extreme that something artificial is prohibitory 

again you are on about this ridiculous nonsense.  DCA is square in the middle of the most urbanized area of the region.  KNYC is in the middle of Central Park surrounded by trees for fucks sake and still has an absolutely massive UHI effect.

DCA's temp rarely varies significantly from mine inside the District in a more residential (but still urban) area.  When I lived downtown (surrounded by mid-rise buildings with a reading from the roof of a 10 story building), it was almost always exactly what DCA reported if not slightly warmer at times (particularly in the summer).

DCA's temps today: 31/15
Tenleytown's temps today: 33/13

DCA is never going to reflect exactly what your climate is because you live outside the beltway in the suburbs.

 

[pazzo83]

7 hours ago, WEATHER53 said:

More of a defect than UHI

Im presuming they have absolutely zero snow, none, within 100 yards of the station?

My low was 13 with 95% snowcover.  You are absolutely wrong about this.

[pazzo83]

1 hour ago, TSG said:

Also not quite sure how you expect the ~300ft of trees that are stuck between a small city and over 400 acres of paved parking lot and tarmac to be the primary driver of temperature there lol

You do realize there are 100000000x more trees around IAD and BWI, right?

been fighting this battle with him for a while - don't expect much logic or evidence to come from that corner

[snowmagnet]

10 hours ago, Interstate said:

So you are saying kids do not have a winter coat, gloves, and a hat?  That is really all that is needed.  If they do not have that equipment... They cannot be possibly be dressed for any weather under freezing.  Most if not all Elementary school kids have a parent at the bus stop or walking them to school.  Yes it was cold, but not two hours late cold.  Plus it did not warm up that much... so those kids face the same thing going home.

Yesterday schools should have been closed.  And yeah, these kids are used to coming to school in hoodies and crocs or sneakers. While most of our county has money, there are quite a large number of families that don't and also can't drive their kids to school when it's too cold to walk a mile. I volunteer with refugees and have been trying to get many of them warm clothes and coats, but many don't have any.  

[TSG]

11 minutes ago, pazzo83 said:

been fighting this battle with him for a while - don't expect much logic or evidence to come from that corner

Oh I know haha. I genuinely enjoy analysis like this. I do stuff like this fairly often for work to assess potential micro-climate effects on solar plant production.

I might just turn this into a mini thesis level copypasta