our first nudge towards autumn comes thursday through friday

[earthlight]

it's certainly been a while. but i think we'll all have a good time tracking this overnight tomorrow night. models have backed off a bit on the h850 temps reaching 0 c in the northwest burbs, but it's still plenty cool enough to get into the lower 40's. the higher elevations and suburban areas of nw nj may touch the upper 30's. the city is a tough forecast...it's still tough to get the heat out there. but with good radiating, clearing by overnight thu into fri morning, relatively light northwest winds..i think they may scrape the upper 40's.

no matter how you slice it, the northern 1/3 of the us is experiencing the first real crisp air of the year. the drop in dew points is going to be noticeable as well.

http://coaps.fsu.edu/~maue/temperature/gfs/us_mint_7days.png

[CAT5ANDREW]

This is going to be a shocking cooldown for us as we have not seen the high dewpoints and warmth end on such a dramatic note here in many years.Make no mistake about it,many of us are going to have our teeth chattering by this time tomorrow.

[earthlight]

This is going to be a shocking cooldown for us as we have not seen the high dewpoints and warmth end on such a dramatic note here in many years.Make no mistake about it,many of us are going to have our teeth chattering by this time tomorrow.

yeah, your body takes time to adjust. 60's in february or march feels like we're being blowtorched. it's definitely going to feel brisk tomorrow night. in the interior, it will actually be very literally "cold" with temperatures dropping into the upper 30's.

i'm not a big fan of it, i'll take a warm summer night by the pool over any kind of cold weather. but seasons change, and we have to embrace it.

[earthlight]

nam mos shows the interior doing very well with radiating tomorrow night. the city stays near 50..which i think is fair. that's been my forecast low for three days now at central park. look at sussex, nj though..down to 38 there, and even 43 in morris county, nj as well.

[earthlight]

just for comparison purposes here's the gfs mos for the same time periods. pretty strong agreement on all accounts. not bad--we can typically see some big differences on the two models given the resolution/etc. http://www.meteo.psu.edu/~gadomski/MOSPA_0z/avnmos.gif

also--the new okx forecast has a low of 44 in the city thursday night.

[CAT5ANDREW]

just for comparison purposes here's the gfs mos for the same time periods. pretty strong agreement on all accounts. not bad--we can typically see some big differences on the two models given the resolution/etc. <a href='http://www.meteo.psu.edu/~gadomski/MOSPA_0z/avnmos.gif' class='bbc_url' title='External link' rel='external'>http://www.meteo.psu...A_0z/avnmos.gif</a>also--the new okx forecast has a low of 44 in the city thursday night.

This is going to be similar to Sept 1991 and Sept 1993,that was the last time the low temp was below 45 during still calender summer.

[earthlight]

This is going to be similar to Sept 1991 and Sept 1993,that was the last time the low temp was below 45 during still calender summer.

well, my 1 and 3 year old self probably was shocked by the cold during those events as well.

[CAT5ANDREW]

well, my 1 and 3 year old self probably was shocked by the cold during those events as well.

Sheez,I was 24 and 26 years old those times.

Either way you look at it,it is good to see this type of cool air this early.The subways have got to be aired out of their ovenlike heat.

[gkrangers]

When is this happening? If I'm out until 9-10PM tomorrow night, will I be cold without a jacket?

[NorEaster27]

Uptons point forecast for central manhattan is showing a 45 degree low tonight:

http://forecast.weat...n&FcstType=text

That seems super agressive and may be an error of the click and point forecast system. If KNYC can get below 50 degrees, that would be very impressive and the earliest sub 50 degree reading in years.

[Fantom X]

When is this happening? If I'm out until 9-10PM tomorrow night, will I be cold without a jacket?

It's happening tonight.

[Sundog]

Uptons point forecast for central manhattan is showing a 45 degree low tonight:

http://forecast.weat...n&FcstType=text

That seems super agressive and may be an error of the click and point forecast system. If KNYC can get below 50 degrees, that would be very impressive and the earliest sub 50 degree reading in years.

There's no way that's right. I bet they have a low of 51 or 52 at best with the rest of Manhattan in the mid 50's, unless there's super CAA coming through that I'm not aware of.

[bluewave]

The lowest 9/1-9/19 temperatures in NYC since 1990:

2010...57

2009...53

2008...52

2007...50

2006...52

2005...58

2004...52

2003...57

2002...55

2001...53

2000...52

1999...55

1998...54

1997...52

1996...54

1995...53

1994...53

1993...52

1992...52

1991...53

1990...44 with two 49 degree lows

[NorEaster27]

Mid 50s looks good for NYC tonight, low 50s would be impressive. I dont see the CAA strong enough for anything below 50.

[IsentropicLift]

There is a small amount of SBCAPE developing just ahead of the cold front, right now ranging from 100-500 J/KG with greater amounts as you head east. It looks like we are going to escape the steady rain per the latest radar and NJ especially has a good chance at seeing thunder. Did anybody get that thunderstorm just before midnight that skirted the far west? I just saw lightning but my buddy up in Warwick reported nickle sized hail.

[tornadojay]

Uptons point forecast for central manhattan is showing a 45 degree low tonight:

http://forecast.weat...n&FcstType=text

That seems super agressive and may be an error of the click and point forecast system. If KNYC can get below 50 degrees, that would be very impressive and the earliest sub 50 degree reading in years.

Agreed... A good technique for low temp forecast is to take the 850 mb forecasted temperature down moist adiabitically.. If you had done that for last night, you pretty much get the city's low right on the nose.. We had an 850 temp of about 15 or so this morning, which brought down moist adiabitically puts you at about 23 celcius or about 73-74 degrees. That was pretty much the low in NYC. 850's for tonight are forecasted at about 4C. Bring that down moist adiabitically and you're looking at about 12C or about 53-54 degrees. I predict tonight's low in NYC will be within one or two degrees of that.

By the way, if anyone is interested in hearing about some of the temperature forecasting techniques we learned up at SUNY Albany, I'm more than happy to share with you all. We were taught via a very structured and logical approach, which works pretty well. The rules we used are designed to work for the Albany area, however, they should work well, especially in the burbs of NYC. For NYC proper, it's fairly straightforward, because you don't have the affects of radiational cooling. Every semester, we play in a forecasting contest and so you live, eat, and breathe this stuff.. I'm actually playing in the contest as an Alum so I have vested interest in the weather up in Albany now.

I think upper 60's is a possibility with a good brisk downsloping wind tomorrow.. In reality, those 850 temps generally support mid 60's.. I'd say 66-68 is possible tomorrow.

[Stormlover74]

And I've noticed regardless of season the forecasted lows are almost always 2 to 3 degrees too low in the city and urban areas while more on target in the interior despite greater differences due to elevation etc. That's why I said I think we need a forecast low of no higher than 47 to assure getting below 50. If they say 49 I figure 52. In the end I suppose it doesn't matter much unless its a frost or freeze situation or during a winter precipitation event.

Agreed... A good technique for low temp forecast is to take the 850 mb forecasted temperature down moist adiabitically.. If you had done that for last night, you pretty much get the city's low right on the nose.. We had an 850 temp of about 15 or so this morning, which brought down moist adiabitically puts you at about 23 celcius or about 73-74 degrees. That was pretty much the low in NYC. 850's for tonight are forecasted at about 4C. Bring that down moist adiabitically and you're looking at about 12C or about 53-54 degrees. I predict tonight's low in NYC will be within one or two degrees of that.

By the way, if anyone is interested in hearing about some of the temperature forecasting techniques we learned up at SUNY Albany, I'm more than happy to share with you all. We were taught via a very structured and logical approach, which works pretty well. The rules we used are designed to work for the Albany area, however, they should work well, especially in the burbs of NYC. For NYC proper, it's fairly straightforward, because you don't have the affects of radiational cooling. Every semester, we play in a forecasting contest and so you live, eat, and breathe this stuff.. I'm actually playing in the contest as an Alum so I have vested interest in the weather up in Albany now.

I think upper 60's is a possibility with a good brisk downsloping wind tomorrow.. In reality, those 850 temps generally support mid 60's.. I'd say 66-68 is possible tomorrow.

[tornadojay]

And I've noticed regardless of season the forecasted lows are almost always 2 to 3 degrees too low in the city and urban areas while more on target in the interior despite greater differences due to elevation etc. That's why I said I think we need a forecast low of no higher than 47 to assure getting below 50. If they say 49 I figure 52. In the end I suppose it doesn't matter much unless its a frost or freeze situation or during a winter precipitation event.

For my particular zone, they are almost always too low on temp.. I am 20 miles north of the city.. but my county is pretty extreme.. You go from basically 12 miles from Manhattan at a low elevation to as much as 40 miles up in Bear Mountain which is a few thousand feet in elevation. Rockland is the smallest county in NY State so I guess it doesn't make sense to split the county in two separate zones, however, the gradient of weather is pretty extreme.

They will bust for sure, at least in my town.. They have lower 40's.. I just don't see how that is possible with the winds they are forecasting. Generally, in my town, if winds are ripping, we usually don't go much below the city's temp.. It actually wouldn't even surprise me if we don't go much below 50 or hang right around there. I think they are a good 5-8 degrees too low.

[gkrangers]

It's happening tonight.

Tis what I meant.

[MJO812]

International falls had temps in the lower 20s this morning. Really impressive for this time of the year. I think the low in the city tonight will be in the low 50s.

[ag3]

Posted the euro in the other thread. Has 44-49 as lows for city. 52-56 for ocean facing and Suffolk County. Would always give the most weight to the euro.

In my experience, on low NW wind nights, the urban areas don't radiate as well due to urban heating. But when there is a cranking 30-40mph wind, even the urban areas drop rapidly.

[Drz1111]

For my particular zone, they are almost always too low on temp.. I am 20 miles north of the city.. but my county is pretty extreme.. You go from basically 12 miles from Manhattan at a low elevation to as much as 40 miles up in Bear Mountain which is a few thousand feet 1600 ft in elevation. Rockland is the smallest county in NY State outside of NYC so I guess it doesn't make sense to split the county in two separate zones, however, the gradient of weather is pretty extreme.

FTFY.

[pazzo83]

Posted the euro in the other thread. Has 44-49 as lows for city. 52-56 for ocean facing and Suffolk County. Would always give the most weight to the euro.

In my experience, on low NW wind nights, the urban areas don't radiate as well due to urban heating. But when there is a cranking 30-40mph wind, even the urban areas drop rapidly.

Water temps surrounding Manhattan are still WELL into the 70s. No way we get below 50. 55 might even be a stretch. We've been above 70 (in the park) since 7am on 9/13. The PWS by me (this one is pretty accurate, at Hunter College on the UES) has been above 70 since 9/12 early in the AM.

[tornadojay]

FTFY.

yep.. all true.. thanks for the fixes

[tornadojay]

Water temps surrounding Manhattan are still WELL into the 70s. No way we get below 50. 55 might even be a stretch. We've been above 70 (in the park) since 7am on 9/13. The PWS by me (this one is pretty accurate, at Hunter College on the UES) has been above 70 since 9/12 early in the AM.

with a Northwest wind direction, I don't know how much impact, if any, water temps would have tonight, however, I do agree and don't think conditions support temps in the 40's in the city.. either tonight or tomorrow night.

[ag3]

NAM is still a few degrees warmer then the euro.

NAM drops the city to 50-52 tonight while the euro is 46-49.

[tornadojay]

NAM is still a few degrees warmer then the euro.

NAM drops the city to 50-52 tonight while the euro is 46-49.

I think the Euro might be going for a bit colder conditions at 850 mb as well.. looks like it might be more in the 3-4C range whereas the GFS looked like 5-6C.. didn't look at the NAM.

[ag3]

I think the Euro might be going for a bit colder conditions at 850 mb as well.. looks like it might be more in the 3-4C range whereas the GFS looked like 5-6C.. didn't look at the NAM.

Yeah. The euro has 3-4C in the city.

The 12z NAM is actually colder at the 850 level. Shows it at 2C at hour 18 and hour 21.

The 0z GFS has 850 temps of 3.0C for NYC.

[tornadojay]

Yeah. The euro has 3-4C in the city.

The 12z NAM is actually colder at the 850 level. Shows it at 2C at hour 18 and hour 21.

The 0z GFS has 850 temps of 3.0C for NYC.

ok. Once you start getting in that 0-2 range, then I think you start getting a shot at upper 40's... If things come in colder than what's modeled, it could happen... my gut feel still thinks it stays even several degrees above 50, but we'll see what happens.

[Shades]

Posted the euro in the other thread. Has 44-49 as lows for city. 52-56 for ocean facing and Suffolk County. Would always give the most weight to the euro.

In my experience, on low NW wind nights, the urban areas don't radiate as well due to urban heating. But when there is a cranking 30-40mph wind, even the urban areas drop rapidly.

I agree. The High won't be overhead so the winds will doubtfully go calm and most likely be above 10mph throughout the night with the ensuing CAA. This allows for more uniform temps across the board, and if the suburbs are getting into the 40s, NYC will not have a problem doing so as well into the upper 40s. I would even reason that tonight will be cooler than Friday night, IN THE CITY; By then the winds will be calm with the high crossing over, for more ideal radiational cooling (which the city does not do so well this time of year), suburbs are a different story, but tonight I'd have to go with the greater possibility of 40s in NYC.