Sept 24, 2013: Temperatures To Slowly Moderate

Updated 9/25 morning with new forecast update

Forecast Highlights:

gfs_namer_120_850_temp_mslp_precipAn unseasonably cool air mass remains in place over the area, with Central Park reaching 47 degrees this morning, the coolest September low since 2000. Temperatures will slowly moderate into the low-mid 70s through the week and the weekend with dry conditions persisting, with the next rain event expected on Monday as the next frontal system affects the area.


<< September 22 | September 23 | September 24 >>

Monday, September 23 Observations:

9.23.13With a strong cool air mass in place, chilly temperatures were observed again across the area, with morning lows falling to 39 degrees in Sussex, NJ and 50 degrees in Central Park, the second time this has occurred this month. Mostly sunny skies were observed during the day with highs climbing into the low to mid 60s inland and the mid to upper 60s for the rest of the area. The highest temperature was 68 degrees in Teterboro, NJ and JFK airport, and the lowest high temperature was 61 degrees in Port Jervis, NY.



Today – Saturday: Slowly Warming Up

As previously mentioned, Central Park fell to 47 degrees this morning, making it the coolest September low temperature since 2000, when temperatures reached 46 degrees on 9/27 and 43 degrees on 9/29. Central Park last fell below 50 degrees in September of 2009, with a low of 49 at the very end of the month. Other notable low temperatures across the area include 33 degrees in Sussex, NJ and 37 degrees in Westhampton Beach, NY. Mainly sunny skies are expected again today with highs rising into the upper 60s to low 70s across the area, with clear skies again tonight and lows a few degrees warmer than those of this morning.

On Wednesday, a shortwave trough will pass south of the area, which will help to keep the cool air mass in place through the late week; as this shortwave will stay south of the area, mostly sunny skies are expected to continue over the area with temperatures peaking in the upper 60s-low 70s for most locations and the low-mid 70s near NYC. Thursday and Friday may be a degree or two cooler across the area with mostly sunny skies expected to continue, with a slight warm up on Saturday as temperatures reach the low to mid 70s.


Sunday – Early Next Week: Rain Possible, Coastal Low Offshore

By the time the next frontal system approaches on Monday, it will have been 9 days since the last rain event, which occurred on Saturday, 9/21. A cold front is expected to approach the area, producing scattered showers across the region; uncertainty comes into play regarding a potential coastal low depicted on the models, as the Wednesday shortwave stalls off the southeast US coast late in the week while interacting with moisture from the Gulf of Mexico as a low pressure likely forms in the that region, which eventually gets picked up by the approaching trough on Sunday and Monday and tracks north, possibly NW with ridging present to its east. The more progressive models such as the GFS and UKMET keep this to the east of the area, while the stronger ECM takes it northwest towards the region with more widespread rain for Monday. It is worth noting that the last time the models showed a potential tropics-related low pressure affecting the area last week, it turned out to have been a false signal as the models quickly backed away from the scenario, and the medium range model scenarios need to be approached with caution; at this time I kept a chance of rain on Monday due to the approaching front, but this potential scenario will be watched over the next few days should it continue to be depicted on the model guidance and end up far west enough to affect the area, which is uncertain at this time.

Updated 9/25: It appears at this time that some of yesterday’s model guidance may have been too exaggerated with the western component of the storm track, with the storm staying mostly, if not entirely to the east. At this time, a further east track that keeps most of, if not the entire area west of the coastal low appears more likely, subject to some changes given the time range, although the storm is still expected to track north parallel to the coast offshore.

A cool down is likely towards the middle of next week, but as the previous pattern outlook noted, there is less cold air in Canada available to be pulled into the region compared to recent cool spells, and while a cool down in temperatures is likely, it may not be as cold as the current trough over the region. The possibility still remains for a stronger cool down after the first few days of October, however, which will be monitored with future updates as well. Stay tuned for more information on the longer range outlook.

11 thoughts on “Sept 24, 2013: Temperatures To Slowly Moderate

  1. Anonymous Reply

    As of today, is there any similar setup to last week with the shortwave moving east and then retreating back into Long Island with clouds and showers for a day expected sometime later this week or weekend?

    • NYC Area Weather Post authorReply

      This has been noted in the forecast discussion as the possibility is now there for a coastal low to brush parts of the region on Monday. Should it end up far west enough to affect the area, it would result in a cloudy and rainy Monday, although there is still some uncertainty regarding how far west it ends up.

  2. Anonymous Reply

    By the way, what was the cause of the morning showers and evening clouds on Monday, 9/16 in the area?

    • NYC Area Weather Post authorReply

      The morning showers were associated with a cold front moving through the region, while the evening clouds were due to another vorticity maximum moving through the area but with less moisture than was present ahead of the front.

  3. Anonymous Reply

    Was the vorticity maximum that was producing clouds in the evening related to the cold front from the morning?

    • NYC Area Weather Post authorReply

      The vorticity max came in on the backside of the same trough; when the surface front was over the area in the morning with a vort max nearby, the second vort max was over northern Michigan, and didn’t move through until 0z (8 PM) that evening.

  4. Anonymous Reply

    Did that same vorticity max cause clouds off the coast the following day, 9/17?

  5. Anonymous Reply

    Was the dry shortwave that moved through on Wednesday, 9/18 also related to leftover moisture from the cold front and vorticity max on Monday, 9/16?

    • NYC Area Weather Post authorReply

      These shortwaves were two different systems; when the Monday s/w moved offshore, the Wednesday one was still way to the west, over Wyoming and Montana.

    • NYC Area Weather Post authorReply

      These shortwaves were two different systems; when the Monday s/w moved offshore, the Wednesday one was still way to the west, over Wyoming and Montana.

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