Oct 3, 2013: Rain Finally Returns Next Week

Forecast Highlights:

gfs_namer_090_850_temp_mslp_precipAfter yesterday’s warmth with highs near the mid 80s, with three record temperatures tied or broken, a weak cold front moved through with the only noticeable change being slightly cooler temperatures. After a few isolated storms possible on Friday, warm and dry conditions will continue into the weekend, with a cold front approaching early next week bringing the first widespread rain event to the region in over half a month (image credit: NCEP MAG).

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Wednesday, October 2 Observations:

10.2.13An unseasonably warm air mass spread into the region, with mostly sunny skies, a west wind, and 850mb temperatures surging to near 14-15C. Along with the recent dry conditions, this resulted in unseasonably warm temperatures, peaking in the low to mid 80s for most of the area with eastern LI/SE CT in the mid-upper 70s and northeast NJ in the mid to upper 80s, breaking records in numerous locations. The highest temperature was 87 degrees in Teterboro, NJ, and the lowest high temperature was 76 degrees in Montauk, NY and New London, CT.



Today – Friday: Slightly Cooler; Isolated Storms Possible Friday

Last night, a weak cold front moved through the area, with little change other than slightly cooler temperatures and the wind direction briefly shifting to the NW this morning before returning to the southwest later today. Mostly sunny skies are expected to continue today with high temperatures peaking in the mid 70s to low 80s across the area. As a strong low pressure develops in the Midwest, which will be mentioned more in depth with the pattern analysis in the next section, a warmer air mass will spread towards the Great Lakes, with the cold front retreating back north as a warm front, expected to move through NYC on Friday. This will result in more widespread cloud cover and the possibility of isolated thunderstorms, especially north of NYC. High temperatures are expected to reach the upper 70s to low 80s from NYC and further west/south, with highs in the mid or possibly low 70s further north and east towards SE NY, Long Island and Connecticut, where the warm front will be slower to move through.


Weekend – Next Week: Rain Returns; Temps Stay Near-Above Average

Pattern Analysis: The current synoptic pattern consists of widespread ridging in the eastern half of the US with a strong trough digging into the northwestern US, which will become negatively tilted and briefly vertically stacked by Friday night. This will lead to the development of a relatively strong low pressure in the Midwest region, which is expected to result in a significant early season snowstorm in Wyoming and into parts of Nebraska and the Dakotas, and severe thunderstorms to its east. The trough will then continue to track northeast towards Canada, with the warm front that previously moved through on Friday holding in place as a stalled frontal boundary, likely staying near or northeast of NYC, and with the surface cold front approaching the region but slowing down due to persistent ridging near the western Atlantic Ocean.

Meanwhile, the Caribbean is being closely monitored as a strong tropical disturbance, labeled 97L, currently near the northeastern Yucatan Peninsula tracks northwest, and is likely to become the 11th named tropical storm of this year’s hurricane season; considering it is already at tropical storm strength, it would be named tropical storm Karen upon formation. Ridging will persist over the southeastern US and western Atlantic, with Karen being steered to the NW, then north along the western periphery of the ridging. The marginally favorable environment in the Gulf of Mexico is supportive of intensification into at least a moderate or possibly strong tropical storm, with landfall favored between eastern Louisiana and western Florida.

6z GFS at hour 90, representing the potential setup of the trough and 97L, subject to changes given the time range (Image credit: PSU e-Wall).

f90By that point, the interaction between 97L and the cold front becomes key regarding any potential impact on the region. The GFS is among the more progressive models, bringing 97L up the East Coast with a strong surface low pressure producing widespread heavy rain and wind; the ECM, however, is slower with the front, and keeps the heaviest rain with 97L well west of the area. An original source of these differences was the handling of the Midwest low pressure, with the GFS keeping the low moving due northeast, a much faster and less amplified scenario than the rest of the guidance which briefly stalled the low near Iowa/South Dakota and was slower to exit that region, with a slower frontal passage. The GFS did trend towards this scenario with the morning runs, but uncertainty continues regarding the exact orientation of the trough and the track, strength and timing of Invest 97L which will also have an impact on whether it is fully picked up by the trough keeping it well to the west, or interacts with energy left behind from the trough and tracks up the coast. Should 97L affect the area, it would likely be around Monday night into Tuesday with the possibility for heavy rain. There is still a fair amount of uncertainty at this time regarding 97L’s eventual track and setup that will play a role in how much rain the area gets and whether the heaviest rain stays near or west of the region, however, and the storm will continue to be monitored for potential impacts over the next few days.


Forecast for NYC Area: Friday’s warm front is expected to stall nearby on Saturday as a stalled frontal boundary, which will keep more cloud cover in place with high temperatures likely in the low-mid 70s east of NYC and the mid 70s to near 80 degrees from NYC and further west. As the front slowly but gradually lifts northeast, a slight warm up is expected on Sunday with partly sunny skies. Monday will feature increasing cloud cover as the cold front approaches, with temperatures slightly cooling down into at least the mid to possibly upper 70s. A tropical disturbance or tropical storm remnants are likely to reach the region, but with uncertainty regarding how much rain falls and whether the heaviest rain stays near or west of the area; at this time, I kept a high probability of rain for Monday night into Tuesday, increasing further west, but with the outlook subject to some changes. Stay tuned for more information on the early week outlook over the next few days.

6 thoughts on “Oct 3, 2013: Rain Finally Returns Next Week

  1. Anonymous Reply

    Are the thunderstorms tomorrow expected to reach the southernmost parts of NYC and Long Island?

    • NYC Area Weather Post authorReply

      While the highest probability of storms tomorrow is north and west of NYC, isolated to scattered storms are possible in southernmost NYC and Long Island especially from the late afternoon into the evening and early overnight hours.

  2. Anonymous Reply

    can you make a weather call for next weekend (Sat-Sun) yet for central ct

    • NYC Area Weather Post authorReply

      Current indications support a mostly sunny, dry and slightly warmer than average weekend; as this is a little over a week away, changes are still possible to this forecast though.

    • NYC Area Weather Post authorReply

      Saturday could feature a few isolated showers, but with thunderstorms unlikely as the frontal boundary is likely to settle near Long Island at this time, which should result in cooler temperatures as well. The same scenario applies for Sunday; more widespread rain/storms are expected towards Monday night into Tuesday though.

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