A wet, windy New Year’s Eve in NYC will give way to a very mild day to start 2019. However, for reasons outlined below, I don’t believe that record warm temperatures will be broken tomorrow. Strong winds will be a distinct possibility, though, and as such the National Weather Service has issued a wind advisory for the area. I think sustained winds could reach 30 mph, especially early in the day.
My Forecast
High: 57°F | Low: 36°F | Max sustained winds: 30 mph | Total precipitation: 0.04″ –
verification for temperatures and precipitation will come from METAR data for the period between 1AM Tuesday and 1AM Tuesday (06Z Tuesday to 06Z Wednesday) at LGA. Wind speed verification will draw on the daily climate summary from the National Weather Service.
Verification
High: 60°F | Low: 40°F | Max sustained winds: 36 mph | Total precipitation: 0.02″ – this wasn’t a great forecast, aside from the precipitation. I was once again overly conservative on max wind speeds. Following layer mean wind analysis results would have yielded an almost perfect forecast here. For temperatures, I think the main issue was that the low level clouds I thought would materialize based on the forecast soundings available the day before just never came to be. This allowed high temperatures (and hence low temperatures) to become warmer than I forecast. In this case, perhaps it would have been prudent to consider that winds would be downsloping from the northwest, hence drying out somewhat at lower levels. This wind direction also favors clearing conditions following a cold front passage from the west.
Synoptic Set Up
NYC will start the day off in the warm sector of a low pressure center tracking northeast through New England. This low will continue to deepen as it progresses east. The tightening pressure gradient will induce strong winds, and a trailing cold front will cross the region bringing about much colder air in its wake. Temperatures will peak early in the day and drop steadily through the day. The low temperature will occur late in the forecast period.
High Temperatures
Steady warm advection overnight with a warm front and warm sector associated with the parent low above will mean that temperatures increase to the mid-50s by day break. Forecast soundings from both GFS and MOS indicate, persistent, low overcast that I believe will be pivotal to keeping temperatures from going above 60°F. These low overcast clouds should block out enough sun to keep things a bit cooler than otherwise would be. Forecast soundings also show some upper level clouds that would help block additional sun. For these reasons, I’m siding with cooler NAM MOS guidance that calls for 55°F, and bumping up a couple degrees. Cold advection should take hold quickly in the afternoon in the wake of the trailing cold front. This will usher in westerly and northwesterly winds, which will downslope and warm a touch but will still overall bring colder air into the area. Once this cold advection takes place, temperatures should start to fall.
Low Temperatures
Because of the factors above, the low temperature should end up coming in late in the evening/overnight period going into Wednesday. I believe there’s not too much reason to deviate from MOS guidance which averages out to be about 35°F.
Max Sustained Winds
A well-mixed boundary layer is forecast to develop with pretty strong winds aloft in the late morning hours. A period of efficient downward momentum transfer should allow fast winds from above to mix down to the surface. Layer mean wind analysis suggests that winds could be as strong as 35 mph, however, I’m going a bit lower with sustained winds topping out at 30 mph since neither set of MOS guidance goes over 20 mph.
Total Precipitation
It’s clear at this point that the bulk of precipitation will fall before the beginning of the forecast period. However, both sets of MOS guidance, SREF and GEFS means all suggest some precipitation early in the overnight period. I’m going with a composite average of various sources at 0.04″.
