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NYC Weather Update & BK Half Marathon – May 14, 2014

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We’ve been fortunate that a persistent high pressure off of Nova Scotia has been stalling the arrive of a storm system earlier forecast to bring showers during the midweek period.

Our luck is about to run out, however, as the low pressure center and associated frontal boundaries will finally make their approach over the NYC area.

Thursday – overnight, a warm front is projected to pass through our area, bringing along a chance of drizzle, and the possibility for dense fog tomorrow morning as lower levels of the atmosphere become saturated with the coming southerly flow. Once the warm front passes over us, we will see a noticeable increase in temperatures, with highs forecast to be in the mid-upper 70s and possibly low 80s in interior portions of the region. Although the probability is low, there could be a couple showers and stray thunderstorms as well.

Friday – as the cold front associated with the low pressure center below draws closer, chance of precipitation will increase steadily during the course of the day. To start off, lighter showery precipitation should move in during the morning and early afternoon hours. Thereafter, heavier precipitation, and possibly thunderstorms, will move in especially during the evening and overnight hours. Due to the ground being somewhat saturated from the last round of rain we got, there could be some flash flooding in the heaviest down pours. Temperatures will be a bit cooler than Thursday in the upper 60s to around 70.

L and H correspond to approximate locations of surface low and high pressure centers. Notice the strength (high amplitude) of the associated upper trough and ridge
L and H correspond to approximate locations of surface low and high pressure centers. Notice the strength (high amplitude) of the associated upper trough and ridge

Saturday (BK Half Marathon Race Day) – good news for you runners out there as it appears the weather will cooperate for race day. The pesky slow-moving frontal boundary responsible for the rain on Friday will finally clear the area early Saturday morning, just in time for the start of the race. There may be some light showers early, but once the front clears conditions should start to improve. I would estimate start time temperature to be in the low 60s, with a high temperature forecast to be in the low 70s.

Simulated radar image from the North American Model (NAM)
Simulated radar image from the North American Model (NAM) for Saturday at 8AM EDT

Sunday – a return to nice weather as the cold front has passed through and high pressure builds in temporarily. Partly cloudy with a high in the low 70s.

NYC Weather Update – May 11, 2014 – BK Half Marathon

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Hey folks, I got a special request to provide an weather analysis for the Brooklyn Half Marathon, which is scheduled for next Saturday, May 17th. A friend at the Road Runners informs me there are also pre-race activities going on at Brooklyn Bridge Park Pier 2 starting Wednesday.

Synopsis

First, in brief, I believe that Race Day itself should be dry, perhaps with a slight chance of showers but later in the day (as per the National Weather Service’s current forecast). Unfortunately, the mid-week pre-race activities won’t be quite as lucky as I’ll explain shortly. It is also worth noting that 6 days out, this forecast can still change, but I’ll be posting again Wednesday with a more up to date analysis.

Your Week

Moms are going to be thrilled that Mother’s Day today will be a spectacular day weather-wise. Subsequent to the passage of the cold front last night, today will feature clear conditions with warm temperatures in the upper 70s to low 80s and comfortable humidity.

Monday will be another nice day with summer like weather, temperatures right around 80 and increasing humidity due to the influence of the Bermuda High (which slowly shifts westward through the course of the spring into the summer, when it begins to dominate our weather with hot, humid air blasting from the southwest).

Tuesday a nearly stationary front will slowly push into our area, sparking the potential for some thunderstorms Monday night, and periods of showers during the day Tuesday (around 30% chance each of the following 3 days). Temperatures will be much cooler than Monday only in the low 70s.

Wednesday the stationary front above turns into a backdoor cold front (retrograde, progressing from east to west as opposed to the general pattern of west to east), continuing the potential for unsettled weather with periods of showers and a cooler day in the mid 60s.

Thursday brings another day of unsettled weather, with a series of weak impulses moving along a nearly stationary cold front just to our west. Temperatures will be slightly higher in the upper 60s.

Screen Shot 2014-05-11 at 10.02.08 AM

Friday is the last day we’re stuck in this pattern of unsettled weather. The reason behind this prolonged period of unpleasant weather is the strong ridge of high pressure you see off the coast of Nova Scotia in the following upper air forecast from the Global Forecast Model. This strong high pressure will set up a blocking pattern on the trough of low pressure depicted. As this trough finally passes through our area, the best chance for steady showers and thunderstorms this week will occur. Temperatures will range in the mid-upper 60s.

Screen Shot 2014-05-11 at 10.01.29 AM
Note the strong ridge that corresponds to an area of high pressure, and the trough that denotes low pressure to the west of the high

Saturday (Race Day) – at this stage, models seem to suggest that the cold front and low pressure system will have cleared New York just around start time on Saturday. Clouds should diminish during the day as the frontal boundary pulls away, however, can’t rule out a few spot showers lingering.

Screen Shot 2014-05-11 at 10.16.15 AM