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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

NYC Nowcast – May 10 @ 2:40PM EST

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A batch of strong showers with some rumbles of thunder is approaching the NYC area. For the remainder of the afternoon and evening, strong to possibly marginally severe thunderstorms may pass through ahead of an advancing cold front. Damaging wind gusts and small hail are the primary threats.

Screen Shot 2014-05-10 at 2.37.04 PM

Otherwise, expect broken clouds to cloudy skies and nice warm afternoon in the upper 70s to low 80s across the area. A line of thunderstorms is likely to fire up again later this afternoon into the evening hours as the cold front actually approaches.

Screen Shot 2014-05-10 at 2.35.22 PM

Atmospheric instability is continuing to increase as we are in the warm sector ahead of the advancing cold front. Low level lapse rates and shear profiles are marginally conducive to the growth of some strong to severe thunderstorms.

NYC Weather Update – May 8, 2014

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We have a similar setup as last week that’s bringing overcast and rainy conditions to the region. A warm front well to our south is causing southeasterly/easterly winds off the cold Atlantic to stream in and saturate the atmosphere. Today, temperatures will be cooler with highs in the upper 50s.

Another mature cyclone with areas of precipitation and associated frontal boundaries
Another mature cyclone with areas of precipitation and associated frontal boundaries

Unsettled weather conditions will continue Friday with the approach and passage of the aforementioned warm front. Temperatures will be warmer in the upper 60s, with a chance for showers and thunderstorms throughout the day.

Saturday looks like a warmer copy of Friday, again with the chance for showers and thunderstorms during the day and with increasing chance for precipitation in the evening/night hours as the cold front depicted above makes its way through. High temperatures will be in the mid 70s despite the cloud cover.

Sunday should be the best day of the weekend (just in time for Mother’s Day), with the frontal boundaries having passed over, skies should clear and allow for temperatures to top out near 80 in the city.

Monday the period of good weather continues to start the next work week, with high temperatures again possibly hitting 80 and mostly sunny skies.

 

NYC Weekend Weather – May 2, 2014

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It’s been a wild weather week that started with a tornado outbreak across half a dozen states in the South, and torrential rain fall that dropped as much as 2 feet in Florida, and as much as 6-8″ across the Northeast (resulting in incredible scenes like this landslide in Baltimore).

Fortunately, the weather has taken a turn for the better and will remain that way much of the coming week. This weekend is shaping up to be a nice one with temperatures on Saturday and Sunday reaching into the upper 60s to the low 70s across the region. There is a chance on both days of popup showers or thunderstorms in the afternoon, especially in inland areas with better daytime heating.

GFS model output for this coming Wednesday. Note the strong trough out west (dip in the contour lines), and a ridge over our region (bulge towards the north of contour lines)
GFS model upper air (500mb absolute vorticity) output for this coming Wednesday. Note the strong trough out west (dip in the contour lines), and a ridge over our region (bulge towards the north of contour lines). Ridges correspond with high pressure and good weather while troughs denote low pressure and poor weather.

We’re finally turning the corner on warmer spring temperatures as the start to next week Monday-Wednesday will continue to feature high temperatures consistently in the low-mid 60s (about average). Dry and mostly sunny skies should also predominate as a ridge of high pressure (see above) builds in over our region.

 

NYC Weather Update – Apr 30, 2014

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Are you wondering why today is so cool with highs barely touching 50, but tomorrow is forecast to have high temperatures in the low 70s? It’s because there’s a warm front currently situated to our south. Let me clarify the two most common types of frontal boundaries:

  1. A warm front delineates a boundary where the airmass behind the front is significantly warmer than the airmass ahead of it.
  2. A cold front, not surprisingly, applies to the reverse situation and delineates a boundary where the airmass behind the front is significantly colder than the airmass ahead of it.

Currently, a warm front sits south of us, causing an onshore flow (easterly winds) off the frigid Atlantic Ocean. Why the easterly winds? Looking at the image below, you’ll see yellow contour lines that demarcate isobars of pressure. In the Northern Hemisphere, air flows counterclockwise around a low pressure center and clockwise around a high pressure center. The counterclockwise flow also applies to the frontal boundaries attached to a low pressure center.

In our present situation, the air flows towards the east (counterclockwise) south of the west-east oriented warm front (in red), and then from the east to west north of it. Hence, we are experience very cool conditions, and the moisture being funneled off the Atlantic Ocean into our region is fueling these steady showers.

Current surface analysis from the WPC with my overlay showing movement of the warm front to our south.
Current surface analysis from the WPC with my overlay showing movement of the warm front to our south.

We should actually see temperatures begin to rise overnight as the warm front pushes through the area. Once this occurs, we will be in what is referred to as the “warm sector”, which is an area that sits behind a warm front and ahead of an advancing cold front. This type of setup is favorable for the development of thunderstorms.

Therefore, Thursday will be a warm, cloudy day with high temperatures in the low 70s and a chance of showers and thunderstorms in the morning.

Friday, with the cold front having passed through, conditions will clear up and we’ll have a nice, sunny day, with temperatures near 70. There will be a chance for afternoon showers.

Saturday continues the trend of nice weather with another day in the upper 60s and mostly sunny skies. Again, there will be a chance for afternoon showers, especially inland where daytime heating can produce enough energy (and instability) to induce those showers.

One other note about today and tomorrow, and that’s the whopping headline numbers for how much rain is forecast to fall, with totals ranging from as high as 3″+ in the western portions of the Tristate to 1.5″+ in the east. This could easily cause flooding in poor drainage areas, small streams, and urban areas.Screen Shot 2014-04-30 at 1.50.54 PM

 

 

NYC Weather Update – Apr 28, 2014

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After a beautiful start to the work week, we are looking at a wet and cool mid-week before things clear up this coming weekend.

A low pressure center that is currently pounding the Midwest and Lower Mississippi Valley with hail, tornadoes, and severe storms will slowly move into the Great Lakes region. Once it does so, a strong area of high pressure situated over Quebec will prevent the low from making steady progress.

Therefore, Tuesday-Thursday will each see a chance for rain showers, in particular on Wednesday when a warm front associated with the aforementioned low pressure center makes its approach towards our region. Due to the long duration of the precipitation event and the possibility of heavy downpours Wednesday, there may be some localized small stream and urban street flash flooding.

Temperatures Tuesday and Wednesday will be quite cool with highs only in the mid 50s caused by onshore winds from the cool Atlantic waters flowing from the southeast and east ahead of the warm front. Once the warm front passes through on Wednesday night, temperatures will jump dramatically as we enter the warm sector behind the warm front and ahead of an advancing cold front. High temperatures Thursday could easily top 70.

A persistent low pressure center is forecast to track very slowly across the Great Lakes this week.
A persistent low pressure center is forecast to track very slowly across the Great Lakes this week.

Friday should see an end to this period of active weather as the high pressure over Canada weakens and finally allows this low to lift out of the area. Highs will be pleasant in the mid to upper 60s.

NYC Midweek Weather Update – Apr 23, 2014

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You can feel that cold front has passed, can’t you? A stiff northwest wind is ushering in an unseasonably cool air mass, and temperatures will be quite a bit lower than yesterday, with high temps about 10 degrees less than yesterday in the mid-upper 50s. Cloud cover should continue to diminish throughout the day.

Windy and cool weather persists Thursday – with high temperatures again struggling to hit 60. The breezy conditions and very dry air mass in place will lead to conditions conducive to the spread of wildfires.

GFS model's output for Friday
GFS model’s output for Friday

Our next shot of rain comes Friday, with a weak low pressure system moving over the Great Lakes and a trailing cold front. Forecast models suggest the system weakens as it approaches, hence lowering the chances for rain. If it rains, only light, showery precipitation is expected. High temperatures Friday will be slightly warmer, in the low 60s.

Saturday & Sunday – So far, we have a nice weekend on tap with mostly sunny skies and temperatures slightly below average in the low-mid 60s both Saturday and Sunday.

NYC Afternoon Weather Update – Apr 22, 2014

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Altocumulus clouds over the Empire State Building
Altocumulus clouds, preceded by cirrus clouds (earlier today and yesterday) are indicative of approaching frontal boundaries

Just a quick afternoon update for you all. It’s been quite a warm afternoon as warm air continues streaming into the area ahead of an approaching cold front. The frontal boundary is still quite a ways off, however, you can already see increasing cloudiness in the form of these altocumulus over the city. Some precipitation is beginning to show up over portions of western NJ. The atmosphere right over NYC is still on the dry side, with humidity recorded at LaGuardia Airport recently only at 47%, and dewpoint temperatures only 44 degrees. This should serve to limit the potential for convective activity and thunderstorms later in the day. In fact, as the area of precipitation to our west enters the region, showers may break up or scatter upon entering the relatively drier airmass.

NYC Weather Update – Apr 21, 2014

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Brilliant start to the week this Monday with comfortable and seasonable high temperatures in the low-mid 60s.

HPC forecast

Tuesday – A cold front will rapidly approach the region from the west. Ahead of this cold front, warm, moist Gulf air will flow in, allowing for high temperatures to edge close to 70. Given the moisture content and warm temps, there is some potential for enough instability in the atmosphere to support the growth of thunderstorms later in the afternoon hours. Some of these storms could produce small hail. Thunderstorms, should they form, would be mostly limited to inland areas west of NYC as the marine layer near the coast tends to exert a stabilizing influence.

Wednesday and Thursday will be similar weather-wise with high temperatures suppressed in the upper 50s to low 60s due to the influence of strong winds from the north and northwest in the wake of the departing cold front. We should see clear and sunny skies both days. Excellent conditions for radiational cooling on both nights will allow lows to drop into the upper 30s and low 40s across the region.

The next chance for rain will be this Friday into the weekend with another cold front moving in from the middle of the country.

NYC Weekend Weather Update – Apr 18, 2014

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SunnySkies

Sunny skies are your headline for weather this weekend. After what’s been a rudely cold interruption to spring, we’re returning to more seasonable temperatures and a calm weather pattern.

High pressure will dominate the area Saturday leading to sunny conditions with temperatures rising into the mid-upper 60s.

Sunday – high temperatures will be somewhat inhibited by onshore winds off the ocean as the high pressure center moves to our northeast and winds turn to the northeast and east.

Monday – the streak of pleasant weather continues after a cold start to the morning with highs again reaching the low 60s under sunny skies.

Next chance of precipitation will be Tuesday with a weak low pressure system and cold front moving in from the Great Lakes.