Tag Archives: cold front

NYC Weather Update – Apr 30, 2014

Flooding, NYC, Rain, Storms, Thunderstorms, Weather Update, Weekend, , , , , , , ,

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 15, 2014

NYC, Rain, Snow, Storms, Thunderstorms, Weather Update, , , , , ,

Wet, windy, and cold conditions will predominate our weather today. We’ve already hit our high temperature for the day and will see temperatures continue to plummet throughout the course of the day as rain and the attendant strong cold front moves in later this afternoon. Gusty winds in excess of 40mph, and some rumbles of thunder are possible in the stronger rain showers.

Untitled1

The heaviest rain will be this afternoon/evening, ending gradually overnight. Behind the cold front responsible for this heavy rain, a biting northwest wind will drop temperatures down into the low-mid 30s! Again, there is some small potential for snow flurries across NYC during the tail end of this storm.

Untitled

We could be looking at rainfall totals up to 2″ in the area, crazy wet for this time of year. Now, Wednesday, you’ll feel the impact of the passage of that cold front, as northwest winds will persist around 15-20mph, suppressing high temperatures in the mid-40s, much below the seasonal average.

Thursday and Friday will both be dry days with high pressure moving over the region, but high temperatures will remain below normal with an onshore breeze blowing in from the east and northeast. Overnight lows both days will remain quite cold in the mid-upper 30s. You thought you didn’t need that winter weather gear anymore, eh?

NYC Weather Update, Heavy Rain, Lunar Eclipse – Apr 13, 2014

NYC, Rain, Snow, Storms, Weather Update, , , , , ,

This extended period of pleasant weather is about to come to an abrupt halt early this week. We do have one more day of decent weather in store Monday, when high temperatures will again hit 70 under cloudy skies. You’ll notice increasingly humid conditions as a breezy south wind continues to pump Gulf moisture our way.

Tuesday gets nasty, showery rain should begin to overspread the area during the morning hours, however, the heaviest rain should occur later in the afternoon and evening hours. High temperatures will be significantly cooler Tuesday with highs around 60 due to the clouds and rain, and a stiff south wind increasing from 15mph to 25mph later in the day. As the cold front passes through the area, much colder air will flow in, overnight lows will be only in the mid 30s. There is a chance for snow flurries to occur during the night, although accumulation is unlikely.

NAM simulated radar imagery for 8PM EST Tuesday
NAM simulated radar imagery for 8PM EST Tuesday

 

Precipitable water forecast, for as much as 1.25-1.5" of rain across the area.
Precipitable water forecast, for as much as 1.25-1.5″ of rain across the area.

Wednesday you’ll feel the effects of the passage of the cold front. Although skies will be sunny, high temperatures will struggle to even top 50. The cool trend should continue until the end of the week, with highs Thursday again in the low 50s.

Sadly, due to the expected cloudy conditions, we’ll most likely not be able to see the upcoming lunar eclipse.

NYC Weekend Weather – Apr 4, 2014

NYC, Rain, Storms, Weather Update, Weekend, , , , , , ,

A chilly start to the weekend as we have cold easterly winds off the ocean, and a deck of clouds overhead. Rain will pick up in coverage and intensity as the day goes on, and it promises to be more or less a washout tonight.

Cloud deck building over the area, bulk of the actual rain is still off to our west over Central PA
Cloud deck building over the area, bulk of the actual rain is still off to our west over Central PA

Fortunately, the frontal system responsible for the rain will clear out of the area by Saturday. Sunny conditions will prevail, with winds turning from the east to the west and picking up to 15-20mph by the afternoon. High temperatures should top out around the mid-upper 50s, right about average for this time of year. Clear skies overnight Saturday will allow for good radiational cooling, and low temperatures could dip into the mid-upper 30s across the region.

Sunday promises to be the best day of the weekend, with high pressure firmly in control over the region. Sunny skies should allow for a mild day with high temperatures approaching 60.

The next storm system moves into the area later Monday into Monday night, with another chance for rain. Temperatures Monday could top 60 again with warm air flowing ahead of an approaching cold front.

NYC Weather, The Week Ahead: Return of the Polar Vortex

Noreaster, NYC, Snow, Storms, Weather Update, , , , , , ,

A most unwelcome weather pattern in store for the NYC area this coming week: the polar vortex will make its return! Refer to my earlier post about the Arctic oscillation providing conducive conditions for the influx of frigid air into the Northeast for an in-depth analysis on this.

Sunday – another day of fairly mild temps near 50 ahead of the first of several cold fronts. This frontal system has the potential to bring some rain showers along the coastal areas and NYC proper, with some accumulating snow in higher elevations north and west during the overnight hours Sunday. Overall conditions are not that favorable for a high impact event, so I wouldn’t expect anything too out of hand.

Monday – with the passage of the cold front, a cooler day is in store with highs in the mid 40s and winds picking up from the northwest, 15-25mph and gusts up to 35mph. Monday night, the chill sets in.

Tuesday – highs will only top out around freezing in the city as the polar vortex takes hold. A dry day with increasing clouds as we watch the next storm system move in Tuesday night.

Wednesday – all eyes turn to the North Carolina coast as forecast models suggest the development of an area of surface low pressure that then tracks northeast into offshore waters of Long Island. As is generally the case this far out, uncertainty about the storm track, snow-to-liquid ratio, and available moisture make it difficult to be certain as to the impact of this storm. At the minimum, would expect something like 1-3″ in the city with snowfall totals increasing eastward. High temps again struggling to make it above freezing.

Screen shot 2014-02-22 at 9.05.23 PM
Possible nor’easter in store Wednesday

The remainder of the week will see the polar vortex become entrenched with high temps only in the mid-upper 20s. At least there aren’t any more storms on tap until the weekend!

NYC Midweek Weather – Feb 19, 2014

NYC, Weather Update, Weekend, , , ,

Sorry about the lapse in posts! Tuesday ended up being a pretty active weather day with showers moving through the area (thank goodness temps were warm enough so that it wasn’t more snow).

Your weather forecast for this week: rain has already dissipated across the region. Thursday starts out as a mostly sunny day, and highs should top out in the low-mid 40s, slightly above average in the city. Clouds will build throughout the day as a frontal system approaches from the west. Overnight Thursday, chances of precipitation increase along with the passage of a warm front.

Friday, temps continue to increase to the mid 50s ahead of an approaching cold front. Expect a mostly cloudy day, with showers and the potential for a line of stronger thunderstorms accompanying the frontal boundary passing in the afternoon.

Things dry out this weekend, with temps falling back to the mid 40s Saturday and Sunday. Another reinforcing cold front passes through Sunday, dipping high temps in the beginning of next week into mid 30s, below the average of around 40. No major storms on the horizon past Friday!

Screen shot 2014-02-19 at 7.56.09 PM

Nor’easter Update – 7PM Feb 13, 2014

Noreaster, NYC, Snow, Storms, Weather Update, , , , , , , ,

We’ve enjoyed a period of relative calm as the dry slot (orange outlined in purple below) mentioned earlier pushed in over the area, leading to a lull in heavy precipitation and more of misty drizzle. However, these conditions will not last as the nor’easter will gain strength overnight.

The mid-upper level low that is responsible for bringing in this dry slot will gradually move over the surface low pressure center currently located offshore of central NJ. Once the low pressure systems stack up, the surface low will rapidly deepen. As this occurs, the warm front extending from the nor’easter’s core will rotate to the NW of the storm center.

This frontal boundary will push moist air (greens and yellows in this image below) ahead of it, leading to the formation of a new heavy band of snow – technically a “frontogenetically induced deformation band”. Within this band, snowfall rates may hit 1-2″ per hour, and an additional 4-8″ could accumulate across the region (except eastern Long Island). Interior areas where temps have remained cold could see an additional 8-12″ overnight.
Screen shot 2014-02-13 at 7.03You can already see in the radar image below that precipitation is already filling back in across southern NJ and the WAS-BAL-PHL corridor.

Screen shot 2014-02-13 at 7.03.52 PM