Tag Archives: wind gusts

NYC Blizzard Update – Jan 26, 2015

A major nor’easter will be bringing a high impact blizzard throughout the NYC region tonight through Tuesday midday. Beginning this evening, snowfall will increase in coverage from south to north. Periods of heavy snow are expected with snowfall rates of 2-4″ per hour, with thundersnow occurring in the heaviest bands of snow. Extended periods of high winds, with sustained winds at least 35mph and gusts over 40mph (even up to 60mph) will lead to blowing and drifting snow, blizzard conditions, and near-zero visibility. Widespread snowfall totals of between 18″-24″ possible throughout the area, with locally higher amounts.

Snowfall Totals

Since yesterday afternoon, forecast models have backed off a bit on the overall total accumulations. At this point yesterday, the quantitative precipitation forecast (liquid water equivalent total) was as high as 2.7-2.8″ and broadly over 2.5″ across much of the area. As seen below, those liquid water equivalent numbers have gone down by about half an inch.

Liquid water equivalent forecast totals
Liquid water equivalent forecast totals

This decrease in overall precipitable water has led to a corresponding downgrading of the overall snowfall totals. Using a 12:1 snow to water ratio, a drop in precipitable water by half an inch translates to a decrease in snow totals by 6″. Indeed, the National Weather Service has decreased the likely totals from 27″+ for many places to closer to 20-22″.

Snowfall accumulation total forecast
Snowfall accumulation total forecast
Highest probabilities for snowfall totals in excess of 18" during the 48 hour period ending 7AM Wednesday now rests over Southern New England, with the bullseye setting up right over Boston and immediate suburbs.
Highest probabilities for snowfall totals in excess of 18″ during the 48 hour period ending 7AM Wednesday now rests over Southern New England, with the bullseye setting up right over Boston and immediate suburbs. Here in NYC, we are in the range of 30%-50% probability of receiving over 18″ – notice how abruptly the probability goes up as you go further north and east.

Timing

Light snow has already begun falling over the area, however the heaviest snow will not be occurring until after 8PM tonight. The most intense period of this storm is expected overnight tonight, as a deformation banding feature forms and begins moving slowly inland. Based on the simulated radar loop below from the NAM (North American Model), the peak intensity of snowfall looks like it will occur between 1AM-7AM overnight into Tuesday. Snow appears to taper off over NYC by 1PM tomorrow.

It does appear that a secondary set of banding snow will linger over eastern areas of the metro region throughout the afternoon Tuesday until as late as 4PM tomorrow.

By the way, part of the reason the main area of highest snowfall totals is now shifting to Southern New England and Boston is because it is anticipated that these areas will see moderate to heavy snow for much longer than we will here.

NAM model simulated radar output for this storm
NAM model simulated radar output for this storm

Impacts

Snow, heavy at times, beginning in earnest this evening especially after 8PM. Some thundersnow possible, with the most intense snow occurring overnight. Strong sustained winds up to 35mph with gusts over 40mph and as high as 60mph will lead to blizzard conditions with blowing and drifting snow cutting visibilities down to near zero.

Caveats

Forecasters have been pointing out that there continues to be some slight disagreements between different models even though this storm is imminent. Snowfall total forecasts for storms like this one are notoriously difficult to predict with a high degree of accuracy prior to the event itself. This is due to the fact that the exact placement, movement, and intensity of the deformation banding feature on the northwest flank of the low pressure center is hard to foresee until the storm is ongoing. With snowfall rates as high as 2-4″ per hour within this banding feature, a difference of a couple hours under it could translate to 4-8″ difference in overall accumulation in any one location. Same thing with location, as one location that misses the most intense portion of the banding feature could easily miss out on 6″+ in total accumulation. Furthermore, a slight change in the thermal profiles within this type of storm could alter the snow to water ratio to be higher, and of course, a change from 12:1 to 15:1 would result in a dramatic difference in totals.

NYC Weekend Weather – Oct 18, 2014

We get one last day of late summer-like temperatures today before autumn comes back with a vengeance. A cold front has already passed through the city and you can already notice the winds beginning to shift to the northwest. This will herald a much cooler temperature trend. For the remainder of today, we can expect temperatures near 70 with some clouds building behind the front. There could be a sprinkle or two but nothing serious.

Sunday forecast map
Sunday forecast map

Sunday will be noticeably more cold with high temperatures struggling to hit the mid-50s and with a gusty northwest wind. Gusts could top 30mph at times with sustained winds 15-25mph. Overnight lows into Sunday and Sunday night will be downright chilly in the 40s. Some interior areas could see frost Sunday night.

Monday the winds will abate as the pressure gradient between the departing cold front and high pressure to the west eases. Temperatures will remain cool at only around 60.

Tuesday and into later this week we will see the impact of a frontal system that moves through from the Great Lakes and develops as a coastal low off the Mid-Atlantic. Current models seem to suggest that this low will linger for a few days offshore, so we could see multiple rounds of rain as bands rotate around the storm center.

gfs_namer_078_1000_850_thick

 

Winter Climate Outlook

The Climate Prediction Center has released its 3 month temperature and precipitation long range outlooks for the months ahead. As you will see, CPC has the NYC area in a zone of 33% chance of seeing a wetter and warmer than average winter. Call it a hunch, but I still think we’ll get a couple nasty Nor’easter type blizzards. Warmer than average of course doesn’t imply we won’t get freezing temperatures. A slightly warmer atmosphere would allow for more moisture and energy for coastal storms to feed off.

temp precip