Category Archives: Outside of NYC

2014 Atlantic Hurricane Season Outlook – Jun 2, 2014

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Yesterday marked the official start to the 2014  Atlantic Hurricane season (June 1 – November 30), so this is as good a day as any to talk about the forecast for this season. The graphic below shows the National Hurricane Center’s official 2014 Hurricane Season Outlook that was released last month. This forecast is probabilistic, i.e. it gives a range of numbers and chances that this season will either exceed or fall below the forecast total.

National Weather Service National Hurricane Center's forecast summary for 2014
National Weather Service National Hurricane Center’s forecast summary for 2014

Explanation

In the NHC’s parlance, Named Storms refers to tropical or subtropical storms that produce sustained winds in excess of 39mph (this is the criteria for a tropical or subtropical storm) at any point in their life cycle. Hurricanes refer to the named storms that end up producing sustained winds in excess of 74mph, and Major Hurricanes refer to hurricanes that make it to Category 3 or higher on the Saffir-Simpson classification scale. Accumulated Cyclone Energy (ACE) is a rough measure for the overall intensity of a tropical cyclone and is calculated as follows:

The ACE of a season is calculated by summing the squares of the estimated maximum sustained velocity of every active tropical storm (wind speed 35 knots (65 km/h) or higher), at six-hour intervals. Since the calculation is sensitive to the starting point of the six-hour intervals, the convention is to use 0000, 0600, 1200, and 1800 UTC. If any storms of a season happen to cross years, the storm’s ACE counts for the previous year.[2] The numbers are usually divided by 10,000 to make them more manageable. The unit of ACE is 104kn2, and for use as an index the unit is assumed. Thus:

\text{ACE} = 10^{-4} \sum v_\max^2

where vmax is estimated sustained wind speed in knots. (Source – Wikipedia)

Hence, a high ACE number corresponds to a very intense storm or storm(s).

Outlook

As you can see from the above image, the NHC is calling for a normal to slightly below normal season for the Atlantic with 8-13 named storms, 3-6 hurricanes, and 1-2 major hurricanes. Despite the fact that the forecast calls for a normal to below normal season, it only takes one landfalling hurricane or major hurricane to inflict serious damage to a coastal area. Even with just tropical storms, huge amounts of rain can fall leading to major flooding.

El Niño’s Impact

One of the reasons why the forecast is calling for a normal to below normal season is that it appears an El Niño event is initiating and forecast to increase in intensity. El Niño refers to a phenomenon that occurs when the ocean surface of the Eastern Pacific Ocean becomes abnormally warm (La Niña refers to the opposite effect, when the Eastern Pacific cools abnormally).

This anomalous warming of the Eastern Pacific leads to all sorts of global climate impacts. Among these is a noticeable decrease in the incidence of Atlantic hurricanes, and an increase in the number of Eastern Pacific hurricanes. In fact, you can see in the same outlook, NHC is calling for a near normal to above normal hurricane season for both the Eastern and Central Pacific. The reason behind this is simple: hurricanes feed on heat to grow, so the warmer the water below a storm, the greater the potential for that storm to grow.

Map of sea surface temperature anomalies as of 6/2/2014
Map of sea surface temperature anomalies as of 6/2/2014

As you can see from the map above, there is a region of abnormally warm sea surface temperatures extending west into the Eastern Pacific from the coast of Ecuador and Peru (yellow & orange). At the same time, there is a large area of much cooler than normal sea surface temperatures extending from the west coast of Africa into the Central Atlantic (light and dark blue). Incidentally, these cool temperatures off the coast of Africa are in a region that is notable for spawning some of the strongest hurricanes, the Cape Verde type hurricane. Clearly, if this temperature anomaly keeps up, it will serve to inhibit the formation of tropical storms and hurricanes in that region.

Memorial Day Weather – May 23, 2014

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Just a quick update on your Memorial Day Weekend weather.

Saturday, still looks like there’s a chance for showers and isolated thunderstorms in the NYC metro area in the afternoon hours of Saturday. High temperatures will be mild in the low 70s under mostly cloudy skies.

In Oberlin, temperatures will be around the same in the low 70s, but skies will be clear and sunny.

Sunday will see clearing skies for the NYC metro area and warmer temps in the upper 70s and even low 80s particularly inland. Cooler at the shore with some (especially the south facing shore of  Long Island) with a sea breeze and highs in the low-mid 70s. Still, an all around excellent beach day.

Oberlin will remain sunny with clear skies and highs in the upper 70s.

Monday will be the warmest day of the weekend with highs in the low 80s in the NYC area and mostly sunny skies.

Oberlin may see some clouds building in over the course of the day with an approaching storm system, but not expecting any rain. Highs in the upper 70s.

Visibility for Tonight’s Meteor Showers

Again, it is looking like the NYC area will miss out on the chance to see these meteor showers with cloud cover expected to be widespread. Good viewing for Oberlin though!

Cloud cover forecast for select locations (blue line). Red box indicates best viewing window for the meteor showers.
Cloud cover forecast for select locations (blue line). Red box indicates best viewing window for the meteor showers.

NYC Weather Update – Meteor Shower Visibility – May 22, 2014

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Today was an active weather day for the NYC area, particularly over New Jersey and upstate. A funnel cloud was spotted up in the Albany area, and a few severe thunderstorms exhibiting strong rotation (the strongest thunderstorms-supercells-often feature a single internal circulation called a mesocyclone)  formed ahead of a cold front that’s still slowly pushing its way over western New Jersey. Some of these storms produced large hail over interior parts of the NYC metro area.

Friday there will continue to be a risk for thunderstorms during the afternoon hours, otherwise it should be a mostly cloudy day with his right around 70.

In Oberlin, tomorrow should see skies gradually clearing with his in the mid-upper 60s.

GFS model output for 5PM EDT Friday, May 23, 2014
NAM model simulated radar image for 5PM EDT Friday, May 23, 2014
Saturday still cannot rule out a lingering risk of thunderstorms and showers in the PM hours on Saturday as shortwaves (impulses of energy) continue to spin around the backside of the departing low pressure system that’s brought us this period of unsettled weather. Highs will again be around 70, depending on if breaks in clouds develop.
By Saturday, skies should clear out over Oberlin, allowing temperatures to rise into the low 70s.
GFS model output for 2PM EDT Saturday, May 24, 2014
NAM model simulated radar image for 2PM EDT Saturday, May 24, 2014

Sunday and Monday are still on track to be the best days of the Memorial Day weekend with temperatures in the upper 70s Sunday and low 80s Monday.

Camelopardalis Meteor Shower Visibility

Now about that meteor shower, will you be able to see it in NYC? Sadly, the answer is probably not, due to a forecast that calls for mostly cloudy skies. With cloudy conditions, light pollution is amplified as the light cast off from the city gets reflected back down even more. It will be a different story for Oberlin, though, where skies are forecast to clear due to the influence of building high pressure well before the anticipated peak of the meteor showers.

NWS hour by hour graphical forecasts. Red boxes indicate the forecast peak for the new Comet 209P/LINEAR Camelopardalis meteor shower.
NWS hour by hour graphical forecasts. Red boxes indicate the forecast peak for the new Comet 209P/LINEAR Camelopardalis meteor shower. The blue line represents the percentage of the sky that’s forecast to be covered with clouds. 

NYC Nowcast – Afternoon Tstorms – May 22, 2014

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The Storm Prediction Center in Norman, OK has placed western portions of our region under a slight risk for severe weather this afternoon, with the primary threat being damaging winds and hail.

UntitledMid-upper level conditions are favorable for the development of thunderstorms with some rotating updrafts. Unidirectional winds at various levels, as well as wind speed shear, could impart enough rotation on storm cells to cause marginally severe wind damage and some hail. The highest potential will be over Eastern Pennsylvania and New Jersey where sufficient solar heating could produce CAPE (Convective Available Potential Energy, measured in joules per cubic kilogram) values of between 1000-1500 J/kg^3.

Storm Prediction Center in Norman, OK has placed western portions of our region in a slight risk area for severe weather this afternoon
Storm Prediction Center in Norman, OK has placed western portions of our region in a slight risk area for severe weather this afternoon

A small cluster of thunderstorms is already initiating along the western New York/Pennsylvania border ahead of a weak cold front. These storms should expand in coverage and increase in intensity as skies are clear ahead of the frontal boundary, allowing for a good influx of energy for storms to feed off of. The current thinking is that isolated severe thunderstorms reach our region by around the 4-6PM time frame. The chances of these storms remaining severe over NYC and coastal areas is low, since there will be a stabilizing influence from the cool marine layer offshore.
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New Meteor Shower (!!) & Memorial Day Weekend Special Weather Update – May 21, 2014

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Memorial Day Weekend Forecast

Weather conditions will gradually deteriorate through the course of the day today as an approaching storm system draws closer to our area. Cloud coverage, scattered showers, and possible thunderstorms associated with a warm front should increase in coverage during the course of the day. High temperatures should be on the mild side in the mid-70s.

Thursday – as of now, the National Weather Service calls for the aforementioned warm front to approach but not clear our region by Thursday morning. As such, cooler southeast and easterly winds off the ocean will keep temperatures on the cool side with highs only in the mid-upper 60s. There will be a persistence chance for showers and thunderstorms as multiple impulses of energy ride up and along the frontal system, with a break probably occurring between early Thursday morning and later Thursday afternoon/evening.

Friday – in NYC, although the warm and cold fronts associated with this latest storm are forecast to have cleared through the area by Friday, an upper level low situated over the Canadian Maritimes will continue to allow impulses of energy (shortwaves) to rotate into our area providing the spark for a continued chance of showers and thunderstorms, especially Friday afternoon and evening. This upper low will be slow to move east due to a strong blocking “omega” high pressure center located over the central North Atlantic. High temperatures will again be around the upper 60s.

For Oberlin, conditions will begin to improve earlier with the chance of rain ending by Thursday, partly sunny skies Friday with gradual clearing and highs in the upper 60s.

NAM output simulated radar image for Friday at 2PM EDT
NAM output simulated radar image for Friday at 2PM EDT
GFS model output of 500 mb heights and absolute vorticity for Friday at 2PM EDT
GFS model output of 500 mb heights and absolute vorticity for Friday at 2PM EDT

Saturday – we’ll see an tenuous area of high pressure trying to build in from our west. However, there may still be a marginal chance of PM showers. Otherwise, expect gradually improving conditions with temperatures climbing back up into the low 70s.

Sunday and Monday (Memorial Day) – These will be the best days of the weekend with dry, mostly sunny, and warm conditions. High temperatures will continue to climb into the mid-upper 70s Sunday and possibly topping 80 Monday (this applies to both Oberlin and NYC). Next chance at rain will be Tuesday.

A New and Spectacular May Meteor Shower? – About Comet 209P/LINEAR & Camelopardalis 

A friend of mine brought to my attention that a newly discovered and possibly brilliant meteor shower is forecast to take place in the early morning hours of Saturday, May 24th.

In brief, Earth is forecast to pass through the debris trail of a comet “Comet 209P/LINEAR” (discovered in 2004) during the overnight hours Friday into Saturday. Researchers are forecasting that the debris trail Earth passes through is one that has accumulated dust from as early as 1800 to 1924. As such, expectations are that we could see about an average of 200-400 meteors an hour (some estimates call for a meteor storm of 1000 meteors an hour!), i.e. between about 3-7 meteors per minute. Furthermore, the setup for this event is such that Southern Canada and the East Coast of the U.S. are ideally positioned to view this event. In the image below, the red line represents the forecast position of the radiant line (point from which meteors appear to emanate and where you would see the highest number of meteors), note that this line runs almost direct over Washington DC. Also, notice that the moon is in waxing gibbous phase, reducing its potential to overpower the meteor shower.

Screen Shot 2014-05-20 at 10.02.43 PM

Timing and Visibility

The forecast zenith of this meteor shower is between 2AM-4AM Eastern Daylight Savings Time on Saturday, May 24th. Right now, the forecast for this time window calls for mostly cloudy skies over NYC as well as points east and north (i.e. New England). Partly cloudy skies are forecast the points further south and west (i.e. along the Jersey Shore, Washington DC/Northern, Eastern Virginia, Western Pennsylvania), with the best viewing conditions being in the DC metro area and Eastern Virginia where mostly clear skies are forecast. A word of caution: cloud cover forecasts even this close to the day of are notoriously difficult to pin down due to the fact that even small changes in initial conditions can lead to large shifts in a forecast. However, with high pressure building over the east coast throughout the course of the weekend, we should have generally good chances to view this shower.

My recommendation is that you go check this out in an area with minimal light pollution if  you can. I think we’re in for a what I hope will be a good show!

Where to Look

The radiant point for this forecast meteor shower will be situated in the relatively obscure constellation Camelopardalis (named by the Romans for a hybrid animal that looks like both a camel and leopard, now known as a giraffe). As you’ll see below, this constellation is located slightly below the North Star (Polaris), and a bit to the right of the Big Dipper.

You can read a more in-depth analysis of this meteor shower here. I’ve grabbed and edited a couple images from this entry.

Screen Shot 2014-05-21 at 6.21.47 AM

 

NYC Weather Update | First Look @ Memorial Day Weekend – May 19, 2014

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All preliminary indications are that this Memorial Day weekend should see fairly good weather, as you can read in the detailed discussion below. First, for your work week forecast:

For the remainder of the day today, there is a slight chance of a pop up shower or thunderstorm as cumulus clouds continue to build. This risk will cease as the sun begins to go down, and cuts off the heat source for these clouds. Overnight lows will fall into the low 50s in the city (not as cold as last night, as some clouds are expected to stick around early and stunt the potential for good radiational cooling), with 40s in the interior.

Tuesday will be the best day of the week, with high pressure briefly building in from the west. This will lead to mostly clear skies and warm temperatures in the upper 70s (also partially due to an incoming warm front).

Beginning Wednesday, we will see a period of unsettled weather as a relatively slow moving storm system approaches. This system will develop over the Great Lakes, and a warm front is forecast to be approaching our area during the day Wednesday. There will be an increasing chance of showers throughout the day as the warm front nears, with the best chance for precipitation in the late evening and overnight hours. Temperatures will be slightly lower than Tuesday in the mid-70s.

HPC's Day 3 forecast for the US
HPC’s Day 3 forecast for the US

Thursday there is a bit of uncertainty regarding the eastward progression of the warm front mentioned above. If the warm front has already passed over us, then we’ll be in the warm sector between the warm front and approaching cold front. This would lead to favorable conditions for some thunderstorms. Otherwise, we would expect mostly cloudy skies and a chance for more showery precipitation. High temperatures will be similar to Wednesday.

Friday, with the cold front Thursday having moved through and high pressure slowly building in, we would expect a good day weather-wise. However, as you see in the following image, the center of the now occluded low pressure is forecast to remain nearly stationary off the coast of New England. This is due to a blocking high over the North Atlantic (not pictured). Therefore, a chance of showers is forecast for both Friday and Saturday, with skies gradually clearing from mostly cloudy to mostly sunny Saturday. High temperatures Friday is forecast to be in the low 70s.

Screen Shot 2014-05-19 at 1.52.00 PM

Now, the all important initial weekend forecast: as depicted above, high pressure building over the Great Lakes should progress generally southeast towards the Carolinas during the weekend. This should translate into improving weather each day during the weekend and increasing temperatures. Saturday, Sunday, and Monday should see high temperatures climbing from the low to mid 70s, and skies clearing to become mostly sunny.

For those of you reading this forecast who are traveling towards Oberlin and points west, the forecast for those parts is actually even better than for New York City in terms of sunshine, although, as you know temperatures will be slightly cooler in Ohio than here.

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.

 

Deep South Severe Weather Outbreak – Apr 28, 2014

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A major severe weather outbreak is currently underway for portions of the Deep South from Louisiana up through Tennessee, extending east from the Mississippi to western Alabama. As you can see in this satellite image, there are numerous supercell thunderstorms with high cloud tops piercing into the tropopause, indicative of extremely strong updrafts. Low level helicity (a measure of the vorticity and spin imparted on the air) is also high, along with abundant moisture and convective available potential energy (CAPE) will continue to fuel dangerous storms capable of spawning multiple tornadoes, damaging wind gusts, and severe hail.

Major severe weather outbreak over the Deep South viewed from space
Major severe weather outbreak over the Deep South viewed from space

NYC Weekend Update & Severe Weather in the Plains

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The atmosphere over the area the past couple days has been both exceptionally dry and abnormally cool. This trend will end Friday with the approach of a cold front and low pressure system. Because the air mass currently in place is so dry, it will be difficult for the air to moisten at the outset Friday. Thus, forecasters are calling for a mostly dry day with increasing cloud cover, and rain showers moving in over the course of evening and overnight hours. High temperatures Friday will remain in the low 60s.

North American Model simulated radar image for Saturday @ 2PM EST
North American Model simulated radar image for Saturday @ 2PM EST

Saturday will remain a cloudy day with the chance for showers diminishing but still present. As the simulated radar image above suggests, there should be a break in precipitation between Friday evening and Saturday afternoon. However, it does appear that there is enough upper air support for afternoon showers and even some scattered thundershowers are possible Saturday afternoon. High temperatures will be warmer in the upper 60s. Skies should gradually clear once showers pass through, so the latter half of the day will still be sunny.

Sunday temperatures will cool off again with the passage of the cold front Saturday, however, sunny skies will return with high pressure building. Temperatures should be pleasant in the low 60s. Monday looks at this point to be a clone of Sunday.

 

Severe Weather in the Great Plains Sunday

It’s definitely severe weather season at this point in the Plains States and Tornado Alley. These areas have been repeatedly pummeled the past few days by severe hail storms. This weekend promises to be no different. As you can see below, a strong low pressure center is forecast to develop in the lee side of the Rockies Sunday with central pressure as low as 988mb.

Meanwhile, in the upper atmosphere, a vorticity maximum (see below) is forecast to form, with an area of strong divergence just to its east near the forecast center of the surface low. Upper level winds will be largely unidirectional. These are all ideal conditions for a severe weather outbreak. As a result, a wide swath of the Plains States from central Texas through Oklahoma, Kansas, and into Southeastern Nebraska have been placed under a Slight Risk area for severe weather by the Storm Prediction Center.

Note the strong low pressure center forecast to develop over the lee side of the Rockies - central pressure of 988mb
Note the strong low pressure center forecast to develop over the lee side of the Rockies – central pressure of 988mb
Upper air charts for Sunday afternoon. Note the strong vorticity maximum (area of dark red) over eastern Colorado.
Upper air charts for Sunday afternoon. Note the strong vorticity maximum (area of dark red) over eastern Colorado.

 

Cool gif – Severe Thunderstorms in the Plains, Apr 3, 2014

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Check out this satellite loop of a line of severe thunderstorms over eastern Oklahoma extending northeast into western Missouri. You can see the classic telltale signs of explosive thunderstorm growth here. Notice how at the outset, the line of clouds near the center of the frame are relatively thin, but then balloon out as time goes by. What’s happening here is that the cumulonimbus (thunderstorm) clouds along this line are growing so rapidly that they are hitting the top of the troposphere. Since water vapor has a difficult time penetrating into the stratosphere, it gets forced out laterally instead. Indeed, the Storm Prediction Center in Norman, OK has issued a mesoscale discussion, along with severe thunderstorm warnings and tornado watches for much of the area.

storm