Monthly Archives: June 2014

NYC Weather – Independence Day – Jun 30, 2014

June 30, 2014NYC, Outside of NYC, Rain, Storms, Thunderstorms, Tropical/Hurricanes, Weather Updateheat wave, hot weather, independence day, july 4 weather, national hurricane center, new york weather, nhc, nyc, nyc weather, nyc wx, thunderstorms, tropical depression, tropical weather, weatherLei Zhao

Lots to talk about on the last day of June, which brings with it the opening of a warm trend and possible mini heat wave. A stubborn low pressure system over the Plains States is pushing warm and humid air from the Gulf ahead of a leading cold front. As a result, Tuesday will feature warm, muggy conditions with highs in the upper 80s, maybe even touching 90.

Wednesday, that frontal boundary comes closer, and with the heat and humidity in place, we’ll have the right conditions for some pop-up showers and thunderstorms later in the day. However, coverage is expected to be widely scattered. Highs again will be in the upper 80s, possibly hitting 90.

Thursday -as the cold front makes its approach in earnest, a pre-frontal trough is forecast to develop, and this should help spark off more widespread showers and thunderstorms than on Wednesday. Expect high temperatures to be somewhat lower due to cloudy skies, but still warm and humid in the mid to upper 80s.

Friday (Independence Day) – A lot of weather forecasters were saying earlier this weekend that July 4th was going to be a nice day with no rain. Sadly, that doesn’t appear to be the case now, as the timing of that pesky cold front has slowed down somewhat. This does mean you could see rain and or thunderstorms during the day Friday and into Friday night, but at least the heat will break somewhat with temperatures only around 80.

Cold front right on top of us Friday could rain on your July 4th plans.

First Named Tropical System of the Atlantic Hurricane Season?

Over the weekend, a disturbance off the east coast of Florida began to show signs of increasing organization, to the point that the National Hurricane Center now gives the system an 80% chance of forming into a tropical depression in the next 2 days. If it does, then it will become the first named tropical system of the 2014 Atlantic Hurricane Season.

High resolution satellite image of the incipient tropical system off the east coast of Florida

Why does this matter to us? Well, as it currently stands, it appears this tropical system/possible storm may impact our weekend weather here in the Northeast. Some forecast models have this storm moving to the near offshore waters of the Northeast by Saturday (indicated in pink circle below). This could bring the potential for rain to parts of the Northeast, in particular, New England. Fortunately, it doesn’t appear as though this storm will strengthen much (below you see the lowest pressure at the center of 1012mb, for reference, normal pressure at sea level is 1013mb), and in fact, it will likely make a transition to becoming an extratropical cyclone/storm rather quickly after it moves north of Florida. Still, it’s a bit too early to tell just where this storm will go, so it bears monitoring.

Possible storm tracks as illustrated by GFS ensemble members — Possible storm tracks as illustrated by several different forecast models

NYC Weather Update – Jun 25, 2014

June 25, 2014NYC, Thunderstorms, Weather Update, Weekendnws, nyc, nyc wx, spc, storm prediction center, thunderstorms, weat, weather, weekend weather, wxLei Zhao

A warm and humid day out there in the Tri-State this afternoon. You can feel it’s potential thunderstorm weather. In fact, the Storm Prediction Center has issued a mesoscale discussion (analysis of weather conditions conducive to severe weather on a medium scale – 10km-500km). Very moist air, warm temperatures, combined with a slowly approaching cold front set the stage this afternoon for possible development of strong to marginally severe thunderstorms. This is especially the case over inland areas, as depicted below. In general, expect a line of showers and maybe a couple thunderstorms to pass through the area later this evening into the overnight areas when the cold front finally pushes through.

Screen Shot 2014-06-25 at 2.08.45 PM — Storm Prediction Center Mesoscale Discussion http://www.spc.noaa.gov/products/md/md1147.html

Thursday – there could be some lingering showers in the AM, but things will dry out quickly and clouds will slowly give way to sunnier skies. High temperatures will be a bit cooler than today, in the upper 70s to low 80s.

Friday – a splendid end to the work week with mostly sunny skies and comfortable, less humid conditions and temperatures in the low 80s.

Canadian high pressure will move slowly to our east, ushering in some warm air and calm skies

Saturday and Sunday will both again feature excellent weather as a high pressure system works its way over our region following this cold front. As the high pressure slowly slides to the southeast, it will bring us southerly winds that will usher in another period of warm and humid weather. Saturday will be the better day of the weekend with high temperatures in the low-mid 80s and lower humidity. By Sunday, temperatures will begin ramping up into the mid-80s with an increase in humidity. Early next week, we’ll be looking at a continuing warming trend with high temperatures in the mid-upper 80s Monday and near 90 Tuesday before our next chance of rain.

NYC Weather Update – Jun 19, 2014

June 19, 2014NYC, Rain, Weather Update, Weekendbeach weather, nyc, nyc wx, rain, sunny, warm weather, weather, wxLei Zhao

We’re going to get some welcome relief to the brief warm spell we’ve had so far this week, as a large area of showers over Pennsylvania will move east slowly during the course of the day today. You can already feel a change in the air, with temperatures generally 10 degrees (or more) cooler this morning than at this time yesterday.

Friday – the cold front responsible for bringing us showers today will move through to our south and usher in a cool, dry air mass from Canada in its wake. High pressure will then build over Quebec and dominate the area through at least Monday. Temperatures will be pleasant near 80 with mostly sunny skies.

Saturday and Sunday – the pattern of pleasant, mild and seasonable temperatures will set the stage for the formal beginning of summer (Saturday, June 21st is the day of the summer solstice, the longest day of the year). Temperatures both days will range in the upper 70s to low 80s, with low humidity and sunny skies.

Monday and Tuesday – this stretch of nice weather continues into the beginning of the next work week, with high pressure slowly moving off to the east, but still warm and nice. Temperatures again will be in the low 80s with mostly sunny skies.

Our next chance at rain will come Wednesday with a cold front associated with a two storms systems that will merge (one over the Mississippi Valley, the other moving from Ontario).

NYC Nowcast – Jun 13, 2014

June 13, 2014Nowcast, NYC, Rain, Severe Weather, Thunderstormscape, friday, nowcast, nyc, severe thunderstorms, severe weather, severe wx, thunderstorms, weather, wxLei Zhao

You’ve felt the air warm up and become more humid as the warm front that brought our first round of rain passed through earlier today. Now, we’re getting set for a second round of heavy showers and thunderstorms associated with a pre-frontal trough that’s slowly progressing east towards the area from Eastern Pennsylvania.

Ahead of this line of showers and thunderstorms, the air has destabilized readily with the ample sunshine earlier this afternoon. CAPE (Convective Available Potential Energy – a measure of how much fuel there is for thunderstorms to feed off of) is between 1000-1500 J/Kg over Northeastern New Jersey and NYC. This should allow for this line of storms to hold up and perhaps strengthen before hitting NYC. In fact, a couple sever thunderstorm warnings have already been posted for cells over Northeastern New Jersey.

NYC Weather Update + World Cup Weather! Jun 12, 2014

June 12, 2014NYC, Outside of NYC, Rain, Thunderstorms, Weather Update, Weekendbelo horizonte, bermuda high, brasilia, brazil, cold front, cuiaba, curitiba, fifa, football, fortaleza, high pressure, manaus, natal, porto alegre, recife, rio de janeiro, salvador, sao paolo, warm front, weekend, world cup, worldcupLei Zhao

Two part update today – first to address NYC weather, and then to discuss the outlook for next week down in Brazil during the opening week of the FIFA World Cup.

Friday – the work week closes out with the wettest day so far with a warm front passing through tonight, and then a cold front following shortly thereafter tomorrow. This will translate to mostly cloudy skies, with a round of rain tonight, followed by a period of scattered rain showers and thunderstorms, and then ending with another round of heavier rain and thunderstorms Friday night. Temperatures will be much warmer than today after the passage of the warm front with highs in the low 80s.

Screen Shot 2014-06-12 at 2.56.59 PM — NAM model output simulated radar image for Friday morning @ 5AM

Luckily for us, the cold front passes through quickly Friday and leads to a splendid stretch of weather beginning with a sunny, mild and pleasant Saturday and Sunday. High temperatures will be in the low 80s both days under clear skies. This is due to an area of high pressure building in from the west behind the cold front.

Warm Spell Next Week

This same high pressure area will track to the southeast during the weekend. By mid-week next week, the high pressure center will be offshore of the Southeastern US, and link up with the Bermuda High. As you may know, Bermuda Highs typically cause hot, humid weather in our region, and this will be no exception. Temperatures will steadily increase each day Monday, Tuesday, and Wednesday, such that by Wednesday, we’ll be looking at highs in the mid-upper 80s. This area of high pressure will also block any precipitation from impacting us until at least next Thursday into Friday when a low pressure system with a trailing cold front is forecast to pass through the Great Lakes.

World Cup Weather

The World Cup is upon us!!! With opening kickoff just a few minutes away, I thought it’d be useful to talk about weather down in the host country, Brazil. As you know, it’s currently autumn in the Southern Hemisphere, but you wouldn’t be able to tell based on the forecast high temperatures for most of the Brazilian cities with games going on next week. High temperatures will range from the upper 70s-upper 80s depending on where you are.

The highest temperatures will be in Manaus, which not surprisingly sits in the Amazon basin. That’s also the city where you can expect the highest likelihood of rain and thunderstorms. Most of the coastal Brazilian cities that are hosting games will have pleasant conditions and high temperatures in the low 80s this week. Fair weather should be the story as high pressure will tend to dominate this week.

GFS model output for S. America on Tuesday

For your reference, here’s a map with dates of games being held in each host city. I’ll be keeping an eye on the weather and posting any relevant updates as they come up.

Really Cool Image – Von Karman Vortex Street

June 12, 2014Cool Images, Outside of NYCbaja california, cloud street, hpc, isla de guadalupe, nws, satellite, satellite images, von karman, vortex street, vortext street, wpcLei Zhao

When air flows are blocked by obstructions, such as buildings, trees, mountain ranges, or in this case, a mountainous island, all sorts of interesting effects can occur. Just as flowing water hitting a rock will form swirling eddies, flowing air has the same tendency, which you can plainly see int he image above. We’re usually not able to see these effects so vividly, though you’ll often feel them in the form of turbulence.

From the Facebook page of the National Weather Service Weather Prediction Center:

One of the lead forecasters at WPC was taking a look at the visible satellite imagery in the Pacific near the Baja California Peninsula and noticed some swirly action. If you take a look, there’s several swirls being caused by a volcanic island called Isla de Guadalupe. There’s also one right next to the coastline. How many can you count!?

We have satellite and radar imagery on our webpage alongside the surface analysis–if you want to take a look, visit our website (www.wpc.ncep.noaa.gov) and take a look under the current weather!

NYC Weather Update – Jun 9, 2014

June 9, 2014NYC, Rain, Storms, Thunderstorms, Weather Updatebackdoor front, cold front, nyc, nyc weather, rain, thunderstorms, warm front, weather, work week weather, wxLei Zhao

An unsettled week is in store for us after a spectacular stretch of warm, sunny conditions this past weekend. The good news is, it looks as though the pattern of rain during the week, but clearing and warm weekends is set to continue.

Tuesday – a high pressure center over New England will swing a backdoor cold front through tomorrow. This will lead to a chance of showers during the afternoon hours, with cloudy conditions otherwise and highs in the mid-upper 70s.

Wednesday – essentially a repeat of Tuesday in terms of sensible weather. A stationary front will sit just south of NYC and allow for an increasing chance of showers and possibly a few scattered thunderstorms. Temperatures will be in the same range as Tuesday.

Thursday will probably bring the best chance of significant showers and thunderstorms coming ahead of an approaching warm front. Cloudy again, with a chance of showers and thunderstorms throughout the day, and a high in the upper 70s.Friday – the warm front mentioned above will slowly progress through the area during the day Friday, once again bringing a chance for showers and thunderstorms, with mostly cloudy skies and highs once again in the upper 70s.

High pressure finally builds in during the day Saturday, which should lead to diminishing clouds, eventually mostly sunny skies for the rest of the weekend, and warmer temperatures in the low 80s.

NYC Weekend Weather Update – Governor’s Ball, Jun 6, 2014

June 6, 2014NYC, Weather Update, Weekendgovernor's ball, governor's island, governorsballnyc, high pressure, new york city, nyc, nyc weather, weather update, weekend weather, wxLei Zhao

A lot of you may be going down to Governor’s Island this weekend to check out the Governor’s Ball this weekend, which promises to have spectacular weather for an outdoor music festival!

Today – winds from the north will diminish today as an area of high pressure builds in over NYC from the Ohio Valley. Temperatures will be seasonable near 80 with mostly sunny skies. If you’re on Governor’s Island itself, you might experience slightly cooler temperatures due to breezes off the harbor.

Saturday – day two of a weekend of glorious weather, as temperatures continue to climb with the high pressure sits right over us. Expect clear skies with warm highs in the mid 80s. Excellent weather for a grill out or just any outdoor activity period.

Sunday – yep, you guessed it, yet another day of ridiculously nice weather, with highs in the low-mid 80s, and a mostly sunny sky.

Next chance for rain and thunderstorms comes Monday in advance of a complex frontal system.

NWS Weather Prediction Center's forecast for Sunday — NWS Weather Prediction Center’s forecast for Sunday

2014 Atlantic Hurricane Season Outlook – Jun 2, 2014

June 2, 2014Climate, Outside of NYC, Tropical/Hurricanesatlantic hurricanes, atlantic ocean, climate, el nino, hurricane forecast, hurricanes, la nina, nhc, pacific oceanLei Zhao

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 v_max 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

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.

NYC Weather Update – Jun 2, 2014

June 2, 2014NYC, Rain, Thunderstorms, Weather Updatecold front, new york, nyc, rain, weather, weekend weather, wxLei Zhao

Great day to start the week, with warm temperatures and sunny skies. Highs will top out in the low 80s today.

Tuesday, clouds will begin to build in ahead of a cold front approaching from the Great Lakes. Temperatures will remain warm with southwest flow and the cold front pushing warm air ahead of it. High temperatures should be around the low 80s with a chance of rain increasing into the afternoon.

Wednesday – a chance of showers and embedded thunderstorms persist through the Wednesday and Thursday timeframe. Temperatures will again be warm in the low 80s ahead of the cold front. Otherwise, generally mostly cloudy skies.

Thursday – the cold front is finally expected to pass through NYC on Thursday. This should set the stage for the best chance of significant precipitation this week. We may again see some thunderstorms, though none severe. Temperatures will cool off a bit with the rain and in the wake of the cold front, with high temperatures in the upper 70s.

Friday – high pressure builds in for Friday, remaining anchored and increasing in intensity over the weekend. This will translate to another splendid weekend of seasonable temperatures and sunny skies. Highs will be in the upper 70s to low 80s.

The Weekend – as mentioned above, high pressure will set the stage for seasonable temperatures and pleasant conditions during the weekend. Expecting high temperatures in the low 80s with mostly sunny skies. The high pressure will also block a storm system forecast to develop over the plains from entering our area until next week.

LZ | Weather

Weather updates & posts for NYC region