All posts by Lei Zhao

NYC Weekend Weather – Hurricane Arthur – Jul 3, 2014

July 3, 2014NYC, Tropical/Hurricanes, Weather Updatearthur, atlantic hurricane season 2014, hurricane arthur, hurricane season, new england, new york, north carolina, nyc, nyc wx, outer banks, severe weather, severe wx, thunderstorms, tropical storm arthur, ts arthurLei Zhao

Lots going on in the realm of weather over the coming weekend. First, to start off with today, the Storm Prediction Center has again placed our area under a slight risk of severe weather this afternoon and evening. We could see a repeat of the type of storms from last night as a cold front makes its approach from the west. Even though temperatures are lower today and sunlight limited, there’s still more than enough instability in the atmosphere to fuel a few strong to severe thunderstorms later today. Because we’re looking at another round of possibly torrential rain from today’s storms, many areas are under a flash flood watch. Part of this moisture is due to the influence of Hurricane Arthur to our south.

Hurricane Arthur

As of this morning, Arthur strengthened into the 2014 Atlantic Hurricane Season’s first hurricane and is currently sitting offshore of South Carolina with sustained winds of about 90mph. Forecasters are increasingly confident that Arthur will have enough time over warm water and low wind shear areas to grow into a Category 2 storm before getting recurved out to sea and making extratropical transition.

Track Forecast for Hurricane Arthur

Arthur is now forecast to brush by the Outer Banks of North Carolina sometime later today, and move to just about the 40N, 70W benchmark offshore of the Northeast by 8PM Friday. Given this current forecast track, confidence is increasing that we’ll continue to see heavy rain and showers through out Friday into Friday night, though not directly from Arthur itself. Rather, Arthur will be interacting with that cold front mentioned above to throw a wrench in everyone’s July 4th plans. Conditions should begin to improve rapidly Saturday as Arthur accelerates northeast, pushed by the cold front. We should see a return to sunny skies and seasonable weather Saturday with highs around the low 80s. Of particular concern are areas in Southeastern New England, which could see tropical storm conditions on Friday night into Saturday morning. Any deviation westward of this current forecast track would mean increased impacts on the Northeast, so this storm is worth watching closely. Regardless, high surface and dangerous riptides will be present on all Atlantic shorelines.

Tropical Storm Arthur Update – Jul 2, 2014 @ 18:00 EDT

July 2, 2014NYC, Outside of NYC, Tropical/Hurricanes, Weather Update2014 atlantic hurricane season, hurricanes, north carolina, nyc, nyc weather, nyc wx, tropical cyclones, tropical storm, tropical storm arthur, tropical weather, tropical wx, ts arthurLei Zhao

Current satellite imagery of Tropical Storm Arthur shows a storm that is increasingly organized, with well established outflow in all quadrants, a symmetrical appearance, and spiral bands around the whole storm. An eye feature continues to grow more clear. The National Hurricane Center current analysis of Arthur indicates a storm with sustained winds of 70mph, just below the 75mph criteria for a Category 1 hurricane.

Intensity Forecast

Current forecast reasoning shows low wind shear conditions over the next 48 hours, which should allow Arthur to continuously strengthen. Max winds are currently forecast at 85mph.

Track Forecast

As of right now, it seems Arthur has taken a jog to the west, so model forecasts have been pushed west as well. As a result, portions of the Outer Banks in North Carolina have now been placed under a hurricane warning. This slightly more westerly route also means increased potential for impacts in southeastern New England late Friday into Friday night. For NYC, we’ll be looking at soaking rains from the tropical moisture brought up by this storm tomorrow as well as Friday, however, confidence is decreasing that Arthur will rain out our fireworks in NYC.

NYC Afternoon Weather Update – Severe Tstorms in Vicinty – Jul 2, 2014

July 2, 2014Cool Images, Nowcast, NYC, Severe Weather, Weather Updatenew york city, nyc, nyc weather, nyc wx, severe thunderstorms, severe weather, storms tstorms, thunderstormsLei Zhao

You may have already experienced it, but if you haven’t you’re probably seeing some huge clouds forming on the horizon. We’re in for some stormy weather this evening, as the Storm Prediction Center and our local forecast office have us under a Severe Thunderstorm Watch. The hot, humid atmosphere, along with ample sunshine earlier today, has made the atmosphere moderately unstable, with CAPE values in the 2000-3000 J/Kg. This, along with mid-upper unidirectional shear will supply ample energy for strong to severe storms, with the greatest threat being frequent cloud to ground lightning and damaging winds.

As you see above, there are already strong storms in our vicinity. The storms north of the city have met severe thunderstorm criteria (wind gusts in excess of 58mph, hail greater than 1/4″ in diameter, or a tornado). More storms are forming to our southwest, so NYC itself should not be immune to the threat later on. Check out this image of a classic towering cumulonimbus (thundercloud) below!

Tropical Storm Arthur Update – Jul 2, 2014

July 2, 2014Tropical/Hurricanes, Weather Updatearthur, atlantic hurricane season 2014, florida, hurricanes, tropical storm arthur, tropical storms, tropical weather, ts arthur, weatherLei Zhao

A quick update on TS Arthur, before a more substantial post later this afternoon. Based on the latest satellite imagery, it appears that Arthur is continuing to gather strength. You can see below that a central eye feature is beginning to form, and that spiral bands have now begun wrapping around the west side of the storm. While Arthur continues to struggle with dry air on its western side, it does seem that this is gradually being overcome. The inner core of the storm is displaying relatively symmetrical outflows, a sign that the storm is strengthening.

As of 11AM EDT, the National Hurricane Center analysis indicated that Arthur now has sustained winds of 60mph, and is moving north.

Tropical Depression One Update – Jul 1, 2014

July 1, 2014Tropical/Hurricanes, Weather Update2014 atlantic hurricane season, atlantic hurricanes, td one, tropical depression, tropical depression one, tropical weather, weatherLei Zhao

Overnight, the area of disturbed weather mentioned in my previous post intensified enough that the National Hurricane Center upgraded the storm to the 2014 Atlantic Hurricane Season’s first tropical depression.

As you can see below in a satellite image captured at 7:45AM EDT this morning, TD One is showing increasing signs of organization. You can clearly see overshooting tops (the bubbly looking clumps of clouds), which are clouds that are breaking up through the tropopause and into the lower stratosphere. This is a hallmark sign of intense thunderstorm updrafts, where warm, humid air is rapidly moving upwards in the atmosphere. You can even see the beginning of what may eventually become a spiral band forming directly south of the storm’s center.

National Hurricane Center has issued tropical storm warnings for the Eastern Florida coast. TD One’s sustained wind speeds are at 35mph, only 4mph shy of tropical storm criteria. In fact, as of this writing, TD One may have already become Tropical Storm Arthur, our first named storm of the 2014 Atlantic Hurricane Season.

Storm Track Forecast

TD One is forecast to begin a turn towards the north, then northeast over the period of the next day or so. Thereafter, it is forecast to steadily accelerate in forward speed towards the northeast as a cold front currently approaching our region from the west begins to steer the storm. It appears in the latest model runs that the storm may make a landfall in the Cape Hatteras area of North Carolina, and the move offshore of the Northeast Friday night into Saturday.

Intensity Forecast

Although the strongest thunderstorms are currently confined to the southern half of the storm, there is high confidence that the storm will continue to organize and become a tropical storm shortly. The National Hurricane Center is also now forecasting that TD One will have sufficiently good conditions to strengthen into a weak hurricane by the time it makes its closest approach to North Carolina. It will eventually get absorbed by the cold front mentioned above and make an extratropical transition somewhere off the coast of the Canadian Maritimes.

What This Means for Us

The tropical moisture from this storm is increasingly likely to throw a damper on July 4th plans for the area, when the storm and approaching cold front will interact to produce the chance for heavy rain, thunderstorms, and possibly some strong wind gusts. However, even though this is forecast to occur within the next 3-4 days, there is still a good deal of uncertainty as to the final track of this storm, especially as it approaches the Northeast. More updates soon!

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.

LZ | Weather

Weather updates & posts for NYC region