Tag Archives: rain

Hurricane Lane: The Wettest Tropical System Ever Recorded in Hawaii and the Second Wettest for US

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Hurricane Lane, the twelfth named storm of eastern Pacific hurricane season, slammed the state of Hawaii with strong winds and flooding rains over the weekend. It was the wettest tropical cyclone on record in the Aloha state.

The storm, according to the NWS, peaked at category-5 strength, but weakened as it approached Hawaii. While it did not make landfall, its outer rain bands still packed a punch that was felt across the island chain. The Big Island, however, was one of the hardest hit. In the town of Mountain View, about 15 miles southwest of Hilo, 52.02 inches of rain was reported. That is the second highest rainfall total ever recorded from a tropical cyclone in the entire United States. The highest total, 60.58 inches, fell in Nederland, Texas during Hurricane Harvey in 2017.

The slow moving nature of Lane and the orographic lift provide by the mountainous terrain of Hawaii helped push the rainfall total into the record books. Falling in a relatively short period of time, the relentless precipitation caused widespread flooding, mudslides, and road closures. It also forced mass evacuations as well as a number of water rescues.

While the eastern and central Pacific basins produce about 15 named storms a year, they rarely hit Hawaii. This is largely because of the state’s location in the vast Pacific Ocean. Sitting at about 20°N latitude, most storms pass south of the archipelago or dissipate in the relatively cooler waters to its north and east.

The last hurricane to make landfall in Hawaii was Iniki, a category-4 storm, in 1992.

Source: NWS

Storm Breaks Daily Rainfall Record in NYC

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August has only just begun and it is already New York City’s wettest August in seven years. This is largely due to the strong thunderstorms that swept through the city on Saturday and unleashed more than half a month’s worth of rain in just a few hours.

According to the NWS, 2.9 inches of rain was measured in Central Park, setting a new record for the date. The previous record of 2.39 inches had been in place since 1983. On average, the Big Apple gets 4.44 inches of rain for the entire month of August.

The torrential rain, which came on the heels of NYC’s wettest July in fourteen years, flooded roadways and caused power outages across the city. Significant delays and cancellations were also reported at the area’s airports.

This type of heavy rain event, according to NOAA, is expected to become more common in the northeast as global temperatures continue to rise and precipitation patterns change.

Record rain floods the streets on the upper east side of Manhattan. Credit: ScooterCaster/NY1

July 2018: Wettest July in Fourteen Years for NYC

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July is usually the wettest month on the calendar for New York City and this year it did not disappoint. In fact, it was an overachiever. In all, 7.45 inches of rain was measured in Central Park. That marks the city’s wettest July in fourteen years. Of this impressive total, 2.24 inches fell on a single day, which caused flash flooding around the five-boros. The city, on average, gets 4.60 inches of rain for the entire month.

In terms of temperature, July started with an extended heat wave and then produced some below average readings toward the end of the month. Highs ranged from a relatively cool 77°F to a steamy 96°F. However, with six days in the 90s, the warmth won out in the end. The city’s mean temperature for the month was 77.6°F, which is 1.1°F above average.

Powerful Thunderstorm Brings Funnel Cloud and Flooding to NYC

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An intense thunderstorm swept through New York City on Tuesday afternoon. With bands of torrential downpours, it unleashed nearly half a month’s worth of rain in just a few hours.

According to the NWS, 2.24 inches of rain was measured in Central Park. While that is an impressive total, it did not break the daily rainfall record for the date. That honor belongs to June 17, 1995 when 3.13 inches of rain was reported. New York City, on average, gets 4.60 inches of rain for the entire month of July.

Funnel cloud forms over NY Harbor. Credit: Michael Uturn/Twitter

The powerful storm also produced a funnel cloud over New York Harbor. However, according to the NWS, it did not reach down to the surface and therefore was not a tornado.

The heavy rain, on the other hand, produced a number of problems on its own. It caused flash floods and disrupted travel across the city. Torrents of water poured into several subway stations creating underground waterfalls and parts of the FDR Drive, a major highway on the east side of Manhattan, were closed due to flooding. Significant delays and cancellations were also reported at the area’s airports.

This type of heavy rain event, according to NOAA, is expected to become more common in the northeast as global temperatures rise and precipitation patterns change.

Heavy rain causes flooding on FDR Drive in NYC. Credit: Patch

What is a Monsoon and How Do They Affect the US?

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The summer phase of the North American Monsoon is in full swing. But what, you may wonder, is a monsoon and how do they affect the United States?

While most people associate a monsoon with rain, that is only half the story. It is actually a wind system. More specifically, according to NOAA, a monsoon is “a thermally driven wind arising from differential heating between a land mass and the adjacent ocean that reverses its direction seasonally.” In fact, the word monsoon is derived from the Arabic word “mausim”, meaning seasons or wind shift.

In general, a monsoon is like a large-scale sea breeze.  During the summer months, the sun heats both the land and sea, but the surface temperature of the land rises more quickly. As a result, an area of low pressure develops over the land and an area of relatively higher pressure sits over the ocean. This causes moisture-laden sea air to flow inland. As it rises and cools, it releases precipitation. In winter, this situation reverses and a dry season takes hold.

Monsoon wind systems exist in many different parts of the world. In the US, we have the North American Monsoon that impacts states across the southwest. Summer temperatures in the region – mostly desert – can be extremely hot. Readings in the triple digits are not uncommon. This intense heat generates a thermal low near the surface and draws in moist air from the nearby Gulf of California. In addition, an area of high pressure aloft, known as the subtropical ridge, typically moves northward over the southern U.S. in summer. Its clockwise circulation shifts the winds from a southwesterly to a southeasterly direction and ushers in moisture from the Gulf of Mexico. This combination of heat and moisture rich air produces thunderstorms and heavy rainfall across the region. In fact, summer monsoon rains are reported to supply nearly 50% of the area’s annual precipitation.

Replenishing reservoirs and nourishing agriculture, these seasonal rains are a vital source of water in the typically arid southwest. Conversely, they can also cause a number of hazards such as flash flooding, damaging winds and hail, as well as frequent lightning.

Monsoon season in the American southwest typically runs from mid-June to the end of September.

The North American Monsoon pulls moist air (green arrows) inland over the typically arid southwest region of the US. Credit: NOAA/NWS

Subtropical Storm Alberto Makes Landfall in Florida and Travels North to Canada

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Subtropical storm Alberto, the first named storm of the 2018 Atlantic hurricane season, made landfall near Laguna Beach in the Florida Panhandle on Monday. It was the second time this decade that a named storm hit the southeast coast on Memorial Day.

Classified as a subtropical storm, Alberto was a hybrid between a tropical storm and a regular low-pressure system usually found at higher latitudes. A tropical system is fueled by the latent heat released by the evaporation of ocean water while a regular storm is powered by the temperature contrast between air masses. Hybrids are able to access both energy sources.

Despite this somewhat confusing hybrid status, Alberto still packed a punch. Strong winds, downed trees, and heavy rain were seen across a large swath of the southeastern United States. A wind gust of 59-mph was reported at Fort Tyndall Air Force Base near Panama City, FL. Storm surge flooding was another concern. Water levels rose between 1 and 3 feet from Tampa Bay, FL to the Mississippi River delta in Louisiana.

Moving northward, heavy rain from the remnants of Alberto unleashed flash flooding in the several states and caused landslides in North Carolina’s Blue Ridge Mountains. Nearly 10 inches of rain was reported in Black Mountain, NC.

Forming in the waters off the Yucatán Peninsula in Mexico on May 25, Alberto traveled all the way to Lake Huron near the Canadian border before dissipating on May 31. It was the first named storm to reach that far north this early in the season, according to researchers at the University of Miami.

The Atlantic hurricane season officially begins on June 1.

Track of Subtropical Storm Alberto. Credit: Supportstorm

Catastrophic Flooding Hits Ellicott City Twice in Two Years

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For the second time in less than two years, heavy rain unleashed catastrophic flooding in Ellicott City, Maryland this Sunday.

According to the NWS, the area received between 8 and 12 inches of rain in less than four hours. On average, the area gets 4 inches of rain for the entire month of May. This massive amount of precipitation in such a short period overwhelmed streams throughout the region and turned Ellicott City’s historic Main Street into a raging river. The floodwater, which reached as high as the second floor of most buildings, damaged or destroyed numerous businesses and swept away dozens of cars and trees. Local officials say that one man, a sergeant with the National Guard, was killed while trying to rescue people from the fast flowing water.

This type of rainfall is considered a one in one thousand year event. However, that does not mean it can only happen once every thousand years. It is the recurrence interval, a statistical calculation that means an event has a one in one thousand chance (0.1%) of happening in any given year in a given location. Ellicott City experienced an eerily similar event in July 2016.

There were several drivers behind this deadly deluge. First, “training” thunderstorms developed along a stationary front. This is a situation where strong thunderstorms continuously form over the same area – like train cars traveling along a track – dumping excessive amounts of rain.

Although climate change did not cause these storms, it has altered the environment in which they form and is making them more common. As greenhouse gases warm the atmosphere, the air is able to hold more water vapor. More specifically, according to the Clausius–Clapeyron relation, for every increase of 1°F, the saturation level of the atmosphere increases by about 4%. That means there is more evaporation from oceans, rivers, and lakes, and therefore more water vapor available to condense and fall as precipitation.

Another major player in Sunday’s flood was the area’s topography. Founded as a gristmill town in 1772, Ellicott City sits in a valley surrounded by several streams that feed into the Patapsco River. Just ten miles outside of Baltimore, it is a highly urbanized area with extensive amounts concrete and asphalt. These impervious surfaces leave the rainwater with no place to go but racing downhill and through the town.

All of these factors will have to be considered as Ellicott City decides how to rebuild for the second time in two years.

Torrential rain turned Main Street in Ellicott City, MD into a raging river. Credit: S. Baranoski

Powerful Thunderstorm Batters NYC

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The first severe thunderstorm of the season barreled through the New York City metro area early Tuesday evening. Strong winds and heavy rain were reported across the region.

After an unseasonably hot and humid day, a fast moving cold front moved in from the west and triggered the violent storm.  According to the NWS, 0.58 inches of rain was reported in Central Park and wind gusts at JFK airport reached 55 mph. It is also interesting to note that the temperature in the city dropped from 88°F to 68°F in less than one hour.

The powerful and fast moving storm knocked down trees and caused power outages throughout the area. Rolling through the city a little after 5PM, the storm also wreaked havoc on the evening commute. All MetroNorth Railroad lines out of Grand Central Terminal were suspended because of downed trees on the tracks. Additionally, the city’s three airports reported significant delays.

Outside of the city, the storm turned deadly claiming the lives of at least five people. That number includes an eleven year old girl who was crushed by a tree while sitting in a car in Newburgh, NY. No injuries or fatalities were reported in the five boroughs.

A powerful thunderstorm moves across NYC. Credit: southerlysweet/Instagram

April 2018: Unseasonably Cold and Wet in NYC

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April felt like a wild ride of weather in New York City this year. It produced both a record-breaking snowfall and a balmy summer preview with temperatures in the 80s. However, with 19 out 30 days posting below average readings, the cold won out in the end. The city’s mean temperature for the month was 49.5°F, which is 3.6°F below normal.

While unseasonably chilly, the month was not a record breaker. That dubious honor, according the NWS, belongs to April 1874 when the monthly temperature was only 41.1°F. The city’s warmest April on record was April 2010 with a mean temperature of 57.9°F.

In terms of precipitation, this April was unusually wet with 14 out of 30 days producing rain or snow. In all, the city received 5.78 inches of rain, which is 1.28 inches above average. Of that total, 49% fell during a single heavy rain event on April 16. Snow was also abundant with 5.5 inches measured in Central Park. Coming down during a single storm on April 2, it set a new daily snowfall record for the date. On average, the city gets 0.6 inches of snow for the entire month.

April was a wild ride of weather in NYC. Credit: The Weather Gamut

Why Heavy Rain Events are Becoming More Common

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Torrential rain events and the flooding they cause are nothing new. Global warming, however, is helping to make them more likely.

Heavy rainfall trends in NYC. Credit: Climate Central

According to the most recent National Climate Assessment, heavy precipitation events have increased in both frequency and intensity across the United States. While there are seasonal variations with different regions, the greatest increases have been observed in the northeast.

Climate scientists attribute this increase in heavy precipitation to our warming world. As greenhouse gases warm the atmosphere, the air is able to hold more water vapor. More specifically, according to the Clausius–Clapeyron relation, for every increase of 1°F, the saturation level of the atmosphere increases by about 4%. That means there is more evaporation from oceans, rivers, and lakes, and therefore more water vapor available to condense and fall as precipitation.

Heavy rain events have a number of consequences, including an increased risk of both flash floods and river floods. This, in turn, is a threat to life and property. Over the long-term, it also affects insurance rates and property values. According to NOAA, individual billion-dollar flooding events (excluding tropical cyclones) in the U.S. have added up to $39 billion in losses since 2010.

As our global temperature continues to rise, experts say we should expect to see more extreme rain events, even in areas where overall precipitation is projected to decrease. In other words, when it rains, it will likely pour.

Downpours have been getting more frequent and intense across the US. Credit: Climate Central and NCA4