Answers About New York Weather

March 4, 2009 T I M E S B L O G


Answers About the Weather

Taking Questions Ask the Meterologist

I. Ross Dickman is answering City Room readers’ questions.

Following is the first set of responses from I. Ross Dickman, meteorologist in charge of the National Weather Service team serving New York City and the metropolitan region. This week, he is answering City Room readers’ questions about his experience and observations working with weather, community planners and emergency managers in the region. Post a question for Mr. Dickman in the comments box below. Please note that this Q. and A. was scheduled before Monday’s snowstorm.

Maybe you could describe the chain of events leading up to the forecasts for this particular storm. When is a decision made to put out an alert or a warning? How did it play out in this case? How precise can you be about the timing of a storm, when it will hit? What data goes into that prediction?

— Posted by Weatherman

For the March 2, 2009, snowstorm, the forecasts were right on target. The local National Weather Service forecast office here in Upton, N.Y. on eastern Long Island issued winter storm watches and warnings with more than 24 hours of lead time as well as heightened awareness of the event that occurred several days in advance. As you might imagine, timely and reliable dissemination of forecasts and warnings is critical to the protection of life and property. When forecast confidence increases to at least 50 percent based on the interpretation of forecast model output, a watch is issued. When forecast confidence increases to at least 80 percent, a warning is issued. Our goal is to issue watches with lead times of 24 to 36 hours and warnings 12 to 18 hours in advance of the storm. For this storm, we provided longer lead times than our goals.

The National Weather Service follows a specific forecast process for all weather situations before putting out a forecast or warning. The process goes something like this: Observations including satellites, upper air data and radar are collected by the local forecast office and then checked for quality, analyzed, and then infused into a suite of computer models at the National Centers for Environmental Prediction. Millions of calculations occur with these models to generate predictions of storm behavior and the general conditions of the atmosphere. The model results are then evaluated and used in the National Weather Service forecast and warning process.

Unfortunately, these models cannot account for all of the short-term changes in the atmosphere, resulting in forecast error or uncertainty. Interpretations of the model guidance are then translated into forecasts and warnings that are coordinated between the national centers and surrounding local forecast offices to ensure consistency. Once completed, the issuing office generates forecast and warning products for release to the public and emergency management groups.

Somehow it seems that New York City is becoming windier. What is causing this, and where do these strong winds we’ve been having recently come from? Thank you.

— Posted by Darinka Zaharieff

Winds in New York City are greatly affected by the buildings, which can greatly increase speeds. We do not have any indication that winds have been on the increase in recent years. Statistically, February and March are the windiest months for New York City, and August and September have the least wind. The National Oceanic and Atmospheric Administration’s National Environmental Satellite, Data and Information Service operates the National Climatic Data Center in Ashville, N.C. The Climatic Data Center is the world’s largest archive of climate data, much of which is online for researchers and the public to query.

When the water surrounding Lower Manhattan rises, what is the projected annual rate of increase? Are the rising waters expected to affect the Hudson and the East Rivers similarly, and what measure do engineers recommend to revamp the seawall?

— Posted by Rima Blair

While I can’t comment on the engineering aspects, I can affirm that rising sea levels and other phenomena like hurricanes are a real threat to the New York City region.

The Center for Climate Systems Research at Columbia University cites these threats. According to the researchers: “Regional sea level trends of the past century range between 0.08 to 0.16 inches per year (2 to 4 millimeters per year). From a suite of sea-level rise scenarios based on an extrapolation of historical trends and outputs from several global climate model simulations, the researchers projected a rise in sea level of 11.8 to 37.5 inches (30 to 95.5 centimeters) in New York City and 9.5 to 42.5 inches (24 to 108 centimeters) in the metropolitan region by the 2080s. Flooding by major storms would inundate many low-lying neighborhoods and shut down the metropolitan transportation system with much greater frequency.”

Severe hurricanes and associated storm surge have the most serious immediate threat to the coastline. The National Oceanic and Atmospheric Administration’s Sea, Lake and Overland Surges From Hurricanes model (SLOSH) shows a Category 3 hurricane on the worst-case track projection has the potential to bring nearly 25 feet of water into Lower Manhattan and surrounding areas.

Is it likely that we will have another big snow event during the rest of the season (winter-spring 2009)? Statistically speaking, where is the coolest place in Brooklyn to chill out during the dog days of summer?

— Posted by Brooklynite

While we could have another significant snowstorm (six inches or greater) this month, it is not likely. Typically, New York has one big snow a year, most commonly in February. On average, March has only a 1 in 5 chance of a significant snowstorm. Interestingly, we have to go all the way back to March 13-14, 1993, to the last time that we had a snowfall of six inches or more, though we came close on March 16, 2007, with 5.5 inches.

As for where to cool off in summer in Brooklyn — Coney Island is the place. The daily sea breeze keeps temperatures the coolest around during a hot summer afternoon.

How can I be a Weather Service storm spotter?

— Posted by David

Your National Weather Service offers the Skywarn Spotter Program to volunteers who are willing to assist Weather Service meteorologists in making warning decisions. A free three-hour spotter training class will be offered this spring, which will be posted to our Skywarn Web site by April 3. You will have to register for a class. You will be trained to recognize and report features associated with rapidly developing, mature, and dissipating thunderstorms that cause hazardous weather. For further information on our Skywarn program, please contact Brian Ciemnecki.

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