AGENCY TESTIMONY
Challenges in predicting flash floods
0:05:12
ยท
104 sec
The testimony highlights the inherent difficulties in accurately predicting flash floods, emphasizing the short lead times and high variability in rainfall patterns. These challenges significantly impact the city's ability to prepare and respond effectively to flash flood events.
- Explains the limited lead time (often only an hour) for accurate flash flood predictions
- Discusses the challenges in predicting rainfall at smaller scales (borough, neighborhood, or street level)
- Highlights how small changes in storm patterns can lead to significant differences in impact
Heather Roiter
0:05:12
To understand how the city responds to flash flood emergencies, it's important to understand the science behind it and the challenges with respect to flash flood prediction.
0:05:20
It is difficult to predict flash floods far in advance as they're inherently uncertain with respect to heavy rainfall predictions.
0:05:27
There's very little lead time, perhaps only an hour or so, to accurately identify the precise location and intensity of rainfall.
0:05:34
This means that the National Weather Service might be able to identify flash flood threats for the tri state area or for the city as a whole with enough lead time to activate our flash flood plan and warn the public.
0:05:46
But predicting rainfall at smaller scales such at a borough, neighborhood, or street level is not possible until the storm is barreling down in the city.
0:05:55
The high variability of where rain falls means flood advisories and flash flood warnings are issued only an hour or so in advance or in some cases as the storm is ongoing.
0:06:06
This is compounded by the fact that small changes in the intensity, movement, and development of the storm can change in can change in the sorry.
0:06:15
Development of the storm result can have large changes in the forecast.
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A shift to only a few miles can be the difference between minimal or major or potentially a catastrophic impact.
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No two storms will ever be the same.
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Each will leave its own unique impact on the city even if the weather patterns between storms are similar.
0:06:35
This is to say that future storms will produce flooding in areas that perhaps haven't seen significant flooding in the past.
0:06:42
When we consider these factors and layer them into our vast and varied landscape of New York City in addition to the forecast challenges and variability of heavy rainfall, you begin to understand all that we take into account as we plan and respond to storms.