rainfall totals

Heavy Rainfall and Flooding Recap 4/29-4/30

Miguel Pierre Uncategorized , , , , ,

Torrential downpours trained over the region late in the afternoon and overnight. Widespread rainfall totals between 4″ to 6″ fell along the I-95 corridor between the immediate New York City and Philadelphia metro areas. This caused moderate to major flooding in low-lying areas and along streams and rivers. A mudslide also buried two cars in Port Washington on Long Island.

DIXRadartotalrainfallCentral Park in New York also set a daily record rainfall record of 4.97″ for April 30th (storm total for two days is 5.12″). This was also the 10th wettest day recorded. Daily rainfall records were also set in LaGuardia Airport 5.26″ and JFK Airport 4.68, Newark Airport 5.24″.  LaGuardia and JFK had their 4th wettest days record. Newark had their 6th wettest day recorded.

An omega block this week caused a large cut-off low to from over the Central US.  “A cut-off low” is a storm that breaks away from jetstream and spins around very slowly, due weak steering currents. These lows sometimes bring prolific rainfall totals to our area. Especially during the spring or summer. So much moisture is transported from the Gulf of Mexico and the Atlantic and then is forced to rise and condense into very heavy rains.

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Heavy Rainfall Likely Saturday Night

Miguel Pierre Spring Wx ,

As I discussed previous post heavy rainfall is likely weekend. Particularity during Saturday night. Latest guidance is showing rainfall totals between 2″ – 3″ for much of the area. With locally heaver amounts between 3″-4″. Especially N&W of NYC.

The 12z NAM today has area of very heavy rainfall moving through NJ, SE NY and CT between 7pm – 1am Saturday night. Bukfit sounding for LGA shows a 50-60kt LLJ, pwat near 1.35″ and a large of strong omega.  There is also an area 600-800mb frontogenesis moving through the area tomorrow night. All this translates into strong lift and high moisture content over the area. Strong winds aloft are being prevent from reaching the due to strong inversion near the surface. However, downpours could bring down some portion of these winds down to the surface.

Bukfit sounding for LGA 12z NAM shows a 50-60kt LLJ, pwat near 1.35" and a large of omega
12z NAM Bukfit sounding for LGA  shows a 50-60kt LLJ, pwat near 1.35″ and a large of omega
12z NAM showing 600mb-800mb frontogenesis Saturday night
12z NAM showing 600mb-800mb frontogenesis Saturday night

The 12z ECMWF is also showing a 50kt+ LLJ and moving pwats over 1.25″ – 1.50″ through tomorrow night. Another aspect of this storm that needs to be watch frontogentic forcing  and elevated instability, behind the upper-level low Sunday afternoon and night.The 12z NAM shows enough dynamic cooling and cold air advection, for rain to change wet snow. Especially for inland areas. At this time, I am skeptical of this solution. But it’s not impossible to happen.