As Hurricane Sandy so dramatically demonstrated five years ago yesterday (October 29th), even coastal New England is sometimes subjected to tropical storm and hurricane conditions. Sandy is notorious for a number of reasons, not least of which are its infamous “left turn” into coastal New Jersey and the hybrid storm aspects that brought an early-season blizzard to the mountains of West Virginia. This year, parts of the northeastern United States are once again being subjected to a hybrid “Frankenstorm” (or “Franken-Philippe”), though thankfully with weaker winds, much less snow, and much less coastal flooding. However, as we’ll see below, the impacts from this hybrid of a cold extratropical low pressure and the remnants of Tropical Storm Philippe are still substantial.

GOES16 Loop 0532z 30Oct 0902z 30Oct

Figure 1. Loop of infrared satellite imagery from the GOES-16 satellite, covering the period from 1:32am EDT to 5:00am EDT on 30 October 2017.

The infrared satellite imagery above illustrates the evolution of the storm in the early hours of the morning on 30 October. By this point, the main low pressure system that initially made landfall in New Jersey had rocketed north into southern Quebec, Canada, but also of interest is the remnant circulation of Tropical Storm Philippe just offshore. The low pressure qualified as a meteorological “bomb” given its central pressure dropped 29 mb in a 24-hour period. The deeper clouds, indicated by the oranges and reds south and east of Cape Cod, are associated with the remnant thunderstorms of Tropical Storm Philippe, which was scooped up by the storm’s cold front on Saturday. Additionally, a tight low-level swirl in the clouds can be seen on the southern edge of this area of thunderstorms, highlighting the strength of that remnant circulation. Philippe’s remnants clipped southeastern Massachusetts earlier this morning, leading to some impressive (and damaging) wind gusts (Figure 2).

Max Winds Boston Nws

Figure 2. Maximum wind gusts observed in the Taunton, MA National Weather Service coverage area, as of 7am EDT on 30 October 2017.

As impressive as the winds were in some locations, there were also a number of daily precipitation records set at sites across the Northeast. Among the daily precipitation records set for October 29th are:

  • 2.78″ at LaGuardia Airport, New York (old record 2.45″ in 1973)
  • 4.02″ at Islip, NY (old record 1.83″ in 2011)
  • 3.12″ at Trenton, NJ (old record 3.11″ in 1973)
  • 2.63″ at Hartford, CT (old record 1.42″ in 2003)
  • 2.51″ at Worchester, MA (old record 1.72″ in 2003)

Across a huge area of Pennsylvania, New York, New Jersey, and the New England states, maximum 24-hour rainfall values exceeded 10-year average recurrence interval (ARI) values, indicating that a comparable storm in terms of rainfall should only be expected about once every ten years on average. There were even isolated pockets of rainfall that exceeded 100-year values, which has predictably led to some serious flooding (Figure 3).

River Gauges

River gauges in the New England area, showing the state of flood conditions along a number of different streams as of Monday afternoon (October 30th). Refer to http://water.weather.gov/ahps2/index.php?wfo=gyx for the most up-to-date conditions.

MetStat’s preliminary analysis, which shows storm-total rainfall (Figure 4) from MetStormLive and maximum 24-hour average recurrence intervals (Figure 5), can be found below.

72hr Sum Detailedmap 1

Figure 4. Preliminary MetStormLive analysis of the total precipitation across the Northeast from 8:00am EDT on 27 October 2017 to 8:00am EDT on 30 October 2017.

 

Qpeconus Final Max24hr ARI In72hrs 20171027 1300 To 20171030 1200 Ari Detailedmap

Figure 5. Average recurrence interval (ARI) values associated with the maximum 24-hour rainfall at each location within the 72-hour storm period.

As always, MetStat will continue to monitor flooding events such as this one and general precipitation nationwide. To learn more about our real-time analysis capabilities, visit this page, or check out this one to learn more about storm analysis, and use the sidebar on the right side of your screen to sign up for additional updates from this blog.