June 13, 2013 Storm Summary

June 13, 2013 Heavy Rain

An unusually strong non-tropical low pressure for June affected the Northeast on June 13-14, 2013, following tropical storm Andrea and another low pressure earlier in the same week that brought Central Park to near record June rainfall. While impacts from this storm were less significant than originally expected, it managed to produce another 1-3 inches of rain in the Northeast and a widespread severe weather outbreak in the Mid Atlantic region.

 

 


June 13, 2013 Storm Archive

June 9 – Rain, Cooler Temps Tomorrow
June 10 – More Rain Tonight, Thursday
June 11 – Heavy Rain, Storms Likely On Thursday
June 12 – Heavy Rain, Flooding Tomorrow
June 13 Storm Updates

Radar Archiveto be added soon


Storm History

The low pressure originated in the Plains region on early Wednesday, June 12, tracking northeast towards Illinois as a strong shortwave tracked southeast into the Great Lakes around a strong central US ridge. By Wednesday evening, a widespread severe weather outbreak occurred in the Great Lakes region, with an MCS developing over northern Indiana, NW Ohio and southern Michigan. This MCS continued to track east into the rest of Ohio overnight, producing widespread wind damage reports, while the low pressure intensified and continued to quickly track east under the MCS.

On Thursday morning, the storm deepened to a minimum pressure of 998 mb and slowed down over northern PA, near the NY/PA border. The MCS weakened, with a severe thunderstorm persisting over southern PA and NJ, while widespread moderate to heavy rain and chilly temperatures developed to the north and NE of the low pressure, over central NY state. The low pressure continued to slowly track east along the NY/PA border through the afternoon while a new MCS developed over Virginia and heavy rain persisted over central New England. By the evening hours, as another shortwave entered Virginia, the low pressure relocated over New Jersey, reaching its peak strength with a minimum pressure near 996 mb, unusually strong for a June low pressure this far south with non-tropical origins, while heavy rain redeveloped further south, over northern NJ into southern New England, further enhanced by the Virginia MCS which tracked offshore and merged with the heavy rainfall to the north. The storm then continued to gradually move offshore.

 


Forecasting The Storm

While tropical storm Andrea a week earlier was a relatively easy forecast, this storm was much more complicated to forecast, and the model guidance failed to reach a consensus even the day before the storm. Some of the models struggled to handle the development of the MCS in the Ohio Valley which would later affect the storm impact in the Northeast region, with differences regarding the track, timing and intensity of the storm complicating the forecasts of the storm.

NAM run from 6/12 morning (6z run), 36 hours out, showing heavy rain over the area on 2 PM Thursday with the low pressure in south PA. This run brought 2″ rain to NYC and 3-4″ just to the north. Image from NCEP Model Analysis and Guidance.

Signs for a strong low pressure initially showed up several days prior to the storm, around June 8-9, with the GFS showing a low pressure tracking over the Mid Atlantic with 2-4 inches of rain in the NYC area. The ECM and CMC were initially more suppressed, faster and weaker with the storm, but trended towards a stronger and further north storm with the 6/11 afternoon runs, showing the low tracking through southern PA with 2-4 inches of rain in the area and temperatures only in the mid-upper 50s for highs. The GFS and NAM, meanwhile trended further north, showing the low tracking over northern PA into NYC with highs reaching the upper 60s-low 70s; the heavy rainfall of 2-5 inches was modeled to stay to the north, with a risk of strong thunderstorms in NYC.

The model guidance became more complicated with the 6z and 12z runs on June 12, the day before the storm. Except for the ECM run, the rest of the 12z guidance incorrectly showed a much weaker, progressive and further south low pressure, with the low tracking over southern PA into Delaware, quickly exiting by Thursday evening with a minimum pressure near 1000mb and a narrow heavy rain band of 1-2 inches near and south of NYC; New England was modeled to receive insignificant rain totals under 1/2 to 1 inch. The overnight runs into the morning of 6/13 corrected this trend, showing approximately a 996mb low over central PA into central NJ with the heaviest rain staying north of the area.

In the two days before the storm, the models had several errors with the storm. Before the aforementioned south trend, the low was modeled too strong, with a minimum pressure near 990-994mb, with one NAM run showing a minimum pressure as low as 988mb. In reality, the minimum pressure was around 996 mb. Rain totals were exaggerated on some of the models, as high as 3-4 inches, locally 5 inches, from NYC and further north. The GFS was too progressive, taking the storm offshore by Thursday evening, while the ECM was too slow, briefly stalling the storm off the NJ coast with moderate to heavy rain persisting through Friday evening. Additionally, the south transfer of the low wasn’t modeled to be as significant as it was; models that had the low over central-southern PA took it into southern NJ with heavy rain over the area, while those that had it over northern PA then took it over NYC, correctly keeping the heavy rain north of the area but showing temperatures too high and exaggerated rainfall amounts with the storm. The day before the storm, steady rain was forecast to fall in NYC throughout the day taking into consideration a central PA-central NJ track; in reality, the low tracked over the NY/PA border, with dry conditions lasting for nearly 6 hours when rain was forecast to fall.

 


Storm Impact in the Northeast

Radar image from 10:08 AM Thursday, showing the initial round of rain over New York state with the severe thunderstorm from the leftovers of the MCS over south NJ. Radar images from the National Weather Service.

The Mesoscale Convective System (MCS) that affected the Ohio Valley region on Wednesday night with severe thunderstorms and strong wind gusts weakened as it entered Pennsylvania on Thursday morning. Throughout the morning hours, steady moderate to heavy rain developed and intensified north of the low pressure over New York state, while a severe thunderstorm left over from the MCS tracked into southern New Jersey. While occasional showers fell north and west of NYC through the early morning hours, steady moderate-heavy rain and thunder affected the area between 9 AM and 12 PM.

 

Radar image from 2:58 PM Thursday, showing the area with dry conditions, rain bands in central New England, and developing severe storms in VA.

After the initial line of rain moved offshore, the area dried out as the low pressure continued to track east along the NY/PA border and the heavy rain band shifted north to focus over central New England. Even though the heavy rain and unseasonably cold temperatures in the 50s stayed north of the area, the warm front was still stuck to the south, near south-central NJ, placing the area under cloudy skies and chilly temperatures in the upper 50s and lower 60s. These dry conditions continued from 12 PM through the rest of the afternoon and late afternoon hours as heavy rain continued to fall to the north. To the south of the warm front, temperatures peaked in the 90s as severe thunderstorms developed over Virginia, producing widespread wind damage.

Radar image from 10:48 PM Thursday, showing the rain bands consolidating over the area and southern New England as the leftover rain from the MCS, just offshore, merges with the rain bands.

By the evening hours, the low pressure shifted southeast, ending up over southern New Jersey by 8 PM. A heavy thunderstorm developed near northeastern PA around 5-6 PM, moving east into central New Jersey as moderate rain to its north spread into the western half of the area. Throughout the next few hours, the rain bands in central New England began to sink south, consolidating over southern New England and northern New Jersey closer to the low pressure in southern NJ, and the MCS previously over Virginia tracked offshore and merged with the rain bands to the north, further enhancing rainfall over the northern half of the NYC area. Moderate to heavy rain continued to fall through the rest of the evening and early overnight hours as wind direction shifted to the north with temperatures falling into the 50s, with rain mostly moving out of the area around 3-5 AM on early Friday.

 


Storm Rain Totals

The map below shows estimated rain totals from Andrea across the region. Actual totals may be slightly higher or lower than shown below.

As previously mentioned, impacts from the storm in the Northeast region were less significant than originally expected; rainfall amounts of were nearly half of the original forecast of 2 to 4 inches, and winds were not as strong as forecast as well. Regardless, the rain that fell from this storm was enough to result in additional minor flooding for parts of the region, especially following tropical storm Andrea and another low pressure earlier in the week that brought Central Park to near record June rainfall totals with over 9 inches in the 1-week period. The highest rain totals in the region were found in eastern NY and Massachusetts, locally as high as 2.5 to 3.5 inches; in the NYC area, 1/2 to 1 inch was observed in most of Long Island, with 1 to 2 inches for the rest of the area.

Below is a list of rain totals from airport observations across the area from the National Weather Service:

Northern NJ:
1.58″ – Teterboro, NJ
1.41″ – Newark, NJ
1.36″ – Sussex, NJ
1.28″ – Caldwell, NJ

Southeast NY:
1.98″ – Montgomery, NY
1.58″ – White Plains, NY

New York City:
1.58″ – Central Park, NY
1.14″ – JFK Airport
1.13″ – LaGuardia Airport

Long Island and South CT:
1.52″ – Bridgeport, CT
1.48″ – New Haven, CT
1.49″ – Montauk, NY
0.91″ – Islip, NY
0.87″ – New London, CT
0.81″ – Westhampton Beach, NY
0.69″ – Farmingdale, NY
0.61″ – Shirley, NY

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