June 13, 2013 Storm Updates

Occasional updates will be posted below on the heavy rain, wind and severe thunderstorm event affecting the region today and tonight. Updates will also be posted on Twitter.


Yesterday’s forecast discussion
Twitter updates
5-Day Forecast

Final storm rain totals in NYC: (Updated 8 AM)

Central Park – 1.58″
JFK Airport – 1.14″
LaGuardia – 1.13″

Blog Updates: (Regional radar from the National Weather Service)

12:15 AM Storm Update


As of 12 AM, the low pressure is located off the New Jersey coast, approximately east of Philadelphia and south of western LI. The minimum pressure is near 996-997 mb and the low is tracking to the east.

Light to moderate rain continued to fall over the last 2 hours, locally heavy in LI and southern CT, with rain totals so far generally between 3/4 and 1.25 inch, locally higher in some spots. Light to moderate rain will continue to fall through the mid overnight hours as temperatures fall into the 50s with a breezy NE wind later turning to the north, with the rain mostly ending by Friday morning except for Long Island and southern CT, which will see showers persisting a bit longer. Friday will otherwise be mostly cloudy with highs in the upper 60s to low 70s along with a risk of scattered showers from NYC and further north/west in the afternoon and evening hours.

So far, Central Park is at 1.15″ for the storm, with the final storm total likely approaching 1.5 inch. This will place this month at least as the 3rd wettest June on record; currently, 1903 is the 3rd wettest June on record with 9.78″, followed by 2009 with 10.06″ and 2003 with 10.27″. Additional rain is expected next week, and this month is still on track to become the wettest June on record in NYC and perhaps one of the 10 wettest months on record.

This is the final storm update for tonight. A forecast update will be posted on Friday morning, followed by a post-storm analysis on Friday night or Saturday morning.

10:15 PM Storm Update


The complicated forecasting of this storm continues, as after dry conditions for the majority of the day, with much less rain than expected falling through the late afternoon hours, the current round of rain is overperforming for parts of the region compared to the earlier expectations for tonight, with heavy rain and thunder having affected NYC earlier before shifting into Long Island and CT, where widespread moderate to heavy rain is currently falling; these storms have produced 1/2 to 3/4 inch for some locations in just an hour. As such, the storm total rain forecast for the area was slightly increased again to 1-2 inches, locally higher, as was forecast from earlier this morning. Steady rain will continue to fall through the early-mid overnight hours with temperatures gradually falling into the 50s, with the rain gradually tapering off from west to east with Long Island expected to see showers through Friday morning.

Storm updates will continue to be posted through 12 AM; the forecast discussion originally planned for tonight will be posted on Friday morning instead. A post-storm overview will be posted on Friday night or Saturday morning, analyzing the forecasting of this storm and what went wrong with the forecast.

9:15 PM Storm Update


As of 9 PM, the low pressure was located over central New Jersey, approximately east of Philadelphia. The minimum pressure is about 997 mb, and the low is tracking to the east.

Since the last update, the low pressure shifted southeast from northern PA into central NJ as expected, and will continue to track east and offshore. Since 6-7 PM, another round of rain moved into the area, with locally heavy rainfall observed in parts of NYC and Long Island. Currently, light rain is redeveloping across northern NJ, with another band of moderate rain over NE PA and southern NY to continue sliding SE, keeping steady light to moderate rain over the area through the mid-late overnight hours west of NYC and into Friday morning east of NYC, with temperatures gradually falling into the 50s in the next few hours as the wind direction shifts to the north.

Another 1/2 to 1 inch, locally higher to the north of NYC, is expected with the upcoming round of rain, although the recent heavy thunderstorms increased totals across parts of the area as well, with localized totals near 1 inch in Long Island and NYC so far. Storm totals are expected to end up between 1 and 2 inches across the area.


5:00 PM Update: A weak line of showers and thunderstorms is developing over northeast PA, with a heavy thunderstorm near Allentown, PA, moving east. This area of rain is likely to reach most of the area by 5:30 to 7 PM, with rain and thunder redeveloping for the evening, followed by occasional showers through the mid overnight hours. At least another 1/2 inch of rain is expected tonight for most places, up to 1 inch in some areas.



4:10 PM: Forecast Bust


As of 4 PM, the low pressure was located over north central PA. The minimum pressure is about 998 mb and the low is tracking to the SE. The warm front is currently located near approximately central New Jersey.

As the last update noted, this storm has not behaved as expected, with several notable differences, including the morning storms that were not modeled properly, the low pressure tracking further north than expected, a line of severe thunderstorms over Virginia which appears to have suppressed storm development over Pennsylvania, and the axis of heavy rain setting up further north than expected. Other than a brief round of heavy rain in the morning, the NYC area was mainly dry for the day so far, with totals generally near to less than 1/2 inch across the area so far.

As the low pressure slides southeast into central NJ this evening and tonight, additional showers are expected to develop this evening and continue through the mid overnight hours as temperatures steadily fall into the 50s and the wind direction shifts to the north, although the heavier rain will stay to the north, over New England, with at least another 1/2 inch of rain likely, possibly locally higher. Overall, storm total rainfall is expected to range from 1/2 to 1.5 inch, which is lower than the original outlook for 2-4 inches.

1:45 PM: Rain Forecast Lowered


As of 1 PM, the low pressure was located over north central PA. The minimum pressure is about 998 mb, and the low is tracking to the ESE. The warm front is extending SE of the center into the southern half of New Jersey.

Since the last round of rain cleared the area, no rain has fell, and occasional breaks in the cloud cover were observed. Probability of severe weather in southern Pennsylvania and New Jersey appears lower than previously expected for later today, and the radar appears clear for the area at least through the late afternoon with a risk of isolated showers. Additional rain is likely later this evening into early tonight, but based on the latest trends, it appears that the rain totals for today are likely to underperform compared to the forecast, perhaps significantly so.

The latest rain outlook, including what already fell so far, is for 1/2 to 1.5 inch of rain, locally higher. The lower rain amounts fortunately reduce the risk of flooding in locations that have been hit hard with heavy rains in the last week. If necessary, additional updates may be posted later today.

11:50 AM Storm Update

1538As of 11 AM, the low pressure was located over the NY/PA border SSE of Buffalo, NY. The minimum pressure is about 998 mb, and the low is tracking to the ESE. The warm front is slowly pushing northeast, and is extending from central PA to about southern NJ.

The earlier round of heavy rain has moved out of locations west of NYC, and will clear the rest of the area by at least 12:30 PM with dry conditions for the next few hours. Clearing in the cloud cover is occurring in central PA, and parts of the area especially from NYC and south/west are likely to see occasional peeks of sunshine. The warm front will continue to advance closer to the area, before stopping its northward progression likely around central NJ as the low pressure tracks southeast into east central PA and central NJ. Additional rain and thunderstorms are expected later this afternoon and evening, continuing into the early overnight hours before becoming lighter, with a storm total of 1 to 2 inches expected in the southern half of the area, potentially up to 3 inches in some spots.

10:35 AM Storm Update

1408As of 10 AM, the low pressure was located over the NY/PA border south of Buffalo, NY. The minimum pressure is about 998 mb, and the low is tracking to the east. The warm front is extending SE of the low, through central PA into NE Maryland and Delaware.

A batch of heavy rain from the weakening MCS is currently affecting the area, with light to moderate rain and thunder, locally heavy, observed over the last hour. Another area of heavy rain is currently located over central NJ, north of a line of severe thunderstorms in southern NJ, and will affect the area through 12-1 PM, producing additional heavy rain. By the time this round moves out, at least 1/2 inch of rain is expected across the area, up to/over 1 inch in some locations north and west of NYC. Drier conditions are expected for the early-mid afternoon before additional storms, locally heavy, affect the area later this evening.

The current rain forecast remains 1 to 3 inches, with the higher amounts further north into interior SE NY and Connecticut. Depending on observations later this morning into the early afternoon, it is possible that forecast rain amounts may need to be further reduced.

8:50 AM Storm Update


As of 8 AM, the low pressure was located over NW Pennsylvania. The minimum pressure is 998 mb, and the low is tracking to the east. The low is forecast to continue tracking southeast into central Pennsylvania and central New Jersey later this afternoon before tracking offshore south of Long Island tonight.

Last night, a widespread MCS affected the Ohio Valley into the western Mid Atlantic region with heavy rain and strong wind gusts. The MCS is currently over the region, with severe thunderstorms extending from southern PA southwards, with rain and occasional rumbles of thunder further north. Some of the models did not handle this aspect of the storm correctly, either mishandling or failing to show the storms from central PA and further south. Additionally, clearing in the rain coverage area can be seen over western PA and southwest NY, where some clearing in the cloud cover is ongoing as well. This is setting up further north than modeled, with most models showing rain in NW PA at this time. Another observation to make is that the low pressure appears to be slightly stronger than modeled so far.

Short term outlook: Rain from the MCS will spread into the area, with rain and occasional thunder, heavy at times, starting between 9 AM in western areas, 9:30 in NYC and 10 in eastern areas, and ending by at least 11 AM-12 PM further west and 12-1 PM further east. Based on current observations further west where the rain has moved through, at least 1/2 to 1 inch of rain is expected with this round, locally up to 1.5 inch. After the initial round of rain moves out, drier conditions are temporarily expected as the rain shifts north of the area, and a few peeks of sunshine are not out of the question especially near or south of NYC, but with the warm front expected to stay to the south. As the low pressure shifts southeast through central Pennsylvania into New Jersey, rain and thunderstorms, heavy at times, are likely again in the evening and early overnight hours, possibly strong from NYC and further south with strong wind gusts the main risk, with the rain likely to end around the early-mid overnight hours.

Based on the latest observations compared to the model guidance, including the steady rain focusing north of the area and more clearing in the rain and cloud cover in western PA than modeled, I lowered the rain forecast to 1 to 3 inches across the area, with locally higher totals possible north of NYC. Windy conditions are expected tonight, with an east wind becoming north at 10-25 mph mph, gusting up to 30-40 mph, and while the warm front is expected to stay south of the area, strong thunderstorms are possible as north as NYC, with strong wind gusts the main risk. Stay tuned for more updates throughout the day.

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