July 22, 2011: Excessive Heat Continues

– The 5-Day Forecast page was updated for the short term, through Sunday, though the forecast beyond Sunday was discussed below. The 5-Day Forecast page will be updated tomorrow morning through Wednesday.
– Two updates will be posted tomorrow morning; one will be a brief update about tomorrow’s heat and the risk of isolated thunderstorms, and the other will be a summary of this week and forecast verification.
– A new “Tropics” page was created. Updates will be posted in this page starting tomorrow morning.
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Heat Summary:

Across the area, today was one of the hottest days ever recorded in the New York City area, and across parts of the area and the region, even broke all time heat records. Newark, NJ reached an all time record high of 108 degrees, which produced a heat index well into the 110s when combined with dew points in the upper 60s to lower 70s. In addition to Newark’s record, Bridgeport in Connecticut tied their all time record high of 103 degrees. Central Park’s 104 degree high temperature is their 2nd warmest temperature on record, and Teterboro’s 104 degrees is two degrees below the all time high temperature of 106 degrees. Below are the high temperatures today across the area, from the National Weather Service:

New York

104 degrees – LaGuardia Airport

104 degrees – Central Park
103 degrees – JFK
100 degrees – Islip (Long Island)
98 degrees – Montauk (Long Island)

98 degrees – White Plains
New Jersey

108 degrees – Newark (Essex)
104 degrees – Teterboro (Bergen)
103 degrees – Caldwell (Essex)
100 degrees – Morristown (Morris)
99 degrees – Sussex (Sussex)

Connecticut

103 degrees – Bridgeport
101 degrees – New Haven
95 degrees – New London

Even though the temperatures were already hot enough, the humidity made the heat even worse. When Newark reached 108 degrees, the humidity resulted in a heat index of 117 degrees. Heat indices in the 110s were observed across most of the immediate NYC area due to dew points in the 70s combined with very hot temperatures. During July 2010, the area also observed a heat wave early in the month with similar temperatures, but during that heat wave, the humidity was not as significant as it was with this heat wave. The heat index values observed with this current heat wave are abnormally high and are quite rare for the NYC area.

Today brought the worst of this heat wave. Tomorrow, unfortunately, won’t bring any significant improvements as the heat and humidity continue with the only difference being slightly lower temperatures and humidity. Sunday will bring relief in the form of a cold front, which will be followed by much cooler temperatures on Monday along with the risk of thunderstorms. This cool down is only brief, however, as another heat wave is possible once again late next week.

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Tonight’s Outlook:

Temperatures are still very warm across most of the area, and as of 9 PM, temperatures were in the mid 80s inland, lower to upper 90s in the immediate NYC area, and in the upper 80s to lower 90s east of NYC. Temperatures will continue to gradually drop overnight, reaching the mid 70s inland, upper 70s to mid 80s in the immediate NYC area, and the mid 70s to lower 80s in Long Island and southern Connecticut. With the humidity still in place, the heat index value will stay high, dropping into the upper 80s at the lowest in NYC/Newark. There is the potential that if low temperatures end up in the mid to upper 80s in NYC/Newark, these locations could break the record for the highest minimum temperature.

Tomorrow’s Outlook: Heat Continues

Tomorrow will bring only minor improvements as the heat and humidity continue across the area. Temperatures at 850 mb, which were near 24 degrees celsius today, will slightly lower tomorrow to around 22 degrees celsius. As a result, high temperatures will be slightly lower as well, reaching the mid to upper 90s inland, lower to mid 100s across most of the immediate NYC area with a west wind. With a WSW wind in Long Island/southern CT, however, temperatures will be lower than those of today, reaching the mid 90s in southern Connecticut and the mid to upper 90s in Long Island, except for the immediate southern coast which should stay in the lower 90s.

Dew points will be slightly lower as well, reaching the upper 60s to lower 70s across the area. This will result in slightly lower but still dangerous heat index values across the area, which are expected to end up near 100 degrees inland, 105 degrees in the immediate NYC area, and 95-100 degrees in Long Island/southern Connecticut.

Partly sunny skies are expected tomorrow, but as the cold front approaches, thunderstorms may be possible tomorrow afternoon. At this time, the NAM model is the most bullish with this storm risk, showing widespread precipitation tomorrow afternoon which prevents temperatures from getting into the 100s in the area. The rest of the models, however, are drier, and the parallel NAM run is much drier as well. At this time, I put a risk of isolated thunderstorms in the forecast, and any storms that form could become strong with the instability in place, but widespread activity is not expected, and most places are expected to stay dry at this time. Another update will be posted tomorrow morning, which will discuss any storm risk tomorrow.


Sunday – Monday: Relief From Heat
A cold front will move through on Sunday, bringing needed relief from the heat. Temperatures will still be hot, reaching the upper 80s to lower 90s across the area with a few mid 90s possible in NE NJ, but the humidity will be much lower, with dew points dropping into the lower to mid 60s across the area, which will keep the heat index below 95 degrees. In addition to the cooler temperatures, scattered thunderstorms are possible, but are not expected to be widespread at this time.
Monday, however, will bring much cooler temperatures. A low pressure to the north of the area will move east, bringing a SE wind into the area. Meanwhile, mostly cloudy skies are expected along with widespread showers and thunderstorms. This will bring a much more significant cool down into the area, with temperatures only reaching the lower to mid 80s from NYC and further west, and the upper 70s to lower 80s in Long Island and southern Connecticut.
Tuesday And Beyond: Heating Up Again
As the low pressure moves out by Tuesday, warmer temperatures will begin to return. The low pressure will likely keep a weak trough around the NE around Tuesday/Wednesday, which will bring a WNW wind into the area along with temperatures in the lower to mid 80s across most of the area and a few upper 80s in the immediate NYC area. By late next week into next weekend, there is some uncertainty with the exact scenario, but it appears that the ridge briefly shifts east again closer to the area, allowing another strong surge of heat to potentially affect the region. Should this scenario verify, the heat is likely to be weaker and shorter lasting than what we are current seeing, but the potential is there for temperatures to surge well into the 90s once again for a day or two in the area, with a few 100s possible across parts of the Northeast/Mid Atlantic once again. Stay tuned for more information on the longer range with a brief update tomorrow morning.

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