August 2: Storms For Weds/Thurs, Tropical Trouble?

Blog Updates:

– The 5-Day Forecast page has been updated for the area tonight.
– The Severe Weather/Tropics page was not updated tonight, as both Wednesday/Thursday’s severe weather risk, as well as Tropical Depression 4, are discussed below.


Today was partly cloudy across the area, with a few showers but not as widespread or heavy as yesterday, when heavy thunderstorms, mainly west of NYC, were stationary, with amounts locally reaching 2+ inches. While the clouds and showers/storms are expected to last through Thursday night, the temperatures are only going to warm up even more, which combined with increased humidity, is going to lead to an uncomfortable week ahead.

Tomorrow’s Outlook:

Tomorrow will be partly to mostly cloudy across the area, with a SSW wind expected. High temperatures will be much warmer than today, in the mid to upper 80s inland and the upper 80s to lower 90s for the immediate NYC area. Long Island and S CT should reach the lower 80s with the onshore wind.

Humid conditions will return tomorrow, with dew points rising back into the upper 60s to lower 70s. While most of the area should stay dry, isolated showers and thunderstorms are possible tomorrow, and with the moist and humid air mass, any storm that forms will be capable of producing heavy rainfall.

Wednesday And Thursday: Hot, Humid, And Potentially Strong/Severe Storms

By Wednesday, the area will start to feel the effects of a slow moving cold front, which will bring the next risk of severe weather to the area on Thursday, the first since July 25. During the day on Wednesday, including the overnight hours, scattered showers and thunderstorms are expected, which combined with precipitable water values over 2 inches, will be capable of producing heavy rainfall. The parameters support at least isolated strong to severe thunderstorms, but are not very favorable, which would support a 10-15% risk of severe weather at most.

A SSW wind is expected for Wednesday, which combined with a warm air mass entering the area, will lead to high temperatures in the upper 80s inland, and the upper 80s to lower 90s for the immediate NYC area. Dew points will also be in the upper 60s and 70s, which will make it feel even warmer.

For Thursday, however, a higher risk of severe weather appears to exist at this time. The latest model solutions bring the cold front closer to the area on Thursday, with very supportive parameters, including high CAPE/LI, wind shear over 30 knots, and Lapse Rates over 6.0. All of these factors support a severe weather risk for Thursday. At this time, I mentioned this possibility in the 5-Day Forecast, however there is still some uncertainty as the models are not yet in an agreement. Stay tuned for more details on this potential.

Starting Friday, a cooler air mass is expected to move into the area. As a result, there will be less humidity, with temperatures similar to those of last weekend, with high temperatures in the upper 70s to mid 80s, and low temperatures in the 50s inland and 60s for the rest of the area.

Tropical Depression 4:

The 4th tropical depression of the year formed earlier today, out of a tropical wave that was mentioned as being likely to develop into a tropical depression or storm in Saturday’s update. Should this storm reach tropical storm status, it will be named Colin.

Tropical Depression 4’s Intensity: At this time, Tropical Depression 4 is under a favorable environment, however its appearance is not very good at this time, with the storm also moving quickly. It is likely that this storm intensifies to reach tropical storm status, most likely either late tonight or tomorrow morning.

TD4 is expected to become at least a moderate tropical storm, however there is more uncertainty afterwards, as some models bring in higher wind shear, which would significantly weaken this storm. However, there is the possibility that TD4 stays under the anticyclone it’s currently under, which is providing TD4 with a favorable environment, and TD4 ends up becoming a hurricane. Until Saturday, these are the percentages I’d give for the intensity:

– 5% chance that TD4 stays a strong Tropical Depression or weak Tropical Storm, then becomes an open wave due to its fast motion.
– 75% chance that TD4 is named Colin, and becomes a moderate to potentially strong Tropical Storm.
– 20% chance that TD4 remains under favorable conditions, and intensifies into a hurricane.

Tropical Depression 4’s Track: This is the most uncertain part about TD4 so far. Most of the models are taking TD4 WNW, if not NW, then recurve it out to sea near Bermuda. Most of these models, however, quickly intensify this storm, which is an unlikely solution considering that they also intensified this storm too quickly before it became a tropical depression. With TD4 currently moving west, south of its forecast track, I decided to lean towards a southern track for TD4, taking it just north of the Leeward Islands. The northern track is not impossible, however I do not think that it is likely at this time.

For the longer range is where there is the most uncertainty. Some models have been bringing TD4 into the area, most notably today’s 00z GGEM run which had a strong tropical storm tracking from southern NJ into Long Island. Other models, however, keep it much further south, taking it towards the southeastern US. More details will come on Tropical Depression 4’s future track and potential impact on the area as details become clearer.

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