THE "WHY" BEHIND GETTING DUMPED ON TOMORROW NIGHT...

Meteorologists use a variety of tools to find the biggest threats associated with thunderstorms.  one of these values that they monitor is called "Precipitible Water Value" or PWATs.

This value shows how much water the atmosphere is capable of holding at a given time, and consequently, how much rainfall is possible with any one storm (or a number of them hitting one location). For tomorrow, the PWAT value shows that storms will have near-maximum conditions to deliver copious rainfall amounts across the region. Values shown in this graphic (see below) show that the atmosphere will be primed to deliver over 2 inches per hour rainfall rates in some cases with any given storm!

I suspect that if this trend holds, the NWS might consider issuing flash flood watches later today for parts, or all of the area for late tomorrow afternoon into tomorrow night.

BREAKING DOWN THE STORMS TOMORROW...

i put together a map of the storms for tomorrow highlighting two zones. the first zone is for north and west of NYC and the second zone is from NYC and points to the east.

I have a feeling that the storms are going to play out like they did a couple of weeks ago on July 26th. In that instance, a lot of the activity that was the strongest stayed west of the Hudson River and it weakened as it came east.

However, further east, there still remains a flash flood threat, which includes the NYC metro area. The storms will be loaded with moisture and could dump well over an inch in just an hour's time.  The flooding threat will be a bigger problem for the Monday morning commute the further east you go because the storms will take longer to clear those areas. Overall though, if the forecasts hold, the morning commute Monday should not be impacted too severely.

DOG DAYS OF AUGUST ARRIVE WITH CLASSIC SUMMERTIME PATTERN

PREDICTABILITY OF FORECAST PERIOD THROUGH WEDNESDAY-MEDIUM
PREDICTABILITY OF FORECAST PERIOD THURSDAY AND FRIDAY-LOW


1. still a threat in most forecasts for a risk of a thunderstorm through Sunday. Then, things get more active beginning Sunday late afternoon/night into Monday early morning, when fast moving storms roll through and hit most everybody. Severe weather possible in the form of strong wind gusts, but overall, it's a flash flood threat.

2. Saturday: Humidity will start to rise by midday, and become increasingly oppressive through Monday midday. Most uncomfortable conditions look like Sunday, with full-on spike in dew point. Actual temp near 90 both days, but "reelfeels" and "heat index" values near 100.

3. Monday afternoon through Tuesday, increasingly less humid conditions. Tuesday is the best day of the week, with no precip possibilities. Highs in the mid 80s.

4. By Wednesday and Thursday, a risk of a shower/storm creeps back in, along with the humidity. Better chance for storms thursday, before another cool-down tries to establish itself over the area.

5. Ernesto to become a Caribbean hurricane and threaten Mexico/South Texas by the middle of next week.

FUN WITH ERNESTO...

The track of Tropical Storm Ernesto is going to be very critical for the future evolution of the storm and its impact on the US coast.

That is an obvious statement.

But what is less obvious is the intensity forecast . Joe Bastardi of Weatherbell has a strikingly different forecast altogether intensity-wise than that of the National Hurricane Center, which just issued its forecast around 11 PM EDT.

SInce 5pm, the NHC track has shifted with the corrected fix on the actual center of the storm. This is typical in early storm development; the initialization of the storm's position is very elusive in the developing stages, and often times, Recon flights are necessary to hone in on the exact position.

I put together a slide showing the national hurricane Center forecast versus theWeatherbell forecast. I used the AccuWeather graphics for the second graphic but keep in mind,  JB does not work for AccuWeather any longer.

The difference is a stark. The national hurricane Center has a formidable hurricane rolling through the Caribbean in 60 to 72 hours. On the other hand JB has the storm being ripped apart by what he sees as  stronger than usual winds near the Central American coast for the very same time period.

VIDEO: MUGGY AND UNSETTLED THROUGH MONDAY

PREDICTABILITY OF FORECAST PERIOD REMAINS LOW THROUGH MONDAY

WHY SO MUCH "CHANCE" OF STORMS THIS WEEK?

UNSETTLED, MUGGY WEATHER TO HIGHLIGHT THE UPCOMING WEEK...

PREDICTABILITY OF FORECAST PERIOD THROUGH FRIDAY--LOW

Although Sunday (today) and Monday still look mostly dry around here, the overall pattern will promote the opportunity for numerous showers and heavy thunderstorms for the balance of the week beginning Tuesday. The main culprit will be rich tropical air that will have a free pass into the region from the southern states for much of the week; this muggy air mass will work in tandem with slow moving, small disturbances in the atmosphere to promote the daily occurrence of soaking thunderstorms capable of producing localized flash flooding for some spots.

The best shot at these storms will be on Tuesday and Tuesday night...but as noted already, peak heating during the days from Tuesday onward through Friday could deliver the necessary spark to ignite heavy showers.

Accu-weather Overall Pattern Slide...

To make it more complicated, not everyone will see rain this week. It will be very difficult to pinpoint the exact location of the heavy rainfall until an hour or two before it arrives in most cases. Additionally, a by-product of this unsettled pattern will be to keep the daily high temps in check to normal levels; there are currently no signs of a formidable stretch of 90-degree heat.

Intellicast temps are not that different than what was shown here this past Wednesday for this upcoming week.

So far, the NYC metro area has seen four "heat waves" of three straight days of 90+ actual temps, and none are in sight as we approach August. In fact, odds are that as the El Nino pattern takes a firmer foothold in the northern hemisphere, we will see an marked increase in rainfall, as well as a possible influence from the tropics as the 10th of the month draws near.

"weather overview" terms to help kick the point-and-click:

PREDICTABILITY OF FORECAST PERIODS

HIGH- most credible sources are in excellent agreement

MEDIUM: most credible sources are in fairly good agreement, with some differences

LOW: widespread differences in forecasts, AND overall low confidence from NWS Upton office

Risk of a shower/thunderstorm-probability of a shower is low. Most of the forecast period will be dry.

Numerous (heavy can be inserted) Showers/thunderstorms- probability of showers is high, and could happen multiple times during the given forecast period. Constant rain is not expected

Rainy conditions-intermittent precip; rain can vary in duration, but usually will last more than an hour. Light to moderate intensity. Less than an inch expected during the forecast period.

Heavy Rain-soaking, constant rainfall for at least an hour (duration can be much longer); amounts over a half an inch. 

Light snow-very light snowfall. Little to no accumulation. Duration depends. 

Snowy conditions-intermittent snow can last more than an hour at a time, but generally average less than 3 inches total.

Heavy Snow-heavy snowfall. Snowfall of at least 3 hours in duration. Totals can be added in

Drizzle-constant drizzle

Occasional Drizzle-intermittent drizzle