Severe Wx

Very Warm & Humid Through Labor Day with Heavy Thunderstorms Likely

Miguel Pierre Flooding, Severe Wx

A deep southwesterly flow, will transport a very warm and humid airmass today with clouds mixing with some sunshine. High temperatures today will depend on the amount of cloud cover. Areas that see more sunshine, could get make run at 90 degrees or higher today. More clouds than sun, highs will be in lower to middle 80s. The forecast highs will compromise between middle to upper 80s. Except near the shore, a southerly winds likely keep high temperatures in lower to middle 80s. A surface trough and shortwave trough (upper-level disturbance) will trigger numerous showers and thunderstorms across the region late this afternoon and tonight.

6z NAM showing a surface temps middle to upper 80s in most areas with dews in 60s (top left). Also a shortwave trough approaching trigging showers and thunderstorms west of New York City
6z NAM model showing a surface temps middle to upper 80s this afternoon in most areas with dews in upper 60s and lower 70s , Also a shortwave trough approaching trigging showers and thunderstorms over Western parts of region late this afternoon.

Models show anywhere between 1000 J/kG and 2000 J/kg of MLCAPE with 25kt to 35kts of shear this afternoon and early this evening. This will support some thunderstorms to become strong to severe with damaging winds being the main threat. Some backing of the low-level winds this afternoon, could support an isolated, weak tornado. Especially over Northern NJ and Lower Hudson Valley. Some hail is also possible out thunderstorms. But threat for large hail is reduced somewhat with high freezing and wet-bulb zero levels. Inhibiting factors for severe weather today, are weak mid-level lapse rates and some cloud cover keeping surface-based instability from reaching extremely high levels. Also with winds more out the south this afternoon, areas near the coast will be more stable and this may cause thunderstorms to weaken. Which is why the Storm Prediction Center has the 15% slight risk northwest of NYC. Overall I’m expecting any severe weather reports to be isolated to scattered across to the region.

6z NAM model showing MLCAPE between 1000 J/kg and 2000 J/kg by early this afternoon over the Tri-State area.
6z NAM model showing MLCAPE between 1000 J/kg and 2000 J/kg by early this afternoon over the Tri-State area.

More likely than the severe weather, is potential for heavy rainfall out of thunderstorms late this afternoon and tonight with pwats (precipitable water values) near or over 2.00″.  With mostly unidirectional shear, some of training of storms with flash flooding possible in  low-lying or poor drainage areas. Depending how showers and thunderstorms setup some places could receive less than .50″ rainfall to locally one to three inches of rain.

6z NAM showing (pwats) precipitate water values 2.00" over greater over the Tri-state area
6z NAM showing (pwats) precipitate water values 2.00″ over greater over the Tri-state area

That all being said, it is not necessary to cancel plans. It will be dry, until late this afternoon for most areas and perhaps until early this evening for coastal areas. If you are at beach, park,pool, etc, be prepared to move indoor as quickly as possible, if a thunderstorm hits. Any thunderstorm whether severe or not, can produce dangerous cloud to ground lightning. Don’t take shelter under trees, as they are huge conductors of electricity. Tomorrow (Labor Day) will continue very warm and humid with mixture of sunshine and clouds. More scattered showers and thunderstorm will still be threat all day tomorrow. As the shortwave trough lingers over the area. Pwats still over 2.00″ will  support heavy rainfall out of any thunderstorm tomorrow. However, with move convective debris or clouds, this will likely keep instability lower. On Tuesday, surface high pressure will build briefly more sunshine. A deep southwesterly flow with 850mb temperatures around 18C will help temperatures rise into the lower 90s, away from the coast. A cold front and upper-level trough approaching from the west will trigger more showers and thunderstorms by Tuesday night.

Check the latest Tri-State 7-day forecast details and summary for more updates for today’s severe threat threat.

Also follow @WeathergunNY for any watches and warnings later this afternoon and night.

Have a nice Labor Day weekend!

Some Heat Returns, Labor Day Weekend Looking Unsettled

Miguel Pierre Severe Wx, Summer Wx, Uncategorized

Some heat is making comeback this week, as ridge builds over the Eastern US. This ridge has been enhanced by Cristobal. Which is now a category 1 hurricane just northwest of the Bahamas and will recurve out to sea this week. Today we saw sunny skies with highs in the middle to upper 80s through much of the local tri-state area. Tomorrow looks pretty same, except a stronger south to southwest flow may keep areas near the shore a little cooler tomorrow.

On Wednesday a cold front will be across the region, during the afternoon. The flow will turn more west to southwest, pumping in more heat and humidity. Temperatures with enough sunshine could get to or above 90F degress for highs on Wednesday for much of NJ and NYC area. Some showers and thunderstorms may form along this cold front. The NAM shows very unstable airmass away from the coast, with MLCAPE values between 1500 J/kg and 2500 J/kg. Shear is also marginal enough for threat of some isolated strong to severe thunderstorms. Other models such as GFS and ECMWF have the atmosphere more capped and stable, keep coverage of showers and thunderstorm very low. It should become clearer tomorrow if we are looking at threat of severe weather.

After this cold passes through Wednesday night, a cooler less humid airmass will be ushered in again. Higher temperatures return to near normal, in the lower 80s for most spots. Heat and humidity may try to return over the Labor Day weekend. As a ridge starting building east again. However, a frontal system approaching the west, may keep unsettled weather conditions for the weekend. At this time, it doesn’t look a like complete washout, and I don’t advise to change any plans yet. But there will probably be some showers or thunderstorms, at some point. Model guidance shows different timing of this system’s warm and cold front moving through the area. This should become clearer as we draw closer.

 

Somewhat Unsettled Weather Continues, No Direct Impacts from Bertha

Miguel Pierre Severe Wx, Summer Wx, Tropics

A weak wave of low pressure moving north, along a stalled frontal boundary, has been producing some showers over eastern parts of the Tri-State area this morning. This system is now moving out of the area and clouds will break for some partial sunshine this afternoon. An 500mb shortwave approaching from the west and south, may trigger some widely-scattered showers or thunderstorms late this afternoon and tonight. Particularly over Northwest New Jersey and the Lower Hudson Valley. Some heavy downpours with any thunderstorms are possible. Instability will be on the low side. So severe thunderstorms are not anticipated. Temperatures will only rise into middle to upper 70s despite some sunshine this afternoon. Which is several degrees below normal.

12z NAM showing shortwave over PA late this afternoon
12z NAM showing the 500mb shortwave over PA late this afternoon

Monday and Tuesday will be partly sunny and warmer with temperatures in reaching the lower to middle 80s. With colder air aloft, there is a chance of an isolated shower or thunderstorm to pop up in the afternoon and early evening hours. Especially, north and west of New York City. Marginal instability and weak shear supports any thunderstorm be slow-moving and produce heavy rainfall. Then a series of disturbances will move across the area, from the west on Tuesday night and Wednesday. Clouds will mix some sunshine, with a chance of some scattered showers and thunderstorms, Heavy rainfall from thunderstorms is again possible. But at this time, with only marginal instability and weak winds fields being shown, severe weather is not expected. A cold front will move across the area on Wednesday night. Fair weather will return on Thursday and Friday, with high temperatures closer to 80 degrees. Which is slightly below normal for this year.

12z model projects. Strong consensus on a recurve between U.S. East Coast and Bermuda.
12z model projects. Strong consensus on a recurve between U.S. East Coast and Bermuda.

Meanwhile, Tropical Storm Bertha continues to churn, just north of Hispaniola  and over Turks and Caicos islands this morning. Currently the storm is poorly-organized with most of the convection east of the presumed center.  Surface observations available in the region this morning, also don’t indicate a closed surface circulation. However, most models continue to show Bertha becoming a strong tropical storm or minimal hurricane in the next few days as it recurves out to sea, midway in between the US East Coast and Bermuda. A few models suggest that Bertha remnants will be absorbed by a non-tropical low developing near the Southeast US Coast this week. Either way, no direct impacts are expected from a tropical system are expected in the Tri-State area. Except for perhaps some rough surf at the area beaches on Tuesday or Wednesday.