Year: 2014

Warmer & Humid Tomorrow with PM T-Storms

Miguel Pierre Flooding, Severe Wx, Short-Term

A warm front move through the area tomorrow morning with some clouds. Winds turn more southwesterly south of this front, transporting a much warmer and humid airmass.  Temperatures over New York City and much of New Jersey will rise into the middle to upper 80s. However, this will be short-lived as a cold front will moving through the area tomorrow evening with some scattered showers and thunderstorms.

The 12z NAM models showing 80s for highs over much of NJ and NYC, with southwest winds. Then some showers or thunderstorms for the northwest.
The 12z NAM models showing 80s for highs over much of NJ and NYC, with southwest winds. Then some showers or thunderstorms for the northwest.

The Storm Prediction Center had issued a slight risk early this morning for these t-storms tomorrow. This was mainly in the warm sector, when instability is more likely to support severe thunderstorms. However, this afternoon look as removed the slight risk entirely. Regardless of what SPC issues, there are some factors going against widespread severe weather. Mid-level lapse rates are poor with a mostly west to southwest flow aloft. While 0-3km helicity values are in 150 m2/s2 to 200 ms/s2 late tomorrow, 0-6km bulk shear is between 25kt to 30kts with 500mb winds a little weak in the area. Clouds in the warm sector also an issue with getting more extreme CAPE values. Some models show SBCAPE near 1000 J/kg over Central and Northern New Jersey. But MLCAPE and NCAPE values are lower. This suggests CAPE will be skinny and will not support very tall updrafts. Southeast winds or sea-brezzes ahead of the warm may also keeps parts of Long Island and NJ shore, in more stable airmass. Which supports thunderstorms to weaken in this area. All this considered, I think will any severe weather will be very low and isolated. Some t-storms might strong enough produce wind gusts near 40mph. There is also very small possibility of very weak spinups (tornadoes) along the warm front nearby). But without more instability, this threat is not heightened here. Models do show very high precipitable water values over 2.20″. So any thunderstorm will be capable produce some very heavy rainfall with flash flooding in poor drainage areas.

12z NAM today precipitable water values over 2.20"+
12z NAM today precipitable water values over 2.20″+

Showers and thunderstorms will taper off later tomorrow night and clearing will take place late. A cooler and less humid airmass is in store starting on Friday. High temperatures will only reach the lower to middle 70s, despite alot of sun. Some uncertainty continues over the weekend as models stall this cold just off the Mid-Atlantic coast on Sunday. Then move a number of waves north up this frontal boundary through early next week. Details will be fine tuned as we get closer.

Unsetteled Weather This Week, Cooler Weather To Follow Next Weekend

Miguel Pierre Long-Range Discussions, Short-Term

Today like another pleasant day with a mixture of sunshine and clouds and east winds keep high temperatures in middle to upper 70s. However, the weather becomes more unsettled starting tonight. Low pressure currently over Carolinas, will slowly move northeastward through Wednesday.  There are some model differences handling of this system. But most models keep this keep this low far enough south and east, to spare most of the region any heavy rainfall. At this time, I expect clouds to increase across the entire region tonight. Some periods of light rain, are possible for the coastal sections, especially over Long Island and Central New Jersey starting late tonight through tomorrow night. Areas farther northwest, will remain dry. I will continue to be monitor this low with future model runs and some nowcasting.  Just a 50 mile shift west will bring more significant rainfall. On the hand, a 50 mile shift further east might mean more sunshine tomorrow, for parts of the area.

Regardless the small differences, there will tight pressure gradient between this low and a strong high pressure over Maine or Nova Scotia. East to northeast winds will increasing to 10mph to 20mph with gusts 25mph near the coast by tomorrow and persist into Wednesday. With a full moon tomorrow, some minor coastal flooding and beach erosion is possible for multiple high tide cycles. Especially along the New Jersey shore and around Western Long Island sound. The National Weather Service in Upton, NY has issued a coastal flood statement for this reason.  Important to note, that this isn’t a powerful storm and any impacts along the coastline, look to be minimal. Strong or damaging winds are not expected out this storm.

Clouds should break for some sunshine later on Wednesday afternoon as this low begins consolidated and track into the Atlantic. Easterly winds, will only allow high temperatures in there middle to upper 70s. Another low pressure system will be track to over the Great Lakes Wednesday night. The warm front associated with this system  through area on late Wednesday night and early Thursday with some isolated showers or thunderstorms possible. If this warm front moves north, as the GFS and the ECMWF to a lesser extent shows, much of the Tri-State area could be in the warm sector with more humidity and high temperatures in middle to upper 80s on Thursday. On the other hand, if the warm front stays further south, we could be stuck with an onshore flow and more clouds. Right now, I will lean towards more reliable GFS and ECMWF model solutions. Regardless, a strong cold front will approach the area with some showers and thunderstorms likely by Thursday night.

Some uncertainty afterwards, as the ECMWF is much slower with the cold front passing through the area. The GFS would much cooler and drier for Friday and Saturday.  While the ECMWF keep more showers and thunderstorms into for Friday and Saturday, with a wave forming along frontal boundary. The GFS might be too progressive and ECMWF might to be strong with the east coast ridge at the end of the week. Regardless of either solution, below normal temperatures look likely starting next weekend and continuing into much of next week. As most guidance shows a strong West Coast ridge, causes a large trough over the Central and Eastern United States.

0zGEFSf192

 

Hot & Humid With Strong Thunderstorms Possible Today

Miguel Pierre Flooding, Severe Wx

Yesterday south to southeast winds, transported a very muggy airmass into region. However, these winds off ocean, cause marine inversion with low clouds to develop. This kept atmosphere from mixing and less stable. Temperatures in the 80s across most of the Tri-state area. Today will be hot and humid as we much deeper westerly to southwesterly flow with 850mb temperatures near 18C this afternoon. This will likely allow for deeper mixing and temperatures to rise into the lower 90s, across much of New Jersey and into New York City. The only caveat here is that some convective debris from decaying showers and thunderstorms Western New York and Pennsylvania early this morning, works it east today.  This could possibly keep high temperatures in the upper 80s.  Closer to coast sea-breezes will develop this afternoon and keep high temperatures in middle to upper 80s.

temp13

A pre-frontal trough developing over the area, will trigger some scattered showers and thunderstorms this afternoon and early this evening. These will form over interior areas for first then move southeast towards the coast. Latest NAM model guidance is showing 2000 – 3000 J/kg of MLCAPE, 20-25kts unidirectional 0-6km bulk shear, precipitable water values 1.5″ – 2.0″ ahead of this activity this afternoon, away from the shore. This is enough instability and moisture for thunderstorms to become strong or severe and produce very heavy rainfall in a short period of time. But shear is insufficient for thunderstorms to sustain their updrafts and organize into bow lines. At this time, I expect scattered thunderstorms to be pulsing up and down in intensity. Isolated damaging wind gusts and flash flooding in poor drainage areas will be the main threats. The Storm Prediction Center has already included much of the area in a 15% slight risk. So stay tuned for any severe thunderstorm watches this afternoon or evening.

namNE_con_mlcape_012A cold front passing through the area, may trigger more showers and thunderstorms early tonight. However with the sun going down, instability will diminish. So these thunderstorms will be less capable of becoming severe. Behind this front is cooler and less humid airmass. Sunday will mostly sunny with high temperatures in the upper 70s to lower 80s. Monday and Tuesday will looking more questionable some model guidance showing a coastal low impacting the area with some rain and wind. Another post here will come later today on this system with new model data. 9/7 Update (that post will be delayed for model data today..)