Forecast Highlights: This fall’s generally mild and dry pattern has continued with few disruptions through November, which is currently on track to easily set the record for Central Park’s warmest November. A brief cold surge …
Forecast Highlights: The Pacific Ocean basin remains extremely active; in addition to one of the strongest El Nino events on record, the East Pacific ocean is currently the site of one of the most intense …
1:00 PM: Snow Squalls over New York, Pennsylvania Accompany Unseasonably Cold Temperatures For the first time since late April, snow returns to the northeast US in the form of snow squalls over New York and …
Forecast Highlights: The last few days have been highlighted by abnormally drastic shifts in the model guidance regarding hurricane Joaquin, the strongest hurricane in the Atlantic Ocean since 2010, which have since largely settled on …
The Pacific Ocean basin remains extremely active; in addition to one of the strongest El Nino events on record, the East Pacific ocean is currently the site of one of the most intense tropical cyclones in recorded history, with hurricane Patricia having explosively deepened into a 200 mph hurricane only hours before landfall over Mexico. While Patricia is an extremely remarkable hurricane by itself, it will also have implications on a strong low pressure system forecast to affect the eastern United States next week, a connection which this post assesses in more detail.
1:00 PM: Snow Squalls over New York, Pennsylvania Accompany Unseasonably Cold Temperatures
For the first time since late April, snow returns to the northeast US in the form of snow squalls over New York and Pennsylvania. This is only the latest addition to the unseasonable cold currently affecting the northeast United States, as a deep trough with origins from northern Canada continues to progress through the region, highlighted by temperatures at the 850 hPa pressure level near -8 to -10C, values that are more typical of a mid-November than a mid-October trough. Even with partial sunshine, temperatures will struggle to rise past the upper 40s across the area today; in recent years, high temperatures this cold in October were normally observed as a result of precipitation or widespread overcast skies.
The regional reflectivity mosaic from the Pennsylvania State University e-Wall, shown to the left, depicts snow squalls over New York and Pennsylvania, which developed in association with steep boundary layer lapse rates and a northwesterly flow off of the Great Lakes, especially over the higher elevations in New York where there is higher low-level humidity and a lower lifted condensation level (LCL), along with cooler temperatures in the 30s. In the lower elevations, despite surface temperatures in the 40s, dewpoints are generally in the 20s throughout the region resulting in wetbulb temperatures near freezing, indicative of snow or graupel with the heavier squalls passing through the Hudson Valley and Connecticut. Temperatures in NYC, most of New Jersey and Long Island are a little too warm to support snow, although isolated showers possibly mixed with graupel cannot be ruled out this afternoon.
With the trough axis shifting east of the region overnight, indicative of upper-tropospheric convergence and subsidence, a surface high pressure will build into Pennsylvania and Maryland, resulting in clear skies and light winds. A persistent light northwesterly breeze will likely prevent much radiational cooling from occurring in Long Island and coastal CT, where the wind will maintain a low-level mixed layer with temperatures slowly falling off into the low 30s, as with NYC where temperatures will likely fall into the mid 30s. Farther inland, however, especially towards western NJ and interior southeast NY, calm winds will allow for a radiational inversion to develop, with temperatures quickly falling off into the mid 20s. Mainly sunny skies with a southwesterly flow will resume on Monday, allowing temperatures to warm back up into the low 50s, followed by a resumption of the warm and dry fall pattern as a ridge builds over the eastern United States in the mid-late week period as temperatures return into the low to mid 70s.
The last few days have been highlighted by abnormally drastic shifts in the model guidance regarding hurricane Joaquin, the strongest hurricane in the Atlantic Ocean since 2010, which have since largely settled on a track far offshore, a major difference from the model consensus just 24-36 hours ago for a Mid Atlantic landfall. Today’s post analyzes some of the factors that contributed to the exceptionally poor model guidance performance for Joaquin, as well as an update on the forecast through the remainder of the week. (Image from Tropical Tidbits)
Following several months of relative inactivity, highlighted by well above normal temperatures and drier than normal conditions with much of the tri-state area in a drought, two major rain events are expected to affect the region this week, ending a 2+ week stretch of no rain. Multiple rounds of rain are expected, especially on Wednesday morning and possibly during the weekend, resulting from the interaction of a deep trough and Tropical Storm Joaquin, potentially amounting to several inches of rain which will aid in easing the drought but with the risk of significant heavy rainfall and storm surge along the coast in the worst case scenario.
The anomalous warm and dry pattern observed throughout this month and much of August continues unabated, with temperatures over 5-7 degrees above normal and only 4 out of 33 days having recorded measurable rain at Central Park. Little relief is in sight with the upper-level ridge persisting through the remainder of the month, although the possibility of at least some rain can’t be ruled out towards September 27-30 with a weak coastal low pressure.
September 2015 started off on an anomalously warm note, with the first week of the month averaging out to at least 5 to 8 degrees above normal. The persistence of upper-level ridging has further suppressed any rain potentials, with the last significant rain event having occurred nearly a month ago. Short-term relief from the heat and drought is on the way, however, as the trough axis shifts eastward towards the Great Lakes, accompanied by a slow frontal passage on Thursday accompanied by much cooler temperatures and potentially heavy rain.
Little relief is expected from the ongoing drought over portions of the area as an anomalously strong upper-level ridge becomes stationed over the eastern half of the US through at least the next 1-2 weeks. With the exception of a possible backdoor cold front late next week, little to no rain is expected during this upcoming period with above to well above normal temperatures, returning into the 90s in parts of the area in the first half of the upcoming week and potentially becoming the first September heat wave since 2010.
A weak cold front moved through the region today, and brought little relief from the expanding abnormally dry conditions as the majority of the rain stayed well inland. As an upper level trough continues to slowly expand eastward, temperatures will cool down on Wednesday and Thursday, only peaking in the upper 70s to low 80s, before rebounding into the upper 80s by the weekend with a risk of isolated thunderstorms, and possibly returning into the 90s by next week with no significant rain event in sight at this time.