bluewave

LGA gusting to 52 mph. http://wxweb.meteostar.com/meteogram/link.shtml?choice=Klga

Severe gust in Philly.

I guess that they are are relying on TPHL.

Be interesting to see if that line is strong enough to verify the warning.

This first batch produced hail just below severe limits in Monmouth County, NJ.

This first line developed very quickly. But you can see both HRRR versions with a second line sweeping through right behind it. Don’t need much sun or clearing to get storms going with such steep midlevel lapse rates.

The storms don’t really develop until they reach our area where the steeper midlevel lapse rates are located. JFK already gusting over 40 mph ahead of the storms. You can see some storms ahead of the main energy firing over NNJ with this steep midlevel lapse rate plume. Kennedy Intl PTSUNNY 52 48 86 S31G41

The squall line is beginning to develop over SE PA.

Also our first year since 1998 when the March maximum temperature was higher than April. Monthly Highest Max Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Mar Apr Season 2020 77 68 77 2019 75 80 80 2018 62 82 82 2017 70 87 87 2016 79 82 82 2015 62 80 80 2014 66 77 77 2013 59 82 82 2012 78 88 88 2011 77 83 83 2010 74 92 92 2009 70 92 92 2008 63 84 84 2007 78 86 86 2006 74 83 83 2005 63 87 87 2004 70 85 85 2003 69 88 88 2002 72 96 96 2001 57 87 87 2000 71 75 75 1999 74 80 80 1998 86 73 86

First time since 2000 that we are getting a cool April after such a warm March. Top 5 warmest Marches in NYC since 2000 Monthly Mean Avg Temperature for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Year Mar Apr Season 2012 50.9 54.8 52.8 2016 48.9 53.3 51.1 2010 48.2 57.9 53.0 2020 48.0 50.9 49.1 2000 47.2 51.0 49.1

The +PNA takes over once the NAO and EPO flip positive. So we still get a lingering trough over the Northeast. It will probably stay in place as long as the MJO remains around phase 3.

If the NAM is correct, then we may be under a severe thunderstorm watch on Tuesday. Very impressive squall line potential with steep midlevel lapse rates and some surface based instability. Could also see an embedded meso spin up in the line with high helicity values.

68 degrees will be the high temperature in NYC for the first 20 days of April. This is -15 below the average maximum of 83 degrees since 2010. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Ending Date Highest Max Temperature Apr 1 to Apr 20 Missing Count 2020-04-20 68 1 2019-04-20 80 0 2018-04-20 82 0 2017-04-20 87 0 2016-04-20 82 0 2015-04-20 80 0 2014-04-20 77 0 2013-04-20 82 0 2012-04-20 88 0 2011-04-20 81 0 2010-04-20 92 0

Tuesday looks like a strong to potentially severe squall line that could change to snow over the higher elevations of the interior Northeast. Very strong cold front for this time of year. Could be another -10 temperature departure on Wednesday. April could be the first month with 3 days to reach -10 since November. Northeast... A powerful upper trough will take on a negative tilt Tuesday as a cold front surges east across NY, PA, and southern New England. Rapid cooling aloft will occur in association with the left-exit region of a cyclonically curved upper jet, with the core of the strong lift swinging east/northeast across NY and New England. Forecast soundings ahead of the cold front indicate SBCAPE up to 100-200 J/kg (depending on the model) is likely within a narrow north-south zone during the day, fueling shallow convection. Long hodographs may sustain convection, with a large cross-boundary component to the deep-layer shear vectors. Given the strength of the system, at least isolated damaging wind gusts will be possible, even with minimal SBCAPE. Cellular storm mode may be present as well given the long hodographs, and small hail is possible. Any severe risk on Tuesday will be highly dependent on instability, and an increase in probabilities cannot be ruled out in later outlooks.

A wild card moving forward may be all that warm water over the Eastern IO. MJO 3 is associated with a trough over the East this time of year. During the summer this pattern can produce a trough over the Midwest or Great Lakes. But the Atlantic and Gulf record SST’s support a strong WAR pattern. How far west this ridge is able to build will determine whether we have a 0 to +2 summer or warmer. In any event, looks like it could be wet and humid if such a pattern sets up. So maybe warmer summer minimums and clouds preventing more frequent 100 days of 2010 to 2013. Be interesting to see how things turn out.

The EPS is cool and wet for us until further notice. The -EPO/-NAO will get some help from a strong +PNA ridge out west. So the trough stays in place over the East.

Yeah, we have become used to at least +2 to +3 monthly departures and top 10 warmest finishes. But Islip was able to set a record low temperature the other day. Record lows have become few and far between. The lack of an April monthly high temperature of 70 or warmer really stands out so far. If this can hold, then it would be the lowest April high temperature on record at Newark. NYC is currently at 3 lowest. This tells you how strong the blocking influence on on pattern is this month. 4/17 30 in 2020 30 in 2005 30 in 1971 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Apr Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Missing Count 1 2020 69 12 2 1940 70 0 3 1931 71 0 4 1966 72 0 - 1937 72 0 5 1998 74 0 - 1997 74 0 - 1988 74 0 Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Apr Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Missing Count 1 1874 64 0 - 1873 64 0 2 1940 67 0 - 1875 67 0 3 2020 68 12 - 1883 68 0 4 1884 69 0 - 1876 69 0 5 1916 70 0

Yeah, a combination of the slowing AMOC and stronger +NAO. https://noc.ac.uk/news/changes-ocean-circulation-cause-largest-freshening-event-ne-atlantic-120-years Changes in ocean circulation cause largest freshening event in NE Atlantic in 120 years Posted: 29 January 2020 A change in the routing of fresh water coming from the Arctic has led to a remarkable reduction in salinity in the North Atlantic Ocean west of the UK, according to research published this week in Nature Communications. An enormous area between UK and Iceland had record-breaking low salinity at the surface by 2016 – the lowest since records began in 1895. Lead author, Professor Penny Holliday from the National Oceanography Centre (NOC), said “This is the first time the physical process causing this reduction in salinity has been identified. This helps us build a picture of the factors influencing environmental conditions, including looking to see whether existing models can reproduce it.” “We care about the environmental conditions because they can impact ecosystem health, and knowing how things are changing is a key step towards managing our marine resources sustainably.” Led by NOC scientists and co-authored by the Scottish Association for Marine Science (SAMS), this study shows that in 2012 to 2016 unusual wind patterns forced Arctic fresh water carried by the Labrador Current away from the eastern North American continental shelf. The cold, fresh water was directed into the North Atlantic Current which carried it towards the UK and Iceland. An unexpected and rapid decrease in salinity, known as the ‘North Atlantic fresh blob’ developed while the region was also cooling and developing a feature known as the ‘North Atlantic cold blob’. Recent research has suggested that the ‘cold blob’ was caused by a combination of high heat loss from the ocean surface to the atmosphere and by a slow-down of a large-scale system of ocean currents carrying heat northwards, referred to the Atlantic Ocean Atlantic Meridional Overturning Circulation (AMOC). This new study emphasises the importance of changes in the local currents of the subpolar region, and in particular in the pathways of fresh water from the Arctic, in changing the environmental conditions of the North-East Atlantic Ocean. The change in the pathway of the Arctic water carried by the Labrador Current has implications for the North West Atlantic too; the regions that were receiving the cold, fresh and nutrient-rich Arctic water before 2012 include the Gulf of Maine, which has experienced damaging marine heatwaves and high salinity in recent years. Professor Penny Holliday explains “Changes in environmental conditions in the eastern North Atlantic and in the Gulf of Maine have recently been attributed to changes in the AMOC and local heat loss. This new study shows the importance of winter wind patterns and local ocean circulation changes in determining the fate of Arctic waters and the subsequent environmental change.” These findings used long-term data sets from on-going research expeditions in the North Atlantic, such as along the Extended Ellett Line, or the OSNAP programme. This research forms part of the Blue-Action project, which aims to understand and simulate links between the Arctic and the global climate system, and the Arctic’s role in generating weather patterns associated with hazardous conditions and climatic extremes. Latest News Upcoming Events Events Calendar Marine Life Talks Interviews with NOC Spokespersons News Archive Events Archive NOC logo

EPS maintains the trough over the Northeast for the remainder of the month. Persistent -NAO and ridge out west. Be interesting to see if we can sneak in a stray 70 degree day for April.

Yeah, March and April are typically the snowiest months of the year in the Rockies and Plains.

Small pockets of cold and snow in a sea of warmth.

Remarkable how that tiny cold departure over the Rockies allowed for snowiest season on record in Boulder.

The strong -NAO/-EPO pattern was the only thing able to suppress the SE Ridge this month. The record winter warmth into March pushed the Atlantic and Gulf SST’s to all-time record warmth for this time of year. We have seen in recent years how persistent these spring -NAO patterns have been.

Only 1 winter month with a -NAO since 2012 vs 8 in the spring. 2012 1.17 0.42 1.27 0.47 -0.91 -2.53 -1.32 -0.98 -0.59 -2.06 -0.58 0.17 2013 0.35 -0.45 -1.61 0.69 0.57 0.52 0.67 0.97 0.24 -1.28 0.90 0.95 2014 0.29 1.34 0.80 0.31 -0.92 -0.97 0.18 -1.68 1.62 -1.27 0.68 1.86 2015 1.79 1.32 1.45 0.73 0.15 -0.07 -3.18 -0.76 -0.65 0.44 1.74 2.24 2016 0.12 1.58 0.73 0.38 -0.77 -0.43 -1.76 -1.65 0.61 0.41 -0.16 0.48 2017 0.48 1.00 0.74 1.73 -1.91 0.05 1.26 -1.10 -0.61 0.19 -0.00 0.88 2018 1.44 1.58 -0.93 1.24 2.12 1.09 1.39 1.97 1.67 0.93 -0.11 0.61 2019 0.59 0.29 1.23 0.47 -2.62 -1.09 -1.43 -1.17 -0.16 -1.41 0.28 1.20 2020 1.34 1.26 1.01