bluewave

The EPO reversal since the winter has been very impressive. The vortex cooled the NP SST’s over the winter. Now the warm blob south of Alaska is making another appearance with the strong ridge. There is also a sharp Atlantic SST gradient with cold to the north and warm south.

NYC is on track for only the 8th time not reaching 70 degrees in April. Pretty impressive that most of the other years were in the 1870’s and 1880’s. Just goes to show how strong this -EPO/-NAO pattern has been. 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 1874 64 0 1873 64 0 1940 67 0 1875 67 0 2020 68 9 1883 68 0 1884 69 0 1876 69 0

The maximum July temperature departure at Newark was +3.5 vs +3.0 for the minimum. JFK came close to their all-time record heat index late in July with the record heat and humidity. There were numerous record highs on July 20th and 21st.

The whole region finished +1 to +2 with numerous top 10 warmest Julys.

It was a +1 to +2 summer across the area with a top 10 warmest July. The only recent cooler summers at 0 to -1 were 2017 and 2014. The record high dew points last several summers made it feel as warm as the warmest summers since 2010. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Jul Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2011 82.7 0 2 1993 82.5 0 3 2010 82.3 0 4 1994 81.9 0 5 2013 80.9 0 6 2012 80.8 0 - 1999 80.8 0 7 2019 80.6 0 8 1955 80.5 0 9 1988 80.4 0 10 2002 80.0 0

This was the first time that I saw it pour pea sized hail along the South Shore. It was enough to briefly whiten the ground.

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.