bluewave

I don’t think anyone will be surprised by December having the biggest CONUS monthly temperature increase. Looks like September will follow in 2nd place. The few areas of cooling wound up near the Plains. Matches the pattern of where the most impressive Arctic outbreaks have occurred like we saw in February.

While we are still in a blocky pattern, the warm spots will make a run on 70° today. Looks like several cooler days coming up before the next 70° chance early next week. So some warmer days in the mix even with the -AO +PNA -EPO pattern. Beyond the next 10 days, we would need to see more of a SE Ridge for an 80° chance near the end of April. Still outside the effective range of the guidance. Euro highs today Next run on 70° possible early next week Blocking pattern in the means next 10 days

The warm spots could sneak in a 70° tomorrow. Then we cool down for several days. Looks like we could make another run on 70° in about a week. Shows how challenging it is to sustain below normal temperatures for more a than a few days at a time. KEWR GFSX MOS GUIDANCE 4/13/2021 1200 UTC FHR 24 36| 48 60| 72 84| 96 108|120 132|144 156|168 180|192 WED 14| THU 15| FRI 16| SAT 17| SUN 18| MON 19| TUE 20|WED CLIMO N/X 49 68| 52 55| 42 57| 42 59| 45 64| 47 67| 46 68| 48 43 62 TMP 55 60| 53 48| 43 51| 45 54| 50 57| 51 59| 51 61| 51 DPT 41 46| 46 41| 34 29| 33 31| 36 37| 37 31| 37 40| 38 CLD PC OV| OV OV| OV OV| PC OV| PC OV| PC PC| PC OV| OV

While the La Niña didn’t have the expected influence on our winter pattern, the tropics are looking more Niño-like. The very strong MJO has resulted in a significant WWB. Today we saw the biggest SOI drop of the year so far. So does this just get us back to ENSO neutral or is another El Niño beginning? It will probably come down to whether a follow up WWB emerges in May. ENSO neutral vs El Niño could have an influence on summer hurricanes and temperatures. The ENSO forecast models are currently in the spring forecast barrier period. Daily SOI 2021 103 1009.79 1010.95 -25.60 Very strong WWB pattern

2010 is always a tough act to follow since it was so much warmer than all the other summers. While last summer was our 2nd warmest, it was almost a full degree cooler than 2010. The spring of 2010 was warm throughout with our last April 90s. NY Coastal climate division 4 https://www.ncdc.noaa.gov/cag/divisional/time-series/3004/tavg/3/5/1895-2021?base_prd=true&begbaseyear=1981&endbaseyear=2010 201006 - 201008 75.2°F 126 3.5°F 202006 - 202008 74.4°F 125 2.7°F 201606 - 201608 74.2°F 124 2.5°F 200506 - 200508 73.9°F 123 2.2°F 201106 - 201108 73.9°F 123 2.2°F 199906 - 199908 73.7°F 121 2.0°F 201206 - 201208 73.4°F 120 1.7°F 201806 - 201808 73.4°F 120 1.7°F 201906 - 201908 73.2°F 118 1.5°F 201506 - 201508 73.1°F 117 1.4°F 194906 - 194908 73.0°F 116 1.3°F 200606 - 200608 73.0°F 116 1.3°F

We trade in warmer and drier blocking for cooler and wetter. Better chances for rain starting today. The pattern usually ends up with closed lows this time of year with strong blocking. So one closed low moves through the next several days followed by another on Thursday. The ensembles are hinting at the Eastern Trough lingering into late April.

The elevated convection will be nice change on Sunday following the 3rd driest start to April on record. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Total Precipitation Apr 1 to Apr 10 Missing Count 1 1881-04-10 0.00 0 2 1900-04-10 0.01 0 3 2021-04-10 0.04 1 4 1909-04-10 0.05 0 5 1963-04-10 0.06 0

The big high temperature winners today were the areas away from the marine influence. MacArthur/ISP PTSUNNY 62 51 67 S10 Central Park MOSUNNY 67 50 54 E8 Poughkeepsie MOSUNNY 72 55 55 S9 SYRACUSE PTSUNNY 79 44 28 VRB7 BUFFALO CLOUDY 81 40 23 VRB3

Not that the La Niña had much influence on our winter, but the very impressive WWB will really warm the ENSO regions in the coming weeks. Hard to say whether this major WWB event will kick off another El Niño. It’s possible that it could just get us back to neutral without any follow up WWBs. Long range ENSO forecasting is very uncertain during the spring forecast barrier.

The 80°+ heat went to our west in March 2012. This was the 2nd March in a row to reach 80° at Newark. I posted a while back how the first 80° of the season has moved up nearly 1 month at Newark since 1970. But the first 90° of the season remains unchanged. This is why Newark only made it to 90° once in April since 2010. While at the same time, 4 years reached 80° in March. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Mar Click column heading to sort ascending, click again to sort descending. Year Highest Max Temperature Missing Count 2021 84 0 2020 80 0 2019 77 0 2018 62 0 2017 73 0 2016 82 0 2015 64 0 2014 67 0 2013 61 0 2012 79 0 2011 80 0 2010 75 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of Apr Click column heading to sort ascending, click again to sort descending. Year Highest Max Temperature Missing Count 2021 71 21 2020 69 0 2019 80 0 2018 84 0 2017 87 0 2016 83 0 2015 82 0 2014 83 0 2013 85 0 2012 88 0 2011 87 0 2010 92 0

Today will probably be our warmest for a while as we are heading into more of an onshore flow pattern. The good news is that we will get some much needed rain on Sunday. Then there will be chances for showers at times as a backdoor/ warm front stalls out near the area. Longer range, the models all agree on more of a +PNA /-EPO for mid-April. KEWR GFSX MOS GUIDANCE 4/10/2021 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 SAT 10| SUN 11| MON 12| TUE 13| WED 14| THU 15| FRI 16| SAT 17 CLIMO X/N 68| 56 62| 49 53| 45 56| 45 52| 41 53| 40 56| 41 63 42 61

Reaching 80°+ in March seems to increase the chances of April having a lower monthly maximum temperature than March. This is what happened last year. If we can pull it off again, then it would be the first 2 years in a row with a March monthly maximum temperature higher than April since 88-89 at Newark. Monthly Highest Max Temperature for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Year Mar Apr Season 1945 89 84 89 1998 86 74 86 1990 86 94 94 2021 84 71 84 1985 84 89 89 1977 84 90 90 1989 83 79 83 1986 83 80 83 2016 82 83 83 1938 82 89 89 2020 80 69 80 2011 80 87 87 2007 80 86 86 1962 80 90 90 1946 80 78 80 1989 83 79 83 1988 77 74 77

Very sharp temperature gradient along the warm front on Sunday. Not much distance between 50s and onshore flow and 70s with warm SW winds. Hopefully, the stalled out front will produce much needed rains for the spring gardens.

Unusual combination of strong south based block and UL east of New England. This produced the near all-time record low relative humidity values in the single digits. So the very dry downslope flow really warmed up as it reached the coast.

This was the first time that Newark dropped below freezing during the first week of April while recording three days of 70° or higher. Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Ending Date Number of Days Max Temperature >= 70 Apr 1 to Apr 7 Minimum Temperature - 2010-04-07 5 44° - 2021-04-07 3 28° - 2005-04-07 3 41° - 1981-04-07 3 37° - 1974-04-07 3 34° - 1967-04-07 3 33° - 1945-04-07 3 33°

The latest Euro brings the warm front through around 7-8 am in Sunday with some rain. Then it has breaks of sun and areas south of the warm front make it into the 70s. It has a round of late afternoon and evening convection as the atmosphere destabilizes behind the front.

Yeah, that was the conclusion of a recent study.

We are pretty much rewriting SST and air temperature climo following such a -AO winter. Notice how much warmer the Western Atlantic is now compared to 2010 and 2011. Those were the last two winters with such a -AO and peak values dipping below -5. There is supposed to be a cold pool off the East Coast after such a -AO winter. But instead, there are near record warm SSTs to our east. The blocking pattern this month so far is linking up with the WAR and boosting heights over the NE. So the average temperature during the first week of April was much warmer than the past years with a low max temperature under 40°. It also resulted in the near record low single digit RH values and highs that keep beating guidance. 4-6-21 4-6-11 4-6-10

This is the first time since at least 1950 that NYC had a warmer than average first week of April with a high temperature under 40°. All the other years were around 10° colder for the first week of April. So like we saw over the winter, this south based blocking pattern is creating new and unusual weather patterns for us. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Lowest Max Temperature Apr 1 to Apr 7 Avg Temperature + Departure 1 1982-04-07 30 41.1 -7.9 2 1975-04-07 37 40.4 -8-6 3 2003-04-07 38 40.6 -8.4 4 2021-04-07 39 51.0 +2.0 - 1995-04-07 39 43.2 -5.8

The dry conditions are allowing the high temperatures to beat guidance. Pretty impressive diurnal range especially in areas that radiated last night. So the warm departure for the day was mostly driven by the high temperature. CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 446 PM EDT WED APR 07 2021 ................................... ...THE ISLIP NY CLIMATE SUMMARY FOR APRIL 7 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1981 TO 2010 CLIMATE RECORD PERIOD 1963 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 68 153 PM 85 2010 55 13 64 MINIMUM 40 519 AM 23 1982 38 2 44 AVERAGE 54 46 8 54

The April forecast looks like a continuation of the winter south based blocking theme with spring wavelengths. This week the south based blocking allowed highs around 70°. Looks like our first chances for heavier rain will come on Sunday. Next week appears generally cooler than this week as the -AO and +PNA gets stronger. But the south based blocking should allow enough ridging near the East Coast. This will keep the coolest temperature departures to our west which has been a frequent theme. Perhaps more rain chances for the gardening interests.

JFK made it down to 10%. March and April typically have our lowest relative humidity readings of the year. It will be interesting to see if anyone can find the relative humidity during the July 1936 dust bowl heatwave.

Ridiculous AO and NAO volatility since February.

I believe the all-time lowest relative humidity at Newark is 5% on 3-30-07 Newark/Liberty MOSUNNY 71 3 7 https://www.wunderground.com/history/daily/us/nj/newark/KEWR/date/2007-3-30 5:51 PM 68 F -5 F 5 %

First time the relative humidity at Newark dropped under 10% since 2012. Newark Liberty SUNNY 69 8 9 https://mesonet.agron.iastate.edu/plotting/auto/?_wait=no&q=157&network=NJ_ASOS&station=EWR&year=2021&var=min_rh&dir=below&thres=0&dpi=100&_fmt=png