What a remarkably cold day. The high temperature at Bradley Airport on 4/4 was 27F which was 29F below normal and was the second coldest April high temperature on record.
What I found most remarkable about yesterday’s chill was the zone of freezing rain that fell in southern Connecticut. As milder air moved in aloft cold air held firm near the surface -in fact for a period of time in the afternoon the temperature fell in New Haven as cold air drained south through the Quinnipiac River Valley.
KHVN 042353Z 01016G22KT 8SM BKN008 OVC021 M02/M04 A2995 RMK AO2 PK WND 36026/2329 SNB27E37 SLP141 P0000 60021 I1000 I6020 T10221039 10000 21022 53026
KHVN 042253Z 36016G22KT 10SM BKN008 OVC017 M02/M04 A2992 RMK AO2 FZRAE35 SLP131 P0001 I1003 T10221039
KHVN 042241Z 36014G21KT 10SM BKN008 OVC017 M02/M03 A2991 RMK AO2 FZRAE35 P0001 I1003 T10171033
KHVN 042153Z 01015KT 5SM -FZRA BR BKN008 OVC017 M01/M03 A2988 RMK AO2 SLP118 P0004 I1003 T10111028
KHVN 042053Z 36012KT 5SM -FZRA BR BKN009 OVC015 M01/M02 A2987 RMK AO2 SLP114 P0004 60016 I1006 I3014 T10111022 53008
KHVN 042025Z 01013KT 5SM -FZRA BR BKN009 OVC015 M01/M02 A2985 RMK AO2 P0001 I1003 T10061022
KHVN 042016Z 02013KT 6SM -FZRA BR SCT009 OVC015 M01/M02 A2984 RMK AO2 P0001 I1002 T10061022
KHVN 042009Z 01015G19KT 6SM -FZRA BR BKN009 OVC015 M01/M02 A2984 RMK AO2 CIG 008V012 P0001 I1001 T10061022
KHVN 042000Z 01011KT 6SM -FZRA BR SCT009 OVC016 M01/M02 A2984 RMK AO2 P0000 I1000 T10061022
KHVN 041953Z 02013G20KT 5SM -FZRA BR BKN009 OVC015 M01/M02 A2984 RMK AO2 SLP104 P0005 I1003 T10061022
KHVN 041940Z 01014KT 6SM -FZRA BR BKN009 BKN015 OVC049 M01/M02 A2985 RMK AO2 P0004 I1003 T10061022
KHVN 041932Z 01013G20KT 5SM FZRA BR SCT009 BKN015 OVC049 M01/M02 A2985 RMK AO2 P0004 I1002 T10061022
KHVN 041902Z 36010KT 4SM -FZRA BR BKN008 OVC015 M01/M02 A2985 RMK AO2 CIG 007V012 P0001 I1001 T10061022
KHVN 041853Z 36012KT 3SM FZRA BR BKN008 OVC015 M01/M02 A2984 RMK AO2 SLP104 P0007 I1005 T10061022
KHVN 041846Z 35010KT 4SM FZRA BR BKN008 BKN014 OVC031 M01/M02 A2984 RMK AO2 P0006 I1005 T10061017
KHVN 041813Z 35012KT 4SM -FZRA BR BKN008 BKN014 OVC031 00/M02 A2985 RMK AO2 P0003 I1003 T00001017
KHVN 041753Z 01009KT 4SM FZRA BR BKN008 BKN012 OVC041 00/M02 A2984 RMK AO2 RAE00UPB00E30FZRAB30 SLP106 P0012 60021 I1003 I6003 T00001017 10022 21006 58008
This was poorly forecast. All of our computer models showed warming in the boundary layer – and I certainly agreed with that. Additionally, getting snow or ice to accumulate on roads this time of year is difficult with the high sun angle and long days. Freezing rain in the middle of the afternoon in April – forget about it on the Connecticut shoreline! Even as of late morning yesterday the National Weather Service didn’t have winter weather advisories in effect for the four southern counties.
Check out the 13z HRRR forecast for New Haven. Only off by about 6C for the surface temperature!! The forecast for Bradley was better – though still off by several degrees Celsius.
The NAM was a bit better than the HRRR (though still too warm) but the NCAR ensemble may have been the winner of the day. The NCAR model did show the possibility of a really unusual April freezing rain event in southern Connecticut.
In fact, even this was underdone with 0.20″ of ice accretion measured by the ASOS at Tweed New Haven. Reports of sporadic damage with up to 1/3″ of ice accretion occurred a bit farther to the north.
This storm was a good reminder to not be too reliant on the HRRR. It’s tempting given its high resolution and hourly updates but in this case it really lead me astray. The NCAR ensembles were the way to go with this one – and I’ll give the NAM a shout out as well for doing much better handling the stubborn low level cold.
Sometimes the weather can care less about climatology – and this storm was one example. What is typically a slam dunk forecast in April – roads will generally be OK in the middle of the day with light (<1″/hour) rates was completely wrong in this case.
An unusual storm and a good learning experience!