If anyone is familiar with the LJS index they would be keenly looking upon Japan and waiting for snow to fall.
Well it looks to be occurring in or around the 20th.
The LJS index ignores all heights and troughs and ridges and strictly goes on precipitation type on or very near Aomori, Japan (a rough correlate to the 40 degree north US coast).
The LJS also utilizes a short lag correlate of only 6-8 days.
The index was created proprietarily over the years by following the east Asia rule. It’s been observed that when precipitation is forecasted as snow over Aomori that often times the US correlate also would be forecasted snow.
The proprietary calculations allow the index to not only predict a date of snowfall but also adjust accordingly for possible heavier snow and increasingly hazardous conditions.
Generally an index of +3.0 or higher means that snowfall can be expected over eastern PA and nearby regions.
An index of +6.0 or higher means that possible snowfall over a good portion of PA and NJ is possible.
Ultimately an index of +10.0 or higher means a multi-region wide multi day storm is possible. This rating is only reserved for the most detrimental snowstorms in central Japan.
I will be calculating the LJS index this year approximately 8-10days in advance of a correlative snowfall date.
Currently modeling shows the first + index rating for the US occurring around the 26-28th of November.
However, modeling in east Asia is extremely volatile so index calculations are usually never made until 2 days prior to a Japanese snowfall. Therefore even though modeling shows snow in Japan on a certain date the index will not be tripped until JMA forecasts are issued. Only at that time can the LJS index be truly calculated.
Cheers, take care and do stay tuned fir LJS index updates!