Northwest Pacific/Bohai Sea Winter Ice Outlook
By: Ernesto Findlay, Meteorologist
As we are approaching this winter season, sea ice begins to develop over areas of the Northwestern Pacific including the Bohai Sea.
The main driver of seasonal weather over the Western Pacific is the ENSO cycle. This cycle is expected to be in its "cold phase", or La Niña, this winter.
Figure 1 depicts the typical weather pattern expected during the La Niña Phase of ENSO. During this phase, strong ridging tends to develop over the Northern Pacific,
with trough anomalies over the Northwestern Pacific, which tends to lead to below average temperatures over the Bohai Sea and the Sea of Japan region.
Figure1. La Niña Phase effect on local weather around the globe during the months of December-February.
The strength and location of the La Niña pattern varies from year to year. Figure 2 depicts the 500mb height anomalies of the top 5 winters (December through February)
which had La Niña patterns closest to the one evolving with the current La Niña cycle.
Strong negative height anomalies were located over the Bohai sea and Sea of Japan during these winters.
Negative height anomalies will allow for cold air originating over Northeastern Siberia to move over the Bohai Sea and Sea of Japan.
As a result, colder than normal temperatures, and higher than normal sea ice cover is expected to develop over this region.
Figure 2. 500mb height anomalies (m) of the top 5 winters (December through February) with La Niña patterns closest to the ones evolving with the current La Niña cycle.
Cool colors indicate lower than normal heights (cooler than normal temperatures).
Finally, the cold air originating from Siberia varies year to year. The main driver of the "cold pool" over Northeastern Siberia is snow cover anomalies in
the late fall and early winter over this region. More/less snow allow for colder/warmer than normal air to build over this region,
resulting in colder/warmer than average cold air outbreaks to move over the Bohai Sea and Sea of Japan Region.
Figure 3 shows snow cover anomalies for the month of October 2020 over Northeastern Siberia. October had higher than normal snow cover over Northeastern Siberia,
which should lead to colder than normal cold air outbreaks over the Bohai and Sea of Japan region this winter.
Figure 3. Snow cover anomalies for the month of October 2020. (Courtesy of Rutgers Global snow Lab)
Given all the factors above, WRI predicts higher than average sea ice to develop over the Bohai sea and Sea of Japan in late winter and early spring.
This is a contrast to some of our long range models like the Climate Forecast System(CFS), which predicts a warm winter with little to no ice over the Bohai sea. However,
given all the factors stated above we believe a colder winter is in store for the Bohai Sea.
During the upcoming active Northwest Pacific winter season, WRI meteorologists are working hard to keep you informed through many of our products including our Dolphin website.
These products are issued to your operations team, allowing for advanced notice of any potential ice/ winter weather concerns.
Contact us today, to receive the most up-to-date information by consulting one of our Meteorologists who are available 24/7 to assist you.
