Ubuntwo wrote:Hammy wrote:September and October really are behaving like 2007 save for the MDR being more favorable.
Gulf: Two Cat 1 hurricanes and a depression in the in 2007, one storm and one Cat 1 in 2021.
Caribbean: 2007 had Cat 5 Felix early in the month and then literally nothing until October 27. This year has gone without a storm in the Caribbean since late August.
Subtropics: Two short lived subtropical storms in 2007 with both transitioning; 2021 similarly only two short-lived subtropical storms, with neither transitioning fully.
MDR: 2007 saw 3/1/0. This was the biggest difference in performance, with 2021 producing 5/2/2.
https://twitter.com/AndyHazelton/status/1449731427583631366
After reading Andy Hazelton's reference to 2007 being the closest analogue to this year, I was curious about what other large scale variables seemed to be at play and were similarly occurring at this time. Both 2007 and 2021 similarly exhibiting a late season transition to La Nina, however I found the following particularly interesting:
"At the beginning of 2007, the Outgoing Longwave Radiation (OLR) Index was strongly negative, which reflected the enhanced tropical convection and cloudiness across the equatorial Pacific. However, this changed significantly in June when the OLR Index increased to a monthly value of +0.6. Subsequently, the OLR Index has been positive, and the index increased to +1.4 in October, which was the highest value of the year. The most recent monthly averaged OLR Index was again positive, but with a slightly lower value of +0.8 in November. The OLR Index increased significantly in December to a positive monthly value of +2.2, and similar to the SOI this was the highest value of the 2007/2008 La Niña." (this from the National Centers for Environmental Information El Nino Southern Oscillation annual report Nov, 2007 - https://www.ncdc.noaa.gov/sotc/enso/200713 ).
The current (10/16) forecast for MJO related anomalies using GEFS operational forecast for 6-15 day indicates a negative flip in the OLR index primarily for the E. Pacific initially, but with significantly more favorable conditions in the E. PAC as well as the E. GOM and Central & East Caribbean toward the second half of that 6-15 day cycle. Perhaps that time frame better coincides with the eventual passing of the anticipated Kelvin Wave around end of Oct.? In years past where the MJO seemed to play a significant factor, we'd typically await for the EPAC to light up for about a week and then waited for it's transition to then propagate eastward into the Caribbean. Remains to be seen if this late season forecast blip will actually pan out.
Some noteworthy comparisons of 2021 and that year shows 2007 ended with a fairly active 15/6/2 season but and primarily exhibited a lot of "slop" storms. Still, 2007 did product a pair of Cat 5 storms (Dean and Felix) which went on to torch Central America and Yucatan. Interestingly enough and in spite of the very high OLR, a late season hurricane did form (Oct 28 - Nov. 2) just east of PR tracking into the north/central Caribbean impacting DR and central Cuba. Oddly one other short lived TS in December (12/11 - 12/13) also formed east of PR and tracked westward to impact PR & Hispaniola (contrary to more typical Climo development in the W. Carib).