This list counts all Eastern Atlantic lows on roughly 9/7. Some GEFS runs have over 100% of members developing, which suggests some members may see two lows at the same time (possibly from two different waves).
Today's 18z EPS actually provides us a clue as to why some members develop two lows: Two waves seem to be advancing west in quick succession, and global models that did develop this wanted to consolidate them into a single system. (This also explains the dropping support from operational runs, as the consolidation process takes too long and is disrupted by shear and/or dry air.) It's still hard to distinguish the waves due to high variance (particularly with GEFS), so I'm just counting all lows regardless of which wave they're showing.
GEFS member low pressure counts (±2, out of 31):
- 18z 8/29: 32 (103%)
- 12z 8/29: 28 (90%)
- 6z 8/29: 27 (87%)
- 0z 8/29: 35 (113%)
- 18z 8/28: 35 (113%)
- 12z 8/28: 22 (71%)
- 6z 8/28: 23 (74%)
- 0z 8/28: 22 (71%)
EPS member low pressure counts (±3, out of 51):
- 18z 8/29 (out to 144 hrs only): 40 (78%, some may not be TCs)
- 12z 8/29: 39 (76%)
- 6z 8/29 (out to 144 hrs only): 32 (63%, some may not be TCs)
- 0z 8/29: 32 (63%, some may not be TCs)
- 18z 8/28 (out to 144 hrs only): 26 (51%)
- 12z 8/28: 37 (73%)
- 6z 8/28 (out to 144 hrs only): 22 (43%)
- 0z 8/28: 31 (61%)
Keep in mind these are just low pressure centers and some may not actually be TCs, especially on the 6z and 18z Euro runs. On the other hand, 6z and 18z Euro may have additional members develop beyond 144 hrs.