MED: 02M/BLAS (HELIOS) - ex-Subtropical Storm

[Europa non è lontana]

I think the cyclone may already be closed again, the last few satellite images before sunset seemed to indicate a closed LLC with convection sheared to the southeast, but given the very small size of the cyclone and the low resolution, I may be misinterpreting the images.

[Vince_and_Grace_fan]

I think the cyclone may already be closed again, the last few satellite images before sunset seemed to indicate a closed LLC with convection sheared to the southeast, but given the very small size of the cyclone and the low resolution, I may be misinterpreting the images.

The ASCAT pass at 18:34 UTC showed still not, but almost, it was better than morning.

[Sciencerocks]

The night time ir clearly shows a well defined LLC.

[Vince_and_Grace_fan]

Yes, the circulation became well-defined in the evening, however, the convection totally dissipated in the early morning hours, so the regeneration was very short-lived.

[DanieleItalyRm]

South Sardinia NEW CONVECTION BLAS TS?

[AJC3]

South Sardinia NEW CONVECTION BLAS TS?

I'd be curious to see a 7-day, high resolution satellite time lapse (both VIS and 3.9UM IR) of the area from the Balearic Islands to Sardinia, along with corresponding scatterometer passes, to see exactly what transpired between STS Blas and the XT low to its NE. There seems to have been a significant amount of interaction between the two. Was there a merger/absorption of one cyclone by the other, or has Blas actually maintained a separate, closed coherent circulation for the past ~6 days?

Edit: It appears there were not one, but two XTCs that Blas interacted with over the past week. The second is still distinguishable as a separate entity to the NW of Blas, so it appears that Blas has rotated around the south side of it. There may have been some sort of merger with a separate cyclone about 2-3 days ago near Mallorca/Menorca?

[Vince_and_Grace_fan]

South Sardinia NEW CONVECTION BLAS TS?

It indeed was a quite interesting feature, but I think at most subtropical, if at all. The redevelopment of the organized convection obviously forced by baroclinic effects as a frontal zone reached this area. This situation was very similar than the "redevelopment" of post-tropical Paulette last year on 23 September, and NHC ofocially didn't declare it to subtropical or tropical at this time. In the post-season report they said: "Early in this post-tropical phase, the low interacted with a baroclinic zone once again, which helped to enhance the surface winds, resulting in a brief increase in strength on 23 September."

[Vince_and_Grace_fan]

Edit: It appears there were not one, but two XTCs that Blas interacted with over the past week. The second is still distinguishable as a separate entity to the NW of Blas, so it appears that Blas has rotated around the south side of it. There may have been some sort of merger with a separate cyclone about 2-3 days ago near Mallorca/Menorca?

Yes, it was two different extratropical cyclone (and upper level low). The first was of which Blas developed by 11 November, but along the remnant frontal features a weaker secondary low formed on the second half of the day, helped by a smaller upper level low. These features interacted with Blas on 13 November and its small circulation temporatily totally merged into the another low pressure area and opened up. As the upper level low weakened and moved to northwest, then west of Blas in the late evening hours, its circulation became closed again. However, the convective burst that occurred at that time quickly decayed in the moring hours of 14 November and Blas was a convection-free low level swirl until the night. Then the second, developing extratropical low (and an upper-level cut-off low from Germany/France) reached the Northwestern Med. Sea from north-northwest and interacted the remnant swirl causing another burst of convection.
I will made satellite animations tomorrow, and you could find almost all the ASCAT pass in this forum.

[DanieleItalyRm]

I believe these are the interactions that occurred between 02M / BLAS and two extra-tropical systems between 10 and 14 Nov. 2021:



02M/BLAS on 10 Nov. 2021 close to the Mallorca island (Balearic).





02M/BLAS in one of its pulsating convections like TS on the night of 13 Nov. 2021



02M/BLAS in the new convention over southern Sardinia with eye feature on 14 Nov. 2021. Floods and 1 victim (4 people rescued):

[Vince_and_Grace_fan]

Here is the video:

[youtube]https://youtu.be/i-TqNBolAVo[/youtube]