jconsor

https://x.com/yconsor/status/1850618329804730523

Some short-term drought relief possible this weekend: https://x.com/yconsor/status/1848326240068837640

Thread on important short-term northward/stronger trends noted regarding Beryl, and how this influences her potential TX/MX impacts: https://x.com/yconsor/status/1808853711629746332

@bluewave Nice model bias charts! Can you please provide the link for them? Thanks.

Yes, within 10 days of the upcoming month is the CFS's more skillful phase. But much of that skill hinges on getting the tropical convection/MJO pattern correct. CFS tends to progress the MJO eastward too slowly beyond 7 days. Look how different it is vs. EPS and GEFS even in the 8-14 day period! CFS hangs the -VP anomalies back over far e. Africa and w. IO, whereas GEFS and EPS progress them eastward into the e. IO and Maritime Continent. Looking at longer-range hovmollers, CFS continues to progress the MJO eastward sluggishly, in a manner that to my eyes doesn't make sense. It has the MJO in phases 4 and 5 in late Mar. Meanwhile, the extended GEFS and EPS have the MJO progressing into phases 8 and 1 by late Mar. The implications are very different! The phase 4 and 5 composites largely support the CFS's warm forecast for the second half of Mar. The phase 1 and 8 composites favor a -NAO, western N. America ridging and eastern US troughing, which would suggest normal to colder than normal temps in the second half of Mar. The forecast SSW event in early Mar should have a significant influence in prolonging blocking near Greenland/-NAO in mid to late Mar. I am not sure that this stratospheric warming will behave like a final warming in terms of its influence, given how strong it is forecast to be and how early (EPS indicates the warming peaking on Mar 6-7, which would be the second earliest final warming in the past 40+ years). I agree that Mar 1-10 will feature well above normal temps in the NE US. Mar 11-15 should see a transition period, and in the second half of Mar I would expect slightly below normal temps. The large magnitude of the warm anomalies Mar 1-10 will likely make it tough for the month as a whole to average below normal. But still, I think the CFS forecast for the second half of the month is highly questionable. I would expect the 500 mb/sfc temp pattern for the last half of Mar to be close to a blend of clusters 2 and 3. Cluster 4 (which the CFS forecast is indicating) is close to the prevailing pattern since Dec.

I don't recommend using the HREF snowfall totals verbatim. Its snow-liquid ratios tend to be too high. IMHO, Best to take the probability-matched mean QPF and then convert to snowfall using expected snow-liquid ratios (should be generally 15 to 18-1 in this case).

ENSO Longitude Index in 12th place since 1950 puts us squarely in Modoki territory. See https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL079203 for more details on the ENSO Longitude Index (ELI)

Dec Modoki Ninos are much more likely to have a -NAO than east-based Ninos. Basin-Wide Ninos have a slight tendency toward +NAO. Given Eric Webb's recent tweet about the implications of Dec NAO in Ninos on the pattern during the rest of the winter, will be very interesting to watch the NAO trends as Dec goes on.

There is a decent chance this system becomes a subtropical or tropical cyclone in the next day or two as it heads NE up the Gulf Stream.

Mesovortex off the coast of SE FL is causing impacts similar to a tropical storm there. Widespread gusts to 50-60 mph, locally up to around 75 mph:

Signal for tropical cyclone formation in the W. Caribbean by late next week (and northward movement thereafter) has grown.

While climo is heavily in favor of no TC development from here on out, the pattern suggests we still need to keep a wary eye on the Caribbean next week.

Thanks for starting the thread, Ed. The ECMWF and EPS have been handling Tammy's intensification and track poorly (GEFS has had better handle). Hopefully with the 12Z run the EPS should be a more useful tool, once recon data is ingested.

Thread on the flooding potential:

I know most of our collective attention is on the potential subtropical system off the SE US coast. However, I think the system in the E. Atlantic (currently given a 70% chance of developing by NHC) is worth watching carefully, since down the road in 7-10 days it has a decent opportunity to reach the Caribbean or western Atlantic. This is a sneaky wave which will likely not develop in the next 3-4 days, but instead continue heading west under a strong ridge. We're dealing with two waves that will likely merge here - firstly the one outlooked by NHC that just came off the African coast, and secondly a low-latitude ITCZ wave currently around 40W. The two systems should combine by late Fri-early Sat into a broad wave. This would initially slow development, due to its large size and lack of concentrated vorticity. This system likely will find better upper level conditions (strong diffluence aloft, deeper moisture) once it passes 40W and clears the strong UL trough in the east Atlantic, and especially as it nears 60W and the Leeward/Windward islands. With a much stronger than usual ridge for this time of year over the central Atlantic, there is a decent chance this system makes it into the eastern and northern Caribbean or heads slightly N of the Caribbean to near the Bahamas.