GaWx

Looks broad on models but chances still increasing for a TC: Tropical Weather Outlook NWS National Hurricane Center Miami FL 800 AM EDT Mon Jun 17 2024 For the North Atlantic...Caribbean Sea and the Gulf of Mexico: Southwestern Gulf of Mexico: Satellite imagery and surface observations indicate that a broad area of low pressure is forming over the Bay of Campeche. Environmental conditions appear conducive for additional gradual development, and a tropical depression or tropical storm is likely to form by midweek while it moves slowly westward or west-northwestward toward the western Gulf coast. Regardless of development, several days of heavy rainfall are expected across portions of southern Mexico and Central America, and these rains are likely to cause life-threatening flooding and flash flooding. Locally heavy rainfall is also expected to spread over portions of the northwestern coast of the Gulf of Mexico by the middle of the week. In addition, gale warnings have been issued for portions of the Gulf of Mexico, and more information on those warnings is available in High Seas Forecasts issued by the National Weather Service. Interests along the western and northwestern Gulf coasts should monitor the progress of this system. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system later today. * Formation chance through 48 hours...high...70 percent. * Formation chance through 7 days...high...70 percent. *This is now Invest 91L.

0Z UKMET: a little further north than the 12Z run; still has a TS NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 54 HOURS FORECAST POSITION AT T+ 54 : 23.6N 94.4W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 19.06.2024 60 23.5N 94.7W 998 35 0000UTC 20.06.2024 72 23.4N 95.6W 997 39 1200UTC 20.06.2024 84 24.9N 97.9W 999 38 0000UTC 21.06.2024 96 CEASED TRACKING

Based on the weaker trend today for the potential SW Atlantic low including the brand new 0Z model consensus, it wouldn’t surprise me if the NHC were to lower the 7 day 30% lemon to 20% soon. I’ve seen enough to feel confident that there won’t be a TC from this. The 0Z ICON, GFS, CMC, and UKMET have no TC from it.

Columbus, GA, was the hot spot of all major reporting stations in/near the SE with 100 today.

The 12Z Euro is weaker than the prior 3 runs with an open wave at hour 108 offshore the Carolinas. The associated pretty unimpressive rain is headed toward N SC/NC.

12Z models so far for low off SE US coast: -ICON has the low further west and this leads to a further SW track into C FL. It is a tad stronger than prior run but is still weak/likely not quite a TD. -GFS similarly comes in further SW into C FL; similarly weak to 6Z with a TD vs the TS of the 0Z -GEFS further S, less active, and not as wet as prior two runs -CMC weaker than the already weak 0Z with nothing closed into SC (similar track to 0Z) -UKMET no TC just like 0Z and unlike the TD that forms on yesterday’s 12Z just offshore Brunswick on Fri moving N to GA/SC border

The UKMET, which did very well last year, is about the same as the prior (May) run with dip to ~-0.9 vs -1.0 in May. Add ~-0.5 for best guess at RONI conversion and you get -1.4/high end moderate. It has 1+2 slightly less cool, 3 about the same, and 4 the least cool with ~-0.2. I’d label this prog neither Modoki nor east based but rather in-between for autumn at least.

Thankfully, we’re in June rather than August/Sept. The strongest I’ve seen on any model so far (which is GFS) is lower end TS. Per history that I posted yesterday, there hasn’t been a June TS hit on the SE US from the E or SE since way back in 1909 though there was a late May TS hit (on SC) in 2020 and another late May TS hit (on Jacksonville) in 2012. 6Z update: ICON weaker than prior run and back to no closed low. GFS is also weaker than its prior run but still has a TD landfall at GA/FL border. *Edit: Oops, I somehow missed Danny of 2021, which hit S SC as a 40 mph TS. That is the only June TS back at least to 1851 (per records) to hit SC from the E or SE. I just edited yesterday’s list of May/June analogs to include this.

0Z Euro weaker than 12Z so far off SE coast. Edit: The 0Z GEFS is much more active and wetter for the offshore SE low than the prior runs.

The 0Z CMC, GFS, and ICON all have a TC off the SE coast. But the 0Z UKMET, which had a TD on the 12Z, doesn’t.

The ICON went from virtually nothing on the 12Z to a nearly closed off low on the 18Z to a TS on the 0Z. It landfalls as what I think is a TD due to slight weakening near Brunswick.

2. Southwestern Atlantic Ocean: An area of low pressure could form by the middle part of next week a few hundred miles northeast of the central Bahamas. Some slow development of this system is possible thereafter while the system moves westward or west-northwestward. * Formation chance through 48 hours...low...near 0 percent. * Formation chance through 7 days...low...20 percent. Forecaster Blake 12Z/18Z GFS/Euro, 12Z UKMET, and 18Z ICON all show something threatening a portion of the coast between FL and SC Thu/Fri. There is moderate support for a WNW moving TD to TS moving ashore among the GFS/EPS members. Go to Tropical thread for more info.

Good call on first alerting us to this area in the SW Atlantic two days ago. 18Z GFS, Euro, and ICON also have something though the ICON does not quite close off to a TD as of the end of the run at 120 just before NE FL landfall.

I’ll be watching. But despite what the 12Z GFS and 5 of the GEFS members show, I’m not worried about it at this point. The consensus of the 12Z GFS, Euro, UKMET (see below) has a TC somewhere along the SE coast late next week. History of TC landfalls from the E or SE to SE US May-June: - 1873 minimal TS GA/FL border 6/2 - 1909 low end TS Ft. Lauderdale 6/28 - 1972: minimal STS Alpha Brunswick 5/27 - 1984 TD 1 St. Augustine 6/13 https://en.m.wikipedia.org/w/index.php?title=1984_Atlantic_hurricane_season&diffonly=true#/media/File%3A1-L_1984_track.png - 2012 high end TS Beryl Jacksonville 5/28 - 2016: TD Bonnie Isle of Palms, SC 5/29 -2020 50 mph TS Bertha Isle of Palms, SC 5/27 *Edit I somehow missed this one: -2021: 40 mph TS Danny Pritchard’s Island 6/28 ———————————- 12Z UKMET has TD at 150 just off GA that moves NNE to Tybee/lower SC GLOBAL MODEL DATA TIME 1200UTC 15.06.2024 NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 150 HOURS FORECAST POSITION AT T+150 : 31.1N 81.1W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 22.06.2024 156 31.9N 80.9W 1012 24 1200UTC 22.06.2024 168 33.8N 80.3W 1014 25

12Z UKMET is similar with 90L and with nothing in the GOM TCGwise fwiw.

More on the accelerated SLR along the SE US: “The rate of sea level rise (SLR) along the Southeast Coast of the U.S. increased significantly after 2010. While anthropogenic radiative forcing causes an acceleration of global mean SLR, regional changes in the rate of SLR are strongly influenced by internal variability. Here we use observations and climate models to show that the rapid increase in the rate of SLR along the U.S. Southeast Coast after 2010 is due in part to multidecadal buoyancy-driven Atlantic meridional overturning circulation (AMOC) variations, along with heat transport convergence from wind-driven ocean circulation changes. We show that an initialized decadal prediction system can provide skillful regional SLR predictions induced by AMOC variations 5 years in advance, while wind-driven sea level variations are predictable 2 years in advance. Our results suggest that the rate of coastal SLR and its associated flooding risk along the U.S. southeastern seaboard are potentially predictable on multiyear timescales.” https://www.nature.com/articles/s41612-024-00670-w https://www.nature.com/articles/s41612-024-00670-w/figures/1

0Z UKMET has nothing (TCwise) in the Gulf but still has the one offshore the E coast though it is weaker than what the 12Z had: GLOBAL MODEL DATA TIME 0000UTC 14.06.2024 NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 30 HOURS FORECAST POSITION AT T+ 30 : 36.5N 70.5W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 15.06.2024 36 37.8N 68.9W 1007 38 0000UTC 16.06.2024 48 40.5N 63.0W 1005 39 1200UTC 16.06.2024 60 45.7N 54.6W 1003 34 0000UTC 17.06.2024 72 CEASED TRACKING

Extra interesting map from my perspective because only area E of Miss. River with >200% of mean snowfall is narrow strip from E FL Panhandle to Charleston, SC. That was entirely due to one very rare storm, the SE coastal storm of Jan of 2018, the biggest since Dec of 1989. Keep in mind that most winters in that area have no measurable snow/sleet.

For Bay of Campeche next week, 12Z UKMET: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 162 HOURS FORECAST POSITION AT T+162 : 19.7N 93.0W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 20.06.2024 168 19.9N 93.1W 1002 34

For Invest 90L, 0Z had actually dropped it but 12Z UKMET got it back: TROPICAL DEPRESSION 90L ANALYSED POSITION : 30.2N 78.1W ATCF IDENTIFIER : AL902024 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 13.06.2024 0 30.2N 78.1W 1011 27 0000UTC 14.06.2024 12 31.9N 77.8W 1009 31 1200UTC 14.06.2024 24 32.2N 76.6W 1007 35 0000UTC 15.06.2024 36 36.6N 72.2W 1005 40 1200UTC 15.06.2024 48 39.1N 68.7W 1000 42 0000UTC 16.06.2024 60 45.2N 60.3W 998 37 1200UTC 16.06.2024 72 52.2N 53.2W 993 32 0000UTC 17.06.2024 84 POST-TROPICAL

The UKMET tends to be too low with winds. But OTOH as you mentioned, highest winds tend to be lower for same pressure due to spreading out as latitude increases.

12Z UKMET: big hit on Canada again TROPICAL DEPRESSION 90L ANALYSED POSITION : 28.0N 83.0W ATCF IDENTIFIER : AL902024 LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 12.06.2024 0 28.0N 83.0W 1011 23 0000UTC 13.06.2024 12 29.4N 79.3W 1008 37 1200UTC 13.06.2024 24 30.9N 77.4W 1005 39 0000UTC 14.06.2024 36 31.5N 76.6W 1004 38 1200UTC 14.06.2024 48 33.3N 75.0W 1001 38 0000UTC 15.06.2024 60 35.6N 72.4W 995 42 1200UTC 15.06.2024 72 39.1N 68.2W 990 51 0000UTC 16.06.2024 84 43.7N 62.3W 983 49 1200UTC 16.06.2024 96 48.2N 55.8W 986 45 0000UTC 17.06.2024 108 54.2N 52.3W 986 41 1200UTC 17.06.2024 120 POST-TROPICAL

I’ve seen it only once, in the following Ben Noll tweet. This tweet was based on the May run of the valuable C3S ensemble of worldwide major models. Hopefully he’ll tweet the June update. I can’t find the direct link to C3S RONI. https://x.com/BenNollWeather/status/1793235394219434190 This is the image from that tweet. Is this from official C3S output or is this instead Ben improvising by taking the C3S ONI output (which the green line matches) and then assuming how much lower RONI would be vs ONI? Regardless, this is suggesting that RONI will be just over 0.5 C cooler than ONI through at least Oct, which seems reasonable. So, the prediction is for a -1.25ish RONI in Oct and still dropping slowly:

0Z UKMET: 990 mb Newfoundland Sunday: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 30 HOURS FORECAST POSITION AT T+ 30 : 30.2N 77.7W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 13.06.2024 36 30.0N 77.4W 1009 39 0000UTC 14.06.2024 48 31.7N 75.9W 1008 33 1200UTC 14.06.2024 60 32.9N 73.8W 1007 36 0000UTC 15.06.2024 72 34.5N 71.8W 1005 32 1200UTC 15.06.2024 84 37.6N 67.7W 1001 41 0000UTC 16.06.2024 96 42.2N 61.6W 993 44 1200UTC 16.06.2024 108 47.8N 55.0W 990 37 0000UTC 17.06.2024 120 53.6N 51.5W 982 42 1200UTC 17.06.2024 132 POST-TROPICAL

More on potential -correlation between 11 yr moving avgs of SSN and Atlantic TC count: Note in the graph below of SSN that it was rather inactive 1875-1935 and active 1935-60. So, did TC count drop 1935-60 vs 1875-1935? Avg TC count 1875-1935 was 8 vs 11 of 1935-60. So, it did the opposite. Of course, some of this rise likely was due to better observation. Also, most of 1935-60 was during +AMO, which itself made it more active then. But, regardless, if there really is a -correlation, this sure didn’t show it back then. And I’d still like to know the scientific connection. TC count by year: https://www.nhc.noaa.gov/climo/images/AtlanticStormTotalsTable.pdf