WxWatcher007

Tropical Storm Fiona Discussion Number 5 NWS National Hurricane Center Miami FL AL072022 1100 AM AST Thu Sep 15 2022 Moderate westerly shear continues to displace Fiona's deep convection about a degree to the east of the low-level center, with convective cloud tops as cold as about -80 degrees Celsius. A recent ASCAT pass showed a solid area of 40- to 45-kt winds, and with the scatterometer's known undersampling characteristics, it's not out of the question that Fiona's intensity could be a little higher. For now, the initial intensity will be held at 45 kt, pending additional data from an Air Force Reserve Hurricane Hunter aircraft that is scheduled to investigate the storm this afternoon. Moderate shear, generally out of the west, is expected to continue for much of the forecast period. That in itself should suppress significant strengthening, but it may not be enough to prevent any strengthening at all. Fiona's current intensity is a testament to its resilience in the face of the shear it has experienced over the past 24 hours. There has been a general uptick in the intensity guidance after 48 hours, and the new NHC intensity forecast has been nudged upward during that time. It is important to note, however, that the official forecast still lies below the IVCN, HCCA, and FSSE consensus aids from day 3 onward, and additional adjustments to the intensity forecast could be required in subsequent advisories if these trends continue. Strong low- to mid-level ridging over the western Atlantic is steering Fiona due west, or 270 degrees at 12 kt, and this general motion, with some gradual decrease in forward speed, is likely to continue for the next couple of days. There is notable model divergence after 36 hours, with the stronger GFS, HWRF, and HMON solutions turning a slower Fiona northwestward over the northern Leeward and Virgin Islands. On the other hand, the ECWMF, UKMET, and all of the consensus aids maintain a faster westward to west-northwestward motion across the far northeastern Caribbean Sea through day 3. Given the expectation that moderate shear is likely to continue, the NHC track forecast favors the less-intense scenarios and shows a solution moving just south of the Virgin Islands and then near Puerto Rico in a few days. After day 3, a weakness near the western extent of the ridge should allow Fiona to gain some latitude and possibly turn toward the northwest, moving across the Greater Antilles into the far southwestern Atlantic. On the whole, the NHC track forecast remains steady from previous predictions, largely following a blend of the TVCN and HCCA consensus aids. Additional watches or warnings will likely be required later today for portions of the Leeward Islands, Puerto Rico, and the Virgin Islands, and interests in these locations should monitor the latest forecast updates. Key Messages: 1. Tropical storm conditions are expected in portions of the Leeward Islands within the warning area by Friday evening. Tropical storm conditions are possible in portions of the Leeward Islands within the watch area by Friday night. 2. Heavy rains from Fiona will reach the northern Leeward Islands Friday afternoon, spreading to the British and U.S. Virgin Islands and Puerto Rico Saturday into Sunday morning, and reaching eastern Hispaniola Sunday. This rainfall may produce flash and urban flooding, along with isolated mudslides in areas of higher terrain. 3. Fiona is expected to move near the Virgin Islands, Puerto Rico, and Hispaniola this weekend and early next week, and watches will likely be issued for some of those areas later today. FORECAST POSITIONS AND MAX WINDS INIT 15/1500Z 16.6N 54.3W 45 KT 50 MPH 12H 16/0000Z 16.6N 56.2W 45 KT 50 MPH 24H 16/1200Z 16.7N 58.7W 45 KT 50 MPH 36H 17/0000Z 16.9N 61.2W 50 KT 60 MPH 48H 17/1200Z 17.2N 63.4W 50 KT 60 MPH 60H 18/0000Z 17.5N 65.2W 50 KT 60 MPH 72H 18/1200Z 17.8N 66.6W 55 KT 65 MPH 96H 19/1200Z 19.3N 68.6W 55 KT 65 MPH 120H 20/1200Z 21.5N 70.4W 60 KT 70 MPH $$ Forecaster Berg

It’s still a little early to be terribly invested. This is far from a lock in bringing continental US impacts and it’ll probably be that way for a few days. Can’t beat the model drama though, especially in this season of bore.

I don’t think I’d make substantive changes to intensity or track yet if I were the NHC absent recon and additional data. This one “overperformed” in terms of intensifying to 50mph, but the environment remains marginal to hostile and that is going to remain the case for at least a few days. That was never in question. That does make me think those quick intensification/early turn ensemble members are going to correct westward eventually. Maybe not enough to change the eventual outcome for the continental US, whatever that is, but we have a long way to go.

As @Superstorm93 posts above, the ensembles still take it over the island, so I think that’s a likely outcome. I was just posting the low positions by comparison. I should have been clearer.

I think it still ends up north of the island. Here are the EPS lows by comparison. I’m sure this’ll bounce around. 00z EPS 06z EPS

Adding to @Weather Will's post, I want to share some of the latest ensemble guidance. While the operational guidance is good for eye candy and can be modestly helpful in identifying the major steering players like ridges and significant troughs, the ensembles are still where it's at to get a sense of track potential and sensitivity. 06z Operational Spaghetti Plot 06z GEFS 00z EPS I like this one in particular. This is Tomer Burg's super ensemble of the major operational ensembles. This is dated (yesterday) but does an excellent job of showing the spread in ensembles. Super Ensemble 12z 9/14 I'd guess if we had an image of the latest ensembles overnight, the spread would remain but the ellipse would probably lean more toward the west with the EPS showing a bifurcated range, moreso than the GEFS. The spread would still be quite large.

06z GEFS guidance would likely carry this out to sea after impacting the Greater Antilles, but it's still early to make a lot of judgment calls. I think I'd favor a more close call over a landfall or wide right solution right now but again, early.

Agree and you can see both the dry air and shear having an impact on morning visible (time sensitive) It'll be interesting to see what recon finds and how the sampling of the environment changes the current intensity and track forecasts.

I think recon will be helpful. While OTS after the Greater Antilles is probably favored at this point, there’s a lot that can change depending on how a complicated pattern unfolds in the Pacific.

Speaking of overperformers, I think the most memorable thing about 2005 other than Katrina was seemingly going to bed with lower end storms in the basin and waking up to find them majors. Wilma went from 110mph at 11pm to 175 at 11am one night lol.

Oh it’s far from perfect and still probably has a ceiling pre Antilles as a result, but for something that wasn’t even supposed to be this organized 48 hours ago, this isn’t bad. Especially in this season of suck.

An overperformer in the basin! Tropical Storm Fiona Tropical Cyclone Update NWS National Hurricane Center Miami FL AL072022 945 PM AST Wed Sep 14 2022 ...DEPRESSION STRENGTHENS TO A TROPICAL STORM... Satellite data indicate that the depression has strengthened to a tropical storm with maximum winds estimated to be near 50 mph (85 km/h). This will be incoporated in the next advisory that will be released before 11 pm AST (0300 UTC). SUMMARY OF 945 PM AST...0150 UTC...INFORMATION ---------------------------------------------- LOCATION...16.8N 52.0W ABOUT 645 MI...1040 KM E OF THE LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES $$ Forecaster Cangialosi

Well damn. Gonna need a title change @GaWx Finally an overperformer Tropical Storm Fiona Tropical Cyclone Update NWS National Hurricane Center Miami FL AL072022 945 PM AST Wed Sep 14 2022 ...DEPRESSION STRENGTHENS TO A TROPICAL STORM... Satellite data indicate that the depression has strengthened to a tropical storm with maximum winds estimated to be near 50 mph (85 km/h). This will be incoporated in the next advisory that will be released before 11 pm AST (0300 UTC). SUMMARY OF 945 PM AST...0150 UTC...INFORMATION ---------------------------------------------- LOCATION...16.8N 52.0W ABOUT 645 MI...1040 KM E OF THE LEEWARD ISLANDS MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 14 MPH...22 KM/H MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES $$ Forecaster Cangialosi

We have Fiona.

Latest ASCAT and microwave passes:

Yeah still a fairly long way to go.

Here’s a great HM inspired thread on the complexities of figuring out the steering pattern. Recon will probably help this a bit, but there’s a lot to sort out with the Pacific having a significant impact on the Atlantic upper level pattern in the next week.

Contender in the long range for the US. Not necessarily New England lol

Although the operationals still have somewhat limited use, the fact that they all basically agree that this runs into the Greater Antilles and still finds a way to intensify in the southwest Atlantic is interesting. Ensembles more or less endorse that idea too. I do think we're past the point where this one fizzles even with land interaction, unless it runs over both Haiti/DR and the length of Cuba. This looks like a TS to me right now. At the moment I think it's going to be just organized enough to survive a day of land interaction but not so organized as to run entirely north of the islands. Not quite an analog, but I can see an Isaias type situation where it's middling along until it gets clear of the islands and begins to turn northward. Tomorrow's recon data for the system itself and the environment ahead will be very helpful. Shear is present and probably caps this before the Antilles, but dry air hasn't slowed this one down much. That alone has me starting to believe this one could be a contender in the long range.

This looks like a TS to me right now. Very nice convection near the LLC.

Far too soon to say. We're just going to be watching this through the weekend to see how the overall steering pattern shakes out.

I’m not so sure land interaction kills this one unless it’s meandering over the mountains, which looks unlikely at this point.

Hard pass. 70 and sunny is better on 9/30.

Often it is but the caveat here is that guidance often has an easier time generally picking out the larger scale steering patterns. We saw that with Earl to an extent. The devil is in the details.