WxWatcher007

All the Cat 5’s to hit the US were TS three days before landfall. That’s incredible to me.

First time the GFS has a quicker consolidation of vorticity in the Gulf. Still delayed development until it’s right on the FL coast, then basically OTS.

PRE?

For posterity when this slides harmlessly OTS after Florida

For our Atlantic Canada folks.

12z Ensembles

Let's take a closer look at our latest area of interest that's expected to move into the western Caribbean and Gulf. The NHC now believes that TC genesis is more likely than not, and with increasing run to run consistency from some operational guidance and ensembles, a forecast for TC genesis is coming into view. 3. Northwestern Caribbean Sea: A broad area of low pressure centered over Central America is forecast to move into northwestern Caribbean Sea by this weekend. Some gradual development of this system is possible thereafter into early next week, and a tropical depression could form while it moves slowly northward, entering the eastern Gulf of Mexico. * Formation chance through 48 hours...low...10 percent. * Formation chance through 7 days...medium...60 percent. I've actually been looking at this region and time period for a little over a week now, as a complicated interaction between an EPAC monsoon trough and broader Central American Gyre (CAG) increased the odds that something could form in the EPAC or Atlantic basin. Normally, we see the CAG a few times a season, usually at the beginning or end of the season, but this time we have the setup during the building climatological peak of the season. Much like the monsoon trough in the eastern MDR last week, the EPAC monsoon trough (ribbon of vorticity) is expected to break apart into distinct areas of vorticity, with one lifting north into the western Caribbean and eventually the eastern Gulf under the influence of an upper level trough. This is where the rubber meets the road. We have a clear area of strong vorticity in Central America and that is gradually moving north. For the last week, the guidance had virtually no run to run consistency over whether a tangible feature would move into the Atlantic basin, let alone develop. Usually, the GFS goes wild with CAG TC formation, but has been silent on development. Now, virtually all major guidance has TC genesis taking shape while the GFS, seemingly behind, does put a disorganized area of vorticity into the Gulf a few days from now. At least today, while the GFS and Euro diverge on development, they are closer than it would appear looking at the general setup. Let's look at the next seven days. The GFS, with more shear and less concentrated vorticity making it to the western Caribbean in a few days takes much longer for a surface feature to develop. The Euro on the other hand, has started to show run to run consistency with lower shear and a more concentrated area of vorticity, leading to development in the eastern Gulf even if the area of vorticity spends time over the Yucatan. Even with the upper low nearby, it is expected to shift west, reducing its influence. In addition, over the region we have an upper-level anticyclone allowing for a pocket of low shear and convective activity. That feature is not expected to go anywhere. Unlike other eastern MDR systems, dry air and subsidence has not been as much of an issue further west, and the influence of the SAL had dramatically diminished, as I posted about a few days ago. Alright, so the Gulf is a furnace so that settles it, right? Hurricane coming? I think it's important to look at what could inhibit development, and I think it's land interaction. It's quite possible that if there is a weaker area of vorticity like the GFS predicts and it lingers over the Yucatan or Central America until a northeast trough pulls it north, there may not be enough time for it to organize, much like it was for Harold this week in the Gulf. That said, I think that's an increasingly low likelihood, so let's talk briefly about what happens after potential development. On the 12z Euro you see the trough that is going to kick TS Franklin OTS or toward Atlantic Canada also allows for whatever develops in the Gulf to lift N/NE. On the Euro, the system hugs the coast before swinging out to sea off the Carolina coast. Other guidance has a different trough orientation/timing that allows for it to come further up the coast. What happens is up in the air, but this is looking like something to watch in the Gulf and along the SE coast. We're going to know pretty quickly which guidance is more correct, as the vorticity lifts north. Watch out for where it lands and how consolidated it is in the next 48-72 hours. I've liked the last week of August for close to home activity for a while now and it looks like that's coming to fruition. How strong the activity is and how much of the coast is impacted remains to be seen.

As nice as this summer has been at times, I do feel like we’ve missed out a bit. No big heat while the Midwest and south have baked. Some severe but no region wide high end event like the Mid-Atlantic moderate. We did flood though.

Worth noting that both the operational GFS and Euro have continued trending toward a direct Atlantic Canada impact in about 6-7 days. That leaves a lot of time for changes but the east trend a few days ago completely reversed.

First time we’ve been seeing run to run consistency on actual development. GFS has vorticity but never gets development going. It’s a complicated forecast, but I do think something is going to lift into the Gulf.

Still worth watching Franklin up there, though it looks like we may be settling on more Newfoundland impacts.

I’m not. I do think something’s going to lift into the Gulf though.

Need the Euro to follow the Canadian

Absolutely wild to record a wind gust that high

Central American Gyre. It’s a broad area of spin over the region that usually appears a few times a year but mostly late season. You can get homebrew spin ups from it in the Atlantic or EPAC but forecasting TC development from it is notoriously difficult. Even on the less bullish GFS, the broad vorticity is there. In the area right above the bottom arrow, you can see higher vorticity in the EPAC that’ll likely spin up. As a monsoon trough on the EPAC side (ribbon of higher vorticity) continues lifting north, it’ll bring more vorticity to the Atlantic. Whether something pops is anyone’s guess. It’s far more complicated than I just described. https://tropic.ssec.wisc.edu/real-time/atlantic/movies/wg8vor4/wg8vor4_loop.html In recent years some of our big dog storms in the Atlantic (Michael/Ida) have come from a CAG. Not saying that’ll happen here but a spin up in the western Atlantic and eastern Gulf would be primed since you have high end OHC and would probably need a low shear environment for even a seedling to organize.

Toss that, but I’ve been looking at potential from a CAG in that region for the last week of August going back a week now. A system in the eastern Gulf into the SE region wouldn’t surprise me. From there probably OTS but who knows. If we get anything this year, it’s not coming from a long track MDR wave IMO with the difficulty we’ve seen getting a proper WAR. It’s homebrew or bust around here.

Looks like some modest organization in between passes. Product: Air Force Vortex Message (URNT12 KNHC)Transmitted: 24th day of the month at 1:07ZAgency: United States Air ForceAircraft: Lockheed WC-130J Hercules with reg. number AF96-5300Storm Name: FranklinStorm Number & Year: 08 in 2023 (flight in the North Atlantic basin)Mission Number: 6Observation Number: 10 ( See all messages of this type for this mission. )A. Time of Center Fix: 24th day of the month at 0:40:10ZB. Center Fix Coordinates: 20.86N 70.54WB. Center Fix Location: 57 statute miles (92 km) to the SE (137°) from Cockburn Town, Turks and Caicos Islands (U.K.).C. Minimum Height at Standard Level: 1,461m (4,793ft) at 850mbD. Minimum Sea Level Pressure: 1003mb (29.62 inHg)E. Dropsonde Surface Wind at Center: From 200° at 9kts (From the SSW at 10mph)F. Eye Character: Not AvailableG. Eye Shape: Not AvailableH. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 32kts (36.8mph)I. Location & Time of the Estimated Maximum Surface Wind Inbound: 50 nautical miles (58 statute miles) to the SW (223°) of center fix at 0:25:30ZJ. Maximum Flight Level Wind Inbound: From 273° at 26kts (From the W at 29.9mph)K. Location & Time of the Maximum Flight Level Wind Inbound: 8 nautical miles to the SSW (205°) of center fix at 0:37:30ZL. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 40kts (46.0mph)M. Location & Time of the Estimated Maximum Surface Wind Outbound: 29 nautical miles (33 statute miles) to the NE (41°) of center fix at 0:49:30ZN. Maximum Flight Level Wind Outbound: From 129° at 41kts (From the SE at 47.2mph)O. Location & Time of the Maximum Flight Level Wind Outbound: 32 nautical miles (37 statute miles) to the NE (42°) of center fix at 0:50:30ZP. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 16°C (61°F) at a pressure alt. of 1,524m (5,000ft)Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 19°C (66°F) at a pressure alt. of 1,523m (4,997ft)R. Dewpoint Temp (collected at same location as temp inside eye): 7°C (45°F)R. Sea Surface Temp (collected at same location as temp inside eye): Not AvailableS. Fix Determined By: Penetration, Wind, Pressure and TemperatureS. Fix Levels (surface & flight level centers within 5nm of each other): Surface and 850mbT. Navigational Fix Accuracy: 0.02 nautical milesT. Meteorological Accuracy: 2 nautical milesRemarks Section: Maximum Flight Level Wind: 41kts (~ 47.2mph) which was observed 32 nautical miles (37 statute miles) to the NE (42°) from the flight level center at 0:50:30Z

Lemon (0/20) put on the western Caribbean by the NHC. Not a surprise, but there remains substantial inconsistency across guidance on the feature. Not often we get a CAG in August, but when they happen, big things can pop. The key to what happens in the next few days is getting vorticity to stay off the Yucatan, but even then with the trough expected to lift whatever's there north it may only delay some level of development.

I feel like we've seen a lot of this lately. I don't recall many storms in recent years being significantly disrupted by the mountainous terrain of Hispaniola. Now that the center is offshore, it's a short flight for recon as they head toward the storm.

12z guidance also moved back toward more direct impacts in Atlantic Canada.

Landfall Tropical Storm Franklin Discussion Number 12 NWS National Hurricane Center Miami FL AL082023 1100 AM EDT Wed Aug 23 2023 Franklin's center appears to have made landfall a little to the south of Barahona, Dominican Republic, shortly before 1200 UTC, and it is now moving northward over the mountainous terrain of the country. Heavy rains have likely overspread much of Hispaniola, although the deepest convection is occurring along the south-central coast of the island. It is assumed that the maximum winds have decreased now that the center is over land, and the initial intensity is set at 35 kt, which is close to the latest UW-CIMSS AiDT and D-PRINT estimates. Franklin's speed has picked up a bit, and it is moving toward the north (005 degrees) at 11 kt. The storm continues to move northward through a break in the subtropical ridge, but it is expected to turn northeastward in the next 24-36 hours when it becomes positioned near the southern extent of a large mid-latitude trough over the western Atlantic. Then, in about 3 days, the central Atlantic ridge is expected to strengthen and block Franklin's eastward progress, forcing the storm to turn toward the north by days 4 and 5. The track guidance is tightly clustered during the first 60-72 hours of the forecast, and the NHC track forecast is very close to the previous prediction and the various consensus aids. After 72 hours, the guidance suggests that the northward turn may be a little delayed. In response, the NHC track has been shifted a bit to the east of the previous forecast at days 4 and 5. Franklin will still be affected by moderate-to-strong west-southwesterly shear when it moves off the coast of Hispaniola later today, so it will likely take some time for the circulation to reorganize itself after moving over the rugged terrain. Otherwise, environmental conditions should support gradual strengthening starting in about 24 hours. In about 3 days, a developing upper-level low near the Bahamas is likely to provide a more favorable diffluent environment aloft over Franklin, potentially fostering more significant strengthening. Although there is a fairly wide range of intensity possibilities in the deterministic and ensemble intensity guidance on days 3-5, the overall guidance envelope has been trending higher. The NHC intensity forecast follows that tendency and is higher than the previous forecast on days 4 and 5. KEY MESSAGES: 1. Heavy rainfall from Franklin is expected across much of Hispaniola into Thursday, which is expected to produce significant and potentially life-threatening flash and urban flooding as well as mudslides, particularly over central Hispaniola. 2. Franklin is bringing tropical storm conditions to portions of the Dominican Republic and Haiti, where Tropical Storm Warnings are in effect, and tropical storm conditions are expected to begin within the Turks and Caicos Islands later today or tonight. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 18.9N 70.9W 35 KT 40 MPH...OVER DOMINICAN REPUB. 12H 24/0000Z 20.5N 70.4W 35 KT 40 MPH...OVER WATER 24H 24/1200Z 22.1N 69.5W 40 KT 45 MPH 36H 25/0000Z 22.8N 68.2W 50 KT 60 MPH 48H 25/1200Z 23.1N 67.0W 55 KT 65 MPH 60H 26/0000Z 23.4N 66.0W 60 KT 70 MPH 72H 26/1200Z 24.3N 65.7W 65 KT 75 MPH 96H 27/1200Z 27.3N 66.7W 80 KT 90 MPH 120H 28/1200Z 31.1N 67.6W 90 KT 105 MPH $$ Forecaster Berg

Canada only, if that. EPS west/GEFS east. The means have been offshore, however, and have generally shifted more in that direction the last 24 hours.