GaWx

They initialized it at 17.6N, 82.0W, which is well to the WNW of that. We’ll see what recon finds this afternoon. This from the just released NHC discussion is probably relevant: “While some mid-level rotation is evident in visible satellite images, surface observations and visible satellite images suggest the low-level circulation remains broad and farther to the southwest.”

Already forecasting 110 mph! Potential Tropical Cyclone Nine Discussion Number 1 NWS National Hurricane Center Miami FL AL092024 1100 AM EDT Mon Sep 23 2024 A broad area of low pressure over the northwestern Caribbean Sea continues to produce disorganized showers and thunderstorms. While some mid-level rotation is evident in visible satellite images, surface observations and visible satellite images suggest the low-level circulation remains broad and farther to the southwest. Nonetheless, the system has a high chance of tropical cyclone formation during the next day or two, and it is likely to bring tropical storm conditions to land areas within the next 36 to 48 hours. Therefore, the NHC is initiating Potential Tropical Cyclone advisories for this disturbance. The initial motion is quite uncertain given the current lack of organization, but the best estimate is northward at about 5 kt. A gradual turn toward the northwest is expected during the next day or so, with the center passing through the Yucatan Channel and into the southern Gulf of Mexico. Thereafter, the system is forecast to accelerate northward across the eastern Gulf of Mexico within the flow between a digging deep-layer trough over the central United States and a ridge over the western Atlantic. This motion should bring the center of the system toward the northeastern Gulf Coast on Thursday. The track guidance agrees reasonably well on this scenario, and the initial NHC forecast lies near the simple and corrected consensus aids. Since the disturbance currently lacks a well-defined center, users are reminded that the average forecast track uncertainty is larger in these situations, and future track adjustments may be required. Given the large size of the tropical-storm-force wind field and fast forward speed that is forecast, storm surge, wind, and rainfall impacts will likely extend well away from the center, particularly to the east of the system. While the system is currently broad and not well organized, the models suggest a more well-defined center should develop during the next day or so. Once the system becomes better organized and develops an inner core, the environmental and oceanic conditions appear favorable for significant strengthening. In fact, the DTOPS statistical guidance shows a 95 percent chance of a 65-kt increase in intensity during the next 72 h, and the hurricane regional models highlight the potential for strengthening to major hurricane intensity. Thus, the NHC forecast shows significant strengthening while the system moves across the eastern Gulf of Mexico, with a 95-kt intensity in 72 h. While this forecast is aggressive, it lies near or slightly below the consensus aids, and future adjustments may be necessary. An Air Force Reserve reconnaissance aircraft is scheduled to investigate the system this afternoon. FORECAST POSITIONS AND MAX WINDS INIT 23/1500Z 17.6N 82.0W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 24/0000Z 18.6N 82.4W 30 KT 35 MPH...TROPICAL CYCLONE 24H 24/1200Z 19.5N 83.7W 40 KT 45 MPH 36H 25/0000Z 20.6N 85.1W 50 KT 60 MPH 48H 25/1200Z 22.1N 86.0W 65 KT 75 MPH 60H 26/0000Z 24.2N 86.0W 85 KT 100 MPH 72H 26/1200Z 27.1N 85.1W 95 KT 110 MPH 96H 27/1200Z 34.0N 83.0W 35 KT 40 MPH...INLAND 120H 28/1200Z 38.5N 87.0W 20 KT 25 MPH...POST-TROPICAL $$ Forecaster Reinhart

BULLETIN Potential Tropical Cyclone Nine Advisory Number 1 NWS National Hurricane Center Miami FL AL092024 1100 AM EDT Mon Sep 23 2024 ...DISTURBANCE FORECAST TO STRENGTHEN OVER THE NEXT FEW DAYS... ...TROPICAL STORM WARNINGS AND HURRICANE WATCHES ISSUED FOR PORTIONS OF MEXICO AND CUBA... SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...17.6N 82.0W ABOUT 130 MI...205 KM SSW OF GRAND CAYMAN ABOUT 350 MI...565 KM SSE OF THE WESTERN TIP OF CUBA MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H PRESENT MOVEMENT...N OR 350 DEGREES AT 6 MPH...9 KM/H MINIMUM CENTRAL PRESSURE...1004 MB...29.65 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of Mexico has issued a Tropical Storm Warning for the Yucatan Peninsula of Mexico from Rio Lagartos to Tulum, and a Hurricane Watch from Cabo Catoche to Tulum. The government of Cuba has issued a Tropical Storm Warning for the Isle of Youth, Artemisa, and Pinar del Rio, and a Hurricane Watch for Pinar del Rio. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Watch is in effect for... * Cabo Catoche to Tulum, Mexico * Cuban province of Pinar del Rio A Tropical Storm Warning is in effect for... * Rio Lagartos to Tulum, Mexico * Cuban provinces of Artemisa, and Pinar del Rio, and the Isle of Youth A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area, in this case within the next 24 to 36 hours. A Hurricane Watch means that hurricane conditions are possible within the watch area. A watch is typically issued 48 hours before the anticipated first occurrence of tropical-storm-force winds, conditions that make outside preparations difficult or dangerous. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM EDT (1500 UTC), the disturbance was centered near latitude 17.6 North, longitude 82.0 West. The system is moving toward the north near 6 mph (9 km/h). A northwestward motion is expected on Tuesday and Tuesday night, followed by a faster northward or north-northeastward motion on Wednesday and Thursday. On the forecast track, the center of the system is forecast to move across the northwestern Caribbean Sea and into the southeastern Gulf of Mexico during the next couple of days. Maximum sustained winds are near 30 mph (45 km/h) with higher gusts. Strengthening is expected during the next few days, and the system is forecast to become a hurricane on Wednesday and continue strengthening as it moves across the eastern Gulf of Mexico. * Formation chance through 48 hours...high...90 percent. * Formation chance through 7 days...high...90 percent. The estimated minimum central pressure is 1004 mb (29.65 inches).

Thanks, Don. It will likely drop further tomorrow. The bottom should be tomorrow although a Wednesday bottom can’t be ruled out.

For the time being after a significant recent drop, SST anomalies seem to be in temporary bounce back mode.

Recon is on the way. Where any possible low level center is found will be very important to say the least.

0Z Euro ens: only very slight E shift and slightly faster; mean landfall is Apalachicola Thu evening; then it goes N into far W GA and then NNW into NE AL. W of GEFS mean.

Hurricane models are way off the chart strong, but are they even useful yet since there’s not yet a definite LLC?

Unlike GFS/Icon, the 0Z Euro doesn’t appear to be shifting E so far. Upper low not shifted E like on those. Landfall Apalachicola late Thu afternoon at 982. Goes near AL/GA line (W of ATL). 12Z went through ATL.

0Z GEFS, with upper low being 250 miles E of 18Z, has its mean landfall 175 miles E of the 18Z’s Pensacola or just E of Apalachicola. The mean then instead of going NNW through AL travels N into SW GA. So, more/fewer members than last run in GA/AL although AL still has a decent # of members.

0Z UKMET vs 12Z is perhaps slightly E/2 mb stronger (985) with landfall still near Apalachicola late Thu evening and then to Atlanta midday Fri: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 24 HOURS FORECAST POSITION AT T+ 24 : 18.8N 83.0W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 0000UTC 24.09.2024 24 18.8N 83.0W 1002 32 1200UTC 24.09.2024 36 18.9N 84.8W 1002 36 0000UTC 25.09.2024 48 19.7N 85.1W 999 38 1200UTC 25.09.2024 60 21.6N 86.2W 996 41 0000UTC 26.09.2024 72 23.4N 86.3W 992 44 1200UTC 26.09.2024 84 25.9N 85.3W 988 52 0000UTC 27.09.2024 96 29.2N 84.8W 985 46 1200UTC 27.09.2024 108 33.1N 84.1W 990 32 0000UTC 28.09.2024 120 36.7N 85.4W 998 19 1200UTC 28.09.2024 132 39.2N 87.9W 1003 24 0000UTC 29.09.2024 144 39.8N 92.2W 1007 13 1200UTC 29.09.2024 156 CEASED T

0Z CMC similar to 12Z with Apalachee Bay at 973 mb late Thu afternoon followed by Atlanta 981 Thu night.

0Z GFS also looks to come in a good bit E of its prior runs. The upper low, similar to the case for the 0Z Icon, is further E. Confirmed: 948 mb left side of Big Bend late Thu afternoon. Not nearly as far E as Icon and then tracks into N-C GA.

The upper low on the 0Z Icon is way to east of prior runs. Landfall 975 mb just N of Tampa Thu afternoon!

0Z Icon is coming in well to the east of recent runs with the upper low well to the east of prior runs.

Wow, Don, until you posted this I wasn’t even aware of the extreme Sep -NAO about to occur. According to the latest GEFS based NAO forecast (see below), it is expected to bottom out way down near -2.7 at some point during 9/23-5! That would easily exceed the record lowest Sep daily NAO as the current record low is -2.371, set on 9/12/1971. The only other Sep with any sub -2 daily was 1986. The record low for any month is -3.254, set on 10/21/2002. 9/22/24 GEFS based NAO forecast:

18Z GEFS mean: even further west near Pensacola, which is 50 miles W of 12Z, and then N into AL

This 18Z Icon is well E of the 12Z, showing that there’s still (not surprisingly) a lot of uncertainty.

Moderate to low end strong as best as I can tell per DJF.

Who’s dismissing Webb? You’re probably not talking about me, but in case you are I take him with a grain due to several bad misses but I’m not dismissing him. If I did, I wouldn’t have quoted him to bring him into the discussion. Taking with a grain and dismissing are two different things (at least the way I define them). I assume you agree. I take many seasonal forecasts with a grain due to the difficulty in making winter forecasts, especially early.

12Z EPS: mean landfall Thu night near Apalachicola and then it moves N fairly close to GA/AL border; many either W half of lower GA or E half of lower AL; mean a bit E of 6Z, which was in E AL and perhaps very slightly E of 0Z

12Z Euro 982 Thu evening in vicinity of Apalachicola; Atlanta Fri AM at 992

GEFS: 12Z mean has a significant shift NW vs prior runs with many more going through AL vs earlier runs

Fortunately Icon, CMC, and UKMET are much weaker though UKMET often is too weak this far out. 12Z UKMET: ~12 hours earlier landfall (Thu night) than and ~75 miles W of 0Z pretty close to Apalachicola at ~987 mb vs ~993 mb on 0Z: NEW TROPICAL CYCLONE FORECAST TO DEVELOP AFTER 42 HOURS FORECAST POSITION AT T+ 42 : 17.9N 85.5W LEAD CENTRAL MAXIMUM WIND VERIFYING TIME TIME POSITION PRESSURE (MB) SPEED (KNOTS) -------------- ---- -------- ------------- ------------- 1200UTC 24.09.2024 48 18.0N 86.0W 1003 29 0000UTC 25.09.2024 60 18.2N 85.5W 1002 30 1200UTC 25.09.2024 72 20.3N 86.2W 998 40 0000UTC 26.09.2024 84 21.7N 86.2W 995 39 1200UTC 26.09.2024 96 24.0N 86.0W 992 44 0000UTC 27.09.2024 108 27.4N 85.1W 989 56 1200UTC 27.09.2024 120 31.3N 84.7W 987 39 0000UTC 28.09.2024 132 36.4N 84.7W 992 21 1200UTC 28.09.2024 144 40.5N 87.2W 996 34 0000UTC 29.09.2024 156 42.3N 91.4W 1000 21 1200UTC 29.09.2024 168 39.0N 94.3W 1004 13

TT 12Z GFS SLPs ~8 mb lower than my source