40/70 Benchmark Posted September 24 Share Posted September 24 1 minute ago, WxWatcher007 said: Much like in the Gulf, shear vector and storm motion matter a lot in how much shear a TC actually encounters. It looks like a shift in shear direction has now given this the space to organize. Just look at visible satellite from yesterday vs now. Tail Doppler shows that the LLC and MLC are pretty well aligned. That likely means the organizational trend (not necessarily intensity, yet) is poised to pick up the pace—if alignment holds. I think we see slow, steady intensification for the next 36-48 hours. 2 Link to comment Share on other sites More sharing options...
SnowGoose69 Posted September 24 Share Posted September 24 Early 12Z guidance definitely a couple less far west benders over GA. Thats very close to NHC/Euro tracks 1 Link to comment Share on other sites More sharing options...
Seminole Posted September 24 Share Posted September 24 14 minutes ago, 40/70 Benchmark said: I think we see slow, steady intensification for the next 36-48 hours. After that all model guidance has 30 to 40 knot shear depicted. Link to comment Share on other sites More sharing options...
40/70 Benchmark Posted September 24 Share Posted September 24 Just now, Seminole said: After that all model guidance has 30 to 40 knot shear depicted. Looks to me like it has a window of nearly ideal conditions on Thursday. Link to comment Share on other sites More sharing options...
jbenedet Posted September 24 Share Posted September 24 The fast track is misleading to fresh water flooding risks. The heavy rain starts tomorrow in Florida panhandle and doesn’t stop for 30 hrs. The interaction with the strong ULL will enhance and prolong the rains, as if this was actually a slow mover. Regardless of exact landfall I think Tallahassee is in an especially vulnerable spot in this regard. 2 1 3 Link to comment Share on other sites More sharing options...
purduewx80 Posted September 24 Share Posted September 24 6 minutes ago, Seminole said: After that all model guidance has 30 to 40 knot shear depicted. Is that shear in the room with us? This is an ideal setup for ventilation and expansive outflow in at least three quadrants. 2 2 1 Link to comment Share on other sites More sharing options...
Hotair Posted September 24 Share Posted September 24 Helene is born. Will there be a new thread ? Or rename this one ? 062 WTNT34 KNHC 241458 TCPAT4 BULLETIN Tropical Storm Helene Advisory Number 5 NWS National Hurricane Center Miami FL AL092024 1100 AM EDT Tue Sep 24 2024 ...TROPICAL STORM HELENE FORMS OVER THE NORTHWESTERN CARIBBEAN SEA... ...HURRICANE AND STORM SURGE WATCHES REMAIN IN EFFECT FOR PORTIONS OF THE FLORIDA GULF COAST... SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...19.5N 84.3W ABOUT 180 MI...295 KM ESE OF COZUMEL MEXICO ABOUT 170 MI...275 KM SSE OF THE WESTERN TIP OF CUBA MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H PRESENT MOVEMENT...NW OR 310 DEGREES AT 12 MPH...19 KM/H MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: A Tropical Storm Warning has been issued for the Lower Florida Keys west of the Seven Mile Bridge and for the Dry Tortugas. A Tropical Storm Watch has been issued for the Middle Florida Keys from the Seven Mile Bridge to the Channel 5 Bridge. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Storm Surge Watch is in effect for... * Indian Pass southward to Flamingo * Tampa Bay * Charlotte Harbor A Hurricane Watch is in effect for... * Cabo Catoche to Tulum, Mexico * Cuban province of Pinar del Rio * Englewood to Indian Pass * Tampa Bay A Tropical Storm Warning is in effect for... * Dry Tortugas * Lower Florida Keys west of the Seven Mile Bridge * Grand Cayman * Rio Lagartos to Tulum, Mexico * Cuban provinces of Artemisa, Pinar del Rio, and the Isle of Youth A Tropical Storm Watch is in effect for... * Middle Florida Keys from the Seven Mile Bridge to the Channel 5 Bridge * Flamingo to south of Englewood * West of Indian Pass to Walton Bay County line A Storm Surge Watch means there is a possibility of life- threatening inundation, from rising water moving inland from the coastline, in the indicated locations during the next 48 hours. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov. A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within the next 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. A Tropical Storm Watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. Wind and storm surge warnings will likely be required for the U.S. later today. For storm information specific to your area in the United States, including possible inland watches and warnings, please monitor products issued by your local National Weather Service forecast office. For storm information specific to your area outside of the United States, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM EDT (1500 UTC), the center of Tropical Storm Helene was located near latitude 19.5 North, longitude 84.3 West. Helene is moving toward the northwest near 12 mph (19 km/h), and this general motion is expected to continue through early Wednesday. A northward to north-northeastward motion at a faster forward speed is expected on Wednesday and Thursday. On the forecast track, the center of Helene will move across the far northwestern Caribbean Sea through tonight, and then move across the eastern Gulf of Mexico Wednesday and Thursday, potentially reaching the Gulf coast of Florida late Thursday. Data from an Air Force Reserve Hurricane Hunter aircraft indicate that the system has acquired a well-defined center of circulation, and maximum sustained winds have increased to near 45 mph (75 km/h) with higher gusts. Additional strengthening is forecast, and Helene is expected to become a hurricane on Wednesday. Continued strengthening is anticipated after that time, and Helene could become a major hurricane on Thursday. Tropical-storm-force winds extend outward up to 140 miles (220 km) to the east of the center. Data from the Hurricane Hunter aircraft indicate that the minimum central pressure is 1000 mb (29.53 inches). HAZARDS AFFECTING LAND ---------------------- Key Messages for Helene can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT4 and WMO header WTNT44 KNHC and on the web at hurricanes.gov/text/MIATCDAT4.shtml RAINFALL: Helene is expected to produce total rain accumulations of 4 to 8 inches over western Cuba and the Cayman Islands with isolated totals around 12 inches. Over the eastern Yucatan Peninsula, 4 to 6 inches of rain are expected with isolated totals over 8 inches. This rainfall brings a risk of considerable flooding. Over the Southeastern U.S., Helene is expected to produce total rain accumulations of 4 to 8 inches with isolated totals around 12 inches. This rainfall will likely result in areas of considerable flash and urban flooding, with minor to moderate river flooding likely, and isolated major river flooding possible. For a complete depiction of forecast rainfall associated with Helene, please see the National Weather Service Storm Total Rainfall Graphic, available at hurricanes.gov/graphics_at4.shtml?rainqpf and the Flash Flood Risk graphic at hurricanes.gov/graphics_at4.shtml?ero. STORM SURGE: The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide... Ochlockonee River, FL to Chassahowitzka, FL...10-15 ft Chassahowitzka, FL to Anclote River, FL...6-10 ft Indian Pass, FL to Ochlockonee River, FL...5-10 ft Anclote River, FL to Middle of Longboat Key, FL...5-8 ft Tampa Bay...5-8 ft Middle of Longboat Key, FL to Englewood, FL...4-7 ft Englewood, FL to Bonita Beach, FL...3-5 ft Charlotte Harbor...3-5 ft For a complete depiction of areas at risk of storm surge inundation, please see the National Weather Service Peak Storm Surge Graphic, available at hurricanes.gov/graphics_at4.shtml?peakSurge. Storm surge could raise water levels by as much as 2 to 4 feet above normal tide levels in areas of onshore winds along the southern coast of Pinar del Rio, Cuba, including the Isle of Youth. Storm surge could raise water levels by as much as 2 to 4 feet above ground level in areas of onshore winds within the warning area along the east coast of the Yucatan Peninsula. WIND: Hurricane conditions are possible within the watch areas in Cuba and Mexico by early Wednesday. Hurricane conditions are possible within the U.S. watch areas Wednesday night and early Thursday. Tropical storm conditions are expected in the warning areas in the Cayman Islands, Cuba, and Mexico today. Tropical storm conditions are expected in the warning area in the Lower Florida Keys beginning on Wednesday, and are possible in the watch area in the Middle Florida Keys beginning late Wednesday. SURF: Swells generated by Helene will affect the southern coast of Cuba and the Yucatan Peninsula of Mexico during the next couple of days. Swells will spread northward toward the west coast of Florida and the northeastern Gulf Coast on Wednesday and Thursday. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 200 PM EDT. Next complete advisory at 500 PM EDT. $$ Forecaster Berg Link to comment Share on other sites More sharing options...
wncsnow Posted September 24 Share Posted September 24 12Z ICON is about 15 mb lower than 6Z at landfall 1 Link to comment Share on other sites More sharing options...
GaWx Posted September 24 Share Posted September 24 Tropical Storm Helene Discussion Number 5 NWS National Hurricane Center Miami FL AL092024 1100 AM EDT Tue Sep 24 2024 An Air Force Reserve Hurricane Hunter measured peak 925-mb flight-level winds of 52 kt to the northeast of the center, which supports an initial intensity of 40 kt. Dropsonde data also indicated that the central pressure is down to 1000 mb. Very recently, data from the plane and one-minute visible satellite imagery indicate that the center has become better defined. Based on these data, the system is being designated as Tropical Storm Helene at this time. Helene is moving a little faster toward the northwest (310/10 kt) as it moves around a mid-level area of high pressure located over Florida and the Southeastern U.S. The high is expected to slide eastward through Wednesday as a deep-layer trough digs southward over the Lower Mississippi Valley. This pattern evolution should cause the system to turn northward and north-northeastward late Wednesday into Thursday. The track guidance is very tightly clustered, which would normally imply high forecast confidence. However, depending on exactly where the center forms could end up shifting the entire guidance suite in future cycles, so it is imperative to not focus on specific landfall locations this far in the future. Satellite trends suggest that the shear over the system is beginning to decrease, and model guidance continues to show relatively low to moderate shear for the next 48 hours or so. In addition, oceanic heat content values are very high, and the system will be moving through an environment of upper-level divergence. Therefore, significant strengthening is anticipated, and the NHC intensity forecast shows the system reaching a peak intensity around 100 kt in 48 hours while over the eastern Gulf of Mexico. There could be some increase in shear around the time the system reaches the coast, given the system's large size, it might only weaken slowly. As a result, there is still a risk that the system could reach the coast as a major hurricane. Helene's forecast radii are at the 90th percentile of hurricane size at similar latitudes. Due to the forecast large size of this system, storm surge, wind, and rainfall impacts will extend well away from the center, particularly on the east side. In addition, the fast forward speed while it crosses the coast will likely result in farther inland penetration of strong winds over parts of the southeastern United States after landfall. FORECAST POSITIONS AND MAX WINDS INIT 24/1500Z 19.5N 84.3W 40 KT 45 MPH 12H 25/0000Z 20.3N 85.2W 50 KT 60 MPH 24H 25/1200Z 21.5N 86.3W 65 KT 75 MPH 36H 26/0000Z 23.2N 86.3W 80 KT 90 MPH 48H 26/1200Z 25.9N 85.4W 100 KT 115 MPH 60H 27/0000Z 29.7N 84.3W 100 KT 115 MPH 72H 27/1200Z 33.9N 83.9W 45 KT 50 MPH...INLAND 96H 28/1200Z 39.7N 86.8W 20 KT 25 MPH...POST-TROPICAL 120H 29/1200Z...DISSIPATED $$ Forecaster Berg Link to comment Share on other sites More sharing options...
WxWatcher007 Posted September 24 Author Share Posted September 24 4 minutes ago, Hotair said: Helene is born. Will there be a new thread ? Or rename this one ? The thread gets renamed, and I try to keep the latest advisory info in the title until landfall. 4 4 Link to comment Share on other sites More sharing options...
Seminole Posted September 24 Share Posted September 24 17 minutes ago, purduewx80 said: Is that shear in the room with us? This is an ideal setup for ventilation and expansive outflow in at least three quadrants. Yep! Misread the 27th for 26th so I was wrong. 1 1 Link to comment Share on other sites More sharing options...
wxeyeNH Posted September 24 Share Posted September 24 What am I missing? As of 11:15 eastern time the LLC seems to becoming more exposed and moving to the SSW. That doesn't seem to indicate immediate strenghtening. https://weather.cod.edu/satrad/?parms=meso-meso1-truecolor-48-1-100-1&checked=map&colorbar=undefined Link to comment Share on other sites More sharing options...
MANDA Posted September 24 Share Posted September 24 Interesting Satellite loop (time sensitive) as center continues to drift sw away from deepest convection. No doubt there are TS winds associated with all the convection to the NE of the LLC so I get the upgrade. Will be interesting to see if convection develops over current LLC or new enter forms under the deep convection. ULL over the Yucatan is backing NW but there is clearly still SW shear affecting Helene. Interesting to watch this develop. I would not be surprised to see nudges east in the track over the next 24 hours or so. Either way depending on how fast Helene can intensify the current track (depending on intensity) could push A LOT of water onto the west coast of FL, especially from just south of Tampa northward. Link to visible loop: https://www.meteo.psu.edu/ewall/PSUGOES_MESO1/loop60.html Link to comment Share on other sites More sharing options...
CoastalWx Posted September 24 Share Posted September 24 @wxeyeNH I noticed that too. It's occurring after the early posts about alignment. We could see a new center develop closer to the convection..but IMO things aren't close to taking off quite yet. 5 Link to comment Share on other sites More sharing options...
schoeppeya Posted September 24 Share Posted September 24 13 minutes ago, CoastalWx said: @wxeyeNH I noticed that too. It's occurring after the early posts about alignment. We could see a new center develop closer to the convection..but IMO things aren't close to taking off quite yet. Yeah what a mess Link to comment Share on other sites More sharing options...
hawkeye_wx Posted September 24 Share Posted September 24 The 12z GFS shows several little pieces of vorticity pinwheeling around each other for the next couple days, which keeps Helene weak. It may be too weak. 1 Link to comment Share on other sites More sharing options...
hooralph Posted September 24 Share Posted September 24 Charlotte Country (Port Charlotte) has already ordered evacuations. Overreaction? Proper reaction? Link to comment Share on other sites More sharing options...
GaWx Posted September 24 Share Posted September 24 12Z GFS: landfall near 975 (weaker than recent runs) Big Bend Thu evening 1 Link to comment Share on other sites More sharing options...
Wormy2005 Posted September 24 Share Posted September 24 @hooralphI think it's a proper reaction, its better to be safe than sorry!! 1 Link to comment Share on other sites More sharing options...
TPAwx Posted September 24 Share Posted September 24 3 minutes ago, hooralph said: Charlotte Country (Port Charlotte) has already ordered evacuations. Overreaction? Proper reaction? Proactive and appropriate IMO for a coastal/low lying county and area. Not in the current cone but as others as noted Helene will push a significant surge along the FL West Coast. 1 1 Link to comment Share on other sites More sharing options...
smokeybandit Posted September 24 Share Posted September 24 6 minutes ago, hooralph said: Charlotte Country (Port Charlotte) has already ordered evacuations. Overreaction? Proper reaction? Their emergency management website only shows they're in the "monitoring" stage. https://www.charlottecountyfl.gov/departments/public-safety/emergency-management/ Link to comment Share on other sites More sharing options...
JP11283 Posted September 24 Share Posted September 24 22 minutes ago, hooralph said: Charlotte Country (Port Charlotte) has already ordered evacuations. Overreaction? Proper reaction? Their Facebook page includes homes that don’t meet 1995 building codes in the order. Seems excessive to me, that's a lot of homes, and there's quite a bit of confusion in the comments. Link to comment Share on other sites More sharing options...
TPAwx Posted September 24 Share Posted September 24 Wouldn't be surprised to see most segments hit or exceed these levels Link to comment Share on other sites More sharing options...
cptcatz Posted September 24 Share Posted September 24 Last few frames of visible satelite make it look like that naked swirl is moving almost due south. Link to comment Share on other sites More sharing options...
Hotair Posted September 24 Share Posted September 24 24 minutes ago, hooralph said: Charlotte Country (Port Charlotte) has already ordered evacuations. Overreaction? Proper reaction? Very appropriate considering the unknowns and the certainty that this event will happen mid week without the luxury for most to prepare over a weekend. Link to comment Share on other sites More sharing options...
GaWx Posted September 24 Share Posted September 24 12Z CMC: 977 Big Bend Thu night, but it only weakens to 978 mb SE of Atlanta! That would be bordering on alltime record low SLPs in that region of GA. The potential damage well inland should not be understated. 1 Link to comment Share on other sites More sharing options...
jbenedet Posted September 24 Share Posted September 24 You can see a PRE setup pretty clearly on the major guidance, but it’s obvious on the 12z CMC. Most guidance currently centered around Tallahassee for the best forcing. 1 Link to comment Share on other sites More sharing options...
jbenedet Posted September 24 Share Posted September 24 10 minutes ago, GaWx said: 12Z CMC: 977 Big Bend Thu night, but it only weakens to 978 mb SE of Atlanta! That would be bordering on alltime record low SLPs in that region of GA. The potential damage well inland should not be understated. Significant -NAO patterns are good for displacing climatological patterns. This syntopic interaction and extra tropical transition is common to what is experienced in the northeast; unusual in the southeast… 1 1 Link to comment Share on other sites More sharing options...
wncsnow Posted September 24 Share Posted September 24 The inland flooding could be devastating with the PRE and Helene combo. Southern Appalachian areas could see as much impact as Florida with flash flooding, mud slides, and high winds in the higher elevations. Some areas along the Blue Ridge could easily see 12-16" of rain with orographic uplift with the SE flow 1 Link to comment Share on other sites More sharing options...
StantonParkHoya Posted September 24 Share Posted September 24 12 minutes ago, GaWx said: 12Z CMC: 977 Big Bend Thu night, but it only weakens to 978 mb SE of Atlanta! That would be bordering on alltime record low SLPs in that region of GA. The potential damage well inland should not be understated. Yeah, call me skeptical. Never seen a TC that didn’t begin weakening rapidly upon LF. 1 Link to comment Share on other sites More sharing options...
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