WxWatcher007 Posted August 30, 2018 Looks like we're close enough to a named system that advisories are starting in about a half hour. Almost certainly a fish storm, but looking likely on the guidance to become the strongest system of the year so far. NHC will initiate advisories at 11 am EDT on Potential Tropical Cyclone Six, located east-southeast of the Cabo Verde Islands. Edited to add. This was the first cone lol 1 Share this post Link to post Share on other sites
yoda Posted August 30, 2018 BULLETIN Potential Tropical Cyclone Six Advisory Number 1 NWS National Hurricane Center Miami FL AL062018 1100 AM AST Thu Aug 30 2018 ...TROPICAL STORM CONDITIONS EXPECTED OVER THE SOUTHERN CABO VERDE ISLANDS ON FRIDAY... SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION ----------------------------------------------- LOCATION...12.9N 18.4W ABOUT 425 MI...680 KM ESE OF THE SOUTHERNMOST CABO VERDE ISLANDS MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H PRESENT MOVEMENT...W OR 280 DEGREES AT 12 MPH...19 KM/H MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: The government of the Cabo Verde Islands has issued a Tropical Storm Warning for the southern islands of Santiago, Fogo and Brava. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Tropical Storm Warning is in effect for... * Santiago * Fogo * Brava A Tropical Storm Warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 1100 AM AST (1500 UTC), the disturbance was centered near latitude 12.9 North, longitude 18.4 West. The system is moving toward the west near 12 mph (19 km/h), and this general motion with a gradual turn toward the west-northwest is expected to continue during the next few days. On the forecast track, the disturbance is expected to move near or over the southern Cabo Verde Islands on Friday. Maximum sustained winds are near 30 mph (45 km/h) with higher gusts. Some strengthening is forecast during the next 48 hours, and the disturbance is expected to become a topical storm during the next day or so. Environmental conditions are favorable for the system to become a tropical cyclone tonight or Friday. * Formation chance through 48 hours...high...80 percent * Formation chance through 5 days...high...90 percent The estimated minimum central pressure is 1007 mb (29.74 inches). HAZARDS AFFECTING LAND ---------------------- RAINFALL: The system could produce total rain accumulations of 4 to 8 inches across the southern Cabo Verde Islands. These rains could produce life-threatening flash floods. WINDS: Tropical storm conditions are expected in the southern Cabo Verde Islands on Friday. NEXT ADVISORY ------------- Next intermediate advisory at 200 PM AST. Next complete advisory at 500 PM AST. $$ Forecaster Avila Share this post Link to post Share on other sites
yoda Posted August 30, 2018 Potential Tropical Cyclone Six Discussion Number 1 NWS National Hurricane Center Miami FL AL062018 1100 AM AST Thu Aug 30 2018 The area of low pressure that moved off the coast of Africa has continued to become better organized, and is producing a large area of disturbed weather with gusty winds, but currently lacks a well-defined center. Environmental conditions are favorable for additional development, and a tropical depression or a tropical storm could form an any time today or Friday. Given the high chances that this system could bring tropical storm conditions to a portion of the southern Cabo Verde Islands, advisories have been initiated on Potential Tropical Cyclone Six. Most of the intensity guidance calls for strengthening and so does the NHC forecast. The system is embedded within the easterly trades and this flow pattern will steer the disturbance toward the west or west- northwest during the next few days. By the end of the forecast period, a turn toward the northwest should begin as the system reaches a weakness in the subtropical high. This is consistent with the output of the global models. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 12.9N 18.4W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 31/0000Z 13.2N 20.1W 30 KT 35 MPH...TROPICAL DEPRESSION 24H 31/1200Z 13.5N 22.0W 35 KT 40 MPH 36H 01/0000Z 14.0N 24.0W 45 KT 50 MPH 48H 01/1200Z 15.0N 27.0W 55 KT 65 MPH 72H 02/1200Z 16.5N 33.0W 65 KT 75 MPH 96H 03/1200Z 18.5N 38.0W 65 KT 75 MPH 120H 04/1200Z 20.0N 42.0W 65 KT 75 MPH $$ Forecaster Avila Share this post Link to post Share on other sites
WxWatcher007 Posted August 30, 2018 1 minute ago, yoda said: Potential Tropical Cyclone Six Discussion Number 1 NWS National Hurricane Center Miami FL AL062018 1100 AM AST Thu Aug 30 2018 The area of low pressure that moved off the coast of Africa has continued to become better organized, and is producing a large area of disturbed weather with gusty winds, but currently lacks a well-defined center. Environmental conditions are favorable for additional development, and a tropical depression or a tropical storm could form an any time today or Friday. Given the high chances that this system could bring tropical storm conditions to a portion of the southern Cabo Verde Islands, advisories have been initiated on Potential Tropical Cyclone Six. Most of the intensity guidance calls for strengthening and so does the NHC forecast. The system is embedded within the easterly trades and this flow pattern will steer the disturbance toward the west or west- northwest during the next few days. By the end of the forecast period, a turn toward the northwest should begin as the system reaches a weakness in the subtropical high. This is consistent with the output of the global models. FORECAST POSITIONS AND MAX WINDS INIT 30/1500Z 12.9N 18.4W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 31/0000Z 13.2N 20.1W 30 KT 35 MPH...TROPICAL DEPRESSION 24H 31/1200Z 13.5N 22.0W 35 KT 40 MPH 36H 01/0000Z 14.0N 24.0W 45 KT 50 MPH 48H 01/1200Z 15.0N 27.0W 55 KT 65 MPH 72H 02/1200Z 16.5N 33.0W 65 KT 75 MPH 96H 03/1200Z 18.5N 38.0W 65 KT 75 MPH 120H 04/1200Z 20.0N 42.0W 65 KT 75 MPH $$ Forecaster Avila Looks like the NHC is putting the breaks on the kind of rapid intensification we see on the guidance. Share this post Link to post Share on other sites
Windspeed Posted August 30, 2018 Here is the 5km SST analysis for 08/29. The estimated location of the surface low is between the southern Cape Verdes and Senegal near the mouth of the River Gambia. SSTs are running around 28°C near to and just south of the Verdes to 27°C further west into the open Atlantic — good for initial development but only marginal on the future TC's forecast path. The GFS OP was very bullish on its previous runs from 0z Wed through 06z Thur. However, the Thur 12z run has backed off rapid development into a hurricane within 36-48 hrs and now has slow strengthening into the MDR. The previous runs even had hurricane force in the southern Verdes, so that is good if the slower-paced development resolves. I think this system does eventually become a hurricane into the central Atlantic, but I'm not as bullish in strength as the GFS has previously shown. The ECMWF has modeled a less favorable environment than the GFS and subsequently much slower development and only tropical storm intensity until it reaches the central Atlantic. 1 Share this post Link to post Share on other sites
WxWatcher007 Posted August 30, 2018 10 minutes ago, Windspeed said: Here is the 5km SST analysis for 08/29. The estimated location of the surface low is between the southern Cape Verdes and Senegal near the mouth of the River Gambia. SSTs are running around 28°C near to and just south of the Verdes to 27°C further west into the open Atlantic — good for initial development but only marginal on the future TC's forecast path. The GFS OP was very bullish on its previous runs from 0z Wed theough 06z Thur. However, the Thur 12z run has backed off rapid development into a hurricane within 36-48 hrs and now has slow strengthening into the MDR. The previous runs even had hurricane force in the southern Verdes, so that is good if the slower-paced development resolves. I think this system probably does become a long-tracking hurricane into the central Atlantic, but not as bullish in strength as the GFS has previously shown. The ECMWF has modeled a less favorable environment than the GFS and subsequently much slower development and only tropical storm intensity until it reaches the central Atlantic. That seems in line with looking at the overall conditions of the MDR and areas just north. Looking at both operational models, western portions of the MDR still look hostile for anything that develops close to the coast of Africa and tracks west. 1 Share this post Link to post Share on other sites
Windspeed Posted August 30, 2018 Very active surface trough extending into Senegal. You can see a more defined MCS with strong convection rotating around it near the mouth of the Gambia. From that location is likely where our LLC closes off over night or tomorrow. Additionally, the surface trough still extends well east into interior Africa, so we likley will have an active wave train in the coming weeks. Will be interesting to see how long this train lasts and also how far east the favorable MJO phase can extend to enhance the MDR somewhat. 2 Share this post Link to post Share on other sites
USCAPEWEATHERAF Posted August 31, 2018 I think we will have a TD6 or Tropical Storm Florence earliest 2am and latest 5am later today. I think Florence becomes a monster. Share this post Link to post Share on other sites
yoda Posted August 31, 2018 21 minutes ago, USCAPEWEATHERAF said: I think we will have a TD6 or Tropical Storm Florence earliest 2am and latest 5am later today. I think Florence becomes a monster. Based off what? And what is a monster? 1 1 Share this post Link to post Share on other sites
Windspeed Posted August 31, 2018 Both the NHC and models have backed off faster development. Visible satellite clearly shows counter-clockwise rotation at the surface with a the broad center now moving just south of Praia in the southern Verdes. You can see some low level swirls rotating north around that center. Did I say broad? The elongated surface low does look to have gained a little latitude over night, perhaps pivoting north around the surface trough and axis of monsoonal flow out of the ITCZ. Is that significant? Does not take much latitude gained to shift genesis and track into lower and marginal SSTs. More importantly, the sheer size of the surface low at this time is going to be responsible for slow development. I am not saying this won't eventually become a TC. We have had plenty similarly large surface lows enter the MDR and become hurricanes, especially in active years. It's just the MDR has not been all that favorable so far. And though it may become more favorable in the coming weeks, this particular potential TC may be a little early for that and struggle. Share this post Link to post Share on other sites
WxWatcher007 Posted August 31, 2018 Everything has been a struggle so far in the basin. Meanwhile, the PAC is on fire. 1 Share this post Link to post Share on other sites
Windspeed Posted August 31, 2018 848 WTNT41KNHC 312033 TCDAT1 Tropical Depression Six Discussion Number 6 NWS National Hurricane Center Miami FL AL062018 500 PM AST Fri Aug 31 2018 High resolution satellite images reveal that the disturbance has developed a well-defined circulation with a cyclonically curved convective band near the center, and plenty of showers in the southern semicircle. The surface pressure in the Cabo Verde Island of Santiago dropped to 1005 mb at 1800 UTC as the cyclone passed to its south. In addition, Dvorak numbers are gradually increasing, and now support classifying the system as a tropical depression. The depression is becoming better organized, and it will most likely reach tropical storm status in the next several hours. The environmental conditions are favorable for some strengthening during the next 2 to 3 days while the shear is low. Later in the forecast period, the shear is expected to increase, and the SSTs will become marginal halting the strengthing process. The models, primarily the HWRF, are a little less aggressive with the intensity, so the NHC forecast is adjusted slightly downward. Now that the center has formed, we have a better estimate of the initial motion, which is toward the west or 270 degrees at 13 kt. The depression is gradually becoming steered by the flow around the subtropical ridge, and consequently it has increased its forward speed. This prevailing flow pattern should keep the cyclone on a general west to west-northwest track for the next 2 to 3 days. After that time, a weakness in the ridge will induce a more northwestward to north-northwestward track over the open Atlantic Ocean. The track guidance is very consistent with this solution mainly for the next 3 days. Thereafter, the confidence in the track forecast decreases as the guidance envelope widens and becomes bounded by the westernmost ECMWF and the easternmost HWFI. The NHC forecast continues to be in the middle of the envelope and is very close to the corrected consensus HCCA, which has had great skill so far this year. FORECAST POSITIONS AND MAX WINDS INIT 31/2100Z 13.8N 24.7W 30 KT 35 MPH 12H 01/0600Z 14.3N 26.7W 35 KT 40 MPH 24H 01/1800Z 14.9N 29.2W 40 KT 45 MPH 36H 02/0600Z 15.8N 31.8W 45 KT 50 MPH 48H 02/1800Z 16.5N 34.5W 50 KT 60 MPH 72H 03/1800Z 18.0N 39.5W 55 KT 65 MPH 96H 04/1800Z 20.0N 44.0W 60 KT 70 MPH 120H 05/1800Z 23.0N 48.0W 55 KT 65 MPH $$ Forecaster Avila Edit: Code. Share this post Link to post Share on other sites
USCAPEWEATHERAF Posted September 1, 2018 23 hours ago, yoda said: Based off what? And what is a monster? Major Hurricane status Share this post Link to post Share on other sites
yoda Posted September 1, 2018 1 minute ago, USCAPEWEATHERAF said: Major Hurricane status And as you can see NHC has Florence not even making hurricane status... major hurricane LOL Share this post Link to post Share on other sites
Windspeed Posted September 1, 2018 Saturday 0z ECMWF has a big change. Though it continues to pummel future Florence at the 400-300mb level across the MDR, keeping it much weaker and steered further west into the surface flow and trades, it also models the pattern differently. Florence survives and is gifted strong 500 mb heights right over Bermuda and the NW Atlantic, with a nice upper ridge right over top. With that setup, unsurprisingly, Florence rebounds and becomes a formidable hurricane well north of the Greater Antilles moving WNW. That's 200 hrs out, mind you, and the first run with a big shift in potential track, so view it with caution and a grain of salt. We'll see if the 12z ECMWF is also onto something or this is just a blurp. 1 Share this post Link to post Share on other sites
shaggy Posted September 1, 2018 3 hours ago, Windspeed said: Saturday 0z ECMWF has a big change. Though it continues to pummel future Florence at the 400-300mb level across the MDR, keeping it much weaker and steered further west into the surface flow and trades, it also models the pattern differently. Florence survives and is gifted strong 500 mb heights right over Bermuda and the NW Atlantic, with a nice upper ridge right over top. With that setup, unsurprisingly, Florence rebounds and becomes a formidable hurricane well north of the Greater Antilles moving WNW. That's 200 hrs out, mind you, and the first run with a big shift in potential track, so view it with caution and a grain of salt. We'll see if the 12z ECMWF is also onto something or this is just a blurp. That's a big shift in one run. It's the euro so certainly cant be ignored but it would need several runs and some serious support from the other models. It will be interesting to see what the ukmet does as time goes on. It did pretty good last season. Share this post Link to post Share on other sites
fountainguy97 Posted September 1, 2018 Euro run is very strange. Has Florence at TD/weak TS status for the next 168hrs. On tidbits the highest 850mb winds I find in that time frame are 46knts.. i find it hard to believe that Florence stays THAT weak. Especially since i see a Dvorak ADT up to 3.5 with winds of 55knts. Share this post Link to post Share on other sites
shaggy Posted September 1, 2018 23 minutes ago, fountainguy97 said: Euro run is very strange. Has Florence at TD/weak TS status for the next 168hrs. On tidbits the highest 850mb winds I find in that time frame are 46knts.. i find it hard to believe that Florence stays THAT weak. Especially since i see a Dvorak ADT up to 3.5 with winds of 55knts. 06z gfs also had a noticable shift west from its 0z run. Still recurves east of Bermuda though. Share this post Link to post Share on other sites
Windspeed Posted September 1, 2018 12z GFS does a similar thing as 0z ECMWF with Florence, keeping upper level conditions less favorable and a weaker TC initially across the MDR; therefore, it is more steered by 850-700 mb flow and further west than previous GFS runs. However, it still differs greatly on pattern beyond 5 days. ECMWF builds heights over NW Atlantic and allows Florence to slip under it. GFS not so much, stalls Florence, then eventually continues to lift Florence up and out east of Bermuda. But we'll see if the 0z ECMWF was merely a blurp in the next hour when the 12z is out. Share this post Link to post Share on other sites
Snow88 Posted September 1, 2018 Dt thinks might not miss ots Share this post Link to post Share on other sites
Windspeed Posted September 1, 2018 Thinking the 0z ECMWF was just a hiccup. 12z is back on a stronger central Atlantic weakeness and trough. Share this post Link to post Share on other sites
Snow88 Posted September 2, 2018 17 hours ago, Windspeed said: Thinking the 0z ECMWF was just a hiccup. 12z is back on a stronger central Atlantic weakeness and trough. 0z Euro has the ridge building. Closer to the U.S. on this run. 1 Share this post Link to post Share on other sites
NutleyBlizzard Posted September 2, 2018 22 minutes ago, Snow88 said: 0z Euro has the ridge building. Closer to the U.S. on this run. Still a long way out, but looking at the Euro's perspective of the 500mb map you have a pressing ridge with no kickers in sight so there's really nothing from stopping Florence eventually making a Mid-Atlantic/NE coast landfall. Share this post Link to post Share on other sites
shaggy Posted September 2, 2018 On 9/1/2018 at 7:49 AM, fountainguy97 said: Euro run is very strange. Has Florence at TD/weak TS status for the next 168hrs. On tidbits the highest 850mb winds I find in that time frame are 46knts.. i find it hard to believe that Florence stays THAT weak. Especially since i see a Dvorak ADT up to 3.5 with winds of 55knts. She is weakening now and the NHC is shifting track further south and west to match up closer to the Euro and Ukmet models. Maybe the euro track is onto something with her weakening already. Share this post Link to post Share on other sites
csnavywx Posted September 2, 2018 The issue is marginal SSTs in the near term and wind shear in the longer term when she gets back over warmer SSTs. There's consistent consensus of about 15-25 knots of wind shear past about 72-96 hours that will hinder strength as well. These issues might be alleviated if it misses the trough at day 6/7 and gets tucked under the ridge as SSTs in the subtropical Atlantic are running well above normal and wind shear would likely abate in that case. The massive upstream wave break caused by STY Jebi's recurve and interaction with mid-latitude westerlies will probably alter the environment for a future Florence track if it misses the trough too. Share this post Link to post Share on other sites
shaggy Posted September 2, 2018 CMC has certainly changed from the last run. From a way east recurve to having a cane threatening the east coast. So maybe a 1000 mile shift west in one run. To say the long range with this one is complicated is an understatement. 2 Share this post Link to post Share on other sites
purduewx80 Posted September 2, 2018 12Z GEM and ECM nearly on top of each other at D10 near the Outer Banks. GEM ensemble mean is farther S. Curious to see the 12Z EPS. 1 Share this post Link to post Share on other sites
Windspeed Posted September 2, 2018 Good lord, if that isn't a Mid-Atlantic/Delmarva weenie run, I don't know what possible could be... Notice the 500 mb heights at the end of that run. That's a block-a-roo and would drive Florence well inland. Still much caution though, this is 200 hrs out and low confidence. 1 Share this post Link to post Share on other sites
csnavywx Posted September 2, 2018 In the shorter run, the storm nearly gets ripped apart by wind shear on that run. The surface low opens up into a wave and the mid-level vortex barely survives before getting into favorable conditions and regenerating. A system that weak will easily miss the first trough and stay south. If it is stronger than forecast though, it could get picked up or deviated far enough to the right to still put it out to sea. The CMC also keeps it fairly weak and ends up with nearly the same solution. Share this post Link to post Share on other sites