Kory Posted July 30, 2014 Share Posted July 30, 2014 Exposed circulation now... Link to comment Share on other sites More sharing options...
Ground Scouring Posted July 30, 2014 Share Posted July 30, 2014 The system behind 93L actually looks a lot more organized...I'm surprised that it isn't an INVEST yet (not that I think it will develop into anything of significance). Several models briefly develop a closed low that loses identity in three days. Also, the environment surrounding it will be more moist than what 93L is moving through. And the system currently has much more convective organization than 93L does. For some reason, the HWRF and the GFDL have been consistently forecasting 93L to be near hurricane intensity by August 1. The 12Z HWRF (and to a lesser extent the 06Z GFDL) also shows 93L developing robust convection within 24 hours. What in the convective parameterization is causing these models to miss the robust SAL / low RH surrounding 93L? Such an error in short-range forecasting would be quite bad. Link to comment Share on other sites More sharing options...
IsentropicLift Posted July 30, 2014 Share Posted July 30, 2014 The system behind 93L actually looks a lot more organized...I'm surprised that it isn't an INVEST yet (not that I think it will develop into anything of significance). Several models briefly develop a closed low that loses identity in three days. Also, the environment surrounding it will be more moist than what 93L is moving through. And the system currently has much more convective organization than 93L does. The 12z GFS intensifies this system for the next two days before it falls apart. Link to comment Share on other sites More sharing options...
phil882 Posted July 30, 2014 Share Posted July 30, 2014 For some reason, the HWRF and the GFDL have been consistently forecasting 93L to be near hurricane intensity by August 1. The 12Z HWRF (and to a lesser extent the 06Z GFDL) also shows 93L developing robust convection within 24 hours. What in the convective parameterization is causing these models to miss the robust SAL / low RH surrounding 93L? Such an error in short-range forecasting would be quite bad. The HWRF is of sufficient horizontal resolution that it does not need a convective parameterization. While there might be other deficiencies in the model physics itself (e.g microphysics) you can't blame this on the convective scheme here. The more problematic thing here is that (as far as I am aware of) most meteorological dynamical models forecasts currently don't really account for aerosols. Thus, the GFS, ECMWF, HWRF ect. don't actually know the SAL is there (other than if its possibly accounted for by IC radiances from POES or GOES). Link to comment Share on other sites More sharing options...
Kory Posted July 30, 2014 Share Posted July 30, 2014 Does 93L looks like it's beginning to open up into a wave? Link to comment Share on other sites More sharing options...
IsentropicLift Posted July 30, 2014 Share Posted July 30, 2014 93L was probably at least a depression on Monday before the SAL began working into the core. Looks like we're getting another small burst of convection near the center. The circulation may no longer be intact. The system behind it looks better. We'll see what the NHC center says at 2PM. Link to comment Share on other sites More sharing options...
IsentropicLift Posted July 30, 2014 Share Posted July 30, 2014 The system currently behind 93L appears to be in a slightly better enviornment. While 93L continues to choke on dry air, the atmosphere does appear to be more moist behind it. Even so, you can see how the dry air to the north is helping to suppress convection north of the center. Link to comment Share on other sites More sharing options...
Ground Scouring Posted July 30, 2014 Share Posted July 30, 2014 Does 93L looks like it's beginning to open up into a wave? It's detaching from the ITCZ and is entering the stronger low-level trades to its immediate NW, so I'd say yes. Within 24 hours, the center will likely be gone, unless new convection were to fire, which is unlikely given the very dry environment. Link to comment Share on other sites More sharing options...
bdgwx Posted July 30, 2014 Share Posted July 30, 2014 The 12z GFS intensifies this system for the next two days before it falls apart. The 12Z FIM intensifies it a bit more than the GFS...still border line TD/TS past 48 hours though. Link to comment Share on other sites More sharing options...
IsentropicLift Posted July 30, 2014 Share Posted July 30, 2014 000ABNT20 KNHC 301734TWOATTROPICAL WEATHER OUTLOOKNWS NATIONAL HURRICANE CENTER MIAMI FL200 PM EDT WED JUL 30 2014For the North Atlantic...Caribbean Sea and the Gulf of Mexico:Showers and thunderstorms associated with an area of low pressurelocated about 1000 miles east of the southern Windward Islands havebeen gradually decreasing since yesterday. However, environmentalconditions are marginally conducive for the development of thissystem into a tropical depression during the next couple of days.Interests in the Lesser Antilles should monitor the progress of thissystem as it moves west-northwestward near 15 mph.* Formation chance through 48 hours...medium...50 percent.* Formation chance through 5 days...medium...50 percent. Link to comment Share on other sites More sharing options...
bluewave Posted July 30, 2014 Share Posted July 30, 2014 The dry and more stable air over the Tropical Atlantic has resulted in a very impressive tropical cyclone statistic. From the beginning of the 2011 hurricane season through today there have been 51 named storms in the Atlantic Basin. Only 2 storms were able to reach hurricane status while in this region since then. Both Humberto in 2013 and Katia in 2011 only made it to category 1 strength in this box. The last major hurricanes occurred back in 2010. http://www.nhc.noaa.gov/2014atlan.shtml Link to comment Share on other sites More sharing options...
phil882 Posted July 30, 2014 Share Posted July 30, 2014 Does 93L looks like it's beginning to open up into a wave? Not yet... it still has a robust low-level circulation as evident on visible satellite imagery. However, without any substantial convection to maintain that surface circulation, it will gradually lose definition. Link to comment Share on other sites More sharing options...
Wannabehippie Posted July 30, 2014 Share Posted July 30, 2014 What is the cause of the increase in the SAL over the past few (couple?) of years? Link to comment Share on other sites More sharing options...
Yeoman Posted July 31, 2014 Share Posted July 31, 2014 Another lame year.. Link to comment Share on other sites More sharing options...
Ground Scouring Posted July 31, 2014 Share Posted July 31, 2014 What is the cause of the increase in the SAL over the past few (couple?) of years? *sarcasm* Anything other than climate change…which is a topic for another thread. *sarcasm* In all seriousness, a more direct cause is the Sahel drought and a shift in the Hadley circulation over the Atlantic. The PDO explanation doesn't really make sense given that previous -PDO cycles coincided with high precipitation in the MDR. Interestingly, although the Indian Ocean has cooled off over the past month, we're still having serious problems with lower-than-average instability. I also can't recall the last time I've seen 26-27° C SSTs so far south and west in the MDR this time of year. That's frigid by climatological standards. Link to comment Share on other sites More sharing options...
wxmx Posted July 31, 2014 Share Posted July 31, 2014 This is probably at least a TD. Convection has returned near the center, and although it's sheared by westerlies, ASCAT shows that it's a vigorous closed low now. Strength maybe very close to 35kts if one takes into account there's a relatively large area of 30kts wind barbs and ASCAT's underestimating bias. Link to comment Share on other sites More sharing options...
Ground Scouring Posted July 31, 2014 Share Posted July 31, 2014 This is probably at least a TD. Convection has returned near the center, and although it's sheared by westerlies, ASCAT shows that it's a vigorous closed low now. Strength maybe very close to 35kts if one takes into account there's a relatively large area of 30kts wind barbs and ASCAT's underestimating bias. WMBas100.png But with the dry air around, the convection will likely fade by tomorrow morning. I wouldn't call it a TD or TS unless convection were to persist as per NHC criteria. SSTA are warmer near the islands, but the system will have its moisture source from the ITCZ cut off as it tracks to the west-northwest. While some of the dry air has mixed out over the past several hours, another trade surge of dry SAL is also approaching from the east. At this point I'm not optimistic, even though the GFDL and the HWRF have raised their intensity estimates over the next two days. Link to comment Share on other sites More sharing options...
wxmx Posted July 31, 2014 Share Posted July 31, 2014 But with the dry air around, the convection will likely fade by tomorrow morning. I wouldn't call it a TD or TS unless convection were to persist as per NHC criteria. SSTA are warmer near the islands, but the system will have its moisture source from the ITCZ cut off as it tracks to the west-northwest. While some of the dry air has mixed out over the past several hours, another trade surge of dry SAL is also approaching from the east. At this point I'm not optimistic, even though the GFDL and the HWRF have raised their intensity estimates over the next two days. Shear is going to diminish to ~10 kts for the next 24 hours. Thermodynamics are mediocre at best, but it will only take a slight organization improvement...or even status quo for a few hours to get numbered. Link to comment Share on other sites More sharing options...
phil882 Posted July 31, 2014 Share Posted July 31, 2014 Shear is going to diminish to ~10 kts for the next 24 hours. Thermodynamics are mediocre at best, but it will only take a slight organization improvement...or even status quo for a few hours to get numbered. Compleatly agree, now that the convection has returned the shear still isn't prohibably strong to prevent TCG. As long as the convection doesn't wane, this should get to TD/TS even if the organization from here on out remains stagnant. Link to comment Share on other sites More sharing options...
negative-nao Posted July 31, 2014 Share Posted July 31, 2014 Here is a better view http://wxweb.meteostar.com/models/noaaport_loop.php?PATH=/var/www/leads_images/satellite/GOE/IR/ Link to comment Share on other sites More sharing options...
Weathergun Posted July 31, 2014 Share Posted July 31, 2014 Up to 70% now. Disco sounds like they may upgrade this later this morning : TROPICAL WEATHER OUTLOOKNWS NATIONAL HURRICANE CENTER MIAMI FL800 AM EDT THU JUL 31 2014For the North Atlantic...Caribbean Sea and the Gulf of Mexico:A well-defined low pressure system located about 650 miles east ofthe southern Windward Islands has been producing organized showerand thunderstorm activity during the past several hours. If thisactivity persists, tropical depression or tropical storm advisorieswill be initiated later this morning. Interests in the LesserAntilles should monitor the progress of this disturbance as it moveswest-northwestward at 15 to 20 mph, and watches or warnings may berequired for some of these islands later today. A HurricaneHunter aircraft is scheduled to investigate the system thisafternoon.* Formation chance through 48 hours...high...70 percent.* Formation chance through 5 days...high...70 percent.$$Forecaster Pasch Link to comment Share on other sites More sharing options...
Wannabehippie Posted July 31, 2014 Share Posted July 31, 2014 Up to 70% now. Disco sounds like they may upgrade this later this morning : TROPICAL WEATHER OUTLOOKNWS NATIONAL HURRICANE CENTER MIAMI FL800 AM EDT THU JUL 31 2014For the North Atlantic...Caribbean Sea and the Gulf of Mexico:A well-defined low pressure system located about 650 miles east ofthe southern Windward Islands has been producing organized showerand thunderstorm activity during the past several hours. If thisactivity persists, tropical depression or tropical storm advisorieswill be initiated later this morning. Interests in the LesserAntilles should monitor the progress of this disturbance as it moveswest-northwestward at 15 to 20 mph, and watches or warnings may berequired for some of these islands later today. A HurricaneHunter aircraft is scheduled to investigate the system thisafternoon.* Formation chance through 48 hours...high...70 percent.* Formation chance through 5 days...high...70 percent.$$Forecaster Pasch Given the dry air around it, and that it will be entering an area of high shear soon, I cannot see this system lasting very long, if it does make it to TD/TS status. Link to comment Share on other sites More sharing options...
IsentropicLift Posted July 31, 2014 Share Posted July 31, 2014 While 93L is still fighting dry air to the north and northwest it does appear to be steadily increasing in convective organization this morning. Link to comment Share on other sites More sharing options...
Weathergun Posted July 31, 2014 Share Posted July 31, 2014 Convection has actually decreased and the LLC has become exposed again, in the last few frames: http://www.ssd.noaa.gov/PS/TROP/floaters/93L/flash-vis-long.html Link to comment Share on other sites More sharing options...
Srain Posted July 31, 2014 Share Posted July 31, 2014 I suspect RECON will not fly today unless there is a dramatic increase in convection N of the exposed center of circulation which is clearly visible this morning. This may have been a TD about 48 hours ago, but the future certainly does not look good for a viable tropical cyclone out of this swirl. Link to comment Share on other sites More sharing options...
IsentropicLift Posted July 31, 2014 Share Posted July 31, 2014 I suspect RECON will not fly today unless there is a dramatic increase in convection N of the exposed center of circulation which is clearly visible this morning. This may have been a TD about 48 hours ago, but the future certainly does not look good for a viable tropical cyclone out of this swirl. The visible loop tells the story. Looking at the IR loop it's not 100% clear if the center is fully exposed or just on the northern edge of the deepest convection. Link to comment Share on other sites More sharing options...
Superstorm93 Posted July 31, 2014 Share Posted July 31, 2014 Even if it somehow managed to survive, looks like it may have to deal with Hispaniola Link to comment Share on other sites More sharing options...
Weathergun Posted July 31, 2014 Share Posted July 31, 2014 NHC tweet: Natl Hurricane Ctr @NHC_Atlantic 8m NHC will not start advisories on Atlantic disturbance this morning. Thunderstorm activity too limited. Link to comment Share on other sites More sharing options...
IsentropicLift Posted July 31, 2014 Share Posted July 31, 2014 Looks like a big convective blowup just south of the center currently Link to comment Share on other sites More sharing options...
Srain Posted July 31, 2014 Share Posted July 31, 2014 Looks like a big convective blowup just south of the center currently A cell 50 miles or so SSW of the LLC isn't enough to warrant an upgrade. We would need to see storms concentrated much closure to the center of circulation before any real chance of 93L developing any further. The exposed center is racing rather quickly to the W/WNW as well and that should inhibit much more in the way of development. Look further E across Africa as we enter the month of August. There is some increase in convection along and N 10 that may weaken the SAL a bit as we move along. We still have a lot of season left. Link to comment Share on other sites More sharing options...
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