Re: When is a POTENTIAL tropical storm alert called?
Posted by Chris in Tampa on 8/22/2017, 3:52 pm
| "Potential Tropical Cyclone: A term used in NWS advisory products to describe a disturbance that is not yet a tropical cyclone, but which poses the threat of bringing tropical storm or hurricane conditions to land areas within 48 hours." From: http://www.nhc.noaa.gov/aboutgloss.shtml#p Even though it has a near 100% chance, it would still seem to be beyond 48 hours until tropical storm conditions along NW Gulf coast. Averaging all the paths of the available models at HurricaneCity, excluding all GFS and CMC ensembles, it could be about two and two and a half days before I would guess conditions might reach those areas, if it develops. I labeled the number of days out from 2pm Tuesday:  Normally I wouldn't include info beyond about 5 days, but it is worth noting in terms of rainfall that the models don't move the potential storm quickly out of the area right now and this area has a history of deadly inland flooding in tropical cyclones, regardless of intensity of the wind. Even through it went up to near 100%, it doesn't mean there will be an advisory at 5pm. When they do want to issue watches and warnings, and it has not yet met the qualifications to be a tropical cyclone, then they would release advisories. It could be 11pm tonight before advisories are started so it gets in the newspapers. 5am Wednesday might put it less than 48 hours until conditions might reach the area. That's going by models. NHC said at 2pm on outlook: "Interests in northeastern Mexico and along the Texas coast should monitor the progress of this system, as it could produce storm surge and tropical storm or hurricane force winds along portions of the Texas coast, and very heavy rainfall across portions of central and eastern Texas from Friday through the weekend." 48 hours before Friday would be sometime Wednesday. So it's possible they might wait until tomorrow to issue a watch and therefore initiate advisories if they have not started advisories by then already. (They say "a tropical depression is expected to form over the southwestern Gulf of Mexico on Wednesday or Thursday", so we could see watches issued before it is officially a depression again.) Generally 48 hours for a watch and 36 hours for a warning. If it got to 48 hours, or perhaps close, they could start advisories. If the next normal advisory time would put it under 48 hours, maybe they would do it further out. And of course this is for these types of conditions reaching the coast, not for the landfall of the center of the storm. (Jim's countdown is for conditions reaching the featured city) Various watch and warning definitions... "Tropical Cyclone: A warm-core non-frontal synoptic-scale cyclone, originating over tropical or subtropical waters, with organized deep convection and a closed surface wind circulation about a well-defined center. Once formed, a tropical cyclone is maintained by the extraction of heat energy from the ocean at high temperature and heat export at the low temperatures of the upper troposphere. In this they differ from extratropical cyclones, which derive their energy from horizontal temperature contrasts in the atmosphere (baroclinic effects)." "Tropical Depression: A tropical cyclone in which the maximum sustained surface wind speed (using the U.S. 1-minute average) is 33 kt (38 mph or 62 km/hr) or less." "Tropical Storm Warning: An announcement that sustained winds of 34 to 63 knots (39 to 73 mph or 63 to 118 km/hr) are expected somewhere within the specified area within 36 hours in association with a tropical, subtropical, or post-tropical cyclone." "Tropical Storm Watch: An announcement that sustained winds of 34 to 63 knots (39 to 73 mph or 63 to 118 km/hr) are possible within the specified area within 48 hours in association with a tropical, subtropical, or post-tropical cyclone." "Hurricane Warning: An announcement that sustained winds of 64 knots (74 mph or 119 km/hr) or higher are expected somewhere within the specified area in association with a tropical, subtropical, or post-tropical cyclone. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the warning is issued 36 hours in advance of the anticipated onset of tropical-storm-force winds. The warning can remain in effect when dangerously high water or a combination of dangerously high water and waves continue, even though winds may be less than hurricane force." "Hurricane Watch: An announcement that sustained winds of 64 knots (74 mph or 119 km/hr) or higher are possible within the specified area in association with a tropical, subtropical, or post-tropical cyclone. Because hurricane preparedness activities become difficult once winds reach tropical storm force, the hurricane watch is issued 48 hours in advance of the anticipated onset of tropical storm force winds." "Storm Surge Warning: The danger of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 36 hours, in association with an ongoing or potential tropical cyclones, a subtropical cyclone or a post-tropical cyclone. The warning may be issued earlier when other conditions, such as the onset of tropical-storm-force winds are expected to limit the time available to take protective actions for surge (e.g., evacuations). The warning may also be issued for locations not expected to receive life-threatening inundation but which could potentially be isolated by inundation in adjacent areas." "Storm Surge Watch: The possibility of life-threatening inundation from rising water moving inland from the shoreline somewhere within the specified area, generally within 48 hours, in association with an ongoing or potential tropical cyclones, a subtropical cyclone or a post-tropical cyclone. The watch may be issued earlier when other conditions, such as the onset of tropical-storm-force winds are expected to limit the time available to take protective actions for surge (e.g., evacuations). The warning may also be issued for locations not expected to receive life-threatening inundation but which could potentially be isolated by inundation in adjacent areas." |
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When is a POTENTIAL tropical storm alert called? - Spin_Doctor, 8/22/2017, 3:14 pm
- I couldn't agree more - cypresstx, 8/22/2017, 3:32 pm
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