Update on National Hurricane Center Products and Services for 2017
1) Storm Surge Watch/Warning becomes operational Beginning with the 2017 hurricane season, the National Weather Service (NWS) will issue storm surge watches and warnings to highlight areas along the Gulf and Atlantic coasts of the continental United States that have a significant risk of life-threatening inundation from a tropical cyclone, subtropical cyclone, post-tropical cyclone, or (pending final NWS approval) a potential tropical cyclone. Storm surge is often the greatest threat to life and property from a tropical cyclone, and it doesn’t always occur at the same times or locations as a storm’s hazardous winds. In addition, while in most cases coastal residents can remain in their homes (or in a secure structure nearby) and be safe from a tropical cyclone’s winds, evacuations are generally needed to keep people safe from storm surge. Having separate warnings for these two hazards will save lives by better identifying the specific tropical cyclone hazards communities face, and by enhancing public response to instructions from local officials.
The storm surge watch/warning areas are determined by a collaborative process between the NHC and local NWS Weather Forecast Offices (WFOs). The primary objective guidance will be P-Surge, an ensemble-based probabilistic system driven by the SLOSH model, the latest NHC official tropical cyclone forecast, and the typical historical errors associated with NHC forecasts. Forecaster confidence, continuity from advisory to advisory, and other subjective factors will also help determine the areas placed under a watch or warning. A graphic (e.g., Figure 1) depicting the watch and warning areas will be available on the NHC website (www.hurricanes.gov) whenever these watches/warnings are in effect.
2) Issuance of Watches, Warnings, and Advisories for Potential Tropical Cyclones Pending final NWS approval, NHC will in 2017 have the option to issue advisories, watches, and warnings for disturbances that are not yet a tropical cyclone, but which pose the threat of bringing tropical storm or hurricane conditions to land areas within 48 hours. Under previous longstanding NWS policy, it has not been permitted to issue a hurricane or tropical storm watch or warning until after a tropical cyclone had formed. Advances in forecasting over the past decade or so, however, now allow the confident prediction of tropical cyclone impacts while these systems are still in the developmental stage. For these land-threatening “potential tropical cyclones”, NHC will now issue the full suite of text, graphical, and watch/warning products that previously has only been issued for ongoing tropical cyclones.
Potential tropical cyclones will share the naming conventions currently in place for tropical and subtropical depressions, with depressions and potential tropical cyclones being numbered from a single list (e.g., “One”, “Two”, “Three”, …, “Twenty-Three”, etc.). The assigned number will always match the total number of systems (tropical cyclones, subtropical cyclones, or potential tropical cyclones) that have occurred within that basin during the season. For example, if three systems requiring advisories have already formed within a basin in a given year, the next land-threatening disturbance would be designated “Potential Tropical Cyclone Four”. If a potential tropical cyclone becomes a tropical depression, its numerical designation remains the same (i.e., Potential Tropical Cyclone Four becomes Tropical Depression Four).
Potential tropical cyclone advisory packages (i.e., the Public Advisory, Forecast/Advisory, Discussion, Wind Speed Probability Product, etc., along with all the standard tropical cyclone graphics) will be issued at the standard advisory times of 5 AM, 11 AM, 5 PM, and 11 PM EDT. Three-hourly Intermediate public advisories will be issued for potential tropical cyclones at 2 AM, 8 AM, 2 PM, and 8 PM EDT when watches or warnings are in effect. The product suite will include a five-day track and intensity forecast just as is done for ongoing tropical cyclones. In addition, the Potential Storm Surge Flooding Map and Storm Surge Watch/Warning graphic would be issued for these systems when appropriate.
Advisory packages on potential tropical cyclones will be issued until watches or warnings are discontinued or until the threat of tropical-storm-force winds for land area sufficiently diminishes, at which point advisories would be discontinued. However, if it seems likely that new watches or warnings would be necessary within a short period of time (say 6-12 hours), then advisories could continue for a short time in the interest of service continuity. Once a system becomes a tropical cyclone, the normal rules for discontinuing advisories will apply. Potential tropical cyclone advisories will not be issued for systems that pose a threat only to marine areas.
Because NHC will be issuing its normal graphical products depicting the five-day forecast track and uncertainty cone for potential tropical cyclones, to avoid potential confusion the Graphical Tropical Weather Outlook will no longer display a formation area for these systems.
3) Experimental Time of Arrival of Tropical-Storm-Force Winds Graphic The arrival of sustained tropical-storm-force winds is a critical planning threshold for coastal communities, as many preparedness activities become difficult or dangerous once winds reach tropical storm force. Frequently, this timing is estimated using the deterministic NHC track, intensity, and wind-field (size) forecasts, but such an approach doesn’t account for forecast uncertainty, and communities can be caught off guard if a storm speeds up or grows in size beyond what was forecast. To provide guidance on when users should consider having their preparations completed before a storm, NHC will begin issuing in 2017 experimental Time of Arrival of Tropical-Storm-Force Winds graphics. These graphics will be driven by the same Monte Carlo wind speed probability model that is currently used to determine the risk of tropical-stormand hurricane-force winds at individual locations – a model in which 1000 plausible scenarios are constructed using the official NHC tropical cyclone forecast and its historical errors.
The primary graphic displays the “earliest reasonable” arrival time, identifying the time window that users at individual locations can safely assume will be free from tropical-storm-force winds. Specifically, this is the time that has no more than a 1-in-10 (10%) chance of seeing the onset of sustained tropical-storm-force winds – the period during which preparations should ideally be completed for those with a low tolerance for risk. A second graphic will show the “most likely” arrival time – that is, the time before or after which the onset of tropical-storm-force winds is equally likely. This would be more appropriate for users who are willing to risk not having completed their preparations before the storm arrives.
Users will also be able to overlay the standard wind speed probabilities, providing a single combined depiction of the likelihood of tropical-storm-force winds at individual locations, along with their possible or likely arrival times. An example of these graphics is shown below.
4) Update to tropical cyclone advisory graphical products
The NHC has updated the look of its tropical cyclone advisory graphics. The suite now has a consistent look across the various graphics, with cleaner fonts and softer colors. One significant enhancement is the addition of the current extent of hurricane- and tropical-storm-force winds to the cone graphic, which will help illustrate that hazardous conditions can occur well outside of the track forecast cone. In addition, a set of radio buttons will allow users to toggle on and off various elements of the cone graphic. Examples of the NHC tropical cyclone graphics can be found at: www.nhc.noaa.gov/aboutnhcgraphics.shtml
5) Annual update to the track forecast error cone The size of the tropical cyclone track forecast error cone for both the Atlantic basin and the eastern Pacific basin will be smaller this year. The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of imaginary circles placed along the forecast track (at 12, 24, 36 hours, etc.). The size of each circle is set so that two-thirds of historical official forecast errors over the previous five years (2012-2016) fall within the circle. The circle radii defining the cones in 2017 for the Atlantic and eastern North Pacific basins are given in the table below:
When Hurricane Sandy made a devastating left hook into the Mid-Atlantic on Oct. 29, 2012, killing nearly 150 people and causing about $70 billion in damage, a narrative took hold in the weather community and the media that made its way to Capitol Hill.
U.S. weather models were late in forecasting that storm's bizarre track when compared to the top model from Europe, which locked onto it more than a week in advance. Many in and out of government began to criticize what they saw as a growing modeling gap across the Atlantic Ocean.
The weather model wars are continuing, and new evidence has emerged that instead of making a leap forward in forecast accuracy as Congress has directed, the U.S. may be about to take a step back, at least when it comes to high-impact events such as hurricanes and tropical storms are concerned.
The issue concerns a looming upgrade to the National Weather Service's top weather forecasting model, known as the Global Forecast System, or GFS. Staff at the National Hurricane Center in Miami, which issues hurricane watches and warnings, are pushing back against a plan to implement changes scheduled for May after simulations revealed the new version would make hurricane track forecasts less accurate for storm systems spinning in the Atlantic Ocean.
In short, their argument is that no upgrade is better than a bad upgrade, and that if the upgrade goes forward as planned, forecasts will suffer. This could put millions of coastal residents in the path of a hurricane at risk, depending on the forecast error.
The planned changes, which the leadership of the National Weather Service have already signed off on, are highly technical, but they amount to attempts to better capture how the atmosphere works.
Computer models are a mainstay of modern weather forecasting. Each takes in thousands of observations from satellites, weather balloons, commercial aircraft, ground stations and more, and then uses complex physics equations and other techniques to project the state of the atmosphere out several days in advance.
In a series of presentations posted to a National Weather Service website, the Hurricane Center documented a decline in forecast reliability, and made known their objection to putting this new model upgrade into service.
Other centers within the National Oceanic and Atmospheric Administration (NOAA) documented either slight improvements, no change, or slight degradations in forecast accuracy with the next model iteration.
Specifically, when forecasters ran the upgraded model on past tropical weather systems, they found storm track forecasts in the Atlantic were about 9 to 10 percent lower than the previous GFS in service already, and there was also a small drop in the accuracy of track forecasts in the eastern Pacific Ocean.
One slide, which was presented to senior management, summarized the Hurricane Center's reservations.
It bluntly states: "The loss of short- to medium-range [tropical cyclone] track and intensity forecast skill for the Atlantic basin in the proposed 2017 GFS is unacceptable to the National Hurricane Center."
The Hurricane Center also expressed concern about how changes in the GFS model would affect other hurricane models that receive inputs from the GFS. Those possible impacts have not been analyzed.
"Therefore, we oppose this implementation," the presentation says.
“After Sandy we spent all this money in supplemental modeling money" to improve hurricane forecasts and better predict the next Sandy further ahead of time, said Ryan Maue, a meteorologist at WeatherBELL Analytics, a private company. "I honestly I don’t know if we ever accomplished that.”
Maue has reviewed the Weather Service presentations and the Hurricane Center's objections. He says the testing clearly shows a step backwards for the forecasting agency.
“This is a severely negative result that would have real-world impacts on forecasting hurricanes especially in the short term," he said of the next GFS model upgrade.
“We're right back to where we started five years ago when we all knew that the GFS sucked,” he said.
The European Center, for its part, is planning to build a next-generation supercomputing center in Italy and continues to outpace the U.S. in terms of forecast accuracy and computing power. Lessening the impact of this disparity, though, is the fact that American forecasters do have access to the European models' simulations.
Florian Pappenberger, the director of forecasts at the European Center for Medium-Range Weather Forecasts in Reading, England, said at his agency, there are cases where the model is tinkered with and the results backslide in accuracy rather than taking a step forward.
“It’s a bit of a shame that this seems to be not working out as had hoped," he said of the GFS model changes. He said sometimes agencies know they will take a hit in forecast accuracy in the short-term in order to reap greater longer-term benefits from future tune-ups.
However, the next upgrade after this one isn't scheduled until the next, completely new GFS is rolled out in 2019.
ENSO is looking +neutral for the summer, maybe even an El Nino Modoki event by August/Sept. PDO is down to basically neutral.
Notable +neutral years:
1980: Allen, Jeanne 2003: Bill, Isabel 2005: *Most active season in recorded history* Emily, Irene, Katrina, Rita, Wilma 2012: Isaac
Notable Modoki years:
1969: Camille 1979: Frederic 2004: Bonnie, Frances, Ivan
EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION issued by CLIMATE PREDICTION CENTER/NCEP/NWS and the International Research Institute for Climate and Society 09 March 2017
ENSO Alert System Status: Not Active
Synopsis: ENSO-neutral conditions are favored to continue through at least the Northern Hemisphere spring 2017, with increasing chances for El Niño development into the fall.
La Niña conditions are no longer present, with slightly below-average sea surface temperatures (SSTs) observed across the central equatorial Pacific and above-average SSTs increasing in the eastern Pacific [Fig. 1]. The latest weekly Niño index values were -0.3°C in the westernmost Niño-4 and Niño-3.4 regions, and +1.5°C in the easternmost Niño-1+2 region [Fig. 2]. The upper-ocean heat content anomaly increased during January and was slightly positive when averaged across the eastern Pacific [Fig. 3], a reflection of above-average temperatures at depth [Fig. 4]. Atmospheric convection remained suppressed over the central tropical Pacific and enhanced over Indonesia [Fig. 5]. The low-level easterly winds were slightly enhanced over the western tropical Pacific, and upper-level westerly winds were near average. Overall, the ocean and atmosphere system is consistent with ENSO-neutral conditions.
Most models predict the continuation of ENSO-neutral (3-month average Niño-3.4 index between -0.5°C and 0.5°C) through the Northern Hemisphere summer [Fig. 6]. However, a few dynamical model forecasts, including the NCEP CFSv2, anticipate an onset of El Niño as soon as the Northern Hemisphere spring (March-May 2017). Because of typically high uncertainty in forecasts made at this time of the year for the upcoming spring and summer, and the lingering La Niña-like tropical convection patterns, the forecaster consensus favors ENSO-neutral during the spring with a ~60% chance. Thereafter, there are increasing odds for El Niño toward the second half of 2017 (~50% chance in September-November). In summary, ENSO-neutral conditions have returned and are favored to continue through at least the Northern Hemisphere spring 2017 (click CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).
Post by crashtestdummy on Mar 21, 2017 11:19:43 GMT -6
Funny: I was reading the post about the forecasting and graphics updates for the 2017 season, and was thinking 'wow, I guess you run a hurricane over New Yorkers, and things start to happen.'
Then, in the very next post, CajunWX posts this quote:
"When Hurricane Sandy made a devastating left hook into the Mid-Atlantic on Oct. 29, 2012, killing nearly 150 people and causing about $70 billion in damage, a narrative took hold in the weather community and the media that made its way to Capitol Hill. "
I knew it!!
Seriously, though, the new graphics and forecasting looks like an improvement, even if they're stepping back on updating the models for a while. I hope it's another slow year, but it's been almost 10 years since the last hit over here, so we're starting to get due, not hat past performance has any bearing on future events.
coffeecups: I'm still lurking at the coming weather!
Apr 17, 2017 16:44:08 GMT -6
coffeecups: WOW! My patio was dry when I got home.
Apr 16, 2017 18:22:16 GMT -6
coffeecups: Came home to Harvey from Slidell. Had a little rain here and there. There was no rain in Slidell when I left at 3:30pm. While in NO EAST, I saw where it looked like it was storming around Covington going towards Slidell. Wet but no rain when I got home
Apr 16, 2017 18:21:07 GMT -6
coffeecups: I will eat some strawberries on my cruise in early May---just a few of course, as long as I stay away from my better half.
Apr 13, 2017 20:39:35 GMT -6
SKYSUMMIT: Yea, had a good bit of strawberries. Did NOT go to the fest though.
Apr 12, 2017 19:48:32 GMT -6
coffeecups: Sky, did you enjoy the strawberries?
Apr 12, 2017 18:43:30 GMT -6
SKYSUMMIT: yea, we're in a quiet lull right now
Apr 10, 2017 21:19:12 GMT -6
coffeecups: At least with the tropical forecast we have more to go on than fantasy.
Apr 9, 2017 18:00:26 GMT -6
coffeecups: Unfortunately for me, strawberries are a widower maker!
Apr 8, 2017 11:46:43 GMT -6
SKYSUMMIT: Man it's gonna be a nice weekend! If you're looking for something to do, head over to the Ponchatoula Strawberry Fest!
Apr 5, 2017 21:35:02 GMT -6
coffeecups: Are you getting like me?
Apr 5, 2017 11:08:26 GMT -6
wsmith0306: Can't believe I've never noticed this before. I must be getting old or blind. or both!
Apr 4, 2017 8:06:37 GMT -6
coffeecups: It felt cool this morning. Very nice weather!!!
Apr 4, 2017 7:13:20 GMT -6
coffeecups: Mary protected me again.
Apr 3, 2017 7:18:35 GMT -6
SKYSUMMIT: LOL wsmith....it's just a little chat box
Apr 1, 2017 8:53:27 GMT -6
wsmith0306: What's this "shoutbox" thing all about? I'm at work, so I'm whispering right now. Hope that's allowed :).
Mar 30, 2017 12:38:44 GMT -6
coffeecups: I'm hoping that I don't see any 'rare' rain events here.
Mar 29, 2017 7:39:51 GMT -6
coffeecups: ps I guess the memory of that snow is probably the only winter that I will get.
Mar 25, 2017 7:16:52 GMT -6
coffeecups: Somewhere around 1956 and 1958 it snowed so much that I thought I was in a blizzard. Of course I was only a child then, but the memory of that has NOT been met or surpassed.
Mar 25, 2017 7:15:41 GMT -6