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Tropical Depression Sixteen Forecast Discussion Number 3
2017-10-05 04:48:43| National Hurricane Center (Atlantic)
Issued at 1100 PM EDT Wed Oct 04 2017 000 WTNT41 KNHC 050248 TCDAT1 Tropical Depression Sixteen Discussion Number 3 NWS National Hurricane Center Miami FL AL162017 1100 PM EDT Wed Oct 04 2017 There have been some structural changes to the depression during the past few hours. Inner-core convection began developing just after the issuance of the previous advisory, and Colombian radar images from San Andres are now showing a well-defined convective band to the east and southeast of the center. Despite these changes, Dvorak satellite estimates remain T2.0 from TAFB and SAB, so the initial intensity is held at 30 kt. The depression probably only has another 12 hours or so before its center moves inland over northeastern Nicaragua, but it is still expected to reach tropical storm strength before that happens. Once the center re-emerges over the waters of the northwestern Caribbean Sea a little after 24 hours from now, high oceanic heat content and low shear should contribute to strengthening. Despite these favorable conditions, the amount of strengthening will be unclear until we know how well the inner core survives crossing over Nicaragua and Honduras. Strengthening is likely to continue through at least day 3 up until the time the cyclone reaches the central Gulf of Mexico. After day 3, there are some indications that higher shear and/or cooler shelf waters over the northern Gulf of Mexico could lead to some weakening, but that scenario is by no means a definite one at this time. Needless to say, there continues to be greater-than-normal uncertainty in the intensity forecast. The updated NHC intensity forecast has been adjusted downward just a bit through day 3 to follow an overall shift in the guidance, although it should be noted that the official forecast still lies above the normally skillful HCCA model. If the intensity forecast is complex, the track forecast is not much easier. For the first 48 hours, the models appear split on how the depression will interact with a disturbance currently located near the Straits of Florida. For example, the ECMWF model shows some interaction with the disturbance's low-level vorticity, which swings the depression more to the east on the right side of the guidance envelope. The GFS, on the other hand, shows no such interaction and has the cyclone on the western side of the guidance envelope. This setup has significant downstream effects after 48 hours because it keeps the ECMWF on an eastern route and the GFS on a western route as the cyclone heads toward the U.S. Gulf coast. The new NHC track forecast has been shifted slightly westward, although it is still not as far west as the consensus aids or the HCCA model. Interestingly, although the ECMWF ensemble mean is close to the operational run on the eastern side of the guidance envelope, there is a high density of members to the left close to the consensus aids, which lends additional support for the westward adjustment. A G-IV mission and Florida special soundings will begin tomorrow to better determine the synoptic steering flow around the cyclone. KEY MESSAGES: 1. The depression is forecast to strengthen and bring tropical storm conditions to portions of Nicaragua and Honduras through early Friday. Heavy rainfall could produce life-threatening flash flooding and mud slides in portions of Nicaragua, Honduras, Costa Rica, and Panama through Friday night. 2. The system could be near hurricane intensity when it approaches the Yucatan Peninsula late Friday or Saturday, bringing direct impacts from wind, storm surge, and heavy rainfall, and a hurricane watch has been issued for a portion of this area. 3. The system is forecast to continue strengthening over the Gulf of Mexico and could affect portions of the northern Gulf Coast as a hurricane this weekend, with direct impacts from wind, storm surge, and heavy rainfall. However, it is too early to specify the timing, location, or magnitude of these impacts. Residents along the Gulf Coast from Louisiana to Florida should monitor the progress of this system for the next several days and heed any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 12.8N 82.7W 30 KT 35 MPH 12H 05/1200Z 13.5N 83.2W 35 KT 40 MPH 24H 06/0000Z 15.1N 83.7W 35 KT 40 MPH...INLAND 36H 06/1200Z 17.6N 84.7W 45 KT 50 MPH 48H 07/0000Z 20.2N 86.3W 55 KT 65 MPH 72H 08/0000Z 25.5N 88.6W 70 KT 80 MPH 96H 09/0000Z 30.5N 87.0W 65 KT 75 MPH...INLAND 120H 10/0000Z 36.5N 82.5W 30 KT 35 MPH...POST-TROP/INLAND $$ Forecaster Berg
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Tropical Depression Ramon Forecast Discussion Number 4
2017-10-05 04:48:42| National Hurricane Center (East Pacific)
Issued at 1000 PM CDT Wed Oct 04 2017 000 WTPZ44 KNHC 050248 TCDEP4 Tropical Depression Ramon Discussion Number 4 NWS National Hurricane Center Miami FL EP192017 1000 PM CDT Wed Oct 04 2017 Mexican radar data, ship observations, and last-light visible imagery indicate that the original low-level center of Ramon has dissipated. Earlier ASCAT data indicated the formation of a new center under convection well to the west, and this has probably become the primary center, if one still exists. As a result, the initial position of Ramon has been adjusted significantly to the west. Whatever remains of Ramon will likely be steered generally westward by a mid-level ridge centered over northern Mexico. Since most of the track guidance no longer depicts a trackable low-level center, the new NHC track forecast follows the trend of the previous advisory, in an effort to maintain some continuity. Therefore, the forecast shows a continued westward motion with a slight increase in forward speed until the cyclone dissipates, in 24 hours or less. Dvorak classifications have decreased and Ramon is now estimated to be a 30 kt tropical depression. All of the dynamical models forecast that Ramon will dissipate quickly, and in fact the most recent runs of the ECMWF and UKMET suggest that only a trough should exist now. There is some indication from the GFS and the GFS-based hurricane models that the mid-level remnants of Ramon could interact with a disturbance to the west in a day or two and regenerate, or contribute to the development of a new tropical cyclone. However, this is not supported by any of the other global models, and 30 kt or more of shear should prohibit significant redevelopment. Even if Ramon dissipates later tonight or tomorrow, locally heavy rainfall is still expected along the immediate coast of southern Mexico through Thursday. FORECAST POSITIONS AND MAX WINDS INIT 05/0300Z 14.8N 101.9W 30 KT 35 MPH 12H 05/1200Z 14.8N 104.0W 30 KT 35 MPH 24H 06/0000Z...DISSIPATED $$ Forecaster Zelinsky
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Tropical Depression Sixteen Forecast Discussion Number 2
2017-10-04 22:51:11| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Wed Oct 04 2017 000 WTNT41 KNHC 042051 TCDAT1 Tropical Depression Sixteen Discussion Number 2 NWS National Hurricane Center Miami FL AL162017 500 PM EDT Wed Oct 04 2017 Visible satellite images show that the depression has lots of curved bands, although it is somewhat lacking any inner core features. An Air Force Reserve Hurricane Hunter flew into the depression this afternoon and found a well-defined circulation, with maximum flight-level winds of 37 kt and SFMR values around 30 kt. These data support keeping the intensity at 30 kt for this advisory. Environmental conditions look quite favorable for strengthening over the next few days, with low shear and very warm and deep water in the path of the cyclone. The various rapid intensification indices are all higher than the last cycle, suggesting an increasing chance of rapid intensification occurring. The fly in the ointment, however, is all of the potential land interaction, first over Central America and then possibly over the Yucatan Peninsula. As a compromise, the intensity forecast is raised considerably from the previous one during the first 3 days, but is still below some guidance, such as the HWRF. The depression continues to move slowly northwestward, steered by a distant ridge over the southwestern Atlantic. However the steering pattern is forecast to change quickly tomorrow as a mid-tropospheric trough over the Florida Straits moves across the northwestern Caribbean into the southwestern Gulf of Mexico. Southerly flow on the eastern side of that trough should cause the cyclone to move much faster to the north-northwest by Friday and northward into the Gulf of Mexico on Saturday. While there is some agreement on the synoptic pattern, the model track agreement is rather poor, even in the short term, with the GFS and ECMWF being 90 miles apart on the forecast track as soon as 24 hours out. This has profound differences down the road, with the GFS-based guidance moving considerably faster and to the left of the ECMWF and UKMET across the Gulf of Mexico. Overall, the guidance has generally shifted a bit westward since the last cycle, so the latest points in the long range have been adjusted in that direction. At this point, I wouldn't focus too much attention on the details of the long-range forecast until the guidance comes into better agreement. A G-IV mission and Florida special soundings have been set up for tomorrow to better determine the synoptic steering flow around the cyclone. KEY MESSAGES: 1. The depression is forecast to strengthen and bring tropical storm conditions to portions of Nicaragua and Honduras tonight through Friday. Heavy rainfall could produce life-threatening flash flooding and mud slides in portions of Nicaragua, Honduras, Costa Rica, and Panama through Friday night. 2. The system is expected to be near hurricane intensity when it approaches the Yucatan Peninsula late Friday or Saturday, bringing direct impacts from wind, storm surge, and heavy rainfall. A hurricane watch could be issued for this area later this evening. 3. The system is forecast to continue strengthening over the Gulf of Mexico and could affect portions of the northern Gulf Coast as a hurricane this weekend, with direct impacts from wind, storm surge, and heavy rainfall. However, it is too early to specify the timing, location, or magnitude of these impacts. Residents along the Gulf Coast from Louisiana to Florida should monitor the progress of this system for the next several days and heed any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 12.5N 82.5W 30 KT 35 MPH 12H 05/0600Z 13.2N 83.1W 40 KT 45 MPH 24H 05/1800Z 14.6N 83.8W 40 KT 45 MPH...INLAND 36H 06/0600Z 16.7N 84.6W 50 KT 60 MPH 48H 06/1800Z 19.5N 85.8W 60 KT 70 MPH 72H 07/1800Z 25.0N 88.0W 75 KT 85 MPH 96H 08/1800Z 30.5N 86.0W 65 KT 75 MPH...INLAND 120H 09/1800Z 35.5N 82.0W 30 KT 35 MPH...POST-TROP/INLAND $$ Forecaster Blake
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Tropical Storm Ramon Forecast Discussion Number 3
2017-10-04 22:35:44| National Hurricane Center (East Pacific)
Issued at 400 PM CDT Wed Oct 04 2017 000 WTPZ44 KNHC 042035 TCDEP4 Tropical Storm Ramon Discussion Number 3 NWS National Hurricane Center Miami FL EP192017 400 PM CDT Wed Oct 04 2017 Geostationary and microwave satellite imagery, along with Mexican radar data, indicate that Ramon is becoming less organized. Although the estimated intensity estimate will be held at 40 kt based on a ship report that may or may not be correct, weakening seems likely. Strong easterly shear is forecast by the global models to persist over Ramon for the next couple of days, and most of these models show the tropical cyclone dissipating in 24 to 48 hours. Based on that guidance and the current trends, the official forecast now calls for the system to dissipate in 48 hours, and this event could occur sooner than that. The center, if it still exists, continues to be difficult to locate but the system appears to be moving a little faster toward the west-northwest or 285/8 kt. A large mid-level ridge to the north of Ramon is expected to steer the cyclone on a slightly north of westward track until it dissipates. The official track forecast is somewhat faster than the previous one and lies roughly in the middle of the track model guidance. The primary concern with this system is locally heavy rains, which should occur predominately in the immediate coastal zone of southern Mexico. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 15.2N 97.7W 40 KT 45 MPH 12H 05/0600Z 15.3N 99.9W 35 KT 40 MPH 24H 05/1800Z 15.6N 102.5W 30 KT 35 MPH 36H 06/0600Z 16.0N 105.0W 25 KT 30 MPH 48H 06/1800Z...DISSIPATED $$ Forecaster Pasch
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Tropical Depression Sixteen Forecast Discussion Number 1
2017-10-04 16:41:38| National Hurricane Center (Atlantic)
Issued at 1100 AM EDT Wed Oct 04 2017 000 WTNT41 KNHC 041441 TCDAT1 Tropical Depression Sixteen Discussion Number 1 NWS National Hurricane Center Miami FL AL162017 1100 AM EDT Wed Oct 04 2017 Satellite images indicate that the area of low pressure in the southwestern Caribbean Sea has become better organized since yesterday and is now a tropical depression. GOES-16 one-minute visible data suggest the center is in between two large curved bands of deep convection, not too far from San Andres Island. The initial wind speed is set to 30 kt, somewhat above the TAFB satellite classification, given recent microwave data. An Air Force Reserve Hurricane Hunter aircraft should be in the area this afternoon to provide a better estimate. Other than land interaction between 24-36 hours, environmental conditions look conducive for intensification of the depression. A large mid/upper-level trough is forecast to drop over the SW Gulf of Mexico, providing a low-shear environment for the cyclone. Rapid intensification is a possibility over the northwestern Caribbean or southern Gulf of Mexico while the system is traversing rather warm and deep waters, although it remains to be seen how separate the depression becomes from a larger gyre over central America. The official intensity forecast is close to the SHIPS model, on the high side of the intensity guidance since much of the GFS-based tracks show much more land interaction than the official forecast. The depression is moving slowly northwestward this morning, around a distant mid-level ridge over the southwestern Atlantic Ocean. However the steering pattern should change quickly tomorrow as the aforementioned mid-tropospheric trough moves across the northwestern Caribbean into the southwestern Gulf of Mexico. Southerly flow on the eastern side of that trough should cause the cyclone to move much faster to the north-northwest by Friday and northward into the Gulf of Mexico on Saturday. As the trough moves away, a building ridge over the southwestern Atlantic is forecast to steer the system to the north-northeast or northeast toward the northern Gulf states. There is a fair bit of model spread for now, partly owing to the representation of the Florida Straits trough. The GFS-based guidance seems to over-amplify the trough, which causes the new tropical cyclone to be pulled northwestward longer than most of the rest of the models. Consequently, this forecast is closer to the UKMET and ECMWF models, on the right side of the model consensus, but must be considered a low-confidence prediction at this time. KEY MESSAGES: 1. The depression is forecast to strengthen and bring tropical storm conditions and heavy rainfall to portions of Nicaragua and Honduras tonight through Thursday. 2. The system is forecast to continue strengthening over the Gulf of Mexico and could affect portions of the northern Gulf Coast as a hurricane this weekend, with direct impacts from wind, storm surge, and heavy rainfall. However, it is too early to specify the timing or magnitude of these impacts. Residents along the Gulf Coast from Louisiana to Florida should monitor the progress of this system for the next several days and heed any advice given by local officials. FORECAST POSITIONS AND MAX WINDS INIT 04/1500Z 12.2N 81.9W 30 KT 35 MPH 12H 05/0000Z 12.7N 82.6W 35 KT 40 MPH 24H 05/1200Z 13.8N 83.5W 40 KT 45 MPH...INLAND 36H 06/0000Z 15.3N 84.1W 35 KT 40 MPH...INLAND 48H 06/1200Z 17.9N 85.0W 45 KT 50 MPH 72H 07/1200Z 23.5N 87.0W 60 KT 70 MPH 96H 08/1200Z 29.0N 86.0W 70 KT 80 MPH 120H 09/1200Z 34.5N 82.5W 30 KT 35 MPH...POST-TROP/INLAND $$ Forecaster Blake
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