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Tropical Storm Humberto Forecast Discussion Number 7

2019-09-14 10:42:57| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Sat Sep 14 2019 000 WTNT44 KNHC 140842 TCDAT4 Tropical Storm Humberto Discussion Number 7 NWS National Hurricane Center Miami FL AL092019 500 AM EDT Sat Sep 14 2019 Convection associated with Humberto has increased a little since the last advisory, as a new burst has occurred to the north of the center. Other convection continues in a large curved band in the eastern semicircle. Reports from an Air Force Reserve Hurricane Hunter aircraft near 0500 UTC indicated that the maximum sustained winds were near 35 kt, and that will be the initial intensity for this advisory. It should be noted that an upper-level trough is located just south of Humberto, and the storm may have some subtropical characteristics due to interaction with this trough. While the motion is still a bit erratic, Humberto now seems to be moving a little faster toward the northwest or 315/6 kt. During the next few days, a low- to mid-level ridge over the eastern United States and the western Atlantic is expected to slide southeastward, with a weakness in the ridge developing due to a mid- to upper-level trough over the northeastern U.S. This change in the steering pattern should cause the storm to slow down and turn northward off the east coast of Florida in 36 to 48 hours. Subsequently, the northeastern U.S. trough should dig southward, and this change should turn Humberto northeastward and then eastward away from the U.S. The track guidance has shifted a little more to the east during the first 72 h, and the new NHC track has been nudged eastward as well during this time. The new forecast track lies near the various consensus models. Southwesterly vertical shear and dry air entrainment caused by the upper-level trough to the south is forecast to diminish during the next 2-3 days while Humberto moves near or over the warm waters of the Gulf Stream. This should allow intensification, and Humberto is expected to become a hurricane in about 48 h. The intensity forecast becomes more uncertain between 72-120 h. Strong upper-level winds associated with the mid-latitude trough over the eastern United States should cause strong shear over Humberto. However, there is a chance that baroclinic forcing from the trough could compensate for the shear, and the GFS, ECMWF, UKMET, Canadian, and HWRF models all show the central pressure falling during this time. The intensity forecast will follow this guidance and show some additional strengthening through 96 h. Overall, the new intensity forecast is similar to, but slightly higher than, the previous forecast. Key Messages: 1. Humberto will likely bring tropical-storm-force winds and heavy rainfall to portions of the northwestern Bahamas today. Significant storm surge is not expected in the northwestern Bahamas from this system. Residents there should follow any advice given by local officials. 2. Since the forecast track has shifted farther to the east, the chance of heavy rainfall affecting the southeastern United States has diminished. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 26.3N 76.0W 35 KT 40 MPH 12H 14/1800Z 26.9N 76.9W 40 KT 45 MPH 24H 15/0600Z 28.0N 77.7W 45 KT 50 MPH 36H 15/1800Z 29.0N 77.9W 55 KT 65 MPH 48H 16/0600Z 29.8N 77.4W 65 KT 75 MPH 72H 17/0600Z 30.8N 74.7W 75 KT 85 MPH 96H 18/0600Z 31.5N 71.0W 80 KT 90 MPH 120H 19/0600Z 33.0N 66.0W 75 KT 85 MPH $$ Forecaster Beven

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Tropical Storm Kiko Forecast Discussion Number 8

2019-09-14 10:39:56| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Sat Sep 14 2019 434 WTPZ43 KNHC 140839 TCDEP3 Tropical Storm Kiko Discussion Number 8 NWS National Hurricane Center Miami FL EP132019 200 AM PDT Sat Sep 14 2019 A 0205 UTC WindSat pass showed that Kiko's low-level structure has become significantly better defined. The storm has also been producing a persistent cluster of deep convection, although microwave fixes suggest that the surface center is located beneath the eastern side of the convective mass. Satellite intensity estimates range from 45-55 kt, but scatterometer data from a few hours ago indicated that maximum winds were between 40-45 kt. Kiko's initial intensity is therefore held at 45 kt, but the cyclone's improved structure likely means that its winds will increase again soon. There's still a swath of dry air to the north and west of the storm, but now that the inner core has become more established, Kiko should be able to take advantage of low shear and sufficiently warm waters to strengthen during the next couple of days. The NHC intensity forecast is very close to the HFIP Corrected Consensus (HCCA) and Florida State Superensemble (FSSE) during the first 36 hours, showing a little more strengthening than the previous forecast, and making Kiko a hurricane in 24 hours. While the new forecast is also a little higher at 48 hours, it's still below the HCCA, FSSE, and HWRF solutions, so additional adjustment could be required in subsequent advisories. Weakening should commence by day 3 due to little to no oceanic heat content and gradually increasing westerly shear. Kiko is moving west-northwestward, or 285/8 kt. Mid-level ridging to the north should drive the cyclone on a westward to west-northwestward heading for the entire forecast period. The most significant gain in latitude should occur from Sunday through Tuesday when Kiko is at its strongest and responds to a break in the ridge between 120W and 130W. While the GFS and ECMWF models still prefer northern and southern solutions within the guidance envelope, respectively, the distance between the two at day 5 has been cut in half in the latest model runs, suggesting that the track uncertainty is not as high as it was previously. The NHC track forecast remains close to the various multi-model consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 17.3N 117.1W 45 KT 50 MPH 12H 14/1800Z 17.4N 118.3W 55 KT 65 MPH 24H 15/0600Z 17.7N 119.7W 65 KT 75 MPH 36H 15/1800Z 18.1N 121.0W 70 KT 80 MPH 48H 16/0600Z 18.6N 122.3W 70 KT 80 MPH 72H 17/0600Z 19.5N 124.7W 55 KT 65 MPH 96H 18/0600Z 20.2N 126.9W 40 KT 45 MPH 120H 19/0600Z 20.6N 129.6W 30 KT 35 MPH $$ Forecaster Berg

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Tropical Storm Humberto Forecast Discussion Number 6

2019-09-14 05:01:29| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Fri Sep 13 2019 000 WTNT44 KNHC 140300 CCA TCDAT4 Tropical Storm Humberto Discussion Number 6...Corrected NWS National Hurricane Center Miami FL AL092019 1100 PM EDT Fri Sep 13 2019 Corrected to change depression to storm in the second paragraph Deep convection has been gradually increasing this evening, and it is currently most organized in a curved band to the east of the estimated center. In addition, data from the NOAA Hurricane Hunters indicate that the depression has strengthened. The maximum flight-level wind at 700 mb was 41 kt and reliable SFMR values were 35 kt. Based on that data, the initial intensity is increased to 35 kt, making the cyclone Tropical Storm Humberto. The data from the aircraft indicate that the cyclone is titled to the northeast with height, likely due to southwesterly wind shear. Humberto has been moving erratically during the past 12 to 18 hours as the cyclone has been trying to organize, but my best guess at the initial motion is 320/5. During the next few days, a ridge to the north of the system over the eastern United States and the western Atlantic is expected to slide southeastward, with a weakness in the ridge developing due to a mid- to upper-level trough over the northeastern U.S. This change in the steering pattern should cause the storm to slow down and turn northward off the east coast of Florida in 36 to 48 hours. The models show the trough over the northeastern U.S. amplifying early next week, which should cause Humberto to turn northeastward and then eastward away from the U.S. The NHC track forecast has been nudged south and east of the previous one to be in better agreement with the latest consensus models. Since there is increasing confidence that the storm will remain well offshore of the coast of Florida, the Tropical Storm Watch for that area has been discontinued. The storm is still feeling some effects of southwesterly shear and drier air, which is causing its lopsided appearance in satellite images and strong tilt in the aircraft data. The atmospheric conditions are expected to gradually become more conducive for strengthening while Humberto moves over the warm Gulf Stream waters. These environmental parameters support intensification, and the cyclone is expected to become a hurricane in 2 to 3 days. The NHC intensity forecast is largely an update of the previous one and in line with the HCCA and IVCN guidance. Key Messages: 1. Humberto will likely bring tropical-storm-force winds and heavy rainfall to portions of the northwestern Bahamas on Saturday. Significant storm surge is not expected in the northwest Bahamas from this system. Residents there should follow any advice given by local officials. 2. Heavy rainfall and scattered flash flooding is possible this weekend in coastal sections of eastern Florida, Georgia, and South Carolina. The chance of heavy rainfall affecting coastal North Carolina early next week continues to diminish. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 25.6N 75.2W 35 KT 40 MPH 12H 14/1200Z 26.5N 76.5W 35 KT 40 MPH 24H 15/0000Z 27.6N 77.6W 40 KT 45 MPH 36H 15/1200Z 28.8N 78.2W 50 KT 60 MPH 48H 16/0000Z 29.8N 78.1W 60 KT 70 MPH 72H 17/0000Z 31.0N 75.5W 70 KT 80 MPH 96H 18/0000Z 31.3N 72.0W 75 KT 85 MPH 120H 19/0000Z 32.3N 67.2W 75 KT 85 MPH $$ Forecaster Cangialosi

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Tropical Storm Kiko Forecast Discussion Number 7

2019-09-14 04:41:58| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Fri Sep 13 2019 000 WTPZ43 KNHC 140241 TCDEP3 Tropical Storm Kiko Discussion Number 7 NWS National Hurricane Center Miami FL EP132019 800 PM PDT Fri Sep 13 2019 Kiko may have finally kicked the dry air out of its inner core. There has been a dramatic expansion of cold cloud tops extending from the center of the cyclone, and recent microwave imagery confirms that convective activity is much greater than it was 24 h ago. Dvorak intensity estimates from TAFB and SAB have gone up and now support an initial intensity of 45 kt. This value is fairly uncertain, and it certainly possible that Kiko has not strengthened quite that much at this point. It has been very difficult to identify the low-level center of Kiko, and the initial motion is a very uncertain 285/8 kt. In the short term, the initial position may actually be the main source of uncertainty in the forecast. The cyclone should head westward or west-northwestward at about the same forward speed for the next couple of days, and the guidance is very tightly clustered. Beginning Monday, Kiko could turn west-northwestward or northwestward if it substantially deepens, as shown by the GFS, HWRF, and HMON models, or it could just accelerate generally westward, as depicted by the ECMWF and UKMET models. The spread grows quite quickly by the end of the forecast period, and the GFS and ECMWF are nearly 500 n mi apart by day 5. The NHC forecast splits these 2 scenarios as a course of least regret, and follows the multi-model consensus closely through the end of the period. Despite its recent convective resurgence, there is still a fair amount of dry air surrounding the cyclone. The environment appears otherwise favorable for strengthening, and most of the guidance calls for additional strengthening. The NHC intensity forecast has been adjusted a little higher, given Kiko's current convective structure, and once again shows Kiko becoming a hurricane in a couple of days. Whatever peak the cyclone reaches, it will likely begin to weaken by day 4 as it encounters cooler waters, drier air, and potentially increased shear. The official intensity forecast is near HCCA throughout the forecast period. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 17.1N 116.3W 45 KT 50 MPH 12H 14/1200Z 17.4N 117.4W 50 KT 60 MPH 24H 15/0000Z 17.6N 118.7W 55 KT 65 MPH 36H 15/1200Z 17.9N 120.1W 60 KT 70 MPH 48H 16/0000Z 18.5N 121.4W 65 KT 75 MPH 72H 17/0000Z 19.4N 124.2W 60 KT 70 MPH 96H 18/0000Z 20.2N 126.4W 40 KT 45 MPH 120H 19/0000Z 20.5N 128.5W 30 KT 35 MPH $$ Forecaster Zelinsky

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Tropical Storm Kiko Forecast Discussion Number 6

2019-09-13 22:43:55| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Fri Sep 13 2019 000 WTPZ43 KNHC 132043 TCDEP3 Tropical Storm Kiko Discussion Number 6 NWS National Hurricane Center Miami FL EP132019 200 PM PDT Fri Sep 13 2019 Kiko has been battling some entrained dry air today, and convection is just now beginning to re-wrap around the center of circulation. The latest subjective Dvorak intensity estimate from SAB supports an initial advisory intensity of 35 kt. An upper trough to the west of Kiko may continue to force dry air into the cyclone's circulation in the near term. Despite this dry air, the cyclone is expected to remain over warm waters and in a low shear environment for the next couple of days, which should allow for some strengthening. By late this weekend, Kiko is expected to be near hurricane intensity. After 48 hours, Kiko is forecast to begin to move over cooler waters, and after 72 hours, westerly wind shear is expected to begin to impact the cyclone. These factors should cause Kiko to steadily weaken late in the forecast period. Kiko is moving westward, or 280/8 kt, to the south of a broad mid-level ridge. A general west to west-northwestward motion should continue for the next several days. There was a notable shift in the guidance this afternoon, suggesting that the cyclone will move with a little slower forward motion than previously indicated. The tightly clustered consensus guidance also made a slight shift to the west. The official forecast is a little slower and to the left than the previous one, but is on the right side of the consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 17.0N 115.2W 35 KT 40 MPH 12H 14/0600Z 17.2N 116.5W 40 KT 45 MPH 24H 14/1800Z 17.5N 118.0W 50 KT 60 MPH 36H 15/0600Z 17.9N 119.4W 55 KT 65 MPH 48H 15/1800Z 18.4N 121.0W 60 KT 70 MPH 72H 16/1800Z 19.4N 123.8W 55 KT 65 MPH 96H 17/1800Z 20.1N 126.1W 40 KT 45 MPH 120H 18/1800Z 20.9N 128.5W 30 KT 35 MPH $$ Forecaster Latto

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