Home › discussion
 

Keywords :   


Tag: discussion

Tropical Storm Philippe Forecast Discussion Number 8

2017-10-29 15:36:09| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Sun Oct 29 2017 000 WTNT43 KNHC 291435 TCDAT3 Tropical Storm Philippe Discussion Number 8 NWS National Hurricane Center Miami FL AL182017 1100 AM EDT Sun Oct 29 2017 Philippe looks the best it ever has, possessing a well-defined low-level center as seen in high-resolution GOES-16 visible imagery, along with at least 45-kt sustained winds based on several recent ship reports. However, the cyclone is sheared with the bulk of the convective cloud shield having been displaced northeast of the center due to southwesterly mid-/upper-level winds of 45-75 kt. Although the exact center of Philippe was difficult to track overnight, the current position is actually on the previous forecast track. Philippe has been moving due east at about 25-27 kt for the past few hours. However, the NHC model guidance is in decent agreement that the cyclone will turn toward the northeast by this afternoon ahead of an approaching frontal system and a powerful deep-layer trough moving quickly eastward across the eastern Gulf of Mexico and Florida. The cold front is currently located only 90-100 nmi west of Philippe's center, and merger with the front along with transition to a extratropical low pressure system is expected by 12 hours, if not sooner. As the aforementioned trough becomes more negatively tilted over the next 24 hours, a strong extratropical low is forecast to develop near or just east of the North Carolina Outer Banks, pulling Philippe's circulation north-northeastward to northward in the 12-24-hour period well offshore of the U.S east coast. Absorption of Philippe's circulation into the larger extratropical low is expected to be completed by 24 hours when the larger low is located over New England. The official forecast track lies to the right of the previous advisory track, mainly due to the recent eastward jog, and lies along the eastern edge of the guidance envelope near a blend of the HCCA and TVCN consensus models. Some additional slight strengthening is possible during the next 12 hours or so, mainly due weak baroclinic forcing and the faster forward speed that is forecast. However, most of the baroclinic energy associated with the negatively tilted mid-latitude trough is expected to remain to the west, triggering the development of the above-mentioned significant extratropical coastal low. In fact, some of the latent heat from Philippe's circulation will likely get drawn into the larger extratropical low developing to its northwest, aiding in that intensification process and increasing the demise of Philippe after 12 hours. FORECAST POSITIONS AND MAX WINDS INIT 29/1500Z 27.8N 77.5W 45 KT 50 MPH 12H 30/0000Z 32.5N 72.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 24H 30/1200Z...ABSORBED BY LARGER EXTRATROPICAL LOW $$ Forecaster Stewart

Tags: number discussion storm philippe

 

Tropical Storm Philippe Forecast Discussion Number 7

2017-10-29 09:41:33| National Hurricane Center (Atlantic)

Issued at 500 AM EDT Sun Oct 29 2017 000 WTNT43 KNHC 290841 TCDAT3 Tropical Storm Philippe Discussion Number 7 NWS National Hurricane Center Miami FL AL182017 500 AM EDT Sun Oct 29 2017 Philippe is a very poorly organized system, and it is a stretch to call it a tropical cyclone at this time. The most trackable center passed near Key West a couple of hours ago and has moved into the Straits of Florida. Given that northwesterly winds are now observed over southeastern Florida, however, it is unlikely that this is a unique center of circulation. Therefore, the advisory location near the southern tip of Florida is more of a mean center position. Given that, the initial motion is a highly uncertain 070/15 kt. Regardless of its precise location, the overall system should turn northeastward to north-northeastward and accelerate considerably ahead of a high amplitude 500 mb trough near the United States east coast. Observations from an Air Force Hurricane Hunter aircraft indicated that the maximum sustained winds were near 40 kt over the Straits of Florida. Deep convection has been displaced well to the northeast of the estimated center by nearly 50 kt of deep-layer shear. The shear is forecast to increase even more, and Philippe is expected to become a post-tropical cyclone within the next 24 hours as it becomes embedded within a cold front that is approaching from the northwest. The above-mentioned trough is likely to induce some baroclinic intensification of the storm today and tonight. By Monday, however, the global models show the cyclone becoming absorbed into a larger and stronger extratropical low near New England. FORECAST POSITIONS AND MAX WINDS INIT 29/0900Z 25.0N 81.0W 40 KT 45 MPH 12H 29/1800Z 29.2N 77.8W 45 KT 50 MPH 24H 30/0600Z 36.0N 72.5W 55 KT 65 MPH...POST-TROP/EXTRATROP 36H 30/1800Z...DISSIPATED $$ Forecaster Pasch

Tags: number discussion storm philippe

 
 

Tropical Storm Philippe Forecast Discussion Number 6

2017-10-29 03:41:32| National Hurricane Center (Atlantic)

Issued at 1100 PM EDT Sat Oct 28 2017 000 WTNT43 KNHC 290241 TCDAT3 Tropical Storm Philippe Discussion Number 6 NWS National Hurricane Center Miami FL AL182017 1100 PM EDT Sat Oct 28 2017 Philippe has a very non-classical structure for a tropical cyclone this evening. A combination of satellite imagery, radar data, and surface observations show that the circulation center is elongated northwest-southeast from southwest of Naples, Florida, to central Cuba with at least three vorticity centers present in this area. The estimated center position is a mean of the multiple vorticity centers, with this position near the region of lowest pressure suggested by the surface observations. Currently, the primary deep convection is located from the northwestern Bahamas southwestward across Cuba into the Caribbean, with a smaller area of convection over the southeastern Gulf of Mexico. The initial intensity remains 35 kt, based mainly on continuity from the previous advisory. The initial motion is a rather uncertain 015/21. A deep-layer trough and developing surface low over the eastern United States should cause Philippe to turn northeastward soon, followed by a rapid northeastward motion across the southern end of the Florida Peninsula into the Atlantic. The cyclone should continue to move around the large baroclinic system until it is absorbed after the 48 h point. The new forecast track is a blend of the previous forecast and the current guidance, and it is shifted to the north of the previous track based mainly on the current initial position. It is unclear how much additional strengthening Philippe can do as a tropical cyclone, as the shear is increasing over the system and water vapor imagery shows dry air entrainment in the southwestern quadrant. However, the upper-level divergence over the system is very strong, and the large-scale models forecast deepening as the center crosses southern Florida and the Bahamas. In addition, the increasing forward speed may increase the maximum winds as well. Based on these factors, the intensity forecast calls for some increase in strength during the next 24-36 h. Philippe is likely to merge with a frontal system associated with the eastern U. S. trough in about 36 h, and the mid-latitude cyclone should completely absorb Philippe after 48 h, if not sooner. KEY MESSAGES: 1. Although the center of Philippe is now forecast to move across the Florida Keys or extreme south Florida, most of the strongest winds are expected to remain well east and southeast of the center. However, tropical-storm-force winds, mainly in gusts, could occur in brief heavy squalls across the upper Florida Keys and southeast Florida overnight. For that reason, a tropical storm watch remains in effect for these areas. 2. Regardless of the exact track of Philippe, the primary threat from this system will be heavy rainfall that can cause localized flooding across portions of Cuba, the Florida Keys, and South Florida. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 24.8N 82.1W 35 KT 40 MPH 12H 29/1200Z 27.6N 78.9W 40 KT 45 MPH 24H 30/0000Z 33.9N 74.0W 50 KT 60 MPH 36H 30/1200Z 40.3N 69.6W 55 KT 65 MPH...POST-TROP/EXTRATROP 48H 31/0000Z 48.0N 67.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 01/0000Z...ABSORBED BY EXTRATROPICAL LOW $$ Forecaster Beven

Tags: number discussion storm philippe

 

Tropical Storm Philippe Forecast Discussion Number 5

2017-10-28 22:52:29| National Hurricane Center (Atlantic)

Issued at 500 PM EDT Sat Oct 28 2017 000 WTNT43 KNHC 282052 TCDAT3 Tropical Storm Philippe Discussion Number 5 NWS National Hurricane Center Miami FL AL182017 500 PM EDT Sat Oct 28 2017 Satellite images, radar data from Cuba and Key West, and surface observations indicate the depression has turned northward over the past few hours, and has also strengthened into a tropical storm. The initial intensity of 35 kt is based on a surface observation of 35 kt in a brief squall from Grand Cayman at 1444Z, a recent AMSU estimate of 37 kt, and average Key West Doppler radar velocities of 40 kt between 10,000-12,000 ft just north of the Cuban coast; the latter data equates to an approximate surface wind speed of 36 kt. The initial motion estimate is now 355/25 kt based on radar data and high-resolution GOES-16 visible satellite imagery over the past 2-3 hours. The low-level wind flow pattern for the next 6 hours or so is forecast to be complex, with a new non-tropical surface low having recently formed about 100 nmi west of Key West, Florida. This feature appears to have developed beneath an upper-level jet entrance region ahead of an approaching cold front. The global, regional, and even the convective-scale models are now showing the center of Philippe moving general northward across the Straits of Florida this evening and merging with the non-tropical low around 0000Z. After the merger over Florida Bay, the various models are in good agreement on Philippe moving northeastward to east-northeastward across extreme southern Florida or the Florida Keys overnight as the cyclone is accelerated ahead of the aforementioned frontal system and strong mid-/upper-level trough. After reaching the northwestern Bahamas by 1200Z Sunday morning, Philippe is forecast to accelerate further towards the northeast at forward speeds of 30-35 kt, by Sunday afternoon and evening, remaining well offshore of the Carolinas. By 36 hours, Philippe is expected to pass about midway between Bermuda and the southeastern United States, and gradually getting pulled north-northeastward up the east side of a powerful baroclinic low that is forecast to develop near Cape Hatteras and move northward near the U.S. east coast. The NHC track guidance is in reasonable agreement on this developing track scenario, and lies between the GFS model, which takes Philippe across the Florida Keys, and the ECMWF model, which moves the cyclone farther north over South Florida. The vertical wind shear affecting Philippe is expected to remain favorable for strengthening to occur for the next 24 hours, along with an additional baroclinic boost from the aforementioned upper-level jet maximum. By 36 hours, strong baroclinic forcing associated with the approaching frontal system are forecast to induce additional strengthening before the cyclone merges with the frontal system and becomes an extratropical low by 48 hours. Dissipation or absorption by a larger extratropical low is expected by 72 hours when the system is located over the cold waters of the North Atlantic. KEY MESSAGES: 1. Although the center of Philippe is now forecast to move across the Florida Keys or extreme south Florida, most of the strongest winds are expected to remain east and southeast of the center. However, tropical-storm-force winds, mainly in gusts, could occur in brief heavy squalls across the upper Florida Keys and southeast Florida overnight. For that reason, a tropical storm watch remains in effect for these areas. 2. Regardless of the exact track of Philippe, the primary threat from this system will be heavy rainfall that can cause localized flooding across portions of Cuba, the Florida Keys, and South Florida. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 23.0N 82.6W 35 KT 40 MPH 12H 29/0600Z 26.0N 80.1W 45 KT 50 MPH 24H 29/1800Z 31.5N 75.3W 50 KT 60 MPH 36H 30/0600Z 36.6N 70.5W 55 KT 65 MPH 48H 30/1800Z 42.0N 66.0W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 31/1800Z...DISSIPATED $$ Forecaster Stewart

Tags: number discussion storm philippe

 

Tropical Depression Eighteen Forecast Discussion Number 4

2017-10-28 17:00:30| National Hurricane Center (Atlantic)

Issued at 1100 AM EDT Sat Oct 28 2017 000 WTNT43 KNHC 281500 TCDAT3 Tropical Depression Eighteen Discussion Number 4 NWS National Hurricane Center Miami FL AL182017 1100 AM EDT Sat Oct 28 2017 Data from an Air Force Reserve reconnaissance aircraft indicate that the low pressure system located over the northwestern Caribbean Sea has developed a well-defined low-level circulation center. Satellite imagery also shows more central deep convection has developed and persisted in the inner-core region since yesterday. Based on these data, the disturbance has been upgraded to Tropical Depression Eighteen. With the recent redevelopment of the inner-core region this morning, the initial motion estimate is an uncertain 020/19 kt. The global models remain in excellent agreement on an approaching frontal system and deep mid-tropospheric trough accelerating the cyclone north-northeastward across west-central Cuba today, followed by a motion toward the northeast tonight and Sunday, with the system passing about midway between Bermuda and the southeastern United States in 36-48 hours. The new NHC forecast track is essentially just an update of the previous advisory due to the good agreement in the global and consensus models, which lie along or just a tad to the west of the official forecast track. The vertical wind shear affecting the cyclone is expected to remain somewhat favorable for strengthening to occur for the next 24 hours or so, with the depression expected to become a tropical storm by tonight. Thereafter, baroclinic processes associated with the aforementioned frontal system are forecast to induce some additional strengthening before the cyclone merges with the frontal system and becomes an extratropical low by 48 hours. Dissipation is expected by 72 hours when the system is located over the far North Atlantic. KEY MESSAGES: 1. While the forecast track of the center lies about 35 miles southeast of the Upper Florida Keys and extreme southeast Florida and most of the winds are expected to remain east of the center, only a slight deviation to the west of the expected track or an increase in the size of the wind field could bring tropical-storm- force winds across these land areas. For that reason, a tropical storm watch has been issued for these areas. FORECAST POSITIONS AND MAX WINDS INIT 28/1500Z 20.8N 82.9W 30 KT 35 MPH 12H 29/0000Z 23.0N 81.8W 35 KT 40 MPH 24H 29/1200Z 26.6N 78.5W 40 KT 45 MPH 36H 30/0000Z 31.5N 74.0W 45 KT 50 MPH 48H 30/1200Z 37.5N 69.5W 50 KT 60 MPH...POST-TROP/EXTRATROP 72H 31/1200Z...DISSIPATED $$ Forecaster Stewart

Tags: number discussion tropical depression

 

Sites : [625] [626] [627] [628] [629] [630] [631] [632] [633] [634] [635] [636] [637] [638] [639] [640] [641] [642] [643] [644] next »