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Tropical Storm Octave Forecast Discussion Number 4
2019-10-18 16:47:26| National Hurricane Center (East Pacific)
Issued at 800 AM PDT Fri Oct 18 2019 000 WTPZ43 KNHC 181447 TCDEP3 Tropical Storm Octave Discussion Number 4 NWS National Hurricane Center Miami FL EP182019 800 AM PDT Fri Oct 18 2019 A 0941 UTC GCOM microwave overpass was instrumental in showing that Octave's center is located to the east of the main convective mass, and also well to the east of a more notable mid-level circulation. Cloud tops have warmed during the past few hours, but the initial intensity is being held at 40 kt based on ASCAT data from overnight. The microwave data and recent conventional imagery show that Octave is at least partially separating from the Intertropical Convergence Zone (ITCZ). The initial motion estimate is now slowly northward, or 360/2 kt. Any additional northward progress is likely to be hindered in 24-36 hours due to the push of low-level northerly winds in the wake of a trough which is dropping southward over the Pacific. After that push, there is some difference between the models on whether Octave moves eastward or westward, so the NHC forecast continues to show a meandering or slow looping motion during the 5-day forecast period. With Octave now moving out of the ITCZ, low-level dry air to the west is wrapping into the cyclone's circulation, which is likely causing the recent waning of convection. SHIPS model diagnostics indicate that mid-level relative humidity is currently 40-50 percent, and these values are expected to decrease to 30 percent or lower in about 48 hours. This decrease in moisture will also coincide with an increase in southeasterly shear, and both factors will likely contribute to a decrease in intensity--and a loss of tropical cyclone status--during the next couple of days. The new NHC forecast closely follows the IVCN and HCCA aids and shows weakening during the next day or two, with Octave likely to degenerate into a remnant low within 48 hours. The low is expected to linger for several more days after that, but the environment does not appear conducive for regeneration into a tropical cyclone. FORECAST POSITIONS AND MAX WINDS INIT 18/1500Z 10.6N 126.6W 40 KT 45 MPH 12H 19/0000Z 11.1N 126.5W 40 KT 45 MPH 24H 19/1200Z 11.6N 126.3W 35 KT 40 MPH 36H 20/0000Z 11.6N 125.9W 30 KT 35 MPH 48H 20/1200Z 11.2N 125.9W 30 KT 35 MPH...POST-TROP/REMNT LOW 72H 21/1200Z 11.0N 126.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 22/1200Z 11.5N 126.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 23/1200Z 12.5N 127.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Berg
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Tropical Storm Octave Forecast Discussion Number 3
2019-10-18 10:34:55| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Fri Oct 18 2019 000 WTPZ43 KNHC 180834 TCDEP3 Tropical Storm Octave Discussion Number 3 NWS National Hurricane Center Miami FL EP182019 200 AM PDT Fri Oct 18 2019 Convection around the center briefly dissipated earlier tonight, but has since redeveloped with cloud tops colder than -70 C. Octave has a ragged appearance, and it is apparent that some northeasterly shear is affecting the cyclone. A recent ASCAT-A overpass showed several wind vectors of 35-40 kt, and therefore the initial advisory intensity has been raised to 40 kt. Octave has slowed to a crawl tonight, with an initial motion of 270/01 kt. Weak steering flow will prevail around the cyclone for the next several days, and a meandering motion is expected throughout the forecast period with a total net motion of only about 100 n mi during that time. The official NHC forecast is between the previous forecast and the track consensus guidance, which resulted in only a slight westward shift in the track beyond day 3. The intermittent bursts of convection are suggesting that the system has been trying to fight off a dry environment. In addition, the shear currently affecting the cyclone is expected to change little in the next 12-18 hours. These moderately negative factors offsetting the warm SSTs should cause Octave to not change much in intensity today. By later tonight, even drier air is expected to begin entraining into Octave's circulation, and at the same time 20-25 kt southeasterly winds aloft will begin to shear the cyclone. These increasingly hostile conditions should cause weakening to begin, and Octave is forecast to become a remnant low between 48-72 hours. The latest NHC forecast is similar to the previous one, and near the intensity consensus. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 9.9N 127.1W 40 KT 45 MPH 12H 18/1800Z 10.3N 127.2W 40 KT 45 MPH 24H 19/0600Z 11.0N 127.2W 40 KT 45 MPH 36H 19/1800Z 11.2N 127.0W 35 KT 40 MPH 48H 20/0600Z 11.0N 126.9W 30 KT 35 MPH 72H 21/0600Z 10.6N 127.4W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 22/0600Z 10.9N 127.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 23/0600Z 11.2N 127.6W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto
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Potential Tropical Cyclone Sixteen Forecast Discussion Number 4
2019-10-18 10:33:56| National Hurricane Center (Atlantic)
Issued at 400 AM CDT Fri Oct 18 2019 000 WTNT41 KNHC 180833 TCDAT1 Potential Tropical Cyclone Sixteen Discussion Number 4 NWS National Hurricane Center Miami FL AL162019 400 AM CDT Fri Oct 18 2019 Although the convection associated with the disturbance has increased during the past few hours, there is no evidence that a well-defined center has formed yet. One can observe several swirls of low clouds rotating within a larger gyre. Most of the global models forecast that the system will become better organized later today, and given the current trend, NHC forecasts that a tropical or most likely a subtropical cyclone will form later this morning. A reconnaissance plane will investigate the disturbance in a few hours. The disturbance is located to the east of an upper trough which is digging along the western Gulf of Mexico, and the upper-level diffluence caused by the trough should induce some strengthening during the next 24 hours or so before the system moves inland. However, the simulated convection by the GFS and the ECMWF models resembles a comma-shape pattern which is characteristic of a subtropical cyclone. After landfall, the cyclone is expected to become extratropical and gradually weaken while it moves northeastward near the southeast U.S. coast. By day 5, the low is forecast to be absorbed by a front over the western Atlantic. Since the center is not well defined, the initial motion is highly uncertain. The best estimate is toward the northeast or 045 degrees at 12 kt. The system should accelerate later today and continue toward the northeast embedded within the flow ahead of the trough. Track models are in remarkably good agreement, and the NHC forecast is in the middle of the tight guidance envelope. Regardless of the exact evolution of the system, portions of the northern coast of the Gulf of Mexico will experience strong winds, locally heavy rains, and storm surge Friday and Saturday. Similar impacts are expected across portions of the Atlantic coast of the southeastern United States Saturday and Sunday. Key Messages: 1. There is a danger of life-threatening storm surge inundation of up to 5 feet above ground level beginning today along the Florida Gulf Coast from Indian Pass to Clearwater, where a Storm Surge Warning is in effect. Residents in these areas should follow advice given by local officials. 2. Tropical storm force winds are likely by later today along portions of the central and eastern Gulf Coast, where tropical storm warnings are in effect. Regardless of the exact track and intensity of the system, these winds will cover a large area, especially east of the center. 3. Isolated flash flooding is possible along the central and eastern Gulf Coast and southeastern United States coast from today through Saturday night. Since soils across the southeast are dry, the risk of flash flooding will be confined to the immediate coast where heavier rainfall is possible. 4. Wind and coastal flooding hazards along the U.S. East Coast will be covered by non-tropical watches and warnings issued by local NWS offices, since the system is expected to lose any tropical characteristics after it moves inland along the Gulf Coast. FORECAST POSITIONS AND MAX WINDS INIT 18/0900Z 24.3N 92.5W 35 KT 40 MPH...POTENTIAL TROP CYCLONE 12H 18/1800Z 26.8N 89.8W 40 KT 45 MPH...TROPICAL STORM 24H 19/0600Z 29.0N 87.0W 45 KT 50 MPH 36H 19/1800Z 31.5N 84.5W 35 KT 40 MPH...INLAND 48H 20/0600Z 33.5N 80.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 72H 21/0600Z 37.0N 72.0W 35 KT 40 MPH...POST-TROP/EXTRATROP 96H 22/0600Z 37.5N 69.5W 30 KT 35 MPH...POST-TROP/EXTRATROP 120H 23/0600Z...DISSIPATED $$ Forecaster Avila
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Potential Tropical Cyclone Sixteen Forecast Discussion Number 3
2019-10-18 04:36:49| National Hurricane Center (Atlantic)
Issued at 1000 PM CDT Thu Oct 17 2019 000 WTNT41 KNHC 180236 TCDAT1 Potential Tropical Cyclone Sixteen Discussion Number 3 NWS National Hurricane Center Miami FL AL162019 1000 PM CDT Thu Oct 17 2019 The disturbance over the southwestern Gulf of Mexico continues to produce a large area of cloudiness and thunderstorms over much of the central and southwestern Gulf of Mexico. The system is not yet a tropical or subtropical cyclone as it still lacks sufficient convective organization and an Air Force reconnaissance aircraft that flew into the disturbance late this afternoon found a broad circulation, but no evidence of a well-defined center. The global models indicate that the circulation will become better defined by early Friday, and that the low will deepen within an area of strong upper-level divergence to the east of an upper-level trough over southeastern Texas. As a result, strengthening is forecast while the system moves over the Gulf of Mexico during the next 24 to 36 hours. While the system is unlikely to develop into a classical tropical cyclone, it is expected to obtain enough organized convection to become a tropical or subtropical cyclone on Friday or Friday night before is reaches the northern Gulf coast. After landfall, the cyclone is expected to become extratropical and gradually weaken while it moves northeastward near the southeast U.S. coast. By day 5, the low is forecast to be absorbed by a front over the western Atlantic. The disturbance is moving northeastward at about 10 kt. The system should accelerate northeastward ahead of the aforementioned trough on Friday, and the northeastward motion should then continue during the next few days. The low is forecast to slow down and turn east-northeastward after 72 hours when the mid-level flow becomes more zonal. The new NHC track forecast uses a blend of the lastest global model fields and is very similar to the previous advisory. Regardless of the exact evolution of the system, portions of the northern coast of the Gulf of Mexico will experience strong winds, locally heavy rains, and storm surge Friday and Saturday. Similar impacts are expected across portions of the Atlantic coast of the southeastern United States Saturday and Sunday. Key Messages: 1. There is a danger of life-threatening storm surge inundation of up to 5 feet above ground level beginning Friday along the Florida Gulf Coast from Indian Pass to Clearwater, where a Storm Surge Warning is in effect. Residents in these areas should follow advice given by local officials. 2. Tropical storm force winds are likely by Friday afternoon along portions of the central and eastern Gulf Coast, where tropical storm warnings are in effect. Regardless of the exact track and intensity of the system, these winds will cover a large area, especially east of the center. 3. Isolated flash flooding is possible along the central and eastern Gulf Coast, mainly Friday and Friday night. Since soils across the southeast are dry, the risk of flash flooding will be confined to the immediate coast where heavier rainfall is possible. 4. Wind and coastal flooding hazards along the U.S. East Coast will be covered by non-tropical watches and warnings issued by local NWS offices, since the system is expected to lose any tropical characteristics after it moves inland along the Gulf Coast. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 24.1N 93.7W 35 KT 40 MPH...POTENTIAL TROP CYCLONE 12H 18/1200Z 26.0N 91.1W 35 KT 40 MPH...TROPICAL STORM 24H 19/0000Z 28.2N 88.5W 45 KT 50 MPH 36H 19/1200Z 30.2N 86.1W 45 KT 50 MPH 48H 20/0000Z 32.2N 82.9W 40 KT 45 MPH...POST-TROP/EXTRATROP 72H 21/0000Z 36.1N 74.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 96H 22/0000Z 37.0N 69.5W 35 KT 40 MPH...POST-TROP/EXTRATROP 120H 23/0000Z...DISSIPATED $$ Forecaster Brown
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Tropical Storm Octave Forecast Discussion Number 2
2019-10-18 04:34:22| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Thu Oct 17 2019 000 WTPZ43 KNHC 180234 TCDEP3 Tropical Storm Octave Discussion Number 2 NWS National Hurricane Center Miami FL EP182019 800 PM PDT Thu Oct 17 2019 Satellite imagery indicates that the cyclone located nearly 1500 mi southwest of the southern tip of the Baja California peninsula has become a little better organized. The latest TAFB Dvorak intensity estimate is 2.5/35 kt. Furthermore, late-arriving ASCAT-C data from earlier today showed a few 30-35 kt wind vectors in the northwest quadrant of the cyclone. Based on these data, the intensity estimate is 35 kt, and the system is now Octave, the 15th named storm of the Eastern Pacific hurricane season. The tropical storm unexpectedly accelerated southwestward for a brief period earlier this afternoon, but it has since resumed a slow westward crawl. Octave is caught in a region of nearly zero net steering flow, and is therefore expected to move very little for the foreseeable future. Due to Octave's jump to the southwest, the NHC track forecast has been generally adjusted in that direction, and is based primarily on a blend of the the GFS and ECMWF global models, both of which call for a slow looping track through 120 h. Octave is located in an environment that could support slight additional strengthening, as shown by the statistical guidance, though the dynamical models suggest it has already peaked. Upper-level convergence and a drier surrounding environment are forecast to become inhibiting factors to the cyclone's convection in about 48 h, and it could become a remnant low soon after. The NHC intensity forecast has been adjusted only slightly to account for the higher initial intensity and follows the intensity consensus. FORECAST POSITIONS AND MAX WINDS INIT 18/0300Z 9.8N 127.2W 35 KT 40 MPH 12H 18/1200Z 10.1N 127.4W 40 KT 45 MPH 24H 19/0000Z 10.7N 127.4W 35 KT 40 MPH 36H 19/1200Z 11.1N 127.1W 35 KT 40 MPH 48H 20/0000Z 11.1N 126.8W 30 KT 35 MPH 72H 21/0000Z 10.6N 126.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 22/0000Z 10.5N 127.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 23/0000Z 11.5N 127.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Zelinsky
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