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Remnants of Four Forecast Discussion Number 8

2017-07-07 22:35:28| National Hurricane Center (Atlantic)

Issued at 500 PM AST Fri Jul 07 2017 000 WTNT44 KNHC 072035 TCDAT4 Remnants Of Four Discussion Number 8 NWS National Hurricane Center Miami FL AL042017 500 PM AST Fri Jul 07 2017 Satellite data and surface observations indicate that the depression no longer has a closed circulation, and the cyclone has degenerated into a tropical wave. Showers associated with the system have continued to diminish and remain disorganized. Based on the lack of organization, this will be the last advisory on this system. The remnants of this cyclone will continue to move toward the west-northwest today, but environmental conditions are not favorable for regeneration. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 16.5N 52.5W 20 KT 25 MPH...REMNANTS 12H 08/0600Z...DISSIPATED $$ Forecaster Avila

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Tropical Storm Eugene Forecast Discussion Number 1

2017-07-07 22:33:56| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Fri Jul 07 2017 000 WTPZ45 KNHC 072033 TCDEP5 Tropical Storm Eugene Discussion Number 1 NWS National Hurricane Center Miami FL EP052017 300 PM MDT Fri Jul 07 2017 The area of low pressure several hundred miles south of the southern tip of the Baja California peninsula has become better organized during the past several hours. Earlier microwave images and current enhanced BD-curve infrared imagery show well-developed deep convective spiral bands over the northeast and southwest quadrants. A recent ASCAT-B overpass indicated that surface circulation has become more symmetric and tropical-storm-force winds are located in the convective band to the northeast of the center. Consequently, the system is being classified as a tropical storm at this time. The initial intensity is set at 35 kt based primarily on the scatterometer data. Eugene is expected to remain in an environment of low shear, warm sea surface temperatures, and a moist low- to mid-level troposphere through 48 hours. Afterward, the cyclone is forecast to traverse decreasing SSTs, which should induce a slow weakening through the remainder of the period. The intensity forecast is weighed heavily on the IVCN multi-model consensus and shows the cyclone reaching hurricane strength before moving over cooler waters. The initial motion is estimated to be northwestward, or 310/7 kt. A retrograding mid-tropospheric trough currently centered over northwestern Mexico has created a weakness in the subtropical ridge, which will allow Eugene to continue moving northwestward through day 5. The global and ensemble models are in good agreement with this large-scale scenario, although the UKMET is a bit of an outlier on the left side of the guidance suite. The NHC track forecast is near the center of the guidance envelope, and is close to the multi-model TVCN and the HFIP corrected consensus HCCA. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 11.9N 111.2W 35 KT 40 MPH 12H 08/0600Z 12.6N 111.9W 45 KT 50 MPH 24H 08/1800Z 13.8N 113.0W 55 KT 65 MPH 36H 09/0600Z 15.1N 114.3W 60 KT 70 MPH 48H 09/1800Z 16.6N 115.5W 70 KT 80 MPH 72H 10/1800Z 19.5N 117.9W 65 KT 75 MPH 96H 11/1800Z 22.0N 120.0W 50 KT 60 MPH 120H 12/1800Z 24.4N 121.8W 40 KT 45 MPH $$ Forecaster Roberts

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Tropical Depression Four Forecast Discussion Number 7

2017-07-07 16:32:55| National Hurricane Center (Atlantic)

Issued at 1100 AM AST Fri Jul 07 2017 000 WTNT44 KNHC 071432 TCDAT4 Tropical Depression Four Discussion Number 7 NWS National Hurricane Center Miami FL AL042017 1100 AM AST Fri Jul 07 2017 The depression consists of a possible circulation center embedded within a very small area of intermittent convection. The areal coverage of the convection has been gradually decreasing since yesterday, and the cloud pattern is not showing much organization at this time. NHC is keeping an initial intensity of 25 kt, and these winds are only occurring in a few remaining squalls. Although the shear is currently low, the depression is moving into a relatively low-moisture environment, and this factor in combination with the fast motion of the cyclone will probably result in weakening. The depression is forecast to become a remnant low or degenerate into a open wave tonight. The depression or its remnants will continue to move toward the west-northwest at about 18 kt embedded within the strong July trade winds. This is the solution of the few models which maintain a distinct perturbation in the flow for a few more days. FORECAST POSITIONS AND MAX WINDS INIT 07/1500Z 15.6N 50.9W 25 KT 30 MPH 12H 08/0000Z 16.5N 53.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 08/1200Z 17.8N 57.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 09/0000Z 19.2N 60.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 09/1200Z 21.0N 63.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 10/1200Z 23.5N 69.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 11/1200Z...DISSIPATED $$ Forecaster Avila

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Tropical Depression Four Forecast Discussion Number 6

2017-07-07 10:42:25| National Hurricane Center (Atlantic)

Issued at 500 AM AST Fri Jul 07 2017 000 WTNT44 KNHC 070842 TCDAT4 Tropical Depression Four Discussion Number 6 NWS National Hurricane Center Miami FL AL042017 500 AM AST Fri Jul 07 2017 The small, tenacious depression has continued to hold its own early this morning with the low-level center now having moved up into the deep convective cloud mass, with the center being north of the previous advisory positions based on earlier scatterometer and buoy wind data. Upper-level outflow is fair in all quadrants, albeit elongated from northwest to southeast, and the vertical wind shear has now shifted from northeasterly to light southwesterly at less than 5 kt. The initial intensity is being maintained at 25 kt based on 0600 UTC satellite classifications of 25 kt from TAFB and SAB, but it wouldn't surprise me if the system isn't a little stronger given the noticeable improvement in the convective cloud pattern since the time of those fixes. The initial motion estimate is 285/19 kt. The new NHC forecast track has been shifted northward of the previous advisory track, but only due to the more northward initial position. Otherwise, there is little change to the previous forecast reasoning. A strong low- to mid-level ridge to the north of the depression should act to steer the small cyclone generally west-northwestward until dissipation occurs in about 96 h. The new forecast track lies down the middle of the tightly clustered model suite, near the consensus model TVCN. The depression is expected to retain that status for another 36 h or so while the vertical wind shear remains relatively low at less than 15 kt. By 36-48 h, westerly vertical wind shear is forecast to increase to around 20 kt, which should induce gradual weakening. The small cyclone is expected to degenerate into a remnant low by 48-72 h and dissipate by 96 h. There is one important caveat to note and that is the UKMET model, which continues to show less weakening and even strengthening in 96 and 120 h when the system is approaching the Bahamas. Although the other global and regional models do not show regeneration at this time, they do however show similar improving upper-level wind conditions east of Florida by 120 h. For now, the official intensity forecast remains similar to the previous advisory and the consensus model IVCN through 48 h, after which the forecast is lower than the intensity consensus. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 15.0N 48.8W 25 KT 30 MPH 12H 07/1800Z 15.8N 51.6W 25 KT 30 MPH 24H 08/0600Z 17.1N 55.1W 25 KT 30 MPH 36H 08/1800Z 18.6N 58.7W 25 KT 30 MPH 48H 09/0600Z 20.1N 61.9W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 10/0600Z 22.8N 67.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 11/0600Z...DISSIPATED $$ Forecaster Stewart

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Tropical Depression Four Forecast Discussion Number 5

2017-07-07 04:37:54| National Hurricane Center (Atlantic)

Issued at 1100 PM AST Thu Jul 06 2017 000 WTNT44 KNHC 070237 TCDAT4 Tropical Depression Four Discussion Number 5 NWS National Hurricane Center Miami FL AL042017 1100 PM AST Thu Jul 06 2017 The depression continues to be poorly organized this evening. Recent scatterometer data indicate that the circulation is losing definition, with the center in that data well to the southeast of the remaining convection. A complication, though, is recent observations from NOAA buoy 41041 that suggest the possibility of a second center closer to the remaining convection and well to the north of the center seen in the scatterometer data. The initial intensity remains 25 kt based mainly on the scatterometer data. It is possible that the system has already degenerated to an open wave, but for now advisories will be maintained until visible imagery becomes available Friday morning. The depression should continue to lose organization due to entrainment of dry air and developing southwesterly shear. The new intensity forecast now calls for the system to degenerate to a remnant low between 12 and 24 h and become a open wave after 72 h. Both of these events could occur earlier than current forecast. It should be noted that the UKMET model suggests the possibility the system could regenerate near the end of the forecast period. However, the other large-scale models do not yet support this scenario. A strong low- to mid-level ridge to the north of the cyclone should steer it westward to west-northwestward until dissipation. The new forecast track lies near the model consensus and is a little to the south of the previous track. FORECAST POSITIONS AND MAX WINDS INIT 07/0300Z 13.4N 46.7W 25 KT 30 MPH 12H 07/1200Z 14.1N 49.6W 25 KT 30 MPH 24H 08/0000Z 15.2N 53.1W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 08/1200Z 16.6N 56.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 09/0000Z 18.3N 60.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 10/0000Z 21.0N 66.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 11/0000Z...DISSIPATED $$ Forecaster Beven

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