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Remnants of Six-E Forecast Discussion Number 5

2020-07-14 22:37:47| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Tue Jul 14 2020 000 WTPZ41 KNHC 142037 TCDEP1 Remnants Of Six-E Discussion Number 5 NWS National Hurricane Center Miami FL EP062020 200 PM PDT Tue Jul 14 2020 A very recent ASCAT-B overpass indicated that the circulation of the tropical depression is no longer closed with light and variable winds evident on its south side. Therefore, the system no longer meets the criteria of a tropical cyclone, and this is the last advisory issued by NHC. The initial intensity remains 25 kt based on the ASCAT data, which showed an area of 20-25 kt winds on the system's north side. The remnants of the depression are currently producing a very limited amount of shower activity, but the associated convection could pulse up and down for another day until the trough moves over cooler waters. The trough is moving westward at about 15 kt and it should continue in that direction for another couple of days until it completely dissipates. For additional information on this system please see High Seas Forecasts issued by the National Weather Service, under AWIPS header NFDHSFEPI, WMO header FZPN02 KWBC, and on the web at ocean.weather.gov/shtml/NFDHSFEPI.php FORECAST POSITIONS AND MAX WINDS INIT 14/2100Z 18.2N 118.0W 25 KT 30 MPH 12H 15/0600Z...DISSIPATED $$ Forecaster Cangialosi

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Tropical Depression Six-E Forecast Discussion Number 4

2020-07-14 16:38:36| National Hurricane Center (East Pacific)

Issued at 800 AM PDT Tue Jul 14 2020 802 WTPZ41 KNHC 141438 TCDEP1 Tropical Depression Six-E Discussion Number 4 NWS National Hurricane Center Miami FL EP062020 800 AM PDT Tue Jul 14 2020 The depression has been moving over a ridge of warmer sea surface temperatures (about 28C) over the past few hours, and a nontrivial amount of deep convection redeveloped soon after the issuance of the previous advisory, albeit at least 60 n mi to the southwest of the low-level center. However, with no appreciable change in the cyclone's structure, the initial intensity remains 25 kt in accordance with the overnight scatterometer data. The depression is forecast to reach waters colder than 26C in 12-24 hours, which should extinguish the remaining deep convection. The updated NHC forecast now shows the depression degenerating into a remnant low by 24 hours, with dissipation by 48 hours. Another scenario is that the depression could dissipate at any time if it opens up into a trough, which is shown by most of the global model guidance. The depression is moving west-northwestward, or 285/14 kt, which is more poleward than has been shown by the dynamical track models. Because of this, the simpler shallow trajectory models are given a higher contribution on this cycle, with the new NHC track forecast ending up a bit north of the previous forecast. The depression and its remnants are expected to gradually accelerate toward the west-northwest or west over the next day or two until dissipation. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 18.1N 116.6W 25 KT 30 MPH 12H 15/0000Z 18.3N 119.1W 25 KT 30 MPH 24H 15/1200Z 18.4N 122.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 16/0000Z 18.2N 126.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 16/1200Z...DISSIPATED $$ Forecaster Berg

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Tropical Depression Six-E Forecast Discussion Number 3

2020-07-14 10:32:28| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Tue Jul 14 2020 000 WTPZ41 KNHC 140832 TCDEP1 Tropical Depression Six-E Discussion Number 3 NWS National Hurricane Center Miami FL EP062020 200 AM PDT Tue Jul 14 2020 Satellite images show that the center of the tropical depression is exposed well to the east-northeast of its decaying mid-level circulation and any scant remaining convection. A pair of recent scatterometer passes indicate that the current wind speed is not more than 25 kt, so that value is used for this advisory. While the system still has a day or so of marginally conducive environmental conditions, the current displacement of the low- and mid-level centers suggests that the depression is unlikely to strengthen. Thus, little change in intensity is forecast through today, and some weakening is likely on Wednesday and Thursday as the cyclone encounters cooler water and higher shear. The timing of remnant low status has been moved to Wednesday since the small, poorly organized depression is expected to fall apart quickly in a more hostile environment. The cyclone continues moving westward and is forecast to move a little faster in that general direction by late today due to the effects of a strong ridge. The most significant change to the forecast is that almost all of the guidance is north of the previous model cycle, so the NHC track prediction is shifted in that direction. None of the models show a closed low after 48 hours, so dissipation is shown after that time, which makes sense given the expected fragility of this system. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 17.3N 115.1W 25 KT 30 MPH 12H 14/1800Z 17.4N 117.4W 25 KT 30 MPH 24H 15/0600Z 17.5N 120.8W 25 KT 30 MPH 36H 15/1800Z 17.2N 124.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 48H 16/0600Z 17.0N 128.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 16/1800Z...DISSIPATED $$ Forecaster Blake

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Tropical Depression Six-E Forecast Discussion Number 2

2020-07-14 04:34:55| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Mon Jul 13 2020 000 WTPZ41 KNHC 140234 TCDEP1 Tropical Depression Six-E Discussion Number 2 NWS National Hurricane Center Miami FL EP062020 900 PM MDT Mon Jul 13 2020 Deep convection associated with the depression has decreased substantially since the last advisory, particularly during the last 3 hours. At 00Z, microwave, visible, and IR imagery showed the depression had a small but well-defined center with a small area of deep convection west of its center. Most satellite-based intensity estimates at that time were 35 kt, which would typically support naming the system as a tropical storm. Since that time, however, it appears that nearly all of the deep convection has dissipated and it is likely that the intensity estimates would be lower if they were valid now. The initial intensity is therefore conservatively held at 30 kt for this advisory, but it is certainly possible that the system is producing tropical-storm-force winds. The NHC forecast is largely unchanged. The cyclone is forecast to move generally westward for the next day or two, steered by a mid-level ridge to the north and low-level easterly flow. Some slight strengthening is possible during the next day or so, but significant strengthening is not expected. An increase of southwesterly shear and cool SSTs should cause the cyclone to become a remnant low and then dissipate within about 3 days. The track and intensity guidance is all in good agreement and confidence in the NHC forecast is fairly high. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 17.0N 114.4W 30 KT 35 MPH 12H 14/1200Z 17.2N 116.7W 35 KT 40 MPH 24H 15/0000Z 17.3N 119.7W 35 KT 40 MPH 36H 15/1200Z 16.9N 123.4W 30 KT 35 MPH 48H 16/0000Z 16.0N 126.9W 25 KT 30 MPH 60H 16/1200Z 16.0N 130.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 17/0000Z...DISSIPATED $$ Forecaster Zelinsky

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Tropical Depression Six-E Forecast Discussion Number 1

2020-07-13 22:34:48| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Mon Jul 13 2020 719 WTPZ41 KNHC 132034 TCDEP1 Tropical Depression Six-E Discussion Number 1 NWS National Hurricane Center Miami FL EP062020 300 PM MDT Mon Jul 13 2020 The small disturbance and intermittent low pressure system that the NHC has been tracking for the past few days has finally developed a well-defined, closed surface circulation based on 1639Z ASCAT-B surface wind vector ambiguity data, and the system is thus being classified as Tropical Depression Six-E. Deep convection developed overnight and this morning, which helped to spin up a low-level center near and just inside of the northeastern portion of the convective cloud canopy. In addition, the forward speed has also decreased from 20 kt down to 14 kt, which has also likely helped to close off the circulation on the south side. The ASCAT scatterometer wind data data supported an intensity of at least 30 kt, and this is consistent with 18Z Dvorak satellite classifications of T2.0/30 kt from both TAFB and SAB. The initial motion estimate is 270/14 kt based on conventional, microwave, and scatterometer satellite fix data over the past 12 hours. The small cyclone is expected to be steered generally westward at about the same forward speed for the next few days due to a strong subtropical ridge situated to the north of the depression. By 96 h, the system is forecast to degenerate into an open wave. The NHC official forecast track lies close to the tightly packed simple consensus models, which is a just a little south of the NOAA corrected-consensus model, HCCA. The current northerly vertical wind shear of about 15 kt affecting the depression is forecast to decrease to below 10 kt in 12-18 hours, and remain that way until the 48-h period. This should allow for some slight strengthening to occur during the next 36 hours or so. By 48 hours and beyond, the cyclone will be moving over sub-26 deg C sea-surface temperatures and the shear is forecast to become westerly to northwesterly at near 20 kt. The combination of these two negative factors should induce significant weakening of the small tropical cyclone, resulting in degeneration to a remnant low by 72 h and dissipation by 96 hours. The official intensity forecast closely follows the IVCN intensity consensus model. FORECAST POSITIONS AND MAX WINDS INIT 13/2100Z 16.6N 112.6W 30 KT 35 MPH 12H 14/0600Z 16.7N 114.9W 35 KT 40 MPH 24H 14/1800Z 16.8N 117.8W 35 KT 40 MPH 36H 15/0600Z 16.8N 120.6W 35 KT 40 MPH 48H 15/1800Z 16.8N 124.2W 30 KT 35 MPH 60H 16/0600Z 16.6N 127.9W 30 KT 35 MPH 72H 16/1800Z 16.5N 131.7W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 17/1800Z...DISSIPATED $$ Forecaster Stewart

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