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Tropical Storm Elida Forecast Discussion Number 6

2020-08-10 10:51:13| National Hurricane Center (East Pacific)

Issued at 300 AM MDT Mon Aug 10 2020 000 WTPZ44 KNHC 100851 TCDEP4 Tropical Storm Elida Discussion Number 6 NWS National Hurricane Center Miami FL EP092020 300 AM MDT Mon Aug 10 2020 After the earlier burst of deep convection and the development of a small 10-nmi-wide low- to mid-level eye noted in passive microwave satellite imagery, convection has waned somewhat and the eye feature has eroded in the northwestern semicircle due to entrainment of dry air, along with some modest northwesterly vertical wind shear. A 0314Z ASCAT-A overpass revealed peak winds of only 43 kt in the northeastern quadrant, along with a radius of maximum winds (RMW) of 10-15 nmi. Satellite intensity estimates range from T3.5/55 kt from TAFB to T4.0/65 kt from SAB, along with a UW-CIMSS SATCON estimate of 53 kt and an ADT estimate of 59 kt. An average of these intensity estimates, and allowing for some undersampling by the scatterometer instrument due to Elida's small RMW, supports maintaining an intensity of 55 kt for this advisory. The initial motion estimate remains west-northwestward or 300/13 kt. Both the forecast track and rationale remain straight-forward and basically unchanged from the previous advisory. Elida is expected to be steered west-northwestward by a deep layer ridge to the north for the next 72 hours or, followed by a westward motion on days 4 and 5 when Elida will be weakening over much cooler waters and becoming a shallower cyclone. The latest NHC track guidance remains tightly packed and, thus, the new official forecast is very similar to the previous advisory track, and lies near the TVCE and NOAA-HCCA consensus track models. The brief intensity hiatus that Elida is experiencing is expected to be short-lived due to the cyclone's small RMW and the vertical shear forecast to decrease to less than 10 kt in the 12-36 hour time frame. This should allow for Elida to strengthen -- possibly even rapidly -- during the next 24 hours, followed by a leveling off in the intensity due to the cyclone moving over sub-26C sea-surface temperatures (SST). By 48-60 h, SSTs less than 25C and modest southwesterly vertical wind shear will combine to induce steady weakening. By 96 h or so, Elida is forecast to degenerate into a post-tropical cyclone. The new official intensity forecast is a little lower than the previous advisory, but is a little above the consensus models IVCN and HCCA. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 18.3N 108.8W 55 KT 65 MPH 12H 10/1800Z 19.1N 110.8W 65 KT 75 MPH 24H 11/0600Z 20.0N 113.5W 75 KT 85 MPH 36H 11/1800Z 20.8N 116.2W 80 KT 90 MPH 48H 12/0600Z 21.5N 118.6W 65 KT 75 MPH 60H 12/1800Z 22.2N 120.7W 55 KT 65 MPH 72H 13/0600Z 22.6N 122.6W 45 KT 50 MPH 96H 14/0600Z 22.2N 125.7W 35 KT 40 MPH...POST-TROPICAL 120H 15/0600Z 21.4N 128.8W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Tropical Storm Elida Forecast Discussion Number 5

2020-08-10 04:35:35| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Sun Aug 09 2020 000 WTPZ44 KNHC 100235 TCDEP4 Tropical Storm Elida Discussion Number 5 NWS National Hurricane Center Miami FL EP092020 900 PM MDT Sun Aug 09 2020 Trends in satellite imagery over the past several hours indicate that Elida continues to quickly increase in organization. There has been an expanding central dense overcast, with the center of circulation presumed to be underneath cloud tops of about -70 C. Satellite intensity estimates TAFB and SAB as well as those from UW-CIMSS support increasing the initial intensity to 55 kt. Environmental conditions favor rapid intensification over the next 24 h or so. The latest SHIPS RI index indicates a better than 30 percent chance of Elida strengthening by 30 kt in the next 24 h, and based on the convective trends, the official forecast closely follows this guidance. By 48 h, the cyclone is forecast to cross the 26 C SST isotherm, and begin to enter a progressively drier and more stable atmospheric environment. This should cause steady weakening to occur. By 96 h, Elida is forecast to have been over waters cooler than 25 C for nearly 36 h. And as a result, the simulated satellite imagery by the GFS, ECMWF, and Canadian models all indicate that the deep convection will dissipate by that time. Therefore, Elida is expected to become a post-tropical cyclone by the 96 h forecast period. The latest NHC intensity forecast is little changed from from previous one, is close to the HCCA model intensity guidance for the next couple of days, then trends towards the SHIPS guidance thereafter. Elida continues to move west-northwestward at 13 k, steered by a mid-level ridge extending from northern Mexico to the east Pacific. This pattern is forecast to remain in place for the next few days. After that time, a slower westward or west-southwestward motion is expected as the weakening cyclone is steered by the low-level trade wind flow. The model track forecasts are in good agreement on this scenario, and the latest NHC forecast track is in the middle of the consensus track guidance. FORECAST POSITIONS AND MAX WINDS INIT 10/0300Z 17.8N 107.4W 55 KT 65 MPH 12H 10/1200Z 18.7N 109.4W 70 KT 80 MPH 24H 11/0000Z 19.6N 112.1W 80 KT 90 MPH 36H 11/1200Z 20.3N 114.8W 85 KT 100 MPH 48H 12/0000Z 21.0N 117.4W 80 KT 90 MPH 60H 12/1200Z 21.6N 119.6W 65 KT 75 MPH 72H 13/0000Z 22.1N 121.5W 55 KT 65 MPH 96H 14/0000Z 22.0N 124.9W 40 KT 45 MPH...POST-TROPICAL 120H 15/0000Z 21.1N 128.3W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto

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Tropical Storm Elida Forecast Discussion Number 4

2020-08-09 22:41:02| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Sun Aug 09 2020 000 WTPZ44 KNHC 092040 TCDEP4 Tropical Storm Elida Discussion Number 4 NWS National Hurricane Center Miami FL EP092020 300 PM MDT Sun Aug 09 2020 Elida appears to be on a strengthening trend. Visible satellite images indicate that the storm's banding features are becoming more tightly wrapped and symmetric around the center. An ASCAT pass from around 16Z showed maximum winds near 40 kt, but since the storm continues to organize, the initial intensity is set a little higher at 45 kt. This intensity estimate is in agreement with the 18Z Dvorak classifications from TAFB and SAB, but slightly below the latest SATCON and ADT values from CIMSS at the University of Wisconsin. Elida is likely on its way to becoming a hurricane as the environmental conditions are expected to remain favorable for strengthening during the next 36 to 48 hours. Now that the storm appears to have a well-defined inner core and outer bands, rapid strengthening is forecast during the next 24 hours with some additional intensification expected until it reaches cooler waters in a couple of days. After 48 hours, cooler waters and drier air should cause a gradual decay of the system, and Elida is expected to steadily weaken and become a remnant low by day 5. The NHC intensity forecast lies at the high end of the guidance, near HCCA, in the short term, but ends near the middle of the guidance envelope at the longer range times. The tropical storm is moving west-northwestward at 13 kt. The track forecast appears fairly straightforward. A mid-level ridge that stretches across northern Mexico and over a portion of the east Pacific should cause Elida to move generally west-northwestward at about the same forward speed during the next few days. After that time, a slower westward or west-southwestward motion is expected as the weakening cyclone is steered by the low-level trade wind flow. The models are in fairly good agreement, and this forecast lies near the various consensus models. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 17.0N 106.4W 45 KT 50 MPH 12H 10/0600Z 17.9N 108.4W 60 KT 70 MPH 24H 10/1800Z 18.9N 111.0W 75 KT 85 MPH 36H 11/0600Z 19.6N 113.7W 85 KT 100 MPH 48H 11/1800Z 20.3N 116.3W 85 KT 100 MPH 60H 12/0600Z 21.0N 118.8W 75 KT 85 MPH 72H 12/1800Z 21.6N 120.9W 60 KT 70 MPH 96H 13/1800Z 21.9N 124.1W 45 KT 50 MPH 120H 14/1800Z 21.3N 127.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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Tropical Storm Elida Forecast Discussion Number 3

2020-08-09 16:37:27| National Hurricane Center (East Pacific)

Issued at 1000 AM CDT Sun Aug 09 2020 000 WTPZ44 KNHC 091437 TCDEP4 Tropical Storm Elida Discussion Number 3 NWS National Hurricane Center Miami FL EP092020 1000 AM CDT Sun Aug 09 2020 Based on a 1128 UTC SSMIS pass, Elida appears to have developed a well-defined low-level structure, with a clear center region surrounded by a cyan ring in the 37-GHz channel. Dvorak classifications from TAFB and SAB are still below tropical storm strength, however the latest UW-CIMSS ADT up to 45 kt. Given the improving microwave structure, I've opted to go on the higher side of the intensity estimates, initializing the maximum wind speed at 40 kt. The overnight tracking of Elida's center appears to have been really good, as the recent microwave pass and first-light visible imagery show it to be very close to where we thought it was. Elida is moving west-northwestward, or 300/15 kt, to the south of a mid-level ridge which extends from Texas west-southwestward across northern Mexico and over the Pacific. This ridge should keep Elida on a west-northwestward track for the next 3 days or so. After that time, a weakening Elida should be steered by lower-level flow and will begin to move more slowly toward the west on days 4 and 5. This forecast unreasoning is unchanged from before, and since there are no errant track models that deviate from this scenario, the new NHC track forecast remains close to the multi-model consensus aids. Elida's structure revealed in the recent microwave pass that the cyclone is likely primed for continued intensification. With low shear, sufficient ocean heat content, and plenty of mid-level moisture, Elida is expected to strengthen to hurricane intensity around this time tomorrow, with a peak intensity occurring in about 2 days. Given the new set of intensity guidance, the NHC forecast has been raised during the first 2-3 days--not as high as the HCCA model but very close to the HWRF and Florida State Superensemble. Rapid intensification is not out of the question given Elida's structure and environment, with the SHIPS RI guidance showing a 1-in-3 chance of a 30-kt increase over the next 24 hours. After 48 hours, Elida will begin to move over cooler waters, and increasing southwesterly shear should cause a rather quick weakening trend. In fact, global models show all of Elida's deep convection dissipating--if not the entire system itself--by day 5, and the NHC forecast calls for the cyclone to be post tropical by that time. FORECAST POSITIONS AND MAX WINDS INIT 09/1500Z 16.4N 105.4W 40 KT 45 MPH 12H 10/0000Z 17.3N 107.4W 55 KT 65 MPH 24H 10/1200Z 18.4N 109.9W 65 KT 75 MPH 36H 11/0000Z 19.3N 112.6W 80 KT 90 MPH 48H 11/1200Z 20.0N 115.2W 85 KT 100 MPH 60H 12/0000Z 20.7N 117.8W 80 KT 90 MPH 72H 12/1200Z 21.2N 120.1W 70 KT 80 MPH 96H 13/1200Z 21.5N 124.0W 50 KT 60 MPH 120H 14/1200Z 21.0N 127.0W 35 KT 40 MPH...POST-TROPICAL $$ Forecaster Berg

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Tropical Storm Elida Forecast Discussion Number 2

2020-08-09 10:49:21| National Hurricane Center (East Pacific)

Issued at 400 AM CDT Sun Aug 09 2020 000 WTPZ44 KNHC 090849 TCDEP4 Tropical Storm Elida Discussion Number 2 NWS National Hurricane Center Miami FL EP092020 400 AM CDT Sun Aug 09 2020 Deep convection associated with the cyclone has increased during the past several hours, particularly in a band in the southeast quadrant. Late-arriving ASCAT data valid around 0330 UTC revealed that the cyclone's low-level wind structure was still somewhat elongated in a SSW-NNE orientation. That said, the ASCAT data also showed a few believable 30-35 kt vectors in the northeast quadrant of the cyclone. That supports an intensity of 35 kt, making Elida the 5th tropical storm of the 2020 eastern North Pacific season. Even with the assistance of the ASCAT pass, it has been difficult to track the center of the tropical storm this morning. The center of Elida appears to have jumped somewhat northward since last night, and further reformations of the center will be possible until the system consolidates some more. The northward adjustment in the position resulted in a slight adjustment to the track forecast in that direction, but overall the tropical storm is still forecast to move generally west-northwestward for the next several days, steered by a mid-level ridge extending over northern Mexico and the southwestern United States. A westward turn is likely near the end of the forecast period as Elida weakens and low-level tradewinds become the dominant steering mechanism. Overall the models are in excellent agreement and confidence in the track forecast is fairly high. All of the statistical and regional hurricane intensity models forecast Elida to strengthen and become a hurricane within 48 h. Since the cyclone does not appear to have a tight inner-core yet, only modest strengthening is forecast for the first 12 h, followed by a faster rate after that. The extent of strengthening is still highly uncertain, and the guidance ranges from a minimal to major hurricane. The new NHC forecast is very similar to the previous one and the multi-model consensus. Elida is forecast to weaken later this week after it reaches cooler waters to the north. FORECAST POSITIONS AND MAX WINDS INIT 09/0900Z 15.8N 104.1W 35 KT 40 MPH 12H 09/1800Z 16.8N 106.1W 40 KT 45 MPH 24H 10/0600Z 17.9N 108.8W 55 KT 65 MPH 36H 10/1800Z 18.8N 111.2W 65 KT 75 MPH 48H 11/0600Z 19.7N 113.8W 75 KT 85 MPH 60H 11/1800Z 20.6N 116.4W 75 KT 85 MPH 72H 12/0600Z 21.2N 119.0W 70 KT 80 MPH 96H 13/0600Z 21.9N 123.5W 55 KT 65 MPH 120H 14/0600Z 21.5N 127.0W 35 KT 40 MPH $$ Forecaster Zelinsky

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