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Tropical Storm Hilda Forecast Discussion Number 2

2021-07-31 04:33:04| National Hurricane Center (East Pacific)

Issued at 900 PM MDT Fri Jul 30 2021 000 WTPZ43 KNHC 310232 TCDEP3 Tropical Storm Hilda Discussion Number 2 NWS National Hurricane Center Miami FL EP082021 900 PM MDT Fri Jul 30 2021 Satellite imagery indicates that Hilda has gotten a little better organized during the past several hours, with the low-level center now near the eastern end of a long convective band that is present in the southwestern semicircle. Satellite intensity estimates are 35 kt from TAFB and 45 kt from SAB, and based on these the initial intensity remains 40 kt. The storm is currently in an environment of light northwesterly vertical wind shear with the bulk of the outflow to the south. Conditions generally appear favorable for strengthening during the next 72 h or so, as Hilda is expected to be over warm sea surface temperatures and in an environment of light to moderate shear. Based on this, the first part of the intensity forecast is unchanged from the previous forecast and calls for Hilda to become a hurricane between 24 and 36 h and peak in intensity around 60 h. After that, the forecast becomes less confident. The cyclone is expected to move over decreasing sea surface temperatures after 72 h, and this should cause gradual weakening as indicated in the official forecast. The official forecast for this period has been nudged downward due to the forecast motion over cooler water. However, the GFS and ECMWF models suggest the possibility that Hilda will interact with other nearby systems - the GFS forecasting with Tropical Depression Nine-E to the west and the ECMWF forecasting interaction with a disturbance to the east. Should either of these interactions occur, Hilda could weaken at a different rate than currently forecast. The initial motion is 290/13. Hilda is located on the south side of a subtropical ridge, and if the storm does not interact with other nearby weather systems a general west-northwestward motion with a decrease in forward speed is expected through the forecast period. The new forecast track is shifted a little north of the previous track, and it lies just to the south of the various consensus models. If Hilda does interact with either Tropical Depression Nine-E or the disturbance to the east, it will lead to erratic motion. FORECAST POSITIONS AND MAX WINDS INIT 31/0300Z 13.2N 114.6W 40 KT 45 MPH 12H 31/1200Z 13.5N 116.3W 50 KT 60 MPH 24H 01/0000Z 14.1N 118.4W 60 KT 70 MPH 36H 01/1200Z 14.7N 120.3W 70 KT 80 MPH 48H 02/0000Z 15.3N 122.0W 75 KT 85 MPH 60H 02/1200Z 15.8N 123.3W 75 KT 85 MPH 72H 03/0000Z 16.5N 124.8W 70 KT 80 MPH 96H 04/0000Z 18.0N 127.0W 60 KT 70 MPH 120H 05/0000Z 19.5N 131.0W 50 KT 60 MPH $$ Forecaster Beven

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Tropical Depression Nine-E Forecast Discussion Number 1

2021-07-30 22:37:29| National Hurricane Center (East Pacific)

Issued at 200 PM PDT Fri Jul 30 2021 000 WTPZ44 KNHC 302037 TCDEP4 Tropical Depression Nine-E Discussion Number 1 NWS National Hurricane Center Miami FL EP092021 200 PM PDT Fri Jul 30 2021 An area of low pressure that NHC has been monitoring during the past several days over the eastern Pacific, has developed a well-defined surface center, as indicated in a recent scatterometer overpass, and has acquired sufficient organized convection to be classified as a 25-kt tropical depression. The northwesterly shear which has been curtailing genesis over the past couple of days has diminished just enough to allow the system to become better organized, particularly, in the east and south portions of the cyclone. The depression is embedded in weak easterly steering currents created by a deep-layer cut-off low and associated trough situated along 125W. As a result, the depression is temporarily drifting west-southwestward, or 255/4 kt. Large-scale models indicate that the cut-off feature will lift northward during the next 24-36 hours allowing a mid-tropospheric ridge to build in over the eastern Pacific. Accordingly, the cyclone should track generally westward at an increased forward speed beyond mid period. The official forecast follows suit and is based on a blend of the top forecast track performers, HFIP Corrected Consensus Approach (HCCA) and the multi-model consensus TVCN. Now that the shear is weakening and the upper tropospheric winds are predicted to become more favorable, (easterly, and little more diffluent) steady strengthening is expected while the cyclone traverses deep, warm oceanic temperatures. The NHC intensity forecast is near the HFIP Corrected Consensus Approach (HCCA) and the IVCN intensity aid and is below the Decay-SHIPS statistical-dynamical guidance beyond the 72-hour period. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 12.3N 125.8W 25 KT 30 MPH 12H 31/0600Z 12.0N 126.4W 30 KT 35 MPH 24H 31/1800Z 11.7N 126.9W 30 KT 35 MPH 36H 01/0600Z 11.7N 127.9W 35 KT 40 MPH 48H 01/1800Z 11.8N 129.5W 35 KT 40 MPH 60H 02/0600Z 12.1N 131.1W 40 KT 45 MPH 72H 02/1800Z 12.5N 132.6W 40 KT 45 MPH 96H 03/1800Z 13.2N 135.8W 45 KT 50 MPH 120H 04/1800Z 13.9N 138.9W 50 KT 60 MPH $$ Forecaster Roberts

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Tropical Storm Hilda Forecast Discussion Number 1

2021-07-30 22:36:59| National Hurricane Center (East Pacific)

Issued at 300 PM MDT Fri Jul 30 2021 000 WTPZ43 KNHC 302036 TCDEP3 Tropical Storm Hilda Discussion Number 1 NWS National Hurricane Center Miami FL EP082021 300 PM MDT Fri Jul 30 2021 A pair of ASCAT passes from a few hours ago indicated that the area of low pressure located about 800 miles south-southwest of the southern tip of the Baja California peninsula has strengthened, and is producing 35-40 kt winds on its east side. In addition, satellite images show a fairly persistent area of showers and thunderstorms on the south side of the circulation and the center appears to be fairly well defined in recent visible images. Based on these data, advisories are now being initiated on Tropical Storm Hilda and the initial intensity is estimated to be 40 kt. Hilda is moving westward at about 14 kt and is embedded in the flow on the south side of a sprawling subtropical ridge that extends from the south-central U.S. westward across the subtropical eastern Pacific. A general west-northwestward motion at about the same forward speed is expected during the next day or two as the synoptic pattern holds. After that time, a decrease in forward speed is predicted due to a combination of the subtropical ridge weakening and the interactions with the areas of low pressure to the east and west of Hilda. The ECMWF is the slowest model at long range due to it showing the most interaction with the low to Hildas east. The NHC track forecast lies generally near the model consensus and roughly between the GFS and ECMWF models. Hilda appears to be in generally conducive conditions for strengthening with SSTs currently around 28 C, abundant mid-level moisture, and fairly low wind shear. Given that these conditions are expected to persist for another couple of days, steady strengthening is forecast during that time period and Hilda is predicted to become a hurricane in 24 to 36 hours. Beyond a couple of days, however, moderate easterly shear, progressively drier air, and decreasing SSTs should end the strengthening trend and induce gradual weakening of the cyclone. The NHC intensity forecast lies near the middle of the guidance envelope, closest to the intensity model consensus IVCN. FORECAST POSITIONS AND MAX WINDS INIT 30/2100Z 12.1N 113.6W 40 KT 45 MPH 12H 31/0600Z 12.6N 115.4W 50 KT 60 MPH 24H 31/1800Z 13.2N 117.6W 60 KT 70 MPH 36H 01/0600Z 13.8N 119.7W 70 KT 80 MPH 48H 01/1800Z 14.3N 121.6W 75 KT 85 MPH 60H 02/0600Z 14.9N 123.1W 75 KT 85 MPH 72H 02/1800Z 15.3N 124.4W 70 KT 80 MPH 96H 03/1800Z 16.6N 126.4W 65 KT 75 MPH 120H 04/1800Z 18.3N 129.5W 55 KT 65 MPH $$ Forecaster Cangialosi

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Tropical Depression Felicia Forecast Discussion Number 27

2021-07-20 22:47:17| National Hurricane Center (East Pacific)

Issued at 1100 AM HST Tue Jul 20 2021 750 WTPZ41 KNHC 202047 TCDEP1 Tropical Depression Felicia Discussion Number 27 NWS National Hurricane Center Miami FL EP062021 1100 AM HST Tue Jul 20 2021 Convection once again has mostly dissipated near the low-level circulation of Felicia. Without any organized deep convection, the clock is now ticking on its remaining lifespan as a tropical cyclone. An ASCAT-A scatterometer pass that was recently received at 1709 UTC had a peak wind retrieval of 32-kt just north of the center. Given the lack of convection since that time, as well as the latest Dvorak estimates decreasing further, Felicia is being downgraded to a tropical depression at this time with maximum sustained winds of 30 kt. Further weakening is anticipated as Felicia remains in a very dry, stable environment. The depression is forecast to degenerate into a remnant low in the next 12 hours and open up into a trough by the end of the week, well south of Hawaii. The latest estimated motion is now to the west-southwest at 255/14 kt. The track philosophy has changed little this advisory as a large subtropical ridge will continue to steer Felicia to the west-southwest over the last few days of its life. The latest NHC track forecast is largely an update of the previous forecast track as the guidance remains tightly clustered along the forecast track. On this track, Felicia will be crossing into the central Pacific basin within the next few hours. This is the last advisory issued by the National Hurricane Center on Felicia. Future information on this system can be found in Forecast/Advisories issued by the Central Pacific Hurricane Center beginning at 0300 UTC...under AWIPS header HFOTCMCP1 ...WMO header WTPA21 PHFO. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 15.3N 139.4W 30 KT 35 MPH 12H 21/0600Z 14.8N 141.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 24H 21/1800Z 14.3N 144.4W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 22/0600Z 13.7N 147.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 22/1800Z 13.2N 150.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 23/0600Z...DISSIPATED $$ Forecaster Papin/Cangialosi

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