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Tropical Storm Erick Forecast Discussion Number 6
2019-07-28 22:47:44| National Hurricane Center (East Pacific)
Issued at 1100 AM HST Sun Jul 28 2019 000 WTPZ41 KNHC 282047 TCDEP1 Tropical Storm Erick Discussion Number 6 NWS National Hurricane Center Miami FL EP062019 1100 AM HST Sun Jul 28 2019 Although Erick's upper-level outflow has continued to improve, the overall convective pattern hasn't changed much. The earlier increase in central convection has been waning somewhat in recent satellite imagery, and the low-level center remains displaced just north of the central convection. However, passive microwave imagery indicates that the center has made a slight west-southwestward jog, possibly due to reformation closer to the strongest convection. The initial intensity has been increased to 40 kt based on a blend of Dvorak satellite intensity estimates of T2.5/35 kt from TAFB and T3.0/45 kt from SAB. An 1807Z partial ASCAT-A scatterometer pass indicated a 36-kt vector in the northeastern quadrant, and allowing for some undersampling also supports the 40-kt initial intensity. The initial motion estimate is 270/15 kt. It is possible that the initial position could be too far north, and a southward shift may be required on the next advisory. However, the general trend in the model guidance remains a westward motion for the next 24 hours or so, followed by a gradual turn toward the west-northwest as Erick moves into a slight weakness in the subtropical ridge. By 72 hours and beyond, the weakness is forecast to fill with the narrow ridge building westward across the Hawaiian Islands. This is expected to force Erick on a general westward to west-northwestward track through the remainder of the forecast period. On the forecast track, Erick is expected to cross into the Central Pacific basin Tuesday morning. The new NHC forecast track has again been shifted south of the previous advisory track, mainly due to the more southerly initial position, and lies down the center of the tightly packed guidance envelope and is close to a blend of the consensus track models HCCA, FSSE, and TVCN. The aforementioned ASCAT-A pass indicated that Erick has maintained a small radius of maximum winds (RMW) of about 20 nmi. The small RMW, low vertical wind shear, and SSTs near 28 deg C continue to support at least steady strengthening for the next few days, and Erick is forecast to become a hurricane in 36 hours. Although rapid intensification (RI) remains a possibility owing to the small RMW and low shear, the recent pronounced dry mid-level intrusion into the inner-core region, along with mid-level shear undercutting the other favorable outflow pattern, is expected to hinder any RI for at least the next 24 hours. By 72 hours, strong westerly vertical wind shear is forecast to affect the cyclone, inducing a steady weakening trend through the 120-h period. The latest Navy COAMPS model has backed off slightly and is now forecasting Erick to become a high-end category-3 hurricane in about 72 hours. However, this scenario has again been disregarded due to the abundance of dry mid-level air expected to affect the cyclone. The official intensity forecast is similar to the previous NHC advisory, and closely follows the HCCA corrected consensus model. FORECAST POSITIONS AND MAX WINDS INIT 28/2100Z 12.0N 131.3W 40 KT 45 MPH 12H 29/0600Z 12.3N 133.5W 45 KT 50 MPH 24H 29/1800Z 12.8N 136.4W 55 KT 65 MPH 36H 30/0600Z 13.5N 139.1W 65 KT 75 MPH 48H 30/1800Z 14.1N 142.0W 75 KT 85 MPH 72H 31/1800Z 15.3N 146.4W 85 KT 100 MPH 96H 01/1800Z 16.2N 150.9W 60 KT 70 MPH 120H 02/1800Z 16.8N 155.9W 40 KT 45 MPH $$ Forecaster Stewart
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