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Tropical Depression Narda Forecast Discussion Number 7
2019-09-30 04:31:53| National Hurricane Center (East Pacific)
Issued at 1000 PM CDT Sun Sep 29 2019 000 WTPZ41 KNHC 300231 TCDEP1 Tropical Depression Narda Discussion Number 7 NWS National Hurricane Center Miami FL EP162019 1000 PM CDT Sun Sep 29 2019 My best estimate of Narda's position based on conventional and microwave satellite imagery, along with surface observations, is inland near Puerto Vallarta, Mexico. There may be other small swirls embedded within a surface trough that lies from the Islas Marias archipelago southeastward to Puerto Vallarta, Narda, and Manzanillo. However, the mid-level circulation center that we have been tracking, which is near ground level in this mountainous region, is the feature that has had the most continuity. A curved band of intense deep convection consisting of cloud tops of -85C to -90C, with isolated overshooting tops to -95C, wraps about half around the center and generally corresponds to 35-kt winds. Due to land interaction, however, the initial intensity is being held just below tropical storm strength or 30 kt. The initial motion is 315/18 kt. A large ridge anchored to the east of Narda is expected to steer the the cyclone northwestward for the next 3 days. This will result in Narda emerging back over the Pacific Ocean in about 6 hours, then passing near or over the Islas Marias islands Monday morning, followed by a track near or just offshore the northwestern coast of Mexico Monday night and Tuesday. A second landfall is expected along the coast of Mexico on Wednesday, followed by dissipation Wednesday night or early Thursday. The new NHC forecast track is similar to the previous advisory, and lies just a tad to the left of the consensus models TVCN and HCCA, which move the center inland in about 24 hours. The intensity forecast remains highly uncertain, and leans toward a consensus of the wind fields in the global models, which show Narda regaining tropical storm status in 6-12 hours as a band of 35-kt winds forms between the center and the mountainous coastline, likely due to funneling/orographic effects. The upper-level environment is forecast to be conducive for additional strengthening when Narda moves over the very warm waters of the Gulf of California after 12-18 hours, but land interaction is expected to temper any significant strengthening. Thus, the intensity forecast is flat-lined at 35-kt, although some fluctuations in the intensity is likely. Due to Narda being forecast to regain tropical storm status, tropical storm warnings and watches have been issued for portions of northwestern Mexico. The primary threat from Narda will continue to be very heavy rainfall, which should result in life-threatening flash flooding and mudslides over portions of the southern coast of Mexico. Rainfall totals of up to 15 inches are possible. This rainfall threat is expected to continue even if the system dissipates as a tropical cyclone. FORECAST POSITIONS AND MAX WINDS INIT 30/0300Z 20.6N 105.2W 30 KT 35 MPH...INLAND 12H 30/1200Z 22.0N 106.4W 35 KT 40 MPH...OVER WATER 24H 01/0000Z 24.0N 108.0W 35 KT 40 MPH 36H 01/1200Z 25.4N 109.4W 35 KT 40 MPH 48H 02/0000Z 26.7N 110.3W 35 KT 40 MPH 72H 03/0000Z 29.2N 111.4W 30 KT 35 MPH...INLAND 96H 04/0000Z...DISSIPATED INLAND $$ Forecaster Stewart
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