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Tropical Storm IRWIN Forecast Discussion Number 24

2017-07-28 10:39:47| National Hurricane Center (East Pacific)

Issued at 200 AM PDT Fri Jul 28 2017 000 WTPZ45 KNHC 280839 TCDEP5 Tropical Storm Irwin Discussion Number 24 NWS National Hurricane Center Miami FL EP102017 200 AM PDT Fri Jul 28 2017 Although conventional satellite imagery shows recent improvement in the banding feature wrapping around the eastern half of the cyclone, an ambiguity solution of a 0514 UTC ASCAT-B overpass indicates that Irwin has weakened. Based on the scatterometer data and a blend of the subjective Dvorak satellite estimates from TAFB and SAB, the initial intensity is lowered to 45 kt for this advisory. The CIMSS wind shear analysis and the SHIPS model both indicate that moderate northeasterly shear, produced by an anticyclone to the north, will be the primary inhibitor for any significant strengthening prior to Irwin's demise in 4 days. Little change in the cyclone's intensity is forecast before the merging of Irwin with Tropical Storm Hilary occurs around the 96 hour period. The initial motion estimate continues as a drift toward the west, or 270/02 kt. The large-scale models indicate this slow motion, or meander, continuing through the 36 hour period. Afterward, Irwin is expected to accelerate northward around the eastern peripheral flow of Hilary. The global and regional models also generally agree with the merging of the two tropical cyclones to occur in 4 days, or less. The official forecast has been adjusted to the right of the previous track forecast beyond 36 hours to align more closely to the TVCX and HCCA consensus models. FORECAST POSITIONS AND MAX WINDS INIT 28/0900Z 14.9N 124.8W 45 KT 50 MPH 12H 28/1800Z 14.9N 124.9W 50 KT 60 MPH 24H 29/0600Z 15.0N 124.8W 50 KT 60 MPH 36H 29/1800Z 15.7N 124.5W 50 KT 60 MPH 48H 30/0600Z 17.4N 124.5W 45 KT 50 MPH 72H 31/0600Z 22.0N 126.3W 45 KT 50 MPH 96H 01/0600Z...DISSIPATED $$ Forecaster Roberts

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Tropical Storm Irwin Forecast Discussion Number 23

2017-07-28 04:54:53| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Thu Jul 27 2017 000 WTPZ45 KNHC 280254 TCDEP5 Tropical Storm Irwin Discussion Number 23 NWS National Hurricane Center Miami FL EP102017 800 PM PDT Thu Jul 27 2017 Irwin's convective pattern has changed little since the previous advisory. A long curved but fragmented band of convection wraps almost 75 percent of the way around the circulation center, yielding a consensus Dvorak intensity estimate of T3.5/55 kt from both TAFB and SAB. However, objective estimates from UW-CIMSS ADT and NHC are T2.9/43 kt and T3.0/45 kt, respectively, which are supported by an earlier UW-CIMSS AMSU estimate of 45 kt. Based on average of these estimates, the initial intensity has been held at 50 kt. The initial motion estimate is a slow drift toward the west, or 270/02 kt. For such weak steering currents, the latest NHC model guidance is in very good agreement on Irwin moving little for the next 36 hours or so, followed by a faster motion toward the north at 48 and 72 hours as the cyclone moves up the eastern and the northern sides of Tropical Storm Hilary. Irwin is then forecast to merge with Hilary by 96 hours. The new NHC track forecast is similar to the previous advisory, and lies close to the multi-model consensus TVCN. The overall environment surrounding Irwin is expected to change little before the cyclone merges with Tropical Storm Hilary, so only minor fluctuations in intensity are forecast, based primarily on slight changes in the vertical wind shear. The new forecast follows the previous advisory and the consensus model IVCN. FORECAST POSITIONS AND MAX WINDS INIT 28/0300Z 14.9N 124.6W 50 KT 60 MPH 12H 28/1200Z 14.8N 124.8W 50 KT 60 MPH 24H 29/0000Z 14.8N 125.0W 55 KT 65 MPH 36H 29/1200Z 15.0N 125.1W 55 KT 65 MPH 48H 30/0000Z 16.4N 124.8W 50 KT 60 MPH 72H 31/0000Z 20.0N 126.0W 45 KT 50 MPH 96H 01/0000Z...MERGED WITH TROPICAL STORM HILARY $$ Forecaster Stewart

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Tropical Storm Hilary Forecast Discussion Number 27

2017-07-28 04:54:46| National Hurricane Center (East Pacific)

Issued at 800 PM PDT Thu Jul 27 2017 000 WTPZ44 KNHC 280254 TCDEP4 Tropical Storm Hilary Discussion Number 27 NWS National Hurricane Center Miami FL EP092017 800 PM PDT Thu Jul 27 2017 Deep convection associated with Hilary has been decreasing during the last several hours, and the convective pattern is now limited to a ragged central dense overcast. This loss of convection appears to be associated with dry air that has wrapped into the circulation, as evident in microwave data. An average of the latest Final T- and CI-numbers from TAFB/SAB, along with ADT values from CIMSS at the University of Wisconsin, support lowering the initial intensity to 60 kt, making Hilary a tropical storm. Hilary still has another 18-24 hours over warm water, and the regional hurricane models respond to this by showing Hilary restrengthening during that time. Given the observed weakening trend over the past day or so and Hilary's current struggle with dry air, the NHC intensity forecast lies at the low end of the guidance during that time frame, and calls for the storm to remain steady in intensity. After 24 hours, Hilary is expected to cross the 26-deg C isotherm and it will be moving over even cooler waters and into a drier air mass during the next few days. These unfavorable conditions should cause weakening, and Hilary is forecast to become a post-tropical cyclone in about 4 days. The NHC intensity forecast is similar to the previous one, and it lies fairly close to the SHIPS and LGEM models. The tropical storm is moving west-northwestward at 7 kt on the south side of a mid-level ridge. This motion with a slight increase in forward speed is expected during the next couple of days as the mid-level ridge strengthens. When Irwin rotates around the eastern and northern sides of Hilary in the 48- to 72-h time frame, Hilary could turn briefly to the left before it absorbs Irwin. Thereafter, a slower motion to the west-northwest is predicted as the weakening storm moves in the low- to mid-level flow. The NHC track forecast is adjusted a little to the north of the previous one, to come into better agreement with the latest consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 28/0300Z 18.3N 117.3W 60 KT 70 MPH 12H 28/1200Z 18.8N 118.4W 60 KT 70 MPH 24H 29/0000Z 19.6N 120.0W 60 KT 70 MPH 36H 29/1200Z 20.5N 122.0W 55 KT 65 MPH 48H 30/0000Z 21.2N 124.3W 55 KT 65 MPH 72H 31/0000Z 22.1N 128.7W 45 KT 50 MPH 96H 01/0000Z 23.2N 132.1W 35 KT 40 MPH...POST-TROPICAL 120H 02/0000Z 24.5N 134.8W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Cangialosi

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PUB Memo: Values and Time Request Discussion Guide

2017-07-28 02:42:10| PortlandOnline

PDF Document, 123kbCategory: July 25, 2017 Materials

Tags: time guide request discussion

 

PUB Discussion Guide (updated) for Water Treat

2017-07-28 02:40:13| PortlandOnline

PDF Document, 71kbCategory: July 25, 2017 Materials

Tags: guide updated water discussion

 

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