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Hurricane LINDA Forecast Discussion Number 13

2015-09-09 04:32:57| National Hurricane Center (East Pacific)

Issued at 800 PM PDT TUE SEP 08 2015 000 WTPZ45 KNHC 090232 TCDEP5 HURRICANE LINDA DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152015 800 PM PDT TUE SEP 08 2015 Cloud tops within Linda's CDO feature have warmed significantly since the previous advisory, likely due to the erosion of eyewall convection in the northern semicircle caused by the entrainment of dry mid-level air as noted in recent microwave satellite imagery. Although the 15 n mi diameter eye remains quite distinct, satellite intensity estimates have decreased sharply. The initial intensity of 100 kt is based on an average of Dvorak satellite T-numbers and CI-numbers from TAFB and SAB. The initial motion estimate is now 325/11 kt. The track and forecast reasoning remain unchanged. The NHC model guidance is in very good agreement on Linda moving northwestward for the next 48 hours, followed by a turn to the west-northwest by 72 hours. After that time, the model tracks are widely divergent based on the intensity and resultant vertical depth of the cyclone on days 4 and 5. The ECMWF takes a weak remnant low due west, whereas the stronger GFS and HWRF models take Linda more poleward. The official forecast at 96 and 120 hours is a compromise of these extremes and lies close to the TCVE and GFEX consensus model tracks. Linda will be moving over sub-26C SSTs and over upper-ocean-heat- content (UOHC) values of near zero about 12 hours, while the hurricane is slowing down to less than 10 kt of forward speed. This should result in significant cold upwelling beneath the cyclone and induce a rapid weakening phase. As result, Linda is expected to weaken to a tropical storm by Thursday morning, a depression by Thursday night, and a remnant low on Friday. The official intensity forecast follows the downward trend of the previous forecast and the IVCN intensity consensus model. Although Linda is forecast to remain well offshore of the Baja California peninsula, large swells are expected to affect portions of the west coast of that peninsula during the next few days. In addition, some of Linda's mid- and upper-level moisture is expected to spread northward into portions of the southwestern U.S. by day 2 and beyond, which could help trigger locally heavy rainfall. For additional information, please consult products issued by the NOAA Weather Prediction Center and your local weather forecast office. FORECAST POSITIONS AND MAX WINDS INIT 09/0300Z 22.7N 115.6W 100 KT 115 MPH 12H 09/1200Z 23.7N 116.5W 85 KT 100 MPH 24H 10/0000Z 25.0N 117.6W 70 KT 80 MPH 36H 10/1200Z 26.1N 118.7W 55 KT 65 MPH 48H 11/0000Z 26.9N 119.8W 40 KT 45 MPH 72H 12/0000Z 27.6N 121.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 13/0000Z 27.8N 123.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 14/0000Z 27.6N 125.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Stewart

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Hurricane LINDA Forecast Discussion Number 12

2015-09-08 22:39:56| National Hurricane Center (East Pacific)

Issued at 300 PM MDT TUE SEP 08 2015 000 WTPZ45 KNHC 082039 TCDEP5 HURRICANE LINDA DISCUSSION NUMBER 12 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152015 300 PM MDT TUE SEP 08 2015 Linda still has an impressive satellite presentation, and appears to have peaked shortly after the last advisory was issued. A distinct eye in infrared imagery is surrounded by a CDO with cloud top temperatures of -70 to -80C. The initial intensity is set to 110 kt based on a blend of the latest Dvorak estimate of T5.5/102 kt from SAB and T6.0/115 kt from TAFB. The 34-kt wind radii were adjusted outward based on an ASCAT-B pass around 1700 UTC. Linda will be crossing the 27C SST isotherm soon, and the cyclone should begin to slowly weaken. Rapid weakening is expected between 24 and 48 hours as the cyclone moves over much cooler SSTs and into a stable, dry environment. Remnant low status is forecast by 72 hours. The NHC intensity forecast is similar to the previous advisory and is close to the latest intensity consensus. The initial motion estimate is 325/12, as Linda has wobbled a bit to the left of the previous track. The overall track forecast reasoning remains unchanged, as a weakening Linda should move northwestward under the influence of a subtropical ridge centered over Mexico. The remnant low is then forecast to turn west- northwestward and westward by the end of the period as it is steered by the low-level flow. The new NHC forecast has been adjusted to account for the initial motion through 36 hours, and is largely an update of the previous NHC track after that time. The NHC forecast continues to lie on the left side of the guidance envelope, between the ECMWF and the multi-model consensus. Although Linda is forecast to remain well offshore of the Baja California peninsula, large swells are expected to affect portions of the west coast of that peninsula during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 21.9N 114.8W 110 KT 125 MPH 12H 09/0600Z 23.0N 115.9W 100 KT 115 MPH 24H 09/1800Z 24.4N 117.0W 80 KT 90 MPH 36H 10/0600Z 25.6N 118.1W 60 KT 70 MPH 48H 10/1800Z 26.5N 119.2W 50 KT 60 MPH 72H 11/1800Z 27.4N 121.2W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 12/1800Z 27.5N 123.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 13/1800Z 27.5N 125.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan

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Hurricane LINDA Forecast Discussion Number 11

2015-09-08 16:34:23| National Hurricane Center (East Pacific)

Issued at 900 AM MDT TUE SEP 08 2015 000 WTPZ45 KNHC 081434 TCDEP5 HURRICANE LINDA DISCUSSION NUMBER 11 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152015 900 AM MDT TUE SEP 08 2015 The satellite presentation of Linda has improved this morning, with an eye becoming apparent in infrared imagery. Dvorak satellite classifications were T6.0/115 kt from TAFB and T5.5/102 kt from SAB, and the UW-CIMSS ADT estimates have increased to T5.9/112 kt. The initial intensity is set conservatively to 105 kt given the rapid change in the satellite presentation and the variation seen in the definition of the eye in recent images. This makes Linda the fifth major hurricane in the eastern North Pacific basin this year. It would appear that Linda is peaking in intensity now, as the cyclone will be moving over progressively cooler SSTs and into a drier more stable environment over the next several days. Slow weakening is forecast today, followed by more rapid weakening due to the above-mentioned unfavorable factors. The new NHC forecast is higher than the previous one through 24 hours to account for the initial intensity, but is similar to the previous official forecast after that time. Linda should become a remnant low in about 3 days over very cool waters west of the Baja California peninsula. Linda has been moving a little faster during the past few hours, with an initial motion estimate of 335/12. The tropical cyclone should turn toward the northwest later today under the influence of a subtropical ridge centered over Mexico. The remnant low is then forecast to turn west-northwestward and westward by the end of the period as it is steered by the low-level flow. The track model guidance has continued to shift toward the right this cycle, and is also a bit faster. The new NHC forecast has been adjusted to account for those trends, and now lies on the left side of the guidance envelope, between the ECMWF and the multi-model consensus. Although Linda is forecast to remain well offshore of the Baja California peninsula, large swells are expected to affect portions of the west coast of that peninsula during the next few days. The analyzed 12-ft seas radii were increased based on data from a recent Jason-2 satellite altimeter pass. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 21.3N 113.9W 105 KT 120 MPH 12H 09/0000Z 22.3N 114.8W 95 KT 110 MPH 24H 09/1200Z 23.7N 116.0W 80 KT 90 MPH 36H 10/0000Z 25.0N 117.2W 60 KT 70 MPH 48H 10/1200Z 26.1N 118.5W 50 KT 60 MPH 72H 11/1200Z 27.3N 120.7W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 12/1200Z 27.5N 122.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 13/1200Z 27.5N 124.5W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brennan

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Tropical Depression GRACE Forecast Discussion Number 13

2015-09-08 16:32:56| National Hurricane Center (Atlantic)

Issued at 1100 AM AST TUE SEP 08 2015 000 WTNT42 KNHC 081432 TCDAT2 TROPICAL DEPRESSION GRACE DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL AL072015 1100 AM AST TUE SEP 08 2015 After the overnight burst of deep convection, thunderstorm activity has diminished and the overall cloud pattern remains disorganized. Data from a recent ASCAT overpass show that Grace's maximum winds have decreased to near 30 kt, so the system is being downgraded to a tropical depression on this advisory. The cyclone is forecast to move through an environment of increasing vertical shear and dry mid-level air for the next few days. These unfavorable factors should cause the system to weaken further, and to degenerate into a remnant low pressure area over the next day or two. The official intensity forecast is the same as the previous one, and is slightly below the latest intensity model consensus. It is possible that Grace could open up into a wave during the next few days, as indicated by the global models. The cyclone continues to move westward at a fairly rapid pace, with the motion estimate remaining at 275/17 kt. The steering pattern is expected to remain uncomplicated. Grace or its remnant should continue to move west or slightly north of west, to the south of a low- to mid-level subtropical ridge throughout the forecast period. The official track forecast is an update of the previous one and remains close to the dynamical model consensus. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 14.3N 42.8W 30 KT 35 MPH 12H 09/0000Z 14.4N 45.4W 30 KT 35 MPH 24H 09/1200Z 14.8N 48.8W 30 KT 35 MPH 36H 10/0000Z 15.3N 52.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 10/1200Z 15.8N 55.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 11/1200Z 16.6N 62.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 12/1200Z...DISSIPATED $$ Forecaster Pasch

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Hurricane LINDA Forecast Discussion Number 10

2015-09-08 10:46:23| National Hurricane Center (East Pacific)

Issued at 300 AM MDT TUE SEP 08 2015 000 WTPZ45 KNHC 080846 TCDEP5 HURRICANE LINDA DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP152015 300 AM MDT TUE SEP 08 2015 Recent microwave data indicate that the inner-core structure of Linda has improved since the previous advisory. A couple of AMSU overpasses show that the primary convective band once again wraps around the center, and that a ragged eye is trying to form. The microwave images and 0516 UTC ASCAT data were very helpful in locating the center of Linda, and these data indicate that the center is more embedded within the CDO than earlier in the evening. The initial intensity is maintained at 80 kt, which is between the various Dvorak intensity estimates. Given the recent increase in inner core organization, the initial wind speed estimate could be a little conservative. Although the official intensity forecast shows no change in strength during the next 12 hours, environmental conditions consisting of warm water and relatively low shear could allow for a little intensification this morning. After that time, gradually decreasing sea surface temperatures and less favorable thermodynamic factors should cause weakening. The spin down should become more rapid in 36 to 48 hours when Linda moves over SSTs below 26 degrees Celsius and into a more stable environment. The tropical cyclone is predicted to become a remnant low in about 72 hours. Linda has been moving a little to the right of previous estimates, and the motion is now north-northwest or 335/9 kt. The model guidance suggests that the motion will bend back toward the northwest later today as the cyclone moves around the western portion of a subtropical ridge over northern Mexico. After 72 hours, the remnant low is expected to turn west-northwestward, and then westward in the low-level flow to the west of the Baja California peninsula. The model envelope has again shifted to the right and the NHC forecast has been adjusted accordingly. Although Linda is forecast to remain well offshore of the Baja California peninsula, large swells are expected to affect portions of the west coast of that peninsula during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 19.8N 113.1W 80 KT 90 MPH 12H 08/1800Z 21.1N 113.9W 80 KT 90 MPH 24H 09/0600Z 22.5N 115.1W 70 KT 80 MPH 36H 09/1800Z 23.8N 116.4W 60 KT 70 MPH 48H 10/0600Z 25.0N 117.7W 50 KT 60 MPH 72H 11/0600Z 26.5N 120.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 12/0600Z 27.0N 122.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 13/0600Z 27.0N 124.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown

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