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Tropical Storm KARINA Forecast Discussion Number 13

2014-08-16 04:33:36| National Hurricane Center (East Pacific)

Issued at 800 PM PDT FRI AUG 15 2014 000 WTPZ41 KNHC 160233 TCDEP1 TROPICAL STORM KARINA DISCUSSION NUMBER 13 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 800 PM PDT FRI AUG 15 2014 The convective pattern of Karina continues to deteriorate, with the coverage of cold cloud tops decreasing during the past few hours. The low-level center is partially exposed on the northeastern edge of the convective canopy due to about 15 kt of easterly shear. A blend of the latest Dvorak CI numbers from TAFB and SAB yields an initial intensity estimate of 40 kt. Little change in strength is expected during the forecast period. The vertical shear is expected to decrease a little by day 3, but the cyclone will be moving over somewhat cooler SSTs by then. The NHC intensity forecast is close to the IVCN intensity consensus through the period. The initial motion estimate is 280/09, as Karina is being steered by a subtropical ridge to the north. This ridge will build westward during the next couple of days, followed by an amplification of a ridge well north of the Hawaiian Islands, which should result in Karina's track bending a little south of due west during the middle of the forecast period. By day 5, the ridging north of Karina will weaken as a mid/upper-level trough amplifies off the west coast of North America. This should result in a collapse of the steering currents and a slow and perhaps erratic motion by the end of the period. The NHC track forecast is largely an update of the previous one and is close to the TVCE multi-model consensus. FORECAST POSITIONS AND MAX WINDS INIT 16/0300Z 17.8N 122.0W 40 KT 45 MPH 12H 16/1200Z 18.1N 123.6W 40 KT 45 MPH 24H 17/0000Z 18.2N 125.6W 40 KT 45 MPH 36H 17/1200Z 18.1N 127.6W 40 KT 45 MPH 48H 18/0000Z 17.8N 129.4W 40 KT 45 MPH 72H 19/0000Z 17.2N 132.5W 45 KT 50 MPH 96H 20/0000Z 17.0N 134.0W 45 KT 50 MPH 120H 21/0000Z 17.0N 134.5W 45 KT 50 MPH $$ Forecaster Brennan

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Hurricane KARINA Forecast Discussion Number 9

2014-08-15 04:34:33| National Hurricane Center (East Pacific)

Issued at 800 PM PDT THU AUG 14 2014 000 WTPZ41 KNHC 150234 TCDEP1 HURRICANE KARINA DISCUSSION NUMBER 9 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 800 PM PDT THU AUG 14 2014 Karina's structure has degraded significantly since the last advisory. A 2326 UTC AMSU pass showed that the low-level center has become displaced from the deep convection due to 20-25 kt of easterly shear, as diagnosed by CIMSS at the University of Wisconsin. In addition, cloud top temperatures have warmed during the past few hours. The initial intensity remains 65 kt based on the latest TAFB Dvorak estimate, but this could be a little generous. The recent evolution of Karina's structure makes the intensity forecast quite tricky. The SHIPS and LGEM models appear to be responding to less of a positive contribution from persistence and GOES satellite predictors, and show much less strengthening than before. The GFDL and HWRF, on the other hand, continue their pattern of showing more immediate weakening. Since vertical shear is expected to remain rather strong for another 36-48 hours, Karina may have a difficult time recovering. Therefore, the new NHC intensity forecast has been lowered for the entire forecast period but still lies above all of the guidance, especially beyond 24 hours. If Karina cannot recover soon, however, subsequent forecasts will likely require additional decreases to fall in line with the preponderance of the intensity model solutions. The mid-tropospheric pattern consists of a mid-level high centered over the southwestern U.S. with a ridge extending west-southwestward over the Pacific. The ridge is steering Karina westward, or 270/11 kt, and the subtropical ridge is expected to keep the cyclone on a westward or west-northwestward track through the forecast period. Karina could begin to interact with one or two adjacent disturbances toward the end of the forecast period, possibly forcing it to move west-southwestward and at a slower speed by day 5. The track guidance envelope shifted to the north on this cycle, but it was not enough to require a significant change from the previous official forecast. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 17.1N 118.3W 65 KT 75 MPH 12H 15/1200Z 17.4N 119.9W 70 KT 80 MPH 24H 16/0000Z 17.9N 122.0W 70 KT 80 MPH 36H 16/1200Z 18.3N 124.2W 70 KT 80 MPH 48H 17/0000Z 18.4N 126.4W 70 KT 80 MPH 72H 18/0000Z 18.0N 130.5W 65 KT 75 MPH 96H 19/0000Z 17.5N 133.5W 65 KT 75 MPH 120H 20/0000Z 17.0N 136.0W 60 KT 70 MPH $$ Forecaster Berg

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Hurricane KARINA Forecast Discussion Number 8

2014-08-14 22:46:33| National Hurricane Center (East Pacific)

Issued at 200 PM PDT THU AUG 14 2014 000 WTPZ41 KNHC 142046 TCDEP1 HURRICANE KARINA DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 200 PM PDT THU AUG 14 2014 Despite moderate northeasterly vertical wind shear, Karina has managed to develop a closed mid-level eye with a diameter of around 10-12 nmi since the previous advisory as noted in recent SSMI/S and AMSU microwave imagery. Visible satellite imagery also indicates that a cloud-filled eye has appeared in the middle of the nearly circular CDO during past hour or so. Satellite intensity estimates are a consensus T4.0/65 kt, and ADT estimates from UW-CIMSS ADT have been steady at T4.4/75 kt for the past couple of hours. As a result of these data, the intensity has been increased to 65 kt. The initial motion estimate is 270/13 kt, which is based primarily on passive microwave satellite position fixes. Karina's apparent westward acceleration is likely due to the low-level center moving or reforming underneath the well-defined mid-level eye. As a result, this westward jog is expected to be a temporary motion, and Karina should slow down somewhat in the near-term. Otherwise, the hurricane is expected to remain on a basic westward track for the next 4 days as Karina is steered by a deep-layer ridge to its north. Afterwards, the cyclone is expected to slow down significantly and make a turn toward the west-southwest or southwest as Karina begins to interact with possible multiple tropical cyclones developing in the central Pacific and eastern Pacific basins. As mentioned in the previous discussion, rather than committing to any one particular model solution this far out in time, the NHC track forecast instead just shows a significant slow down in Karina's motion. The official forecast track is just an extension of the previous advisory track, and lies south of the consensus model TVCE, near the extreme southern edge of the NHC guidance envelope. The GFS-based SHIPS model indicates that the vertical shear is expected to increase to near 20 kt during the 12-24 hour period, while the shear vector veers around to the east. Given the well-defined and small eye mentioned previously, some additional strengthening is expected while Karina remains in favorable thermodynamic and oceanic environments. By 36 hours and beyond, the shear is forecast to decrease significantly, but this will occur when the cyclone is moving over marginal SSTs. The result is that a general leveling off of the intensity is expected, although there could obviously be some fluctuations in the intensity due to internal eyewall dynamics that can not be forecast this far in advance. The official intensity forecast remains well above the consensus model ICON due to the persistent weakening of Karina shown by the GFDL and HWRF models thus far, and instead follows the trend of the SHIPS and LGEM models. FORECAST POSITIONS AND MAX WINDS INIT 14/2100Z 17.1N 117.6W 65 KT 75 MPH 12H 15/0600Z 17.4N 119.1W 75 KT 85 MPH 24H 15/1800Z 17.8N 121.3W 80 KT 90 MPH 36H 16/0600Z 18.1N 123.6W 80 KT 90 MPH 48H 16/1800Z 18.2N 125.8W 80 KT 90 MPH 72H 17/1800Z 18.1N 129.5W 80 KT 90 MPH 96H 18/1800Z 17.7N 132.6W 75 KT 85 MPH 120H 19/1800Z 17.6N 134.2W 70 KT 80 MPH $$ Forecaster Stewart

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Tropical Storm KARINA Forecast Discussion Number 7

2014-08-14 16:47:29| National Hurricane Center (East Pacific)

Issued at 800 AM PDT THU AUG 14 2014 000 WTPZ41 KNHC 141447 TCDEP1 TROPICAL STORM KARINA DISCUSSION NUMBER 7 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 800 AM PDT THU AUG 14 2014 Deep convection has continued to increase and expand into a large canopy of cloud tops of -80C to -85C. Passive microwave satellite fixes indicate that the low-level center is located farther into the northeastern portion of the convective cloud shield and that a mid-level eye feature has developed closer to the center of the cloud mass. However, the mid-level eye is displaced or tilted at least 15-20 nmi southwest of the low-level center due to modest northeasterly shear impinging on the cyclone. Despite the shear conditions, satellite intensity estimate from TAFB and SAB are a consensus T3.5/55 kt, and estimates from UW-CIMSS ADT and AMSU are 57 kt and 55 kt, respectively. Based on these data, the initial intensity estimate is raised to 55 kt. The initial motion estimate is 270/09 kt and is based primarily on microwave satellite position fixes over the past 9 hours. The forecast track and reasoning remain unchanged over the past 24 hours with Karina expected to move in a general westward direction during the forecast period due to the presence of a strong subtropical ridge located to the north of the cyclone. By Day 5, however, the forecast become a little murky due to several models developing multiple tropical cyclones in the central Pacific and eastern Pacific basins that begin to interact with Karina in some form or fashion. Rather than committing to any one particular solution, the NHC track forecast just shows a significant slow down in Karina's motion. The official forecast track has been nudged slightly south of the previous advisory track and lies close to the consensus model TVCE, except at 120 hours due to the expected slower forward speed. Northeasterly shear of 10 to 15 kt has been affecting Karina during the past 12 hours or so, and the shear is expected to increase slightly over the next 24 hours. However, other environmental and oceanic conditions are expected to be favorable for additional strengthening to occur, so the NHC intensity forecast still calls for steady strengthening through the next 36 hours or so, followed by a leveling off of the intensity due to the cyclone moving over marginal SSTs near 26C and into a more stable air mass. The official intensity forecast is essentially just an update of the previous forecast, and remains above all of the available intensity guidance but follows the development trend in the SHIPS model. FORECAST POSITIONS AND MAX WINDS INIT 14/1500Z 17.2N 115.9W 55 KT 65 MPH 12H 15/0000Z 17.4N 117.6W 65 KT 75 MPH 24H 15/1200Z 17.6N 119.9W 70 KT 80 MPH 36H 16/0000Z 17.9N 122.2W 75 KT 85 MPH 48H 16/1200Z 18.1N 124.4W 75 KT 85 MPH 72H 17/1200Z 18.2N 128.4W 75 KT 85 MPH 96H 18/1200Z 17.9N 131.4W 70 KT 80 MPH 120H 19/1200Z 17.8N 133.5W 65 KT 75 MPH $$ Forecaster Stewart

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Tropical Storm KARINA Forecast Discussion Number 6

2014-08-14 10:37:24| National Hurricane Center (East Pacific)

Issued at 200 AM PDT THU AUG 14 2014 000 WTPZ41 KNHC 140837 TCDEP1 TROPICAL STORM KARINA DISCUSSION NUMBER 6 NWS NATIONAL HURRICANE CENTER MIAMI FL EP112014 200 AM PDT THU AUG 14 2014 Deep convection associated with Karina has been expanding during the last several hours, and microwave images suggest that the storm is maintaining a tight inner core. Dvorak intensity estimates from TAFB and SAB were both 3.0/45 kt at 0600 UTC, but recent ADT values from UW-CIMSS are a little higher. The initial wind speed is nudged upward to 50 kt based on the latest trends. East-northeasterly shear of 10 to 15 kt is currently affecting Karina, which is restricting the outflow on the east side of the circulation. Although the shear is not expected to change much during the next 24 to 36 hours, it should lessen beyond that time period. The official intensity forecast continues to call for steady strengthening during the next few days while Karina remains over warm water and in a relatively moist air mass. Gradual weakening is predicted in 4 to 5 days when the system moves over more marginal sea surface temperatures. This forecast is similar to the previous one, and remains at the upper end of the model guidance. Karina is moving westward at about 12 kt on the southwest side of a deep layer ridge centered over northern Mexico and the southwestern United States. This ridge is expected to build westward over the Pacific Ocean, which should keep the storm moving westward at about the same forward speed for the next few days. After that time, the track forecast is complicated by the potential interaction with other low pressure areas moving out of the Intertropical Convergence Zone. The GFS shows a more northerly track of Karina due its interaction with a disturbance to the west of the storm, while the ECMWF shows a more southerly track due to its interaction with the developing system to the east of Karina. The NHC track forecast is between these scenarios, close to the model consensus, and is just a tad to the north of the previous advisory. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 17.4N 115.2W 50 KT 60 MPH 12H 14/1800Z 17.5N 116.9W 60 KT 70 MPH 24H 15/0600Z 17.7N 119.1W 65 KT 75 MPH 36H 15/1800Z 18.0N 121.5W 70 KT 80 MPH 48H 16/0600Z 18.2N 123.8W 75 KT 85 MPH 72H 17/0600Z 18.6N 128.1W 75 KT 85 MPH 96H 18/0600Z 18.2N 131.3W 70 KT 80 MPH 120H 19/0600Z 18.0N 133.5W 60 KT 70 MPH $$ Forecaster Cangialosi

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