Tropical Storm Kristy

Tropical Storm Kristy Track 0800 Hours August 11 2018
Tropical Storm Kristy Track 0800 Hours August 11 2018
Tropical Storm Kristy Satellite 0800 Hours August 11 2018
Tropical Storm Kristy Satellite 0800 Hours August 11 2018

NWS National Hurricane Center Miami FL 800 AM PDT Sat Aug 11 2018

Cold waters and wind shear have taken a toll on Kristy. The cloud pattern has degenerated considerably, and it now consists of a tight swirl of low clouds with some patches of mid- to high-level clouds. It is estimated that the winds have decreased to 30 kt with some isolated spots of higher gusts. The cyclone will continue over cold waters, and although regeneration is not anticipated, some intermittent showers could still develop before dissipation occurs in a couple of days.

Since the post-tropical cyclone is a shallow system, it is now being steered toward the west-northwest or 300 degrees at 4 kt by the low-level trade winds. This general motion with a gradual turn to the west is anticipated during the next day or so.

This is the last advisory issued by NHC on this system.


NWS National Hurricane Center Miami FL 200 PM PDT Fri Aug 10 2018

It looks like Kristy may have peaked in intensity. The cloud tops of the central dense overcast have warmed since 6 hours ago, and any hints of an eye-like feature in visible imagery have disappeared. The initial intensity has been held at 60 kt as a compromise of all available satellite estimates, which still vary widely. Kristy has crossed the 26 C SST isotherm, and steady weakening from this point is likely as the tropical storm moves over progressively colder waters. All of the intensity guidance agrees on this solution, and confidence in the forecast is high. The dynamical models generally agree that cyclone will lose all deep convection by Sunday and become a remnant low.

Kristy is moving due north, and the initial motion estimate is 360/7 kt. Kristy should continue to move generally northward for the next 24 hours or so while it maintains at least some deep convection. Beginning day 2, a turn toward the northwest, and eventually west, will begin as the cyclone becomes increasingly steered by low-level easterly flow to the north. The guidance, especially the GFS, has shifted southwestward again, but is at least in a little better agreement than it was previously. The NHC forecast has likewise been shifted substantially toward the southwest by the end of the forecast period, and remains very close to HCCA and TVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  10/2100Z 19.6N 129.9W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 12H  11/0600Z 20.5N 130.0W   50 KT  60 MPH - Tropical Storm (E Hilo, Hawaii)
 24H  11/1800Z 21.2N 130.3W   40 KT  45 MPH - Tropical Storm (E Hilo, Hawaii)
 36H  12/0600Z 21.6N 130.8W   35 KT  40 MPH - Tropical Storm (E Hilo, Hawaii)
 48H  12/1800Z 22.0N 131.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  13/1800Z 22.8N 133.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  14/1800Z 23.5N 136.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  15/1800Z 24.0N 138.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 800 AM PDT Fri Aug 10 2018

Kristy appears to have at least maintained its strength over the past several hours. A partial hit from the AMSR instrument at 0950 UTC indicated a closed or nearly-closed mid-level eye was present, and this feature was still apparent in SSMI imagery a few hours later. Convection near Kristy’s center has also recovered after a brief decrease earlier this morning. There is a large spread in the latest satellite intensity estimates. Objective estimates from the UW-CIMSS ADT and SATCON are around 50 kt, while the latest subjective Dvorak classification from SAB supports an intensity of 77 kt. The initial intensity has been held at 60 kt as a compromise between the various estimates, but this estimate is perhaps more uncertain than usual.

In the short term, Kristy still has a brief period to maintain its intensity for about 12 hours while the shear is low and it remains over marginally warm SSTs around 26C. In fact, I can’t rule out that Kristy could briefly become a hurricane later today. Beginning tomorrow, the cyclone will be moving over cooler waters, and steady weakening should begin. The intensity guidance is in very good agreement on this solution for 24 hours and beyond. By early next week, the tropical storm will likely lose all convection and become a remnant low, while continuing to gradually spin down over sub-24C waters.

The initial motion is now 010/8 kt. Kristy should continue moving generally northward for the next couple of days, towards a weakness in the subtropical ridge created by John and to the east of a large upper-level trough located over the central Pacific. Once the cyclone becomes a remnant low, it should turn gradually westward, steered by the low-level flow. Even the GFS no longer shows any significant interaction between Kristy and the remnants of John, so the NHC forecast has shifted substantially southwestward by the end of the forecast period, close to the HCCA and TVCN consensus aids. Additional adjustments in this direction may be required if it becomes clear that Kristy will weaken sooner than currently forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 18.9N 129.8W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 12H  11/0000Z 19.9N 129.6W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 24H  11/1200Z 20.9N 129.5W   50 KT  60 MPH - Tropical Storm (E Hilo, Hawaii)
 36H  12/0000Z 21.6N 129.7W   40 KT  45 MPH - Tropical Storm (E Hilo, Hawaii)
 48H  12/1200Z 22.1N 130.1W   35 KT  40 MPH - Tropical Storm (E Hilo, Hawaii)
 72H  13/1200Z 23.3N 131.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  14/1200Z 24.0N 133.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  15/1200Z 24.5N 135.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 200 AM PDT Fri Aug 10 2018

Kristy has become a little better organized since the last advisory, as there is now a small central dense overcast with outer banding in the southern semicircle. Satellite intensity estimates are in the 55-65 kt range, and recent scatterometer data suggests winds are below hurricane strength. Based on these data, the initial intensity is held at 60 kt. There is still some chance that Kristy could become a hurricane during the next few hours. After that, the forecast track takes the cyclone over cooler waters and a steady weakening is forecast. The new intensity forecast, which lies in the middle of the intensity guidance, is nudged downward a little from the previous forecast, although it still calls for Kristy to become a remnant low by 72 h.

The initial motion is 005/7. The track guidance has made a notable westward shift since the previous advisory, as the models generally show less interaction between Kristy and Tropical Storm John. However, there is still a significant spread between the northward tracking GFS and the more westward UKMET and ECMWF. The new forecast track is also shifted westward from the previous track, but it lies to the east of the various consensus models. An additional westward adjustment to the track may be required later if the current model trends continue.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0900Z 18.2N 129.8W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 12H  10/1800Z 19.2N 129.5W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 24H  11/0600Z 20.3N 129.2W   55 KT  65 MPH - Tropical Storm (E Hilo, Hawaii)
 36H  11/1800Z 21.1N 129.2W   50 KT  60 MPH - Tropical Storm (E Hilo, Hawaii)
 48H  12/0600Z 21.8N 129.4W   40 KT  45 MPH - Tropical Storm (E Hilo, Hawaii)
 72H  13/0600Z 23.5N 130.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  14/0600Z 25.0N 132.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  15/0600Z 26.5N 133.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

 

NWS National Hurricane Center Miami FL 200 PM PDT Thu Aug 09 2018

Kristy’s deep convection has been waxing and waning, with an overall decrease a few hours ago followed by a recent increase near the center. The advisory intensity is kept at 55 kt, in agreement with objective ADT values from UW/CIMSS and a subjective Dvorak classification from TAFB. Kristy is over marginally warm waters, in low vertical shear, and with fairly well-defined upper-level outflow. There is a window of opportunity of about a day for additional intensification, and the official intensity forecast follows the intensity model consensus and the LGEM guidance. A weakening trend is likely to commence by Friday night, and Kristy should degenerate into a post-tropical cyclone by late in the weekend.

Visible imagery and some microwave data provided more accurate center fixes than earlier today, and the initial motion is a more confident 360/6 kt. The main steering mechanisms for Kristy are a weak ridge to the north and the large circulation of weakening John to the northeast. There continues to be significant diversity in the track models. The ECMWF and UKMET models, and their ensembles, are substantially to the left of the other guidance with the GFS, HWRF, and HMON much more to north and east, presumably due to interaction with John. Since the weakening John may not be that much of an influence, the official forecast is roughly in the middle of these two extremes and close to the model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  09/2100Z 16.9N 130.1W   55 KT  65 MPH - Tropical Storm (E Hilo, Hawaii)
 12H  10/0600Z 17.7N 129.8W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 24H  10/1800Z 19.0N 129.1W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 36H  11/0600Z 20.3N 128.7W   55 KT  65 MPH - Tropical Storm (E Hilo, Hawaii)
 48H  11/1800Z 21.3N 128.6W   50 KT  60 MPH - Tropical Storm (E Hilo, Hawaii)
 72H  12/1800Z 23.0N 129.0W   35 KT  40 MPH...POST-TROPICAL
 96H  13/1800Z 25.0N 130.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  14/1800Z 27.0N 131.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 800 AM PDT Thu Aug 09 2018

Deep convection has continued to increase in association with Kristy, mainly in a curved band over the northern semicircle of the cyclone. The current intensity estimate is 55 kt in agreement with a Dvorak estimate from TAFB and is close to the latest CIMSS SATCON value. Some additional strengthening is possible before Kristy reaches cooler waters late tomorrow, and the official forecast is close to the IVCN intensity model consensus. A weakening trend is likely to commence tomorrow night, and the system is expected to become post-tropical later this weekend.

Center fixes have a lot of scatter and the initial motion is an uncertain 345/4 kt. There continues to be a lot of spread in the track guidance models. The GFS and its ensemble, along with the HWRF and HMON regional models, are most aggressive in showing Kristy being drawn into the larger circulation of John to the northeast. The UKMET and ECMWF models do not take Kristy nearly as far to the north and northeast as those other models. Since John is weakening, it may not have that much of an influence on Kristy, especially later in the forecast period. For now, the official forecast is shifted a little to the right of the previous one but not as much as shown by the simple and corrected dynamical model consensus tracks.

FORECAST POSITIONS AND MAX WINDS

INIT  09/1500Z 16.1N 130.3W   55 KT  65 MPH - Tropical Storm (E Hilo, Hawaii)
 12H  10/0000Z 17.0N 130.0W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 24H  10/1200Z 18.2N 129.5W   60 KT  70 MPH - Tropical Storm (E Hilo, Hawaii)
 36H  11/0000Z 19.3N 129.0W   55 KT  65 MPH - Tropical Storm (E Hilo, Hawaii)
 48H  11/1200Z 20.4N 128.6W   50 KT  60 MPH - Tropical Storm (E Hilo, Hawaii)
 72H  12/1200Z 22.0N 128.7W   35 KT  40 MPH...POST-TROPICAL
 96H  13/1200Z 23.8N 129.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  14/1200Z 25.5N 130.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 200 AM PDT Thu Aug 09 2018

Deep convection has continued to increase near and to the north and east of Kristy’s center, and cirrus outflow has expanded some in all quadrants. Satellite intensity estimates supported an intensity of 40 kt at 0600 UTC, but the recent increase in convection, along with a Dvorak estimate of T3.0/45 kt from TAFB and and a UW-CIMSS ADT estimate of T2.9/43 kt, justify increasing the advisory intensity to 45 kt.

Kristy has turned to north-northwest and is now moving 345/05 kt. The cyclone is expected to turn toward the north later today, followed by a motion toward the north-northeast or northeast in the 24-48 h time period as Kristy and much larger Tropical Storm John undergo some weak binary interaction. However, the two cyclones separate by 72 h as John weakens over cold waters and its influence on Kristy diminishes, resulting in a turn to the north. By 96 h and beyond, Kristy will also be located over much colder water and is expected to have degenerated into a shallow remnant low pressure, becoming steered more westward by the deep-layer easterly trade wind flow. There remains considerable divergence among the global and regional hurricane models, with the GFS, HWRF, and HMON models keeping Kristy moving northward after 72 h, and the ECMWF and UKMET models moving Kristy westward. The guidance envelope has shifted markedly to the right of the previous forecast track, and the new official forecast track has also been shifted in that direction. However, the new track forecast was not shifted as far east as the consensus models HCCA and FSSE, out of respect for the reliable ECMWF model.

There is a narrow window of opportunity of about 24 h for Kristy to strengthen a little more while the cyclone remains over SSTs of 26-26.5 deg C and in a low-shear environment. After that time, however, cooler waters and the entrainment of much drier mid-level air is expected to induce steady weakening through the remainder of the forecast period, with the cyclone becoming post-tropical by 72 h, if not sooner. The official intensity forecast is similar to the intensity consensus model IVCN through 24 h, and then is a little lower than IVCN after that due to Kristy moving over sub-25 deg C SSTs.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 15.8N 130.1W   45 KT  50 MPH - Tropical Storm (E Hilo, Hawaii)
 12H  09/1800Z 16.5N 130.2W   45 KT  50 MPH - Tropical Storm (E Hilo, Hawaii)
 24H  10/0600Z 17.6N 129.9W   50 KT  60 MPH - Tropical Storm (E Hilo, Hawaii)
 36H  10/1800Z 18.7N 129.3W   45 KT  50 MPH - Tropical Storm (E Hilo, Hawaii)
 48H  11/0600Z 19.8N 128.9W   45 KT  50 MPH - Tropical Storm (E Hilo, Hawaii)
 72H  12/0600Z 21.4N 129.0W   35 KT  40 MPH...POST-TROPICAL
 96H  13/0600Z 22.8N 129.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  14/0600Z 23.5N 132.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 200 PM PDT Wed Aug 08 2018

Kristy’s overall structure hasn’t changed much over the past few hours, but cloud tops associated with the deepest convection have noticeably warmed. The intensity estimates from all agencies have also not changed, so the initial intensity has been held at 40 kt. Unfortunately, the various intensity models have not changed, either and the spread remains high. While the HWRF continues to show Kristy quickly strengthening to hurricane intensity, all of the statistical-dynamical guidance keeps the tropical storm very weak throughout the forecast period. The NHC forecast therefore continues to split the difference between these scenarios and shows slow strengthening for a couple of days while the cyclone remains in a low-shear environment. By days 4 and 5, Kristy is forecast to be moving over much cooler SSTs and through a more stable environment, which should cause it to weaken and become a remnant low.

The track forecast is also still low confidence. Although Kristy is currently moving west-northwestward with an initial motion of 300/5 kt, the models are in good agreement that Kristy will turn northward overnight and tomorrow due to a weakness in the subtropical ridge created by Hurricane John. The uncertainty grows substantially beyond 24 h. The GFS continues to insist on a steering flow that will cause Kristy to become wrapped up in the larger circulation of John, while the UKMET and ECMWF show only a slow northward motion, followed by a turn back toward the west or northwest once the cyclone becomes a remnant low. The NHC forecast has been favoring the western solution, and I don’t see an obvious reason to change that reasoning at this time. Therefore, little change has been made to the track forecast, which lies near a consensus of those two models, a little west of the multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  08/2100Z 14.7N 129.6W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
 12H  09/0600Z 15.3N 130.0W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
 24H  09/1800Z 16.2N 130.3W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 36H  10/0600Z 17.2N 130.3W   50 KT  60 MPH - Tropical Storm (SE Hilo, Hawaii)
 48H  10/1800Z 18.2N 130.0W   50 KT  60 MPH - Tropical Storm (SE Hilo, Hawaii)
 72H  11/1800Z 20.2N 130.0W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 96H  12/1800Z 21.3N 130.7W   35 KT  40 MPH - Tropical Storm (SE Hilo, Hawaii)
120H  13/1800Z 22.0N 132.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 800 AM PDT Wed Aug 08 2018

Kristy has continues to have the structure of a strongly sheared tropical cyclone. The low-level center has been difficult to identify overnight, but recent microwave data indicates that it is displaced to the northwest of the primary convective mass. The initial intensity has been held at 40 kt based on a blend of Dvorak Final-T numbers from TAFB and SAB.

Although the low-level center has been somewhat difficult to track, it appears that Kristy has begun to turn west-northwestward, and the initial motion estimate is 290/7 kt. Little change has been made to the official track forecast, but confidence remains very low. A break in the subtropical ridge created by Hurricane John should allow Kristy to continue turning, resulting in a northward motion by Thursday. Beyond that time, the model spread remains high, fueled by a combination of uncertainty as to how much John and Kristy will directly interact, and how much Kristy will respond to an upper-level trough to the northwest. The GFS is a notable outlier on the east side of the guidance envelope, and is the only model showing Kristy wrapping around the circulation of John. For now, the NHC forecast continues to downplay this possibility, and is a little to the west of the multi-model consensus.

The intensity guidance spread is also high, ranging from the HWRF which makes Kristy a hurricane, to the SHIPS and LGEM which forecast only gradual weakening. Since the shear is forecast to decrease over the next 12 to 24 hours, and Kristy will be moving away from the cold wake of Hector and over warmer waters, at least some strengthening seems likely. By the second half of the forecast period, the cyclone will be passing over much colder SSTs and through a drier environment, which should cause the cyclone to steadily weaken and become a remnant low. The NHC forecast is now close to the model consensus IVCN, which is higher this cycle.

FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 14.4N 129.3W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
 12H  09/0000Z 15.0N 130.0W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
 24H  09/1200Z 15.9N 130.5W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 36H  10/0000Z 16.8N 130.6W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 48H  10/1200Z 17.7N 130.4W   50 KT  60 MPH - Tropical Storm (SE Hilo, Hawaii)
 72H  11/1200Z 19.8N 130.2W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 96H  12/1200Z 21.5N 131.5W   35 KT  40 MPH - Tropical Storm (SE Hilo, Hawaii)
120H  13/1200Z 22.0N 133.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 200 AM PDT Wed Aug 08 2018

Satellite images indicate that Kristy is not well organized, with a dry slot wrapping around the northwestern side of the circulation. In addition the center is on the northwestern edge of an area of deep convection; an artifact of continued shear. A scatterometer pass revealed maximum winds of about 35 kt, which is a fair bit below the satellite estimates. The initial wind speed is held at a possibly generous 40 kt since convection has increased in the past few hours.

Shear from an upper-level low to the north-northeast of Kristy is forecast is relax in a day or so, and by that time the cyclone will probably have mixed the current dry air intrusion. Thus some restrengthening is shown commencing beyond 24 hours. There is only a narrow window for intensification, however, since between 48-72 hours the SSTs should become rather marginal with a possible increase in a shear. The guidance has come down markedly from the last cycle, with most of the models surprisingly showing no increase in strength. This forecast will lower the winds about 10 kt from the previous one during days 1-4, but is still about 10 kt above the consensus at those time frames since the environment doesn’t appear to be that hostile.

No change has been made to the initial motion estimate of 285/7 kt. Kristy should turn northwestward by this evening and then northward late Thursday as a narrow ridge is eroded away to the north of the cyclone. While some binary interaction with Hurricane John is possible, it seems like Kristy will be steered toward John, then turn northwestward in about 96 hours due to weak ridging developing between the cyclones. Model guidance is coming into better agreement on this scenario, with the ECMWF and GFS solutions converging toward the model consensus. The latest NHC forecast is slow to a blend of the corrected-consensus guidance, and is very close to the previous NHC track forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 14.2N 128.5W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
 12H  08/1800Z 14.8N 129.4W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
 24H  09/0600Z 15.5N 130.2W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
 36H  09/1800Z 16.4N 130.5W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 48H  10/0600Z 17.3N 130.5W   50 KT  60 MPH - Tropical Storm (SE Hilo, Hawaii)
 72H  11/0600Z 19.5N 130.0W   50 KT  60 MPH - Tropical Storm (SE Hilo, Hawaii)
 96H  12/0600Z 21.5N 130.5W   40 KT  45 MPH - Tropical Storm (SE Hilo, Hawaii)
120H  13/0600Z 23.0N 132.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 800 PM PDT Tue Aug 07 2018

Kristy has become a little less organized this evening. An upper tropospheric low situated to the northeast of Kristy is producing moderate northwesterly shear which has degraded the cyclone’s cloud pattern. A 2035 UTC AMSR2 overpass revealed that the surface center was partially exposed to the north of the convective banding features. The subjective Dvorak intensity estimates from TAFB and SAB have decreased as well, so the initial intensity for this advisory is lowered to 40 kt.

Statistical and global models all show the upper low to the northeast of Kristy weakening and lifting out in 24 hours or so, which should provide a more conducive upper wind environment for intensification, at least through mid-period. Afterwards, a weakening trend should commence due to an intruding drier/stable air mass and cooler oceanic sea surface temperatures. The HWRF and HCCA show Kristy becoming a hurricane in 48 hours, which still seems quite reasonable and is reflected in the forecast. All of the other guidance reaches just below 65 kt. The NHC intensity forecast is based primarily on these two models, and indicates a peak intensity of 65 kt in 48 hours.

The initial motion is estimated to be 285/7 kt, and Kristy is being steered by a narrow mid-level ridge to the northeast. A complex synoptic steering pattern comprised of an approaching deep-layer low pressure system to the northwest of the tropical storm, and John to the northeast, is forecast by most of the global and regional models to weaken what’s left of the ridge currently steering Kristy. The increasing weakness in the subtropical ridge should cause Kristy to turn northwestward and northward through day 4. At the end of the period, a gradual turn toward the northwest around the periphery of larger John’s circulation. The ECMWF deterministic and ensemble models continue to be outliers in the aforementioned scenario due to less influence from the growing weakness to the north and significantly less binary interaction with John. The official forecast is similar to the previous one, with a slight adjustment to the right and is basically in the middle of the HCCA and TVCE consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  08/0300Z 14.2N 127.8W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 12H  08/1200Z 14.6N 128.7W   45 KT  50 MPH - Tropical Storm (SE Hilo, Hawaii)
 24H  09/0000Z 15.4N 129.6W   50 KT  60 MPH - Tropical Storm (SE Hilo, Hawaii)
 36H  09/1200Z 16.4N 130.0W   60 KT  70 MPH - Tropical Storm (SE Hilo, Hawaii)
 48H  10/0000Z 17.2N 130.1W   65 KT  75 MPH - Category 1 (SE Hilo, Hawaii)
 72H  11/0000Z 19.5N 129.9W   60 KT  70 MPH - Tropical Storm (SE Hilo, Hawaii)
 96H  12/0000Z 22.0N 130.6W   50 KT  60 MPH - Tropical Storm (SE Hilo, Hawaii)
120H  13/0000Z 24.3N 133.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

NWS National Hurricane Center Miami FL 200 PM PDT Tue Aug 07 2018

Geostationary satellite and microwave images indicate that Kristy has well-defined curved bands, but the convection in these bands has decreased during the past several hours. A recent ASCAT pass showed maximum winds of about 40 kt. Based on that data and Dvorak classifications, the initial intensity is again held at 45 kt.

Kristy has been moving just south of due west during the past 12 hours, and the initial motion estimate is 260/11 kt. The models agree that a decrease in forward speed and a turn to the west-northwest is expected to begin tonight or on Wednesday, but that is about all they agree on for the future track of Kristy. There remains significant spread in the models about how the storm will interact with Hurricane John to its northeast. The GFS continues to show Kristy being pulled northward and then northeastward into the outer circulation of John. On the other hand, the ECMWF has been consistent in showing little interaction between the tropical cyclones, and keeps Kristy moving on a westward or west-northwestward path. The NHC official track forecast lies between these scenarios and is close to the recent run of the UKMET model. This forecast has been adjusted to the north and east of the previous one to get closer to the middle of the guidance envelope. It should be noted that the track forecast is of low confidence given the very different model solutions.

Kristy’s struggles are likely due to the influences of dry air and moderate shear. The SHIPS model shows the shear decreasing during the next couple of days, which could allow the storm to gradually strengthening during that time period. Beyond a couple of days, however, cooler waters and a more stable airmass should end the strengthening trend and result in weakening. The NHC intensity forecast is largely an update of the previous one and lies close to the HCCA model.

FORECAST POSITIONS AND MAX WINDS

INIT  07/2100Z 13.7N 127.1W   45 KT  50 MPH - Tropical Storm (SE of Hilo, Hawaii)
 12H  08/0600Z 13.9N 128.2W   50 KT  60 MPH - Tropical Storm (SE of Hilo, Hawaii)
 24H  08/1800Z 14.5N 129.2W   55 KT  65 MPH - Tropical Storm (SE of Hilo, Hawaii)
 36H  09/0600Z 15.4N 129.9W   60 KT  70 MPH - Tropical Storm (SE of Hilo, Hawaii)
 48H  09/1800Z 16.4N 130.2W   65 KT  75 MPH - Category 1 (SE of Hilo, Hawaii)
 72H  10/1800Z 18.5N 130.2W   60 KT  70 MPH - Tropical Storm (SE of Hilo, Hawaii)
 96H  11/1800Z 21.0N 130.8W   55 KT  65 MPH - Tropical Storm (SE of Hilo, Hawaii)
120H  12/1800Z 23.0N 132.5W   45 KT  50 MPH - Tropical Storm (SE of Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Tue Aug 07 2018

The cloud pattern of Kristy is a little better organized with several clusters of deep convection. The Dvorak T-numbers are now 3.0/45 kt, and this data is now in better agreement with the earlier ASCAT pass that was mentioned in the previous discussion. Therefore, the initial intensity is kept at 45 kt. Kristy is within a low shear environment, and most of the guidance indicates gradual strengthening. The NHC forecast brings Kristy to hurricane status in a couple of days while the cyclone remains over warm waters. By the end of the forecast period, the circulation will begin to be affected by cooler waters, which should result in weakening.

The best estimate of the initial motion is toward the west or 270 degrees at 8 kt. The track forecast during the first 24 hours or so is fairly straightforward since the cyclone is embedded within deep easterlies. Thereafter, the easterly flow will be interrupted by the larger circulation of Hurricane John passing to the north of Kristy, and the cyclone will most likely turn northward in response. The spread in the guidance becomes large after 24 to 36 hours with the ECMWF model keeping Kristy on a west-northwest path while the GFS shows a northward motion as Kristy interacts with John. The NHC forecast is in the middle of these two options and very closely follows the multi-model consensus. It should be noted that there is low confidence in the long range track forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  07/1500Z 13.8N 126.5W   45 KT  50 MPH - (SE Hilo, Hawaii)
 12H  08/0000Z 13.9N 127.6W   50 KT  60 MPH - (SE Hilo, Hawaii)
 24H  08/1200Z 14.2N 128.9W   55 KT  65 MPH - (SE Hilo, Hawaii)
 36H  09/0000Z 14.8N 130.0W   60 KT  70 MPH - (SE Hilo, Hawaii)
 48H  09/1200Z 16.0N 130.5W   65 KT  75 MPH - Category 1 (SE Hilo, Hawaii)
 72H  10/1200Z 18.0N 130.5W   65 KT  75 MPH - Category 1 (SE Hilo, Hawaii)
 96H  11/1200Z 20.5N 131.5W   55 KT  65 MPH - (SE Hilo, Hawaii)
120H  12/1200Z 22.5N 134.0W   45 KT  50 MPH - (SE Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 AM PDT Tue Aug 7 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Ileana, located a couple of hundred hundred miles west- southwest of Cabo Corrientes, Mexico, on Hurricane John, located a few hundred miles south of the southern tip of the Baja California Peninsula, and on Tropical Storm Kristy, located several hundred miles west-southwest of Baja California Sur.

NWS National Hurricane Center Miami FL 500 PM PDT Mon Aug 6 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Ileana, located a little more than a hundred miles south-southeast of Manzanillo, Mexico, and on Hurricane John, located a few hundred miles south-southeast of the southern tip of the Baja California Peninsula.

Shower activity associated with an elongated area of low pressure located about 1000 miles southwest of the southern tip of the Baja California peninsula continues to show some signs of organization. Environmental conditions appear conducive for development, and a tropical depression is likely to form during the next couple of days while the system moves slowly toward the west-northwest at 5 to 10 mph. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Mon Aug 6 2018

For the eastern North Pacific…east of 140 degrees west longitude:

The National Hurricane Center is issuing advisories on Tropical Storm Ileana, located a couple of hundred miles southeast of Manzanillo, Mexico, and on Tropical Storm John, located a few hundred miles south-southwest of Manzanillo, Mexico.

An elongated area of low pressure located about 1000 miles southwest of the southern tip of the Baja California peninsula continues to produce a large area of showers and thunderstorms. Environmental conditions appear conducive for development, and a tropical depression is still likely to form during the next couple of days while the system moves west-northwestward at 5 to 10 mph. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high...80 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Mon Aug 6 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Tropical Storm Ileana, located a little more than one hundred miles south-southwest of Acapulco, Mexico, and on Tropical Storm John, located a few hundred miles south-southwest of Manzanillo, Mexico.

Showers and thunderstorms associated with an elongated area of low pressure located about 1000 miles southwest of the southern tip of the Baja California peninsula have increased in coverage overnight. Environmental conditions appear conducive for development, and a tropical depression is likely to form by the middle of the week while the system moves west-northwestward at 5 to 10 mph. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sun Aug 5 2018

For the eastern North Pacific…east of 140 degrees west longitude: The National Hurricane Center is issuing advisories on Hurricane Hector, located well east-southeast of the Big Island of Hawaii, and on Tropical Depression Eleven-E, located south of Puerto Escondido, Mexico.

An elongated area of low pressure location about 900 miles southwest of the southern tip of the Baja California peninsula continues to produce a large area of disorganized showers and thunderstorms. Environmental conditions appear favorable for development, and a tropical depression is expected to form within the next day or two while this system moves slowly westward. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Aug 5 2018

Satellite imagery indicates that showers and thunderstorms associated with an area of low pressure located about 400 miles southwest of Acapulco, Mexico, have become a little better organized overnight. Environmental conditions are expected to remain conducive for additional development, and a tropical depression is likely to form later today or tonight while the system moves west-northwestward off the coast of Mexico. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…near 100 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sat Aug 4 2018

Satellite images indicate that a low pressure area located about 275 miles south-southeast of Puerto Angel, Mexico, has become significantly better defined this morning, and a tropical depression could be forming. If current trends continue, advisories could be initiated this afternoon or evening on this system. The low is forecast to move west-northwestward at 10 to 15 mph, relatively close to Mexico, and interests along the southern coast of Mexico should monitor the progress of this system. Heavy rainfall and gusty winds could affect coastal regions of Guerrero northwestward to Jalisco over the next few days. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Aug 4 2018

A tropical wave located a few hundred miles south-southwest of the coast of Guatemala continues to produce disorganized shower activity. Although this system has the potential to become a tropical depression early next week, strong upper-level winds from another disturbance to the west could prevent tropical cyclone formation while the system moves westward or west-northwestward south of Mexico.

* Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…medium…40 percent.

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