Tropical Storm Marie

Post Tropical Storm Marie Track 1700 Hours October 6 2020
Post Tropical Storm Marie Track 1700 Hours October 6 2020

Tropical Storm Marie Wind Speed FieldTropical Storm MarieNWS National Hurricane Center Miami FL 500 PM HST Tue Oct 06, 2020 (see Tuesday video below)

Patchy shower activity continues nearly 250 n mi to the northeast of Marie’s center–way too far away and way too weak for the system to still be classified as a tropical cyclone. Marie has therefore become a remnant low, with maximum winds set at 30 kt since an ASCAT-C pass around 1800 UTC did not register any winds of tropical storm force. The remnant circulation is expected to gradually spin down during the next few days due to cold waters, dry air, and southwesterly shear of about 40 kt. The global models generally show the remnant low hanging around for the next 3 days and then opening up into a trough by day 4, and that is reflected in this last NHC advisory.

Marie continues moving toward the west-northwest, or 300/7 kt. A fairly weak low- to mid-level ridge to the north should keep Marie on a west-northwestward heading for the next 24 hours, followed by a westward motion with a gradual decrease in speed from 36 to 72 hours. Most of the track models seem to pull the remnant low too far to the north during the next day or so, and the NHC track forecast is therefore near the southern side of the guidance envelope, between HCCA and the previous interpolated official forecast.

This is the last advisory on Marie.

FORECAST POSITIONS AND MAX WINDS

INIT  07/0300Z 22.5N 136.2W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 12H  07/1200Z 22.9N 137.0W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 24H  08/0000Z 23.2N 137.8W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 36H  08/1200Z 23.3N 138.6W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 48H  09/0000Z 23.3N 139.4W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 60H  09/1200Z 23.3N 140.1W   20 KT  25 MPH - Low (ENE Hilo, Hawaii)
 72H  10/0000Z 23.3N 140.7W   20 KT  25 MPH - Low (ENE Hilo, Hawaii)
 96H  11/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 PM PDT Tue Oct 06, 2020 

Marie’s center remains exposed, with limited shower activity displaced more than 110 n mi northeast of the center. Consequently, the system is poised to become a remnant low tonight if organized convection doesn’t redevelop near the center of circulation. The initial intensity is lowered to 35 kt, and is in best agreement with a blend of the various satellite intensity estimates and in deference to this morning’s scatterometer data which indicated numerous 40-kt winds. Marie should continue to gradually spin down during the 36 hours while moving west-northwestward over 24C sea surface temperatures and through an extremely inhibiting surrounding environment. Through the remaining portion of the period, the post-tropical remnant low should turn westward within the low-level easterlies and open up into a trough of low pressure Friday. Only a small along-track adjustment was made to the NHC forecast in order to agree more with the HFIP Corrected Consensus Approach model.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 22.4N 135.6W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  07/0600Z 22.8N 136.4W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 24H  07/1800Z 23.2N 137.3W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 36H  08/0600Z 23.4N 138.1W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 48H  08/1800Z 23.4N 139.0W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 60H  09/0600Z 23.4N 139.8W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 72H  09/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Tue Oct 06, 2020

Marie continues to gradually spin down this morning, and the impressive burst of convection that developed near the surface center last night, now consists of a shrinking cloud mass with significantly warming cloud tops. Assuming some weakening since the last night’s METOP-A and B scatterometer passes indicating peak winds of 40 kt, the initial intensity is lowered to 35 kt which is also supported by a blend of the Dvorak intensity estimates from TAFB and SAB.

Marie is moving over cool oceanic sea surface temperatures and through a high statically stable air mass. The persistent, harsh vertical shear environment has displaced what remains of the cyclone’s associated deep convection well to the northeast of the center. The Statistical-dynamical intensity guidance and the large-scale models are in general agreement with Marie degenerating into a trough of low pressure in 3 days, and the NHC intensity forecast follows suit.

The initial motion estimate is estimated to be west-northwestward, or 295/8 kt. There are no significant changes to the previous forecast track or reasoning. The cyclone should continue moving toward the west-northwest through Wednesday evening. Through the remaining portion of the period, the post-tropical remnant low should continue to gradually spin down while moving westward within the low-level easterlies and open up into a trough of low pressure by Friday.

FORECAST POSITIONS AND MAX WINDS

INIT  06/1500Z 22.1N 135.1W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  07/0000Z 22.5N 136.2W   35 KT  40 MPH - Low (ENE Hilo, Hawaii)
 24H  07/1200Z 22.9N 137.3W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 36H  08/0000Z 23.2N 138.0W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 48H  08/1200Z 23.2N 138.9W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 60H  09/0000Z 23.2N 139.8W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 72H  09/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM HST Mon Oct 05, 2020 

Marie is making one last grasp at holding on to tropical cyclone status. Convection has both deepened and moved closer to the center of the cyclone since the last advisory. Although this convection is still displaced well to the north of Marie’s center, it appears to be sufficient to maintain advisories for the moment. The initial intensity of 40 kt is based on earlier ASCAT data, assuming gradual weakening since then. This assessment may be generous, but we will likely get more scatterometer data before the next advisory.

Despite its recent marginal convective resurgence, Marie is still moving over cold SSTs and through a hostile environment. It is therefore forecast to become a remnant low within 12 h. The aforementioned ASCAT data showed Marie was still producing a wide area of 35 kt or greater winds, and it will take a little while for the large circulation to spin down. Most of the models indicate that Marie will degenerate into a trough of low pressure in about 4 days, and this is reflected in the NHC forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  06/0300Z 21.4N 133.5W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  06/1200Z 21.9N 134.7W   35 KT  40 MPH - Low (WSW Cabo San Lucas, Mexico)
 24H  07/0000Z 22.5N 136.2W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 36H  07/1200Z 22.9N 137.3W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 48H  08/0000Z 23.1N 138.2W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 60H  08/1200Z 23.0N 139.2W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 72H  09/0000Z 22.9N 140.3W   20 KT  25 MPH - Low (ENE Hilo, Hawaii)
 96H  10/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 PM PDT Mon Oct 05, 2020 

Deep convection associated with Maria has all but dissipated and what is left of it has been located over 120 n mi from the exposed the low-level center of the cyclone since around 1400 UTC this morning. A recent ASCAT overpass shows the maximum winds have decreased to 43 kt as of 1800 UTC, and assuming weakening has continued since that time, 40 kt will be the initial advisory intensity.

There are no reasons to believe that the deep convection will redevelop near the center of Marie, as the cyclone is forecast to remain in a hostile environment of 30 plus kt of wind shear, SSTs cooler than 25 degrees C, and a surrounding dry and stable airmass. Therefore, Maria is expected to be declared a remnant low by tonight. The remnant low should gradually spin down and open into a trough by late this week.

Marie continues to move west-northwestward at about 8 kt around a mid-level ridge to its north. A turn to the west-southwest is expected in a couple of days as low- mid-level ridging builds to the northwest of what’s left of the cyclone. The latest NHC track forecast is little changed from the previous one, and is near the various track consensus forecasts.

FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 21.4N 132.7W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  06/0600Z 21.8N 133.8W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)
 24H  06/1800Z 22.5N 135.4W   25 KT  30 MPH - Low (WSW Cabo San Lucas, Mexico)
 36H  07/0600Z 23.0N 136.7W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 48H  07/1800Z 23.4N 137.8W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 60H  08/0600Z 23.3N 138.6W   20 KT  25 MPH - Low (ENE Hilo, Hawaii)
 72H  08/1800Z 23.1N 139.7W   20 KT  25 MPH - Low (ENE Hilo, Hawaii)
 96H  09/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 AM HST Mon Oct 05, 2020

The remains of the deep convection associated with Marie continues to get further displaced from the exposed low-level center due strong upper-level westerly winds, with the gap now over 100 n mi between those two features. The various satellite intensity estimates suggest that the current intensity may only be 45 kt. However, due to fair number of 55-kt wind vectors on the ASCAT overpass early this morning, the intensity is conservatively being lowered to 50 kt for this advisory. Marie is expected to weaken over the next few days in a hostile environment of 30 plus kt of wind shear, over SSTs cooler that 25 degrees C, surrounded by a dry and stable airmass. With the convection now displaced so far from the center, and no regeneration of convection near the center anticipated, Marie is now forecast to become a remnant low by Tuesday night. This could happen even sooner if the current trend continues.

Marie continues to move west-northwestward at about 8 kt around a mid-level ridge to its north. A turn to the west is expected in a couple of days as the cyclone becomes a more shallow system. The latest NHC track forecast is little changed from the previous one, and is near the various track consensus forecasts.

FORECAST POSITIONS AND MAX WINDS

INIT  05/1500Z 21.1N 131.9W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  06/0000Z 21.5N 133.0W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 24H  06/1200Z 22.1N 134.5W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 36H  07/0000Z 22.7N 136.0W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)
 48H  07/1200Z 23.1N 137.1W   30 KT  35 MPH - Low (ENE Hilo, Hawaii)
 60H  08/0000Z 23.3N 138.0W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 72H  08/1200Z 23.3N 138.8W   25 KT  30 MPH - Low (ENE Hilo, Hawaii)
 96H  09/1200Z 22.9N 140.2W   20 KT  25 MPH - Low (ENE Hilo, Hawaii)
120H  10/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM HST Sun Oct 04, 2020 

Marie continues to quickly weaken, and satellite classifications from all agencies indicate that it is now a tropical storm. A blend of those estimates is the basis for the 55 kt initial intensity. Marie is still producing deep convection, mainly to its northeast, but the overall convective pattern is ragged and less organized than it was just 6 hours ago.

Basically no change was made to the NHC track or intensity forecasts. Marie should continue moving generally northwestward for the next several days, and could slow and turn westward once it becomes a shallow remnant low in a few days. Marie remains embedded in a hostile environment, so continued weakening is inevitable. Most dynamical models suggest it will be a remnant low within 60 h, and based on current trends in Marie’s organization, that could be generous. There is disagreement among the models regarding how fast the cyclone will move westward during the middle to late portion of the week, but they all agree it will be a weak remnant low by that time. The NHC track, intensity, and radii forecasts are heavily based on the latest multi-model consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 20.6N 130.1W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 12H  05/1200Z 21.1N 131.2W   45 KT  50 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 24H  06/0000Z 21.7N 132.6W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 36H  06/1200Z 22.4N 134.2W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 48H  07/0000Z 22.9N 135.5W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)
 60H  07/1200Z 23.3N 136.6W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)
 72H  08/0000Z 23.6N 137.4W   30 KT  35 MPH - Low (WSW Hilo, Hawaii)
 96H  09/0000Z 23.7N 139.0W   25 KT  30 MPH - Low (WSW Hilo, Hawaii)
120H  10/0000Z 23.5N 141.0W   20 KT  25 MPH - Low (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 200 PM PDT Sun Oct 04, 2020 

The center of Marie is now totally exposed, well to the south and southwest of a few remaining areas of deep convection. While Marie’s convective pattern resembles a low-end tropical storm, it takes time for systems of Marie’s magnitude to spin down, and the initial intensity of 65 kt is based on a blend of Final-T and CI Dvorak numbers from TAFB. A pair of ASCAT passes near 18Z explicitly showed winds near 55 kt, but it likely under sampled the peak winds of the hurricane’s tight circulation. The ASCAT also showed that Marie’s tropical-storm-force and 50-kt wind radii have not yet contracted very much.

The position of Marie was adjusted a little to the west, and the track forecast has been adjusted in that direction, but is otherwise very similar to the previous advisory for the first 72 h. After that time, the most recent guidance suggests that Marie, then expected to be a remnant low, could turn due west, or even south of due west. This is a pretty big departure from previous solutions, so the NHC forecast has been adjusted in that direction, but not nearly as much as the model consensus. It should be noted that regardless of position, Marie is forecast to be a weak remnant low at 96 and 120 h.

High shear, cool SSTs, and stable surrounding air should cause Marie to continue to quickly weaken for the next few days. Simulated satellite imagery suggests that the system could produce intermittent convection for up to 60 more hours. It isn’t clear how well organized it will be, and given recent trends it is possible Marie will become a remnant low much sooner than currently forecast. The system will likely dissipate sometime near or just after 120 h.

FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 20.3N 129.5W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 12H  05/0600Z 20.7N 130.4W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 24H  05/1800Z 21.4N 131.9W   45 KT  50 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 36H  06/0600Z 22.1N 133.4W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 48H  06/1800Z 22.7N 134.8W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 60H  07/0600Z 23.3N 135.8W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, Mexico)
 72H  07/1800Z 23.7N 136.6W   25 KT  30 MPH - Low (WSW Cabo San Lucas, Mexico)
 96H  08/1800Z 24.0N 138.0W   25 KT  30 MPH - Low (WSW Hilo, Hawaii)
120H  09/1800Z 24.0N 140.0W   20 KT  25 MPH - Low (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 800 AM PDT Sun Oct 04, 2020 

Conventional satellite imagery reveals an increasingly apparent asymmetric/vertical tilt due to persistent west-southwesterly shear. The surface center is beginning to become exposed and is now near the western edge of the deep convective mass. The initial intensity is lowered to 80 kt for this advisory and is based on a compromise of the available subjective and objective satellite intensity estimates. Weakening should continue rather quickly through the forecast period while the shear magnitude increases with time and the cyclone traverses cooler oceanic surface temperatures. Marie should degenerate to a post-tropical remnant low in 3 days, or less, and this is in agreement with the majority of the global/regional and statistical guidance. The intensity forecast is near the IVCN intensity consensus and above the ECMWF and GFS Decay SHIPS which actually show dissipation in less than 4 days.

Maria’s initial motion is estimated to be northwestward, or 315/6 kt, within the mid-tropospheric steering flow provided by a subtropical ridge anchored to the north of the cyclone. Marie should continue moving in either a west-northwestward or northwestward motion through the remainder of forecast period with some reduction in forward speed, day 3 and beyond. The NHC forecast track has been adjusted a little bit south of the previous advisory after the 24 hour period in order to be closer to the various multi-model consensus aids and to conform more with a motion typical of a shallower, vertically limited system moving through the trade wind flow.

ORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 20.3N 128.6W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 12H  05/0000Z 20.7N 129.5W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 24H  05/1200Z 21.3N 131.0W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 36H  06/0000Z 22.0N 132.3W   45 KT  50 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 48H  06/1200Z 22.7N 133.9W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 60H  07/0000Z 23.4N 135.2W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)
 72H  07/1200Z 24.0N 136.0W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)
 96H  08/1200Z 24.8N 136.9W   25 KT  30 MPH - Low (WSW Cabo San Lucas, Mexico)
120H  09/1200Z 25.3N 137.9W   25 KT  30 MPH - Low (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 800 PM PDT Sat Oct 03, 2020 

Marie crossed the 26 degree SST isotherm earlier this evening and the cold waters and accompanying dry,stable air are having a big impact on the storm. Recent microwave imagery shows that the hurricane no longer has an closed eyewall in the southern portion of its inner core. Furthermore, cloud top temperatures have warmed and the hurricane’s eye is barely discernible. A blend of Final-T and CI Dvorak numbers from TAFB is the primary basis for the initial intensity of 100 kt.

Continued rapid weakening is anticipated for the next 36 to 48 h as Marie encounters very hostile environmental conditions. After that time, continued weakening is likely and most of the dynamical models indicate that the cyclone will lose its convection by around day 5, if not a little sooner.

The hurricane is moving northwestward near 7 kt. A ridge extending westward from southwestern U.S. should keep Marie moving generally west-northwestward or northwestward at about the same forward speed for the next several days. Near the end of the forecast period, Marie will likely turn northward ahead of a deep layer trough approaching from the northwest. The spread in the track guidance is quite low, and confidence in the track forecast is fairly high, particularly since almost no change was made to the previous advisory forecast. Both the track and intensity forecasts are based on the multi-model consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  04/0300Z 19.5N 127.9W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 12H  04/1200Z 20.2N 128.8W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 24H  05/0000Z 20.9N 130.0W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 36H  05/1200Z 21.6N 131.3W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 48H  06/0000Z 22.3N 132.5W   45 KT  50 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 60H  06/1200Z 22.9N 133.8W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 72H  07/0000Z 23.7N 135.0W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 96H  08/0000Z 24.7N 136.0W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, Mexico)
120H  09/0000Z 26.0N 136.0W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 200 PM PDT Sat Oct 03, 2020 

Marie is finally beginning to show signs of weakening. Recent GOES-17 infrared satellite imagery indicates cloud tops are warming in the western eyewall, and water vapor imagery shows drier air impinging on the western periphery of the storm. Despite this, there is still deep convection with cloud tops colder than -70 degrees Celsius persisting in the eastern eyewall. The initial intensity is slightly lowered to 110 kt with this advisory based on a blend of TAFB and SAB Dvorak classifications and a 16 UTC SATCON estimate of 114 kt.

Marie is likely beginning to experience increased deep-layer southwesterly wind shear as it moves toward the 26 degree Celsius sea surface temperature isotherm. With environmental conditions becoming increasingly hostile, Marie is expected to steadily, and perhaps rapidly, weaken over the next several days. Marie is forecast to weaken into a tropical storm within 36 hours, as the storm moves over cooler waters and into an environment with 30 kt of vertical wind shear. Steady weakening should continue through early next week, and the system is expected to become a tropical depression by Wednesday and a remnant low on Thursday. Now that the system is finally weakening, the latest NHC intensity forecast reflects a more rapid downward trend supported by the model consensus aids.

Marie’s initial motion is 325/8 kt, slightly more northwestward than the previous advisory. Marie should continue moving northwestward or west-northwestward for the next several days along the southwest periphery of a mid-level ridge centered over the southwestern United States. The latest model guidance remains tightly clustered during the first 2-3 days of the forecast. Then, the bulk of the guidance indicates Marie will slow down and turn more northward late next week ahead of a deep-layer trough to the north of the storm. Given this recurving scenario, there is more significant spread in the guidance at day 4 and beyond, with the GFS still farther to the right than most other models. Overall, the official NHC track forecast has been adjusted slightly right of the previous one in agreement with the TVCE/HCCA aids.

FORECAST POSITIONS AND MAX WINDS

INIT  03/2100Z 19.1N 127.3W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 12H  04/0600Z 19.8N 128.1W   95 KT 110 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 24H  04/1800Z 20.6N 129.1W   75 KT  85 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 36H  05/0600Z 21.3N 130.4W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 48H  05/1800Z 21.9N 131.8W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 60H  06/0600Z 22.5N 133.0W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 72H  06/1800Z 23.0N 134.2W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 96H  07/1800Z 24.0N 135.5W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, Mexico)
120H  08/1800Z 25.5N 136.0W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 800 AM PDT Sat Oct 03, 2020 

Marie shows little signs of weakening this morning as its satellite presentation remains impressive. A closed ring of eyewall convection with cloud top temperatures colder than -65 degrees C surrounds a well-defined 20 nm eye. The initial intensity is maintained at 115 kt based on a T6.0 Dvorak classification from SAB, which is supported by the latest ADT estimates.

Marie is approaching an environment of increasing deep-layer southwesterly shear and SSTs below 26 degrees Celsius, which should induce weakening beginning later today that will continue through early next week. The latest SHIPS guidance indicates the vertical wind shear will strengthen to 30 kt by Mon and continue increasing through the end of the 5-day forecast period. Therefore, Marie is forecast to weaken to a tropical storm by early Monday and a tropical depression by the middle of next week. The NHC intensity forecast is held a bit higher than the model consensus through the first 12-24 hours of the forecast, since Marie has yet to show signs of weakening. As the environmental conditions become increasingly hostile, the official forecast shows more rapid weakening in line with the consensus intensity guidance. By day 5, simulated satellite imagery suggests the system will be a remnant low devoid of deep convection.

Marie’s initial motion is 310/8 kt, and the system is expected to generally continue moving northwestward for the next several days along the southwest periphery of a mid-level ridge. A deep-layer trough is expected to dig north of Marie during the middle of next week, which should begin turning the system more northward toward the end of the 5-day forecast period. A larger spread in the guidance is noted at days 4-5, as it remains somewhat unclear how much the trough will influence the weakening system based on timing differences between the GFS and ECMWF models. Overall, the NHC track forecast remains fairly close to the previous one, with slight changes based on the consensus aids including TVCE and HCCA.

FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 18.4N 126.9W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 12H  04/0000Z 19.1N 127.7W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 24H  04/1200Z 20.0N 128.7W   90 KT 105 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 36H  05/0000Z 20.6N 129.8W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 48H  05/1200Z 21.2N 131.2W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 60H  06/0000Z 21.9N 132.4W   45 KT  50 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 72H  06/1200Z 22.5N 133.7W   40 KT  45 MPH - Tropical Storm WSW Cabo San Lucas, Mexico)
 96H  07/1200Z 23.5N 135.5W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, Mexico)
120H  08/1200Z 24.5N 136.5W   30 KT  35 MPH - Low (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 800 PM PDT Fri Oct 02, 2020 

Although Marie still has an impressive and very symetric appearance, cloud tops associated with the huricane have gradually warmed since this afternoon and its eye became less well-defined for a brief period earlier this evening. The cause of this recent trend is not immediately clear since Marie is still located within a favorable low-shear, high SST environment, and two microwave passses near 00Z (SSMIS and SSMI) did not show any sign of an eyewall replacement cycle. Whatever the reason, it has caused intensity estimates to decrease a little since the last advisory, but not enough to justify lowering the intensity at this time. The intial intensity therefore remains 115 kt for this advisory. With a range of estimates from 90 kt to 127 kt, there is a lot of uncertainty in this assessment.

Although Marie is located in a favorable environment for now, that won’t last much longer. The hurricane is moving toward colder waters and it should begin to experience a large increase in wind shear within the next day or so. The guidance unsurprisingly forecasts that weakening will occur, possibly at a very rapid rate. The NHC forecast is on the high side of the intensity guidance, but still shows Marie becoming a tropical storm within 60 h and a depression by the end of the 5 day period. No changes of note were made to the offficial intensity forecast.

Marie has turned northwestward, and should continue on that general heading for most of the weekend as it moves along the southwest periphary of a mid-level ridge. A slight expansion of the ridge could steer Marie more west-northwestward for a day or two after that. Around day 5, a large deep-layer trough should cause the cyclone to turn nearly northward. While there is considerable spread in the track guidance, limiting confidence in the specifics of the track forecast, every global model forecasts that general evolution. The NHC track forecast is very close to the model consensus and the previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  03/0300Z 17.5N 125.7W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 12H  03/1200Z 18.3N 126.8W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 24H  04/0000Z 19.2N 127.8W   95 KT 110 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 36H  04/1200Z 20.0N 128.8W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 48H  05/0000Z 20.6N 129.9W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 60H  05/1200Z 21.1N 131.4W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 72H  06/0000Z 21.6N 132.7W   45 KT  50 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 96H  07/0000Z 22.5N 134.8W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  08/0000Z 24.0N 136.0W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 200 PM PDT Fri Oct 02, 2020

Marie remains a powerful hurricane this afternoon. A 1530 UTC SSMIS 91 GHz microwave image showed a well-defined, closed eyewall with a 20 nm eye, which is still evident in recent GOES-17 visible and infrared satellite imagery. The initial intensity is held at 115 kt based on T6.0 Dvorak classifications from TAFB and SAB, which are consistent with recent ADT and earlier SATCON estimates. The 34-kt radii are expanded slightly with this package based on recent ASCAT data.

Marie is moving west-northwestward (295 degrees) at 10 kt, around the southwestern periphery of a mid-level ridge centered over the southwestern United States. A break in the ridge should allow Marie to turn northwestward within the next 24 hours and maintain that motion over the next several days. By day 5, an approaching upper-level trough moving across the eastern Pacific Ocean should turn Marie more toward the north-northwest. There is still more noticeable spread in the guidance at days 4 and 5, likely related to differences in the amplitude of the upper-level trough. It is worth noting that the GFS depicts a deeper upper trough, and thus a more drastic northerly turn, than the rest of the global models. Overall, the NHC forecast was again slowed down a bit and shifted slightly to the right to align better with the latest TVCE multi-model consensus and HCCA aids.

Marie is expected to remain in a low-shear environment with sea surface temperatures of 26 degrees Celsius for the next 18-24 hours. Although slight additional strengthening cannot be ruled out, the storm is running out of time before environmental conditions become more hostile. After 24 hours, increasing deep-layer southwesterly shear and cooler waters should support a steady weakening trend through the rest of the forecast period. Marie is expected to fall below hurricane strength by 60 hours and become a tropical depression by day 5. The latest NHC intensity forecast shows a slightly faster weakening trend and remains very close to the IVCN consensus and the HCCA aid.

FORECAST POSITIONS AND MAX WINDS

INIT  02/2100Z 16.9N 125.0W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 12H  03/0600Z 17.6N 126.1W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 24H  03/1800Z 18.6N 127.4W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 36H  04/0600Z 19.5N 128.4W   90 KT 105 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 48H  04/1800Z 20.1N 129.5W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 60H  05/0600Z 20.6N 130.8W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 72H  05/1800Z 21.2N 132.1W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 96H  06/1800Z 22.0N 134.5W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  07/1800Z 23.5N 136.0W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 800 AM PDT Fri Oct 02, 2020 

Marie’s structure has not changed significantly since the previous advisory. A recent AMSR microwave image showed that the hurricane continues to have a closed eyewall that is a little thin on the southeast side, but there are no clear indications that an eyewall replacement is occuring. Dvorak final-T numbers from TAFB and SAB diverged from 6 hours ago, with TAFB’s going up to T6.5 and SAB’s falling to T5.5. In addition, final-T numbers from the objective ADT scheme have decreased since six hours ago. Because of the estimate discrepancies, the initial intensity is being held at 115 kt.

Marie is moving west-northwestward (290 degrees) at 12 kt, just a little to the left of and slower than the previous motion estimate. A large mid-tropospheric high centered over the southwestern United States continues to be the main driver of Marie’s motion, but the hurricane should begin to reach a break in the ridge and turn toward the northwest in the next 24 hours. After that time, a general motion toward the northwest or west-northwest should continue through the end of the forecast period. The spread in the guidance does increase a bit by days 4 and 5, which appears to be related to the depth of the cyclone and how it interacts with the steering flow. Overall, though, the guidance envelope has not shifted, and the NHC forecast was only slowed down a bit to be more in line with the latest TVCE multi-model consensus and HCCA aid.

Marie should remain in a low-shear environment and over waters warmer than 26 degrees Celsius for the next 24 hours, during which time some additional strengthening is possible. Any intensification could be thwarted by an eyewall replacement, but as stated above, that does not appear to be occuring at this time. Increasing deep-layer southwesterly shear and cooler waters should induce a definitive weakening trend after 24 hours, with Marie falling below hurricane strength by day 3, and then becoming a tropical depression by day 5. The NHC intensity forecast has been adjusted downward a bit during the weakening phase and lies near or just above the IVCN intensity consensus and the HCCA aid.

FORECAST POSITIONS AND MAX WINDS

INIT  02/1500Z 16.5N 124.3W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 12H  03/0000Z 17.2N 125.7W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 24H  03/1200Z 18.3N 127.1W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 36H  04/0000Z 19.3N 128.3W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 48H  04/1200Z 20.0N 129.4W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 60H  05/0000Z 20.6N 130.7W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 72H  05/1200Z 21.0N 132.1W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
 96H  06/1200Z 22.0N 135.0W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  07/1200Z 23.5N 137.0W   30 KT  35 MPH - Depression (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 800 PM PDT Thu Oct 01, 2020 

Marie is still strengthening this evening. Satellite images indicate that the hurricane has a well-defined compact eye with a ring of cold cloud tops surrounding that feature. The Dvorak classifications at 0000Z were T5.5/102 kt from both TAFB and SAB, but since the cyclone has continued to strengthen, the initial intensity is increased to 110 kt. This value is below the latest Dvorak ADT numbers that are currently around 6.2/120 kt. Marie has strengthened at an impressive rate of 45 kt over the past 24 hours.

Satellite fixes indicate that the hurricane is moving fairly quickly to the west-northwest on the south side of a mid-level ridge, with the latest initial motion estimated to be 285/13 kt. The system is expected to move slower to the west-northwest or northwest during the next several days as it nears the western periphery of the ridge and moves toward a broad trough well off the California coast. The models are in fair agreement in the short term, but there is a notable amount of spread in the guidance in 4 to 5 days, likely due to differences in the vertical depth of Marie and how much the trough influences its steering. The NHC track forecast remains near the consensus aids, and is largely an update of the previous one.

The major hurricane will likely continue to strengthen during the next 12 to 24 hours while it remains in quite favorable conditions of low vertical wind shear, a moist air mass, and over warm 28-29 C SSTs. It should be noted that eyewall replacement cycles could occur during that time, which might cause fluctuations in the cyclone’s strength. By Saturday, Marie is expected to level off in intensity and then rapidly weaken when the hurricane crosses the 26-deg-C SST isotherm and moves into an environment of increasing west-southwesterly shear and drier air. The NHC intensity forecast remains above the guidance in the short term, but falls in line with the bulk of the models beyond 36 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  02/0300Z 15.6N 122.1W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 12H  02/1200Z 16.3N 123.9W  125 KT 145 MPH - Category 4 (WSW Acapulco, Mexico)
 24H  03/0000Z 17.3N 125.9W  125 KT 145 MPH - Category 4 (WSW Acapulco, Mexico)
 36H  03/1200Z 18.4N 127.4W  115 KT 130 MPH - Category 3 (WSW Acapulco, Mexico)
 48H  04/0000Z 19.4N 128.7W   95 KT 110 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 60H  04/1200Z 20.2N 130.0W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 72H  05/0000Z 20.8N 131.5W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 96H  06/0000Z 22.0N 134.4W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  07/0000Z 23.4N 136.4W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 200 PM PDT Thu Oct 01, 2020 

An eye has formed in visible and infrared satellite imagery since the issuance of the previous advisory, and the surrounding convection continues to have cold cloud tops (as cold as -83C). The width of the coldest tops were a little thin on the southwest side at 1800 UTC, and because of this, subjective and objective intensity estimates were still 90 kt. Since that time, the eye has become more distinct and the convection is becoming more symmetric around the eye, and the initial intensity is therefore set at 95 kt. Marie’s initial position has been adjusted to the south just a bit now that the center is more apparent with the eye formation. This yields a current westward motion of 280/14 kt.

The atmospheric features responsible for steering Marie during the forecast period will be a mid-tropospheric ridge centered over the southwestern United States and a mid- to upper-level low located to the west over the Pacific. The interplay between these features is likely to cause some wiggles in Marie’s future track, but for the most part the hurricane will be moving west-northwestward or northwestward through day 5. The spread in the guidance increases toward the end of the forecast period, with the GFS turning more northward and the ECMWF maintaining a west-northwestward motion. The other deterministic models are in between these two solutions, clustered very close to the various multi-model consensus aids, and that is where the NHC forecast also lies for this advisory.

The environment appears conducive for this phase of rapid intensification to continue, at least for the next 24 hours. Deep-layer shear is just about to decrease to 10 kt or less, and Marie will remain over waters of high ocean heat content for the next 24-36 hours. The intensity guidance decreased a bit on this cycle, which seems odd given the ongoing intensification trend and the favorable environmental conditions. The SHIPS model does still show that the chance for rapid intensification to continue is 3 to 5 times higher than the climatological mean, and therefore the NHC intensity forecast maintains continuity from the previous advisory, showing a peak intensity of 120 kt. This forecast is above the highest intensity models by about 10-15 kt. Weakening is still anticipated, particularly after 48 hours, due to Marie moving over cooler waters and being affected by increasing southwesterly shear.

FORECAST POSITIONS AND MAX WINDS

INIT  01/2100Z 15.1N 120.9W   95 KT 110 MPH - Category 2 (WSW Acapulco, Mexico)
 12H  02/0600Z 15.8N 122.8W  115 KT 130 MPH - Category 3 (WSW Acapulco, Mexico)
 24H  02/1800Z 16.7N 125.0W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 36H  03/0600Z 17.8N 126.8W  115 KT 130 MPH - Category 3 (WSW Acapulco, Mexico)
 48H  03/1800Z 18.8N 128.2W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 60H  04/0600Z 19.7N 129.4W   85 KT 100 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 72H  04/1800Z 20.3N 130.9W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 96H  05/1800Z 21.4N 133.9W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  06/1800Z 23.0N 136.3W   35 KT  40 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 800 AM PDT Thu Oct 01, 2020 

Marie has continued to become better organized this morning. An AMSR image from just after 09Z showed a closed mid-level eyewall, and conventional satellite imagery shows an increasingly symmetric cloud pattern with very cold cloud tops, colder than -80C, around the center. The current intensity estimate is set at 90 kt in agreement with Dvorak classifications from both TAFB and SAB. Marie is moving over SSTs warmer than 28 deg C and in a moist, low-shear atmospheric environment. The SHIPS guidance still shows a significant probability of rapid intensification through tonight, so Marie is likely to become a major hurricane quite soon. The official forecast is a little above the latest corrected model consensus. In a couple of days, the hurricane should be crossing the SST gradient and encountering cooler waters, so a weakening trend is anticipated to be underway within 48 hours.

The estimated initial motion is west-northwestward, or 285/15 kt. For the next couple of days, Marie should continue to move along the southern periphery of a mid-tropospheric ridge associated with a high pressure system centered over California. A slight turn to the right with some deceleration is expected during the forecast period due to a weakness in the ridge near 130W longitude. By the end of the period, Marie is likely to turn toward the northwest while it moves through this weakness. The official track forecast lies very close to the latest multi-model consensus, TVCE, prediction.

FORECAST POSITIONS AND MAX WINDS

INIT  01/1500Z 15.2N 119.5W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 12H  02/0000Z 15.9N 121.7W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 24H  02/1200Z 16.8N 124.1W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 36H  03/0000Z 17.8N 126.2W  120 KT 140 MPH - Category 4 (WSW Acapulco, Mexico)
 48H  03/1200Z 18.8N 127.9W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 60H  04/0000Z 19.6N 129.3W   90 KT 105 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
 72H  04/1200Z 20.4N 130.7W   75 KT  85 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
 96H  05/1200Z 21.7N 133.7W   60 KT  70 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)
120H  06/1200Z 23.8N 136.2W   40 KT  45 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 200 PM PDT Wed Sep 30, 2020 

Marie has continued to become better organized today, with a well-defined convective band that wraps more than completely around the cloud system center. This yields a Dvorak intensity estimate of at least 65 kt, and subjective and objective T-numbers from SAB and UW-CIMSS respectively also correspond to an intensity of 65 kt. Therefore, the system is being upgraded to a hurricane, which is the first for the month of September in this relatively quiet eastern North Pacific hurricane season.

The vertical wind shear has decreased and is forecast to remain low for the next few days. This, combined with a moist low- to mid-tropospheric air mass and warm sea surface temperatures, should lead to an environment that is very conducive for strengthening. In fact, the SHIPS RI Index shows a significant probability of rapid intensification over the next 24 hours. Therefore, the official forecast calls for Marie to become a major hurricane tomorrow with additional strengthening during the succeeding day. This is close to the predictions from the two corrected consensus techniques, HCCA and FSSE. By 72 hours, Marie should have begun passing over progressively cooler waters, so a steady weakening trend is likely to be underway by that time.

The motion continues just north of due west, or 275/14 kt. The track forecast reasoning hasn’t changed much from the previous advisories. Over the next few days, the hurricane should be steered on a westward to west-northwestward course on the south side of a mid-level subtropical ridge. Right around the end of the forecast period, Marie should begin to turn more to the right in response to a weakness in the ridge. The official track forecast is similar to the previous one and lies between the simple and corrected dynamical consensus predictions.

FORECAST POSITIONS AND MAX WINDS

INIT  30/2100Z 14.3N 115.1W   65 KT  75 MPH - Category 1 (WSW Acapulco, Mexico)
 12H  01/0600Z 14.4N 117.3W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 24H  01/1800Z 14.8N 120.0W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 36H  02/0600Z 15.6N 122.5W  115 KT 130 MPH - Category 4 (WSW Acapulco, Mexico)
 48H  02/1800Z 16.6N 124.7W  120 KT 140 MPH - Category 4 (WSW Manzanillo, Mexico)
 60H  03/0600Z 17.7N 126.7W  120 KT 140 MPH - Category 4 (WSW Manzanillo, Mexico)
 72H  03/1800Z 18.6N 128.4W  100 KT 115 MPH - Category 3 (WSW Cabo San Lucas, Mexico)
 96H  04/1800Z 20.3N 131.4W   70 KT  80 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
120H  05/1800Z 21.8N 134.0W   50 KT  60 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 900 AM MDT Wed Sep 30, 2020 

Marie’s satellite presentation has been gradually improving. The center is embedded beneath a central dense overcast feature, and the convective band within the western semicircle has become a little more pronounced and continuous. In addition, a mid-level eye has begun to form, as observed in a 1200 UTC SSMIS microwave pass. Dvorak intensity estimates range from 45-55 kt from TAFB and SAB, and the most recent SATCON estimate was 53 kt (at around 0900 UTC). Based on these numbers and the continued improvement of Marie’s structure, the initial intensity is set at 55 kt.

The stage appears set for Marie to rapidly intensify during the next couple of days. Water vapor imagery indicates that the easterly shear over the cyclone has continued to decrease and should be generally low for the next 3 days, and upper-level divergence will also be in place during that period to help ventilate the storm. The thermodynamics are also favorable for fast strengthening, highlighted by sea surface temperatures of 28-29 degrees Celsius and plenty of moisture in the surrounding environment. Due to these conditions, the NHC forecast explicitly shows rapid intensification during the next couple of days, with a peak intensity likely occuring sometime between 48 and 60 hours. The peak intensity shown in the official forecast has been nudged upward slightly from the previous prediction, following the trends in the intensity guidance, however it’s noteworthy that even this forecast is 5-10 kt lower than the solutions provided by the HCCA consensus aid and the COAMPS-TC model. In about 3 days, cooler waters and then increasing shear (especially on days 4 and 5) should induce a gradual weakening trend.

Marie is moving westward (275/14 kt) to the south of a strong mid-tropospheric high centered near the U.S./Mexico border. This ridge is expected to maintain Marie on a westward or west-northwestward trajectory for the next 2-3 days. Even though a mid- to upper-level low near 130W longitude has caused a break in the ridge, the models have trended toward this feature weakening during the next few days. This has in turn caused many of the models to trend westward with Marie’s track after day 3, as was noted in the previous advisory, but there is also greater spread than there was yesterday. The NHC track forecast remains closest to the TVCE and HCCA consensus aids, near the middle of the guidance envelope, which is bracketed on the right side by the GFS (and its ensemble mean) and the left side by the ECMWF (and its ensemble mean) by the end of the forecast period.

The 12-ft sea radii remain larger than would be expected for a tropical storm of Marie’s size due to a large fetch of southerly swell originating from the Southern Hemisphere.

FORECAST POSITIONS AND MAX WINDS

INIT  30/1500Z 14.2N 113.8W   55 KT  65 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  01/0000Z 14.3N 116.1W   65 KT  75 MPH - Category 1 (WSW Acapulco, Mexico)
 24H  01/1200Z 14.5N 118.9W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
 36H  02/0000Z 15.1N 121.5W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 48H  02/1200Z 15.9N 123.9W  110 KT 125 MPH - Category 3 (WSW Acapulco, Mexico)
 60H  03/0000Z 16.9N 125.9W  115 KT 130 MPH - Category $ (WSW Acapulco, Mexico)
 72H  03/1200Z 18.0N 127.6W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 96H  04/1200Z 19.8N 130.7W   75 KT  85 MPH - Category 1 (WSW Acapulco, Mexico)
120H  05/1200Z 21.1N 133.4W   55 KT  65 MPH - Tropical Storm (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 900 PM MDT Tue Sep 29, 2020

Infrared and passive microwave imagery indicate that Marie has continued to become better organized despite moderate northeasterly vertical wind shear of about 15 kt. The deep convection is now primarily confined to a single tightly curved band that wraps around the west side of the circulation. A late-arriving 29/1718Z ASCAT-C scatterometer pass revealed that Marie has a very tight inner-core circulation with a radius of maximum winds (RMW) of only 10-15 nmi and a small 34-kt wind radii extending outward to only about 20 nmi The scatterometer data also showed some 34-38 kt surface wind vectors in all quadrants.

A blend of the scatterometer wind data and subjective Dvorak intensity estimates of of T2.5/35 kt and T3.0/45 kt from SAB and TAFB, respectively, the intensity has been increased to 40 kt. The initial motion estimate is 275/11 kt. As mentioned in the previous discussion, Marie’s forecast track remains fairly straightforward. The cyclone is expected to move generally westward to west-northwestward for the next few days as it skirts the southern periphery of a deep-layer ridge to the north. Thereafter, a slower motion toward the northwest is forecast as Marie moves into a weakness in the ridge. The new NHC track forecast is similar to but a little to the left of the previous advisory track, and lies down the middle of the tightly packed consensus track model guidance envelope.

Although the GFS- and ECMWF-based SHIPS intensity models have backed off significantly on predicting rapid intensification (RI) on this cycle, several environmental and cyclone structural parameters are still favorable for RI to occur. For about the next 72 hours, sea-surface temperatures (SST) are forecast to remain above 28C, alone with mid-level humidity values above 70 prevent and low wind shear values around 5 kt. Those environmental conditions coupled with Marie’s small RMW should result in RI beginning in about 24 hours and continuing until the 60-h time period. As result, Marie is forecast to strengthen into a hurricane in about 24 hours and possibly become a major hurricane in 60-72 hours. Rapid weakening is expected on days 4 and 5 due to SSTs less than 26C, likely significant cold upwelling owing to Marie’s expected large and strong wind field, and increasing southwesterly vertical shear of 20-25 kt. The NHC official intensity forecast is similar to the previous advisory, and closely follows a blend of the Decay-SHIPS and LGEM statistical models and the corrected-consensus HCCA model.

Marie’s 12-ft sea radii remain larger than would be expected for a small tropical storm due to a large fetch of southerly swell originating from the Southern Hemisphere.

FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z 13.8N 110.4W   40 KT  45 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  30/1200Z 14.1N 112.9W   50 KT  60 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  01/0000Z 14.6N 115.9W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 36H  01/1200Z 15.0N 118.8W   75 KT  85 MPH - Category 1 (WSW Acapulco, Mexico)
 48H  02/0000Z 15.5N 121.4W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 60H  02/1200Z 16.5N 123.8W  105 KT 120 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  03/0000Z 17.6N 125.9W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 96H  04/0000Z 19.8N 129.3W   80 KT  90 MPH - Category 1 (WSW Cabo San Lucas, Mexico)
120H  05/0000Z 21.4N 132.1W   60 KT  70 MPH - Category 1 (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 300 PM MDT Tue Sep 29, 2020 

A WindSat microwave image from earlier this morning indicated that the tropical cyclone’s low-level circulation was becoming better defined, with perhaps the formative stage of a cyan ring seen in the 37-GHz channel. Visible images also show the center tucked just beneath recent bursts of deep convection, and Dvorak estimates have risen to T2.0 and T2.5 from TAFB and SAB, respectively. These data, along with ambiguity analyses of recent ASCAT-B and -C scatterometer passes, indicate the depression has strengthened to Tropical Storm Marie with maximum winds of 35 kt. Marie’s future track is probably the most straightforward part of the forecast. A mid-tropospheric high anchored over the southwestern United States is steering Marie westward with an initial motion of 275/10 kt. This high will remain the main driver, forcing the cyclone westward or west-northwestward for the next 3 days. By days 4 and 5, Marie is likely to reach a break in the ridge and should slow down a bit and turn toward the northwest. There are no notable outliers among the track guidance, and the small spread among the models yields higher-than-normal confidence in the track forecast. The new NHC forecast is very similar to the previous prediction, and is close to the TVCE and HCCA consensus aids.

The intensity forecast is a little more challenging, but mostly because a good proportion of the guidance suggests that Marie will intensify significantly during the next few days. Relatively low deep-layer shear, warm ocean waters, and favorable upper-level divergence all favor strengthening, and several of the various SHIPS Rapid Intensification thresholds are several times higher than their climatological means. In addition, all of the dynamical models, the consensus aids, and the GFS-based SHIPS model bring Marie to hurricane strength within 24 hours. Given these signals, the NHC intensity forecast has been raised from the previous one and lies near or just below the intensity consensus in order to maintain some continuity. But given what is shown by some of the better-performing intensity models, I would not be surprised if subsequent forecasts show a faster rate of intensification or a higher peak intensity. Weakening is expected by days 4 and 5 due to cooler waters and increasing southwesterly shear.

Marie’s 12-ft sea radii are larger than would be expected for a small, just-developing tropical storm due to a large fetch of southerly swell originating from the Southern Hemisphere.

FORECAST POSITIONS AND MAX WINDS

INIT  29/2100Z 13.6N 109.5W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, Mexico)
 12H  30/0600Z 13.9N 111.6W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  30/1800Z 14.6N 114.5W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 36H  01/0600Z 14.9N 117.5W   75 KT  85 MPH - Category 1 (WSW Acapulco, Mexico)
 48H  01/1800Z 15.3N 120.3W   90 KT 105 MPH - Category 2 (WSW Acapulco, Mexico)
 60H  02/0600Z 16.0N 122.7W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 72H  02/1800Z 17.2N 124.9W  100 KT 115 MPH - Category 3 (WSW Acapulco, Mexico)
 96H  03/1800Z 19.6N 128.5W   85 KT 100 MPH - Category 2 (WSW Acapulco, Mexico)
120H  04/1800Z 21.4N 131.6W   60 KT  70 MPH - Tropical Storm (ENE Hilo, Hawaii)

NWS National Hurricane Center Miami FL  900 AM MDT Tue Sep 29, 2020

The tropical cyclone is gradually becoming better organized, with a Central Dense Overcast feature developing near/over the estimated center. The system is experiencing moderate east-northeasterly shear which is currently restricting upper-level outflow over the eastern semicircle of the system. Dvorak classifications from TAFB and SAB indicate that the cyclone’s maximum winds are near 30 kt. The dynamical guidance indicates that the shear will soon diminish, and the atmospheric and oceanic environment is expected to be quite conducive for strengthening during the next few days. The official forecast shows steady intensification with the system becoming a tropical storm by tonight and a hurricane within 72 hours. This is a little below the latest intensity model consensus, which suggests that that the cyclone could be near major hurricane status in about 72 hours.

The center is not easy to locate at this time, so the initial motion estimate of 280/9 kt is more uncertain than usual. A strengthening subtropical ridge to the north of the tropical cyclone should maintain a westward or west-northwestward motion at an increased forward speed for the next 72 hours or so. In 4-5 days, a weakness in the ridge in the vicinity of 130W longitude should cause the system to turn toward the northwest. The official track forecast is a little north and northeast of the latest model consensus.

The dynamical guidance shows an expanding wind field with the tropical cyclone, and the official wind radii forecasts, especially beyond 2 days, are in close agreement with the consensus wind radii forecast technique, RVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 13.3N 108.5W   30 KT  35 MPH - Depression (WSW Acapulco, Mexico)
 12H  30/0000Z 13.8N 110.4W   35 KT  40 MPH - Tropical Storm (WSW Acapulco, Mexico)
 24H  30/1200Z 14.4N 113.2W   45 KT  50 MPH - Tropical Storm (WSW Acapulco, Mexico)
 36H  01/0000Z 14.6N 116.2W   60 KT  70 MPH - Tropical Storm (WSW Acapulco, Mexico)
 48H  01/1200Z 14.7N 119.0W   70 KT  80 MPH - Category 1 (WSW Acapulco, Mexico)
 60H  02/0000Z 15.4N 121.7W   80 KT  90 MPH - Category 1 (WSW Acapulco, Mexico)
 72H  02/1200Z 16.4N 124.0W   90 KT 105 MPH - Category 2 (WSW Manzanillo, Mexico)
 96H  03/1200Z 18.9N 127.6W   85 KT 100 MPH - Category 2 (WSW Cabo San Lucas, Mexico)
120H  04/1200Z 21.0N 130.5W   65 KT  75 MPH - Category 1 (WSW Cabo San Lucas, Mexico)

NWS National Hurricane Center Miami FL 1100 AM PDT Mon Sep 28, 2020

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

  • 1. Showers and thunderstorms associated with an area of low pressure located a few hundred miles south of the southwestern coast of Mexico have increased during the past few hours and have recently begun to show signs of organization. Additional development is expected and a tropical depression will likely form during the next couple of days. The disturbance is forecast to move generally westward for the next several days and then turn west-northwestward by the weekend. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Mon Sep 28, 2020

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

  • 1. A broad area of disturbed weather is located a few hundred miles south of the southwestern coast of Mexico. Shower and thunderstorm activity associated with a small low embedded within this area has decreased since yesterday. However, environmental conditions are expected to gradually become more conducive for development and a tropical depression will likely form within the next two or three days. The disturbance is forecast to move generally westward for the next several days and then turn west-northwestward by the weekend. * Formation chance through 48 hours…high…70 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sun Sep 27, 2020

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

  • 1. A well-defined low-pressure system located a few hundred miles south of the southwestern coast of Mexico is producing a large area of disorganized cloudiness and thunderstorms. The disturbance is forecast to move generally westward for the next several days, and environmental conditions are expected to gradually become more conducive for a tropical depression to form around midweek. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sun Sep 27, 2020

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

  • 1. A small area of low pressure has formed within an elongated region of disturbed weather, a few hundred miles south of the southwestern coast of Mexico. This system is expected to move generally westward for the next day or two, and it could interact with a westward-moving tropical wave during that time. Environmental conditions are expected to support at least gradual development during the next several days and a tropical depression is likely to form later this week. The system is forecast to turn west-northwestward by mid-week and will likely continue moving in that general direction through the end of the week. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Sep 27, 2020

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

  • 1. An area of low pressure is expected to form well south or southwest of the southwestern coast of Mexico in a day or two. Some gradual development is expected thereafter and a tropical depression is likely to form by the end of the week while the system moves generally west-northwestward farther from land. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Sat Sep 26, 2020

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

  • 1. An area of low pressure is expected to form well south or southwest of the southwestern coast of Mexico in two or three days. Some gradual development will be possible thereafter and a tropical depression could form by late next week while the system moves generally west-northwestward farther from land. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…60 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sat Sep 26, 2020

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

  • 1. An area of low pressure is expected to form well south or southwest of the southwestern coast of Mexico in two or three days. Some gradual development will be possible thereafter and a tropical depression could form by late next week while the system moves generally west-northwestward farther from land. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Sat Sep 26, 2020

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

  • 1. An area of low pressure is expected to form well south or southwest of the southwestern coast of Mexico in two or three days. Some gradual development will be possible thereafter and a tropical depression could form by late next week while the system moves generally west-northwestward farther from land. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Sep 26, 2020

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

  • 1. An area of low pressure is expected to form well south or southwest of the southwestern coast of Mexico in a few days. Some gradual development will be possible thereafter and a tropical depression could form by late next week while the system moves generally west-northwestward farther from land. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…50 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Fri Sep 25, 2020

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

  • 1. An area of low pressure is expected to form south or southwest of the southwestern coast of Mexico in a few days. Some gradual development will be possible through the middle of next week and a tropical depression could form while the system moves generally west-northwestward, well off the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Fri Sep 25, 2020

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

The National Hurricane Center has issued the last advisory on Post-Tropical Cyclone Lowell, located about 1300 miles west of the southern tip of the Baja California peninsula.

  • 1. An area of low pressure is expected to form south or southwest of the southwestern coast of Mexico in a few days. Some gradual development will be possible through the middle of next week and a tropical depression could form while the system moves generally west-northwestward, well off the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium...40 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Sep 25, 2020

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

The National Hurricane Center is issuing advisories on Tropical Storm Lowell, located more than 1000 miles west of the southern tip of the Baja California peninsula.

  • 1. An area of low pressure is expected to form south or southwest of the southwestern coast of Mexico in a few days. Some gradual development will be possible through the middle of next week and a tropical depression could form while the system moves generally west-northwestward, well off the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Fri Sep 25, 2020

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

The National Hurricane Center is issuing advisories on Tropical Storm Lowell, located more than 1000 miles west of the southern tip of the Baja California peninsula.

  • 1. An area of low pressure is expected to form south or southwest of the southwestern coast of Mexico in a few days. Some gradual development will be possible through the middle of next week and a tropical depression could form while the system moves generally west-northwestward, well off the coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…40 percent.

NWS National Hurricane Center Miami FL 1100 PM PDT Thu Sep 24, 2020

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

The National Hurricane Center is issuing advisories on Tropical Storm Lowell, located about 1100 miles west of the southern tip of the Baja California peninsula.

  • 1. An area of low pressure is expected to form south or southwest of the southwestern coast of Mexico early next week. Some gradual development will be possible thereafter while the system moves generally west-northwestward. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low...30 percent.

If this storm system is named, it will be named Tropical Storm Marie.

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