Tropical Storm Guillermo

Post Tropical Storm Guillermo Track 1400 Hours July 20 2021
Post Tropical Storm Guillermo Track 1400 Hours July 20 2021

Tropical Storm Guillermo Wind Speed FieldTropical Storm Guillermo NWS National Hurricane Center Miami FL 200 PM PDT Tue Jul 20, 2021 (See Tuesday 5:00 pm video below)

Guillermo’s circulation consists of a tight swirl of low-level clouds, and the earlier brief convective flare up dissipated shortly after the release of the previous advisory. Given that the system has been devoid of organized deep convection for most of the last 18 hours, the system is now considered a remnant low and this will be the last NHC advisory. The initial intensity remains 30 kt based on a recent ASCAT pass that showed an area of 25-30 kt winds north of the center.

The post-tropical cyclone will remain in an dry, stable airmass while moving over SSTs of 24-25C, which should result in a gradual spin down of the circulation. Global model fields indicate that the low will open up into a trough within 48-60 hours, and that is indicated in the official forecast.

The remnant low is now moving a little south of due west, with an initial motion estimate of 265/15. The system is expected to move west-southwestward until dissipation under the influence of the expansive low-level ridge centered over the north-central Pacific. The new NHC track forecast is a little south of and faster than the previous one, trending toward the latest consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 18.7N 126.5W   30 KT  35 MPH - Post Tropical(WSW Hilo, Hawaii)
 12H  21/0600Z 18.2N 128.9W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 24H  21/1800Z 17.5N 131.8W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 36H  22/0600Z 16.8N 134.5W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 48H  22/1800Z 16.1N 137.0W   20 KT  25 MPH - Post Tropical(WSW Hilo, Hawaii)
 60H  23/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 AM PDT Tue Jul 20, 2021

A small burst of convection formed around 12Z, and it’s just large enough to hold on to Guillermo as a 30-kt tropical depression. This small area of convection is located in the northeastern quadrant, and it likely won’t last long as the cyclone remains embedded in a very dry and stable air mass and over cool 24 C waters. Guillermo should degenerate into a remnant low later today, assuming the deep convection dissipates. The continued influences of dry air and cool waters should cause the weak system to spin down, and it should ultimately dissipate in a few days prior to reaching the Central Pacific basin.

The tropical depression is moving westward at 15 kt. A general west-southwestward motion is expected during the next few days as Guillermo, or its remnants, remains embedded in the flow on the south side of a low- to mid-level ridge. The NHC track forecast is just a tad to the north of the previous one and lies near the middle of the guidance envelope.

FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 19.2N 125.0W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX
 12H  21/0000Z 18.8N 127.2W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 24H  21/1200Z 18.2N 130.2W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 36H  22/0000Z 17.5N 132.9W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 48H  22/1200Z 16.9N 135.6W   20 KT  25 MPH - Post Tropical(WSW Hilo, Hawaii)
 60H  23/0000Z 16.4N 138.1W   20 KT  25 MPH - Post Tropical(WSW Hilo, Hawaii)
 72H  23/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 800 PM PDT Mon Jul 19, 2021

Sub-25C waters, dry and stable air, and moderate west-southwesterly shear have taken their toll on Guillermo. The depression has now been devoid of organized deep convection for several hours and mainly consists of a swirl of low- to mid-level clouds. A blend of the latest Dvorak intensity estimates from TAFB, SAB, and the UW-CIMSS ADT indicate that the initial intensity remains 30 kt. The path of the depression should keep it over waters of around 23-24C over the next few days. This combined with the other negative environmental factors should continue to prevent any long-lived deep convection from redeveloping. Therefore, Guillermo is now forecast to become a remnant low on Tuesday. Thereafter, the weakening vortex should open up into a trough within a few days.

Guillermo is now moving a little faster, with a 12-h motion of 270/16 kt as it has become embedded within the easterly flow on the south side of a low- to mid-level subtropical ridge. This ridge is forecast to remain in place for several days, which should keep the depression on a west, or just south-of-west trajectory for the remainder of its existence. The official track forecast is near the previous one through 24 h, and then was nudged slightly to the south beyond 24 h due to a southward shift in the overall track guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  20/0300Z 19.3N 122.0W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 12H  20/1200Z 19.0N 124.5W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 24H  21/0000Z 18.5N 127.4W   25 KT  30 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 36H  21/1200Z 18.0N 130.4W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 48H  22/0000Z 17.6N 132.9W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 60H  22/1200Z 17.3N 135.5W   20 KT  25 MPH - Post Tropical(WSW Hilo, Hawaii)
 72H  23/0000Z 17.0N 138.0W   20 KT  25 MPH - Post Tropical(WSW Hilo, Hawaii)
 96H  24/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 200 PM PDT Mon Jul 19, 2021

Guillermo is now producing a small shapeless area of convection about 70 miles to the southeast of the center, but otherwise, the cyclone consists mainly of a swirl of low clouds. A recent METOP-A scatterometer pass showed an area 25-30 kt winds well north (about 90 miles) of the center. Based on this data, the initial intensity is lowered to 30 kt. With the combined negative contributions of cool sub 25C oceanic temperatures, stiff west-northwesterly shear and entrainment of high statically stable marine-layer air, Guillermo should degenerate to a remnant low by Wednesday night, if not sooner. The large-scale models and the statistical intensity guidance show the cyclone opening up into a trough of low pressure by day 4, and the NHC forecast follows suit.

The depression has increased in forward speed to 15 kt, while moving westward in the fresh tradewind steering flow. A continued westward motion on the south side of a low- to mid-level subtropical ridge at about the same aforementioned speed is forecast during the entire period. The official track forecast is close to the middle of the model guidance envelope and a little to the left of the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 19.3N 119.8W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 12H  20/0600Z 19.2N 122.3W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 24H  20/1800Z 18.8N 125.4W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 36H  21/0600Z 18.4N 128.4W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 48H  21/1800Z 18.1N 131.4W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 60H  22/0600Z 17.8N 133.8W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 72H  22/1800Z 17.6N 136.4W   20 KT  25 MPH - Post Tropical(WSW Hilo, Hawaii)
 96H  23/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL  500 AM HST Mon Jul 19, 2021 

Guillermo’s satellite presentation has continued to deteriorate over the past several hours, although a new, small deep convective burst has developed just to the southeast of the circulation center. An earlier AMSR2 microwave overpass revealed a rather elongated (west to east) and ill-defined circulation with fragmented bands in the southeast quadrant. The initial intensity is lowered to 35 kt and is based on a blend of the TAFB and SAB Dvorak satellite intensity estimates.

Guillermo is moving over cooler (about 25C) water and into a progressively more stable and drier surrounding environment. The statistical-dynamical SHIPS models (GFS/ECMWF) indicate that moderate west-northwesterly shear should also contribute to the cyclone’s degeneration to a remnant low on Wednesday night. The intensity forecast now shows Guillermo becoming a remnant low sooner than the previous advisory and conforms with a consensus of the large-scale models and the SHIPS forecasts.

The initial motion is estimated to be westward, or 275/13 kt. A subtropical ridge anchored to the north of the cyclone should influence a generally westward motion through dissipation at day 5. A few of the global models are now showing the lower levels of the ridge building some to the east-northeast of the Hawaiian Islands which could induce a west-southwestward motion, or slightly left of due west, around mid-period. The NHC forecast is once again adjusted a bit to the left of the previous one and is based on the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z 19.1N 117.8W   35 KT  40 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 12H  20/0000Z 19.0N 119.9W   35 KT  40 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 24H  20/1200Z 18.9N 123.0W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 36H  21/0000Z 18.6N 126.1W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  21/1200Z 18.3N 128.9W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 60H  22/0000Z 18.1N 131.4W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 72H  22/1200Z 17.9N 134.1W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
 96H  23/1200Z 17.9N 139.6W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)
120H  24/1200Z 17.9N 145.6W   25 KT  30 MPH - Post Tropical(WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 500 PM HST Sun Jul 18, 2021 

Guillermo’s convective pattern has eroded significantly since the previous advisory due to northwesterly vertical wind shear and entrainment of drier and cooler air. Earlier ASCAT showed the system was a solid 50-kt tropical cyclone, thus, only slight weakening is indicated on this advisory to allow for some spin down of the vortex. Deep convection will likely return near the center later tonight during the nocturnal convective maximum period, especially since the cyclone is still going to be moving over sea-surface temperatures (SST) near 27 deg C, which should result in some slight re-strengthening or at least hold a steady intensity for the next 24 h or so. By 36 h and beyond, however, Guillermo will be passing over sub-25C SSTs and into a stronger northwesterly wind shear environment, which should induce slow but steady weakening through the rest of the forecast period, with the cyclone becoming a post-tropical remnant low by 120 hours. The new NHC intensity forecast is similar to the previous advisory and closely follows the NOAA-HCCA and IVCN consensus models.

The initial motion estimate is now westward, or 280/13 kt. Guillermo made a due west lurch at about 18 kt after the central deep convection dissipated, which resulted in the vortex becoming a little more vertically shallow. However, the motion over the past few hours has been fairly steady at around 13 kt. The latest model guidance is tightly packed about the previous advisory track, so no significant changes were required since the global and regional models maintain the strong subtropical ridge to the north of Guillermo for the next 120 hours. The official forecast track closely follows a blend of the TVCE and GFEX simple consensus models, and the HCCA corrected-consensus model.

FORECAST POSITIONS AND MAX WINDS

INIT  19/0300Z 18.9N 115.6W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 12H  19/1200Z 19.1N 117.6W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 24H  20/0000Z 19.2N 120.4W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 36H  20/1200Z 19.1N 123.2W   40 KT  45 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  21/0000Z 19.1N 126.1W   35 KT  40 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 60H  21/1200Z 18.9N 128.9W   30 KT  35 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 72H  22/0000Z 18.6N 131.6W   30 KT  35 MPH - Tropical Storm (WSW Hilo, Hawaii)
 96H  23/0000Z 18.3N 136.7W   25 KT  30 MPH - Tropical Storm (WSW Hilo, Hawaii)
120H  24/0000Z 18.3N 141.7W   20 KT  25 MPH - Post Tropical (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 300 PM MDT Sun Jul 18, 2021

Guillermo’s convective pattern has not changed significantly since early this morning, but an ASCAT overpass just after 1600 UTC revealed that its wind field has expanded. The maximum winds in the ASCAT data were a little above 45 kt, so the initial intensity has been increased to 50 kt accordingly. This is just above the latest Dvorak estimates from TAFB and SAB.

A slight additional increase in the maximum winds appears likely during the next day or so, owing to favorable environmental conditions. However, the highly asymmetric structure of Guillermo and its relatively broad inner-core will continue to be limiting factors. In about 24 to 36 h, Guillermo will begin to move over waters colder than 26 deg C, and this should cause the tropical storm to gradually weaken. After about 72 h, a drier and more stable environment will likely also contribute to weakening. Despite those factors, the GFS and HWRF models continue to indicate that Guillermo could maintain at least some deep convection through the full 5-day period. The NHC forecast therefore carries Guillermo as a tropical cyclone through day 5, but it would not be surprising if it became a remnant low sooner than that. The official intensity forecast is slightly higher than the intensity consensus, near the SHIPS and GFS forecasts.

The aforementioned ASCAT data indicated that Guillermo is centered slightly north of previous estimates and the estimated initial motion is slightly faster than the previous advisory, at 290/ 12 kt. The NHC track forecast has been adjusted northward and faster as a result, but the overall reasoning remains the same. A mid-level ridge to the north of Guillermo will likely steer the tropical storm westward beginning tonight. Guillermo should then continue generally westward for the next several days. A slight west-southwestward bend is possible late in the forecast period as the cyclone weakens and becomes primarily steered by low-level flow. The official track forecast is heavily based on the multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  18/2100Z 18.7N 113.8W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 12H  19/0600Z 19.0N 115.7W   55 KT  65 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 24H  19/1800Z 19.1N 118.4W   55 KT  65 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 36H  20/0600Z 19.0N 121.3W   55 KT  65 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  20/1800Z 19.0N 124.2W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 60H  21/0600Z 18.9N 127.1W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 72H  21/1800Z 18.6N 129.8W   40 KT  45 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 96H  22/1800Z 18.2N 135.0W   35 KT  40 MPH - Tropical Storm (WSW Hilo, Hawaii)
120H  23/1800Z 18.0N 140.0W   30 KT  35 MPH - Post Tropical (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 900 AM MDT Sun Jul 18, 2021

Guillermo’s structure has changed little this morning. Very cold overshooting cloud tops associated with deep convection have been observed near the center of the tropical storm during the past couple of hours, however most of the convective activity is still limited to bands extending to the east and south of the tropical cyclone. Dvorak intensity estimates from TAFB and SAB continue to support an intensity estimate of 45 kt. Slight strengthening is anticipated over the next 24 to 36 hours while Guillermo moves over fairly warm waters. The rate of strengthening will likely be limited by moderate northwesterly shear (10-20 kt based on SHIPS diagnostics) and the relatively large size of the system. After that, Guillermo will move over progressively cooler waters and into a drier more stable environment which should cause it to slowly weaken through the middle of the week. The GFS and HWRF forecast that Guillermo will maintain tropical characteristics through the end of the week, and this is reflected in the NHC forecast. However, it is also possible it will become a remnant low by the end of the forecast period.

The low-level center of Guillermo is obscured by nearby convection, but it appears that the tropical storm is still moving west-northwestward, more or less right on the previous forecast track. Consequently no changes of note were made to the official track forecast. A mid-level ridge to the north of Guillermo will steer the cyclone westward for the next several days, likely with a slight increase in its forward speed. Around day 4 or 5, Guillermo is expected to weaken sufficiently so that it will become steered primarily by low-level flow, and a slight bend toward the west-southwest is anticipated. Like the previous advisory, the NHC forecast is very near but just barely slower than the latest multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 17.9N 112.5W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 12H  19/0000Z 18.3N 114.2W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 24H  19/1200Z 18.6N 116.8W   55 KT  65 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 36H  20/0000Z 18.7N 119.6W   55 KT  65 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  20/1200Z 18.7N 122.5W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 60H  21/0000Z 18.6N 125.5W   40 KT  45 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 72H  21/1200Z 18.4N 128.4W   35 KT  40 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 96H  22/1200Z 17.9N 133.4W   30 KT  35 MPH - Post Tropical (WSW Hilo, Hawaii)
120H  23/1200Z 17.5N 138.5W   30 KT  35 MPH - Post Tropical (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 900 PM MDT Sat Jul 17, 2021 

The overall structure of Guillermo has changed little since this afternoon, with the only notable difference being a small burst of deep convection just to the southwest of the center. Recent satellite imagery suggests that the system is tilted, with the mid-level circulation offset a bit to the northeast from the low-level center. Guillermo is a large tropical cyclone, and the sprawling circulation of the storm is producing broken banding over an area over 400 n mi wide. The latest T-numbers from TAFB and the UW-CIMSS ADT have also changed little since 6 h ago, which suggest that the Guillermo’s initial intensity remains 35 kt.

A fortuitous AMSR2 microwave overpass helped to confirm the location of Guillermo’s low-level center a few hours ago, and the initial motion estimate is 290/11 kt. The cyclone is expected to turn to the west on Sunday as it becomes embedded in easterly flow to the south of a mid-level ridge. This ridge should remain in place through the early part of next week. By 72 h, the guidance is suggesting that Guillermo will become a shallow cyclone, and a large low-level ridge to its northwest will become the primary steering mechanism, resulting a slightly south-of-west motion. The official NHC forecast is near the previous one through 60 h, but is a little faster and slightly to the south of it thereafter.

Due to the large size of Guillermo’s circulation, it may take longer than normal for the cyclone to develop a tight wind field, despite being in an environment of low vertical wind shear and over warm waters. Therefore, only gradual strengthening is indicated over the next 36 h. After 36 h, the forecast track of the cyclone takes it over cooler waters with SSTs less than 25C by 60 h. There are also indications that Guillermo will encounter moderate northwesterly shear in a few days, which would entrain stable air located to its north into the circulation. These factors should cause steady weakening beginning in a couple of days. And although not shown in the official forecast, several of the convection allowing models show the cyclone losing most, if not all, of its deep convection and becoming a remnant low by the end of the forecast period. Since Guillermo’s forecast track keeps it fairly close to a tight SST gradient, with warmer waters just south, it is possible that a small deviation of the track to the south could prevent the cyclone from becoming a remnant low so soon. The latest NHC intensity forecast is slightly lower than the previous one due to a decrease in the overall intensity guidance, yet remains on the high end of the guidance through 36 h.

FORECAST POSITIONS AND MAX WINDS

INIT  18/0300Z 17.5N 111.1W   35 KT  40 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 12H  18/1200Z 17.9N 112.6W   40 KT  45 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 24H  19/0000Z 18.3N 114.8W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 36H  19/1200Z 18.5N 117.4W   50 KT  60 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 48H  20/0000Z 18.7N 120.1W   45 KT  50 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 60H  20/1200Z 18.6N 122.9W   40 KT  45 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 72H  21/0000Z 18.4N 125.5W   35 KT  40 MPH - Tropical Storm (WSW Puerto Vallarta, MX)
 96H  22/0000Z 17.9N 130.7W   30 KT  35 MPH - Post Tropical (WSW Puerto Vallarta, MX)
120H  23/0000Z 17.5N 136.0W   30 KT  35 MPH - Post Tropical (WSW Puerto Vallarta, MX)

NWS National Hurricane Center Miami FL 300 PM MDT Sat Jul 17, 2021

Fragmented convective banding has gradually increased since the previous advisory, with a very tight low-level vortex having become evident over the center in high-resolution visible satellite imagery. Low-cloud motion vectors in the inner-core region have been around 45 kt, which equals approximately 34-kt surface winds if the cloud motions represent the 925-mb level. Satellite current intensity (CI) estimates remain T2.5/35 kt from TAFB and and SAB. The latest UW-CIMSS ADT estimate is T2.2/32 kt, with the raw and adjusted T-numbers at 37 kt and 36 kt, respectively. Based on these data, the intensity has been increased to 35 kt, making the cyclone Tropical Storm Guillermo.

The initial motion estimate is 295/12 kt. There are no significant changes to the previous track forecast or reasoning. The global and regional models remain in very good agreement on Guillermo moving west-northwestward today, and then turning toward the west later tonight or early Sunday, with a general westward motion continuing through day 3. By days 4 and 5, the deep-layer ridge to the north of Guillermo is forecast by the models to gradually build southward, forcing the tropical storm west-southwestward. The latest NHC model guidance has converged tightly around the previous forecast track through 96 h, so no adjustments were made. The new official forecast track lies close to the tightly packed consensus models, which are about midway between the stronger GFS track forecast on the right side of the guidance envelope and the weaker ECMWF solution on the left or south side.

Guillermo is expected to remain within a low vertical wind shear regime and a moist mid-level environment, and over sea-surface temperatures (SST) of at least 27C for the next 48 hours or so. These favorable conditions should allow for at least modest strengthening to occur during that time, with the only hindering factor being Guillermo’s large circulation. By 60 hours and beyond, the cyclone will be moving over sub-26C SSTs, which should induce gradual weakening despite the low vertical wind shear pattern. The new NHC intensity forecast is similar to the previous advisory, and closely follows the NOAA-HCCA corrected consensus model, which is above most of the available intensity guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  17/2100Z 17.1N 110.1W   35 KT  40 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 12H  18/0600Z 17.6N 111.7W   45 KT  50 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 24H  18/1800Z 18.0N 113.9W   50 KT  60 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 36H  19/0600Z 18.3N 116.2W   55 KT  65 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 48H  19/1800Z 18.4N 118.7W   55 KT  65 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 60H  20/0600Z 18.5N 121.2W   50 KT  60 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 72H  20/1800Z 18.4N 123.8W   45 KT  50 MPH - Tropical Storm (WSW Hilo, Hawaii)
 96H  21/1800Z 18.1N 128.9W   35 KT  40 MPH - Tropical Storm (WSW Hilo, Hawaii)
120H  22/1800Z 17.8N 134.1W   30 KT  35 MPH - Tropical Storm (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 900 AM MDT Sat Jul 17, 2021

The broad low-pressure system that the NHC has been monitoring for the past few days well offshore the southwestern coast of Mexico has finally developed enough organized deep convection and a well-defined inner-core wind field to be classified as a tropical depression. The initial intensity is estimated to be 30 kt, which is a little below the consensus T2.5/35-kt classifications from TAFB and SAB.

The initial motion estimate is an uncertain 295/15 kt due to the lack of a well-defined center prior to 1200 UTC. Regardless, the global and regional models are in exceptionally good agreement on the cyclone moving west-northwestward today, and then turning toward the west by late tonight or early Sunday, with that general motion continuing through 72 hours. Thereafter, the deep-layer subtropical ridge to the north that will steer the system for the next 5 days is expected to build slightly southward, nudging the cyclone on a west-southwestward track at 96 and 120 hours. The NHC forecast track lies close to but a little slower than the various consensus models out of respect for the slower GFS and GFS-ensemble models, which are forecasting a stronger and, thus, more vertically deep tropical cyclone that should move slower compared to the other weaker models.

During the next 48 hours or so, the cyclone is expected to remain embedded within an environment conducive for strengthening, characterized by light wind shear (<10 kt), sea-surface temperatures (SST) above 27 deg C, and deep moisture through the low- to mid-levels of the troposphere. Furthermore, a large upper-level low located just west of the Baja California peninsula, which has been enhancing the poleward outflows of this disturbance and Hurricane Felicia farther to the west, is forecast to persist for at least the next couple of days. All of these favorable conditions argue for at least modest strengthening during that time, with the only hindering factor being the large size of the system’s circulation. Thereafter, the cyclone will move over sub-26C SSTs, which should act to cap the intensification process despite the low vertical wind shear conditions that are expected to persist.

However, the rate of weakening is forecast to be a little slower than normal due to the southern half of the circulation remaining over warmer waters, which will provide warm moist inflow to help fuel thunderstorms near the inner-core. The NHC intensity forecast closely follows the NOAA-HCCA consensus model through 60 hours, and then is a little above all of the consensus models thereafter.

FORECAST POSITIONS AND MAX WINDS

INIT  17/1500Z 16.8N 109.2W   30 KT  35 MPH - Depression (WSW Zihuatanejo, MX)
 12H  18/0000Z 17.3N 110.8W   40 KT  45 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 24H  18/1200Z 17.9N 112.8W   45 KT  50 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 36H  19/0000Z 18.2N 115.1W   50 KT  60 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 48H  19/1200Z 18.3N 117.5W   55 KT  65 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 60H  20/0000Z 18.5N 120.0W   55 KT  65 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 72H  20/1200Z 18.5N 122.6W   50 KT  60 MPH - Tropical Storm (WSW Zihuatanejo, MX)
 96H  21/1200Z 18.2N 127.7W   40 KT  45 MPH - Tropical Storm (WSW Hilo, Hawaii)
120H  22/1200Z 17.9N 132.9W   35 KT  40 MPH - Tropical Storm (WSW Hilo, Hawaii)

NWS National Hurricane Center Miami FL 1100 AM PDT Fri Jul 16, 2021

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

The National Hurricane Center is issuing advisories on Hurricane Felicia, located almost 1000 miles west-southwest of the southern tip of the Baja California peninsula.

  • 1. A broad low pressure system located a few hundred miles south of the coast of southwestern Mexico is producing a large area of disorganized showers and thunderstorms. Environmental conditions are expected to be conducive for gradual development during the next several days, and a tropical depression is likely to form within the next couple of days and move west-northwestward to westward at around 15 mph, a few hundred miles offshore of the southwestern coast of Mexico. * Formation chance through 48 hours…high..90 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Thu Jul 15, 2021

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

The National Hurricane Center is issuing advisories on Hurricane Felicia, located over 800 miles southwest of the southern tip of the Baja California peninsula.

  • 1. A broad area of low pressure located several hundred miles south of the coast of southern Mexico is producing a large area of disorganized showers and thunderstorms. Environmental conditions are expected to remain conducive for gradual development during the next several days, and a tropical depression is likely to form this weekend and move westward or west-northwestward at around 15 mph, a few hundred miles offshore of the southwestern coast of Mexico. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Thu Jul 15, 2021

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

The National Hurricane Center is issuing advisories on Hurricane Felicia, located about 800 miles southwest of the southern tip of the Baja California peninsula.

  • 1. A broad area of low pressure has formed about 500 miles south of the coast of southern Mexico. Although there is a large area of associated showers and thunderstorms, this activity is currently disorganized. However, environmental conditions are conducive for gradual development over the next several days, and a tropical depression is likely to form this weekend well offshore of the southwestern coast of Mexico, while the system moves westward or west-northwestward at around 15 mph. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Thu Jul 15, 2021

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

The National Hurricane Center is issuing advisories on recently upgraded Hurricane Felicia, located about 750 miles southwest of the southern tip of the Baja California peninsula.

  • 1. A large area of disorganized showers and thunderstorms continue well offshore of the coast of southern Mexico in association with a tropical wave. Environmental conditions are expected to be conducive for gradual development over the next several days, and a tropical depression is likely to form this weekend well offshore of the southwestern coast of Mexico while the system moves westward or west-northwestward at around 15 mph. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…90 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Wed Jul 14, 2021

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

The National Hurricane Center is issuing advisories on Tropical Storm Felicia, located over 600 miles southwest of the southern tip of the Baja California peninsula.

  • 1. Disorganized showers and thunderstorms continue offshore of the coast of southern Mexico in association with a tropical wave moving westward at 10 to 15 mph. Environmental conditions are expected to be conducive for gradual development over the next several days, and a tropical depression is likely to form this weekend well offshore of the southwestern coast of Mexico while the system moves westward or west-northwestward at around 15 mph. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…high...80 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Wed Jul 14, 2021

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

The National Hurricane Center is issuing advisories on recently upgraded Tropical Storm Felicia, located several hundred miles south-southwest of the southern tip of Baja California.

  • 1. An area of disorganized showers and thunderstorms, located over the eastern Pacific south and southeast of the coast of southern Mexico, are associated with a tropical wave moving westward at 10 to 15 mph. Environmental conditions are expected to be favorable for gradual development over the next several days, and a tropical depression is likely to form this weekend well offshore of the southwestern coast of Mexico. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…high...70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Wed Jul 14, 2021

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

The National Hurricane Center is issuing advisories on newly formed Tropical Depression Six-E, located several hundred miles south-southwest of the southern tip of Baja California.

  • 1. An area of low pressure is forecast to develop well south of the coast of southern Mexico late this week and move westward at 10 to 15 mph. Environmental conditions are expected to be favorable for gradual development, and a tropical depression is likely to form this weekend well offshore of the southwestern coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Tue Jul 13, 2021

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

  • 1. Satellite imagery indicates that an area of low pressure located about 700 miles south of the southern tip of the Baja California peninsula continues to show increasing signs of organization. Environmental conditions remain favorable for continued development, and a tropical depression is likely to form tonight or on Wednesday while the low moves west-northwestward at about 15 mph. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…90 percent.
  • 2. An area of low pressure is forecast to develop well south of the coast of southern Mexico late this week and move westward at 10 to 15 mph. Environmental conditions are expected to be favorable for gradual development, and a tropical depression is likely to form this weekend well offshore of the southwestern coast of Mexico. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Tue Jul 13, 2021

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

  • 1. A broad area of low pressure, located about 800 miles south-southeast of the southern tip of the Baja California peninsula, is producing a small but concentrated area of showers and thunderstorms. Environmental conditions are forecast to be favorable for development, and a tropical depression is likely to form in a couple of days while the low moves westward to west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…medium…60 percent. * Formation chance through 5 days…high...80 percent.
  • 2. An area of low pressure is forecast to develop south or southwest of the Gulf of Tehuantepec late this week and move westward at 10 to 15 mph, well offshore of the southern coast of Mexico. Environmental conditions are expected to be favorable for gradual development, and a tropical depression is likely to form this weekend. * 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 Mon Jul 12, 2021

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

  • 1. A broad area of low pressure located over 600 miles south of Cabo Corrientes, Mexico is producing disorganized showers and thunderstorms, mainly to the north of its center. Environmental conditions are favorable for development of this system, and a tropical depression is likely to form later this week well offshore of the southwestern coast of Mexico while the low moves westward to west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…80 percent.
  • 2. An area of low pressure is forecast to develop south of the Gulf of Tehuantepec late this week and move westward at 10 to 15 mph, well offshore of the southern coast of Mexico. Environmental conditions are expected to be favorable for gradual development, and a tropical depression is likely to form this weekend. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Mon Jul 12, 2021

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

  • 1. Disorganized showers and thunderstorms continue in association with a broad area of low pressure located several hundred miles south of Manzanillo, Mexico. Environmental conditions are expected to remain conducive for gradual development, and a tropical depression is likely to form later this week well offshore of the southwestern coast of Mexico while the system moves westward to west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…medium…50 percent. * Formation chance through 5 days…high…80 percent.
  • 2. An area of low pressure is forecast to develop south of the Gulf of Tehuantepec later this week and move westward at 10 to 15 mph, well offshore of the southern coast of Mexico. Environmental conditions are forecast to be favorable for development of this system, and a tropical depression is likely to form by this weekend. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 1100 AM PDT Mon Jul 12, 2021

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

  • 1. A broad area of low pressure located several hundred miles south of Manzanillo, Mexico, continues to produce disorganized shower and thunderstorm activity. Environmental conditions are expected to remain conducive for gradual development, and a tropical depression is likely form in two to three days well offshore the southwestern coast of Mexico while the disturbance moves westward to west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…medium…40 percent. * Formation chance through 5 days…high…70 percent.
  • 2. An area of low pressure is forecast to develop south of the Gulf of Tehuantepec later this week and move westward or west-northwestward at 10 to 15 mph, well offshore of the southern coast of Mexico. Environmental conditions are expected to be favorable for development of this system, and a tropical depression is likely to form by this weekend. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Mon Jul 12 2021

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

  • 1. A broad area of low pressure located several hundred miles south-southwest of Acapulco, Mexico, is producing disorganized shower and thunderstorm activity. Environmental conditions are expected to remain conducive for gradual development, and a tropical depression is likely form within a few days well offshore the southwestern coast of Mexico while the disturbance moves westward to west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…high…70 percent.
  • 2. An area of low pressure is forecast to develop south of the Gulf of Tehuantepec later this week and move westward or west-northwestward at 10 to 15 mph, well offshore of the southern coast of Mexico. Environmental conditions are expected to be favorable for development of this system, and a tropical depression is likely to form by this weekend. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Sun Jul 11, 2021

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

  • 1. A tropical wave located several hundred miles south of Acapulco, Mexico is producing disorganized showers and thunderstorms. Environmental conditions are forecast to be conducive for gradual development, and a tropical depression could form by midweek well offshore of the southwestern coast of Mexico while the disturbance moves westward to west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…medium…60 percent.
  • 2. An area of low pressure is forecast to develop south of the Gulf of Tehuantepec around midweek and move westward or west-northwestward at 10 to 15 mph, well offshore of the southern coast of Mexico. Environmental conditions are expected to be favorable for development of this system, and a tropical depression is likely to form by late this week. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sun Jul 11, 2021

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

  • 1. An area of low pressure is forecast to develop southeast or south of the Gulf of Tehuantepec in the next few days and move generally westward or west-northwestward at 10 to 15 mph, well offshore the southern coast of Mexico. Environmental conditions are expected to support gradual development of this system, and a tropical depression is likely to form around mid-to-late week. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…high…70 percent.
  • 2. Another area of low pressure is expected to form several hundred miles southwest of the southern coast of Mexico within the next few days. Gradual development of this system is possible while it moves westward or west-northwestward at 10 to 15 mph. * Formation chance

NWS National Hurricane Center Miami FL 1100 AM PDT Sat Jul 10, 2021

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

  • 1. An area of low pressure is expected to develop south or southeast of the Gulf of Tehuantepec in a few days. Environmental conditions are expected support gradual development of this system therafter and a tropical depression could form during the middle portion of next week. This system is expected to move generally westward or west-northwestward at 10 to 15 mph through the end of the five day period. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium…60 percent.
  • 2. Another area of low pressure is expected to form several hundred miles southwest of the southern coast of Mexico by early next week. Some slow development of this system will be possible while it moves westward or west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 500 AM PDT Sat Jul 10, 2021

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

  • 1. An area of low pressure is expected to develop south or southeast of the Gulf of Tehuantepec in a few days. Environmental conditions are expected support gradual development of this system therafter and a tropical depression could form during the middle portion of next week. This system is expected to move generally westward or west-northwestward at 10 to 15 mph through the end of the five day period. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…medium...50 percent.
  • 2. Another area of low pressure is expected to form several hundred miles southwest of the southern coast of Mexico by early next week. Some slow development of this system will be possible while it moves westward or west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Fri Jul 9, 2021

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

  • 1. A broad area of low pressure is expected to form several hundred miles south-southwest of the southern coast of Mexico by early next week. Additional development of this system is expected to be slow to occur while moving westward or west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.
  • 2. Another area of low pressure is expected to form south of the Gulf of Tehuantepec by the middle of next week. Environmental conditions are expected to support the gradual development of this system thereafter while moving generally west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…30 percent.

NWS National Hurricane Center Miami FL 500 PM PDT Thu Jul 8, 2021

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

  • 1. A broad area of low pressure is expected to form several hundred miles south-southwest of the southern coast of Mexico by early next week. Gradual development of this system is possible thereafter as it moves generally west-northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.
  • 2. Another area of low pressure is expected to form a few hundred miles south of the Gulf of Tehuantepec by early next week. Gradual development of this system is possible thereafter while it moves west-northwestward to northwestward at 10 to 15 mph. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

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Video: Justin Cruz’s Weather Forecast 7-19-21