Tropical Storm Gonzalo

Tropical Storm Gonzalo Track 1700 Hoirs July 25 2020
Tropical Storm Gonzalo Track 1700 Hoirs July 25 2020

Tropical Storm Gonzalo Wind Speed FieldTropical Storm Gonzalo  NWS National Hurricane Center Miami FL 500 PM AST Sat Jul 25, 2020 (see Saturday video below)

Gonzalo’s structure has degraded further since the last advisory. Late-arriving ASCAT data showed a well-defined tropical wave with winds around 30 kt, but no clear evidence of a closed circulation. Grenada reported max winds of 28 kt with a gust to 40 kt, in line with the ASCAT observations, while multiple observing stations in Trinidad did not report any westerly winds as the system passed.

There has been no evidence of a well-defined center in visible imagery since that time. Given the additional degradation of Gonzalo’s appearance since it moved closest to those islands, it appears that the system has opened into wave and dissipated. Therefore, this will be the last advisory issued by the National Hurricane Center.

Tropical squalls associated with the remnants of Gonzalo will continue to move westward for the next day or so and could bring gusty winds and heavy rain to portions of the southeastern Caribbean. Please consult products from your national meteorological service for information specific to your area.

FORECAST POSITIONS AND MAX WINDS

INIT  25/2100Z 11.0N  63.0W   30 KT  35 MPH - Depression (ENE Playa Madina, Venezuela)
 12H  26/0600Z...DISSIPATED

NWS National Hurricane Center Miami FL AL072020 1100 AM AST Sat Jul 25, 2020

Gonzalo is looking very ragged, with a cloud field that more resembles a tropical squall than a tropical storm. If Gonzalo still has a well-defined center, it is located to the east of the primary area of deep convection and is obscured by cirrus clouds. It is possible that ASCAT data will provide more information on the status of Gonzalo later this morning. For now, the intensity is held at 35 kt based on overnight reconnaissance data, but it is possible that Gonzalo is no longer producing winds of that magnitude except in squalls not directly related to the system’s circulation.

Gonzalo appears to have continued westward since the last advisory, with a somewhat uncertain forward speed estimate of 16 kt. As noted in the previous advisory, Gonzalo is not expected to gain much latitude today and should continue generally westward for the next day or so. Close proximity to land and unfavorable large-scale environmental factors should cause Gonzalo to weaken and open into a trough by late Sunday, if not sooner. No significant changes were made to the NHC track or intensity forecasts which both remain near the multi-model consensus.

Key Messages

  • 1. Gonzalo is causing gusty winds across portions of the southern Windward Islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials.
  • 2. Gonzalo is producing heavy rain over portions of the southern Windward Islands. This could lead to life-threatening flash flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 10.5N  60.5W   35 KT  40 MPH - Tropical Storm (ESE Toco, Trinidad and Tobago )
 12H  26/0000Z 11.0N  63.5W   30 KT  35 MPH - Depression (WSW Porlamar, Venezuela)
 24H  26/1200Z 11.7N  67.3W   30 KT  35 MPH - Depression (ESE Rincon, Bonaire)
 36H  27/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM AST Fri Jul 24, 2020 

Although there has been a recent increase in deep convection in association with Gonzalo, data from an Air Force Reserve Hurricane Hunter aircraft continues to show that the tropical cyclone is poorly organized. The aircraft has not yet found winds to support tropical storm strength, however the advisory intensity will remain a possibly generous 35-kt until the aircraft completes its mission overnight.

There is also some possibility that this recent convective burst could result in some short-term re-organization. However, with the system losing organization over the past day or so, it is becoming less likely that the small cyclone will be able to significantly recover due to the nearby dry mid-level environment. The updated NHC intensity forecast no longer calls for any re-strengthening, and Gonzalo could even become a tropical depression before reaching the Windward Islands. After that time, dry air and Gonzalo’s close proximity to the coast of Venezuela are likely to cause the system to weaken and degenerate into a trough of low pressure. The NHC forecast now calls for dissipation by 60 h, but this could occur sooner.

Gonzalo continues moving generally westward or 270/15 kt. The system is not expected to gain much latitude as it should continue moving westward to west-northwestward within the low-level easterly flow. The track guidance continues to trend southward and the NHC track forecast has again been shifted in that direction. The new track lies to the south of the consensus aids, closest to the GFS and UKMET ensemble means.

Key Messages

  • 1. Gonzalo is forecast to bring tropical storm conditions to a portion of the southern Windward Islands Saturday and Saturday night. Tropical Storm Warnings are currently in effect for some of the islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials.
  • 2. Gonzalo is expected to produce heavy rain over portions of the southern Windward Islands. This could lead to life-threatening flash flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  25/0300Z 10.0N  57.1W   35 KT  40 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 12H  25/1200Z 10.4N  59.4W   35 KT  40 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 24H  26/0000Z 11.3N  62.6W   35 KT  40 MPH - Tropical Storm (ESE Rio Caribe,Venezuela)
 36H  26/1200Z 12.2N  66.0W   30 KT  35 MPH - Depression (ENE Isla La Orchila, Venezuela)
 48H  27/0000Z 12.7N  69.7W   25 KT  30 MPH - Low (ENE San Nicolos, Aruba)
 60H  27/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Fri Jul 24, 2020

An Air Force Reserve Hurricane Hunter aircraft investigated Gonzalo earlier this afternoon and found it to very poorly organized. The aircraft even reported seeing multiple low-level swirls which is surprising given the small size of the cyclone. The highest flight-level winds measured by the plane were 41 kt while the highest believable SFMR values were right around 35 kt. Based on that data, Gonzalo’s intensity has been lowered to 35 kt.

Small systems like Gonzalo are notorious for quick changes in structure and intensity, both up and down. Therefore, despite its current downswing, it is too soon to say for sure that Gonzalo will not restrengthen to some degree before it reaches the southern Windward Islands. That said, confidence in the intensity forecast is a little higher now that we have better data to base the forecast on and it does not seem likely that Gonzalo will overcome the dry air that is currently inhibiting its development. Given the current structure of the tropical storm, the NHC intensity forecast has been lowered significantly, but still allows for some slight restrengthening during the next 24 h. The new forecast is much closer to the intensity consensus, below only the HWRF model which does not appear to have a realistic initialization. Once Gonzalo reaches the eastern Caribbean, weakening is anticipated and the cyclone is forecast to dissipate within 3 days, if not sooner.

Gonzalo has sped westward all day with a motion near 270/16 kt. The guidance continues to insist that Gonzalo will gain a little latitude in the near future, and a general westward to west-northwestward motion is still forecast for the next few days. The NHC track forecast has again been shifted southward, but now lies near the middle of the guidance envelope and very near the various track consensus aids.

Key Messages

  • 1. Gonzalo is forecast to bring tropical storm conditions across portions of the southern Windward Islands Saturday and Saturday night. Tropical Storm Warnings are currently in effect for some of the islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials.
  • 2. Gonzalo is expected to produce heavy rain over portions of the southern Windward Islands. This could lead to life-threatening flash flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 10.0N  55.6W   35 KT  40 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 12H  25/0600Z 10.4N  58.0W   40 KT  45 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 24H  25/1800Z 11.4N  61.1W   40 KT  45 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 36H  26/0600Z 12.2N  64.2W   40 KT  45 MPH - Tropical Storm (ENE Isla La Blanquilla, Colombia)
 48H  26/1800Z 13.1N  67.9W   35 KT  40 MPH - Tropical Storm (ENE Rincon, Bonaire)
 60H  27/0600Z 13.4N  71.1W   30 KT  35 MPH - Depression (ENE Tuputs, Venezuela)
 72H  27/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Fri Jul 24, 2020 

Gonzalo continues to produce bursts of deep convection, especially in the southeast quadrant, but has not become any better organized overall since the last advisory. Microwave imagery overnight indicated the low-level structure of Gonzalo is still largely intact, but this has not translated into better convective organization. ASCAT data valid shortly after 12Z revealed that Gonzalo has accelerated west faster than anticipated and has not strengthened. In fact the strongest winds in the ASCAT data were only 30-35 kt. The resolution of ASCAT likely limits its ability to sample the actual max winds of small storms like Gonzalo, but it is another indication that the cyclone has not strengthened and could be weakening. The initial intensity for this advisory is set at 45 kt, based primarily on the latest TAFB Dvorak fix and the UW-CIMSS SATCON. An Air Force Reserve reconnaissance aircraft scheduled to investigate the storm this afternoon will provide a more information about Gonzalo’s intensity and structure.

Due primarily to the adjusted initial position, the NHC track forecast has been adjusted a fair amount west and south of the previous advisory. Overall Gonzalo is still forecast to move generally westward or west-northwestward through the period, steered by the subtropical ridge to the north. The new NHC forecast lies between the old forecast, adjusted for the new initial position, and the HFIP Corrected Consensus.

The intensity guidance is generally lower than it has been for the last day or so, and none of the operational models forecast Gonzalo to reach hurricane strength. Unfortunately, small storms like Gonzalo are often subject to large swings in intensity, up or down, and that aspect of the forecast remains highly uncertain, even though the spread in the guidance is not particularly high. The NHC forecast has been adjusted only slightly lower for this cycle and is now above all of the guidance at the time the system is forecast to pass through the Windward Islands. A larger adjustment could be made later today if the most recent model trends continue, or if the recon mission finds that Gonzalo is even weaker than the current estimates.

Key Messages

  • 1. Gonzalo is forecast to bring tropical storm conditions across portions of the southern Windward Islands Saturday and Saturday night. Hurricane and Tropical Storm Warning and Watches are currently in effect for some of the islands. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials.
  • 2. Gonzalo is expected to produce heavy rain over portions of the southern Windward Islands. This could lead to life-threatening flash flooding.
FORECAST POSITIONS AND MAX WINDS

INIT  24/1500Z 10.0N  54.2W   45 KT  50 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 12H  25/0000Z 10.5N  56.0W   50 KT  60 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 24H  25/1200Z 11.4N  59.1W   55 KT  65 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 36H  26/0000Z 12.4N  62.3W   60 KT  70 MPH - Tropical Storm (WSW Blaize,St Vincent)
 48H  26/1200Z 13.0N  65.7W   50 KT  60 MPH - Tropical Storm (ENE Kralendijk, Bonaire)
 60H  27/0000Z 13.7N  69.0W   40 KT  45 MPH - Tropical Storm (ENE Noord, Aruba)
 72H  27/1200Z 14.0N  72.0W   30 KT  35 MPH - Low (ENE Riochacha, Colombia )
 96H  28/1200Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 PM AST Thu Jul 23, 2020

After ingesting a hefty portion of dry high statically stable air this morning, Gonzalo appears to be on the comeback trail. Enhanced infrared BD-curve imagery shows that a small Central Dense Overcast with cloud tops of -80C is redeveloping over the surface center. A compromise of the available subjective and objective satellite intensity estimates supports maintaining 50 kt for this advisory.

This morning’s upper air sounding from Barbados revealed a very dry, high statically stable atmosphere with a mean RH of 23 percent and a CAPE of only 327 J/Kg. Consequently, Gonzalo will be moving into a rather harsh thermodynamic environment over the weekend. As a result, the NHC forecast calls for weakening beyond the 48 hour period as it enters the eastern Caribbean sea and dissipation well south of Hispaniola at day 5, or sooner as a few of the global models suggest. The intensity forecast is basically an update of the previous advisory through 48 hours, indicating a hurricane approaching and moving over the southern Windward Islands, and a faster weakening trend beyond day 2, similar to a consensus of the large-scale models.

The initial motion is estimated to be westward, or 275/12 kt within the stiff mid-tropospheric steering flow provided by an anchored subtropical ridge to the cyclone’s north. The song remains the same, with Gonzalo expected to speed up toward the west and west-northwest through the entire period. The NHC official forecast is based on a blend of the various consensus aids and is down the middle of the tightly clustered guidance.

Key Messages

  • 1. The risk of wind and rain impacts from Gonzalo in portions of the southern Windward Islands this weekend continues to increase, however there is significant uncertainty in how strong Gonzalo will be when it moves across the islands.
  • 2. Despite the uncertainty in Gonzalo’s future intensity, hurricane or tropical storm conditions are possible across portions of the southern Windward Islands Saturday and Saturday night. Hurricane and Tropical Storm Watches are currently in effect for some of the islands, and additional watches or warnings could be required tonight or early Friday. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials.
FORECAST POSITIONS AND MAX WINDS

INIT  24/0300Z  9.9N  50.6W   50 KT  60 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 12H  24/1200Z 10.2N  52.5W   55 KT  65 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 24H  25/0000Z 10.7N  55.1W   60 KT  70 MPH - Tropical Storm (ESE Charlotteville,Trinidad and Tobago)
 36H  25/1200Z 11.5N  58.2W   65 KT  75 MPH - Category 1 (ESE Charlotteville,Trinidad and Tobago)
 48H  26/0000Z 12.3N  61.3W   65 KT  75 MPH - Category 1 (ESE Charlotteville,Trinidad and Tobago)
 60H  26/1200Z 13.3N  64.4W   55 KT  65 MPH - Tropical Storm (WSW Port Elizabeth, St Vincent)
 72H  27/0000Z 13.9N  67.3W   45 KT  50 MPH - Tropical Storm (WSW Castries, St. Lucia)
 96H  28/0000Z 14.4N  73.7W   35 KT  40 MPH - Tropical Storm (ENE Tuputs, Venezuela)
120H  29/0000Z...DISSIPATED

NWS National Hurricane Center Miami FL 500 PM AST Thu Jul 23, 2020

Scatterometer data received just after the release of the previous advisory only showed winds of 40-45 kt, but given Gonzalo’s small size, it’s unlikely that the resolution of the instrument was able to capture the maximum winds. Even correcting for that, Gonzalo’s winds were lowered to 50 kt on the 2 PM intermediate advisory, and that still looks good now with satellite intensity estimates ranging from 35 kt to 55 kt. Structure-wise, deep convection has redeveloped on top of Gonzalo’s center, so the storm is not ready to give up its fight quite yet.

There is still greater-than-normal uncertainty in Gonzalo’s forecast intensity due to its small size and how it will behave in an environment of relatively light shear and warm sea surface temperatures counterbalanced by a lot of dry air. The statistical and dynamical hurricane models continue to show strengthening, while several of the global models, in particular the ECMWF and UKMET, still show Gonzalo weakening and opening up into a trough near or after it passes the Windward Islands. Based on the lower initial intensity and the latest guidance, the new official forecast has been lowered slightly, but it still brings Gonzalo to the hurricane threshold in 36-48 hours. Either way, Gonzalo’s small size makes it susceptible to short-term changes in intensity that cannot be reflected in the official forecast. There is more confidence that weakening will occur after Gonzalo moves over the Caribbean Sea, with even the GFS showing the system becoming a trough. Given that, dissipation is now shown in the forecast at day 5.

Gonzalo’s initial motion is westward, or 275/11 kt. There has been no change in the track forecast reasoning, with Gonzalo expected to accelerate toward the west and west-northwest through the forecast period. The track guidance is fairly tightly clustered, showing Gonzalo’s center crossing somewhere through the Windward Islands between 48-60 hours. Some of the models shifted northward a bit on this cycle, and the NHC track forecast has therefore been nudged in that direction close to the multi-model consensus aids, HCCA, and the Florida State Superensemble. However, users should not focus on these relatively small shifts in the forecast track from cycle to cycle, and for the Windward Islands in particular, consider that 48-60 hour forecast points can be off by an average of 60-80 nm.

Key Messages

  • 1. The risk of wind and rain impacts from Gonzalo in portions of the southern Windward Islands this weekend continues to increase, however there is significant uncertainty in how strong Gonzalo will be when it moves across the islands.
  • 2. Despite the uncertainty in Gonzalo’s future intensity, hurricane or tropical storm conditions are possible across portions of the southern Windward Islands Saturday and Saturday night. Hurricane and Tropical Storm Watches are currently in effect some of the islands, and additional watches or warnings could be required tonight or early Friday. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials.
FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z  9.8N  49.4W   50 KT  60 MPH - Tropica Storm (ESE Charlotteville,Trinidad and Tobago)
 12H  24/0600Z 10.0N  51.2W   55 KT  65 MPH - Tropica Storm (ESE Charlotteville,Trinidad and Tobago)
 24H  24/1800Z 10.5N  53.8W   60 KT  70 MPH - Tropica Storm (ESE Charlotteville,Trinidad and Tobago)
 36H  25/0600Z 11.1N  56.6W   65 KT  75 MPH - Category 1 (ESE Charlotteville,Trinidad and Tobago)
 48H  25/1800Z 12.0N  59.7W   65 KT  75 MPH - Category 1 (ESE Charlotteville,Trinidad and Tobago)
 60H  26/0600Z 13.0N  62.6W   60 KT  70 MPH - Tropica Storm (WSW Port Elizabeth, St Vincent)
 72H  26/1800Z 13.8N  65.6W   55 KT  65 MPH - Tropica Storm (WSW Castries, St. Lucia)
 96H  27/1800Z 14.5N  72.0W   40 KT  45 MPH - Tropica Storm (ENE Tuputs, Venezuela)
120H  28/1800Z...DISSIPATED

NWS National Hurricane Center Miami FL 1100 AM AST Thu Jul 23, 2020 

Recently-obtained GCOM and WindSat microwave data from overnight shows that Gonzalo’s center is a little farther south than previously estimated. In addition, the storm’s structure has become a little disheveled since yesterday, with the deep convection losing some organization. SAB’s data-T number responded to this by falling to 2.5, but overall the CI numbers and SATCON support maintaining 55 kt for now.

There is still an incredible amount of uncertainty in Gonzalo’s intensity forecast. Sea surface temperatures to the east of the Windward Islands are warm–close to 29C–and the storm is likely to be moving through an environment of relatively light shear at least for the next 48 hours or so. The ambient environment is not particularly moist, however, with mid-level relative humidity generally around 50 percent, and it already appears that this dry air is affecting Gonzalo. Small cyclones like Gonzalo tend to succumb to any type of adverse environmental conditions quite easily, and it’s possible that the system could struggle during the next couple of days. This is the solution shown by some of the global models, particularly the ECMWF and UKMET. On the other hand, the hurricane statistical and dynamical models, as well as the GFS, continue to show Gonzalo strengthening to a hurricane before it reaches the Windward Islands. Out of an abundance of caution, the official forecast continues to show Gonzalo becoming a hurricane in about 24 hours, but the uncertainty in this scenario cannot be stressed enough. There is a higher degree of certainty that Gonzalo would weaken once it moves over the eastern and central Caribbean Sea, where even the GFS shows it opening up into a wave.

Even with the southward adjustment of the initial position, Gonzalo still appears to be moving westward, or 270/12 kt. The subtropical ridge to the north is forecast to push Gonzalo toward the west or west-northwest, with an increase in forward speed, for the entire 5-day forecast period. Much of the track uncertainty hinges on exactly how strong Gonzalo gets, with the stronger model representations showing the storm making more poleward process. Models such as the ECMWF and UKMET, which keep Gonzalo weak or open it up into a trough, are along the southern side of the guidance envelope. The updated NHC track forecast has been shifted southward some, to account for the new initial position and to be a little closer to the intensity consensus, HCCA, and the Florida State Superensemble.

Key Messages

  • 1. There is an increasing risk of wind and rain impacts from Gonzalo in portions of the southern Windward Islands this weekend, however there is significant uncertainty in how strong Gonzalo will be when it moves across the islands.
  • 2. Despite the uncertainty in Gonzalo’s future intensity, hurricane conditions are possible across portions of the southern Windward Islands. Hurricane Watches are currently in effect for Barbados and St. Vincent and the Grenadines, and additional watches for other islands could be required later today. Interests in the southern Windward Islands should monitor the progress of Gonzalo and follow any advice given by local officials.
FORECAST POSITIONS AND MAX WINDS

INIT  23/1500Z  9.6N  48.3W   55 KT  65 MPH - Tropica Storm (ESE Charlotteville,Trinidad and Tobago)
 12H  24/0000Z  9.8N  50.0W   60 KT  70 MPH - Tropica Storm (ESE Charlotteville,Trinidad and Tobago)
 24H  24/1200Z 10.1N  52.7W   65 KT  75 MPH - Category 1 (ESE Charlotteville,Trinidad and Tobago)
 36H  25/0000Z 10.5N  55.7W   70 KT  80 MPH - Category 1 (ESE Charlotteville,Trinidad and Tobago)
 48H  25/1200Z 11.2N  59.0W   70 KT  80 MPH - Category 1 (ESE Charlotteville,Trinidad and Tobago)
 60H  26/0000Z 11.9N  62.3W   70 KT  80 MPH - Category 1 (WNW Morne Rouge, Grenada)
 72H  26/1200Z 12.6N  65.4W   65 KT  75 MPH - Category 1 (WNW Isla La Blanquilla, Venezuela)
 96H  27/1200Z 14.0N  71.4W   50 KT  60 MPH - Tropica Storm (WNW Tuputs, Bolivia)
120H  28/1200Z 15.5N  77.5W   40 KT  45 MPH - Tropica Storm (WSW Kingston, Jamaica)

NWS National Hurricane Center Miami FL 500 PM AST Wed Jul 22, 2020

Satellite imagery suggests that Gonzalo’s intensification has paused since the last advisory. The cyclone continues to show a central dense overcast, and microwave imagery indicates a small convective ring present under the overcast. However, the CDO has become a bit ragged, and the other banding seen earlier has dissipated. Subjective and objective satellite intensity estimates are in the 45-55 kt range, the the initial intensity remains a possibly conservative 45 kt.

The initial motion is now 270/12. There is no change to the track forecast philosophy. Gonzalo is on the south side of a low- to mid-level subtropical ridge, and this feature should steer the storm generally westward at a faster forward speed for the next 60 h or so. After that time, a motion toward the west-northwest is expected. The new NHC forecast track is again little changed from the previous track, and it lies very close to the consensus models.

The intensity forecast remains very problematic and of low confidence. On one side, the cyclone structure, light shear environment,and warm sea surface temperatures suggest strengthening, possibly even rapidly, should occur. In addition, the SHIPS-based guidance and the HWRF still make the system a hurricane. On the other side, the GFS, UKMET, and ECMWF models continue to forecast the system to weaken to an open wave by 120 h, possibly due to dry air entrainment and large-scale subsidence, and microwave imagery suggests that a tongue of drier air is present west and southwest of the cyclone. The NHC intensity forecast again compromises between these extremes, showing Gonzalo peaking as a hurricane in 36-48 h, followed by weakening in deference to the GFS/UKMET/ECMWF. The new intensity forecast is unchanged from the previous forecast. As noted before, the small size of this system makes it susceptible to significant fluctuations in intensity, both upward and downward.

Interests in the Windward Islands should monitor the progress of this system, as watches could be issued sometime on Thursday.

Key Messages

  • 1. Gonzalo is expected to move near or over the southern Windward Islands this weekend, and could bring direct impacts from winds and heavy rainfall. While it is too soon to determine the magnitude and timing of those impacts, interests in the southern Windward Islands should monitor the progress of Gonzalo.
FORECAST POSITIONS AND MAX WINDS

INIT  22/2100Z  9.9N  45.0W   45 KT  50 MPH - Tropical Storm (WSW Guayaguayare,Trinidad and Tobago)
 12H  23/0600Z 10.0N  46.8W   55 KT  65 MPH - Tropical Storm (WSW Guayaguayare,Trinidad and Tobago)
 24H  23/1800Z 10.1N  49.2W   65 KT  75 MPH - Category 1 (WSW Guayaguayare,Trinidad and Tobago)
 36H  24/0600Z 10.3N  51.8W   70 KT  80 MPH - Category 1 (WSW Guayaguayare,Trinidad and Tobago)
 48H  24/1800Z 10.8N  54.6W   70 KT  80 MPH - Category 1 (WSW Charlotteville,Trinidad and Tobago)
 60H  25/0600Z 11.3N  57.6W   65 KT  75 MPH - Category 1 (WSW Charlotteville,Trinidad and Tobago)
 72H  25/1800Z 12.1N  60.8W   60 KT  70 MPH - Tropical Storm (ESE Blaze, Grenada)
 96H  26/1800Z 14.0N  67.5W   50 KT  60 MPH - Tropical Storm (ENE Kralendijk, Bonaire)
120H  27/1800Z 15.0N  72.5W   40 KT  45 MPH - Tropical Storm (WSW Jacmel, Haiti)

NWS National Hurricane Center Miami FL 500 AM AST Wed Jul 22, 2020 

The cyclone has become a little better organized this morning with indications of it developing convective banding features. Intensity estimates based on Dvorak classifications from TAFB and SAB are 30 kt and 35 kt respectively. I prefer to wait for consensus 35-kt estimates before naming the system, but it seems very likely that we will have Gonzalo over the tropical Atlantic very soon. The intensity forecast for this system is subject to more than the usual degree of uncertainty. Although the cyclone is likely to remain in an environment of fairly low shear, the influences of dry air and large-scale subsidence could inhibit strengthening in a few days. The NHC intensity forecast is similar to the previous one, and calls for some strengthening during the next couple of days followed by a leveling off thereafter. This is below the model consensus, but above the global model predictions which eventually dissipate the cyclone. It should also be noted that the small size of this system makes it susceptible to significant fluctuations in intensity, both upward and downward.

The motion continues a little north of due west or 285/10 kt. A well-defined subtropical ridge is forecast to remain in place to the north of the tropical cyclone during the forecast period. The official forecast, like the previous one, is for a generally westward motion at a fast forward speed over the forecast periods. This is in close agreement with the latest dynamical model consensus.

Interests in the southern Windward Islands should monitor the progress of this system.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0900Z 10.0N  42.4W   30 KT  35 MPH - Depression (WSW Guayaguayare,Trinidad and Tobago)
 12H  22/1800Z 10.2N  44.1W   40 KT  45 MPH - Tropical Storm (WSW Guayaguayare,Trinidad and Tobago)
 24H  23/0600Z 10.2N  46.6W   45 KT  50 MPH - Tropical Storm (WSW Guayaguayare,Trinidad and Tobago)
 36H  23/1800Z 10.2N  49.0W   50 KT  60 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 48H  24/0600Z 10.4N  51.5W   55 KT  65 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 60H  24/1800Z 10.8N  54.2W   55 KT  65 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 72H  25/0600Z 11.3N  57.2W   55 KT  65 MPH - Tropical Storm (WSW Morne Rouge, Grenada)
 96H  26/0600Z 12.7N  64.4W   50 KT  60 MPH - Tropical Storm (WSW Morne Rouge, Grenada)
120H  27/0600Z 15.0N  70.0W   45 KT  50 MPH - Tropical Storm (WNW Rincon, Bonaire)

NWS National Hurricane Center Miami FL 1100 PM AST Tue Jul 21, 2020 

The depression remains quite small in size and its cloud pattern consists of a compact central dense overcast and some convective bands on its west side. The latest satellite intensity estimates and a recent ASCAT pass support maintaining the initial intensity at 30 kt. The initial motion is west-northwestward at 8 kt. The track forecast appears fairly straightforward. A strengthening deep-layer subtropical ridge to the north of the depression should cause the system to accelerate some toward the west or west-northwest during the next several days. This steering pattern should take the cyclone across the eastern Caribbean Islands and into the Caribbean Sea this weekend. The models are in fairly good agreement and there is high confidence in the track forecast.

The intensity forecast is much trickier. The models continue to differ on the evolution of the depression, with the statistical-dynamical models and some of the hurricane regional models showing the system becoming a hurricane within the next few days. Conversely, the global models show little change in strength and even dissipate the system as it moves across the eastern Caribbean Sea. The global models seem to indicate that a combination of the cyclone’s fast forward speed and associated shear, and dry air entrainment should prevent strengthening or lead to weakening. Given the large amount of uncertainty, only small changes were made to the previous prediction. This forecast lies a little below the consensus models giving slightly more weight to the global model solutions. It should be noted that small systems like Tropical Depression Seven are often difficult to predict as they are more likely to fluctuate in strength compared to larger cyclones.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0300Z 10.0N  41.3W   30 KT  35 MPH - Depression (WSW Guayaguayare,Trinidad and Tobago)
 12H  22/1200Z 10.2N  42.7W   35 KT  40 MPH - Tropical Storm (WSW Guayaguayare,Trinidad and Tobago)
 24H  23/0000Z 10.3N  45.0W   45 KT  50 MPH - Tropical Storm (WSW Guayaguayare,Trinidad and Tobago)
 36H  23/1200Z 10.4N  47.5W   50 KT  60 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 48H  24/0000Z 10.5N  50.1W   55 KT  65 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 60H  24/1200Z 10.8N  52.9W   55 KT  65 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 72H  25/0000Z 11.3N  56.0W   55 KT  65 MPH - Tropical Storm (WSW Morne Rouge, Grenada)
 96H  26/0000Z 12.4N  63.1W   50 KT  60 MPH - Tropical Storm (WSW Morne Rouge, Grenada)
120H  27/0000Z 13.7N  70.7W   45 KT  50 MPH - Tropical Storm (WNW Rincon, Bonaire)

NWS National Hurricane Center Miami FL 500 PM AST Tue Jul 21, 2020

Satellite imagery and scatterometer data indicate that the low-pressure area located over the central tropical Atlantic has a well-defined circulation and sufficient organized convection to be designated a tropical depression. Thus, advisories are being initiated on Tropical Depression Seven. The initial intensity is set at 30 kt in best agreement with the subjective satellite intensity estimate from TAFB.

The initial motion is 300/7. The depression is south of a strong subtropical ridge over the central Atlantic, and over the next several days it should turn generally westward and accelerate as it encounters the easterly flow associated with the ridge. The ECMWF, GFS, and UKMET models are in reasonably good agreement on their track forecasts, and the NHC official forecast is close to them and the various consensus models.

The intensity forecast is lower confidence. The GFS, ECMWF, and UKMET models forecast the cyclone to be dissipated or be a weak low by the 120 h point, likely due to to some vertical shear and dry air entrainment. On the other hand, the SHIPS-based guidance and the HWRF forecast the system to be a hurricane at 120 h, shrugging off the shear and dry air. The NHC intensity forecast will be a compromise between these extremes, showing a peak intensity of 55 kt in 60-72 h followed by some weakening based on the global models. The cyclone is small in size, and as a result it could change intensity – both up and down – faster than what is currently forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z  9.8N  40.4W   30 KT  35 MPH - Depression (WSW Guayaguayare,Trinidad and Tobago)
 12H  22/0600Z 10.1N  41.7W   35 KT  40 MPH - Tropical Storm (WSW Guayaguayare,Trinidad and Tobago)
 24H  22/1800Z 10.3N  43.9W   40 KT  45 MPH - Tropical Storm (WNW Guayaguayare,Trinidad and Tobago)
 36H  23/0600Z 10.3N  46.3W   45 KT  50 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 48H  23/1800Z 10.4N  49.0W   50 KT  60 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 60H  24/0600Z 10.6N  51.6W   55 KT  65 MPH - Tropical Storm (WSW Charlotteville,Trinidad and Tobago)
 72H  24/1800Z 11.0N  54.7W   55 KT  65 MPH - Tropical Storm (WSW Morne Rouge, Grenada)
 96H  25/1800Z 12.0N  61.0W   50 KT  60 MPH - Tropical Storm (WSW Morne Rouge, Grenada)
120H  26/1800Z 13.5N  68.5W   45 KT  50 MPH - Tropical Storm (WNW Rincon, Bonaire)

NWS National Hurricane Center Miami FL 200 PM EDT Tue Jul 21, 2020 

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. A tropical wave is producing a large area of disorganized showers and thunderstorms over western Cuba, the northwestern Bahamas, southern Florida, and the adjacent waters of the Atlantic, Caribbean Sea, and the Gulf of Mexico. The gradual development of this system is possible while it moves west-northwestward during the next few days. This system is expected to cross the southeastern Gulf of Mexico this afternoon and tonight, move over the central Gulf on Wednesday, and reach the northwestern Gulf on Thursday and Friday. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system on Wednesday, if necessary. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…medium…40 percent.
  • 2. Showers and thunderstorms associated with the low-pressure area located about midway between the west coast of Africa and the Lesser Antilles continue to get better organized, and a tropical depression appears to be forming. If current trends continue, advisories could be initiated on this system this afternoon. Regardless of development during the next couple of days, less favorable conditions should limit additional development of the system by the weekend. * Formation chance through 48 hours…high…90 percent. * Formation chance through 5 days…high...90 percent.

NWS National Hurricane Center Miami FL 1105 AM EDT Tue Jul 21, 2020

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

Special Tropical Weather Outlook issued to update the status of the reconnaissance mission originally scheduled for the system near the Straits of Florida and to increase the formation chances for the system in the tropical Atlantic.

  • 1. Updated: A tropical wave is producing a large area of disorganized showers and thunderstorms over western Cuba, the northwestern Bahamas, southern Florida, and the adjacent Atlantic and Caribbean waters. Gradual development of this system is possible while it moves west-northwestward during the next few days. This system is expected to move over the southeastern Gulf of Mexico later today, the central Gulf on Wednesday, and the northwestern Gulf on Thursday and Friday. The Air Force Reserve Hurricane Hunter aircraft scheduled to investigate the system this afternoon has been canceled. * Formation chance through 48 hours…low…30 percent. * Formation chance through 5 days…medium…40 percent.
  • 2. Updated: Satellite imagery and recent satellite wind data indicate that the low pressure system located about midway between the west coast of Africa and the Lesser Antilles continues to get better organized. If current trends continue, advisories could be initiated on this system as a tropical depression later today. Regardless of development during the next couple of days, less favorable conditions should limit additional development by the weekend. * Formation chance through 48 hours…high…80 percent. * Formation chance through 5 days…high…80 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Mon Jul 20, 2020 

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. A tropical wave is producing a large area of disorganized showers and thunderstorms over much of Cuba, the central and northwestern Bahamas, southern Florida, and the adjacent waters. Gradual development of this system is possible while it moves west-northwestward during the next few days. This system is expected to be over the southeastern Gulf of Mexico on Tuesday, the central Gulf on Wednesday, and the northwestern Gulf on Thursday and Friday. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system tomorrow, if necessary. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…30 percent.
  • 2. Shower activity has changed little in association with a weak area of low pressure, and its associated tropical wave, located roughly midway between the west coast of Africa and the Lesser Antilles. Environmental conditions are expected to be marginally conducive for development of this system during the next couple of days while it moves westward at 10 to 15 mph over the tropical Atlantic. Late this week, however, less favorable conditions should limit additional development. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…20 percent.
  • 3. A weak area of low pressure located over the northwestern Gulf of Mexico is producing disorganized showers and thunderstorms. Development of this system appears unlikely before it moves inland over Texas later tonight or early Tuesday. Regardless of development, locally heavy rainfall is expected over portions of southeastern Texas and southern Louisiana during the next day or two. These rains could result in localized flash flooding. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low…10 percent.

NWS National Hurricane Center Miami FL 200 PM EDT Mon Jul 20, 2020 

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. Disorganized showers and thunderstorms over Cuba, the central and northwestern Bahamas, and the adjacent Atlantic waters are associated with a tropical wave. This system is expected to move west-northwestward through the Straits of Florida today and tonight, over the southeastern Gulf of Mexico by Tuesday, across the central Gulf on Wednesday, and reach the northwestern Gulf on Thursday. Environmental conditions could become a little more conducive for development of this system once it reaches the Gulf of Mexico. An Air Force Reserve Hurricane Hunter aircraft is scheduled to investigate the system tomorrow, if necessary. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low...20 percent.
  • 2. Shower activity associated with a tropical wave located about 1000 miles west-southwest of the Cabo Verde Islands has changed little in organization during the past several hours. Environmental conditions are expected to be marginally conducive for development of this system during the next few days while it moves westward at 10 to 15 mph over the tropical Atlantic. By Friday and over the weekend, conditions are forecast to become less favorable for tropical cyclone formation. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…20 percent.
  • 3. Surface observations indicate that a weak low pressure area is located over the northwestern Gulf of Mexico. The associated shower and thunderstorm activity has become a little better organized during the past several hours. However, the system is expected to move inland over Texas tonight or Tuesday before significant additional development can occur. Regardless of development, locally heavy rainfall is possible over portions of southeastern Texas and southern Louisiana during the next day or two. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…20 percent.

NWS National Hurricane Center Miami FL 800 AM EDT Mon Jul 20, 2020 

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. Disorganized showers and thunderstorms over the Bahamas, central and eastern Cuba, and the adjacent Atlantic waters are associated with a tropical wave. This system is expected to move west-northwestward through the Straits of Florida today, over the southeastern Gulf of Mexico by Tuesday, across the central Gulf on Wednesday, and reach the northwestern Gulf on Thursday. Environmental conditions could become a little more conducive for development of this system once it reaches the Gulf of Mexico. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...20 percent.
  • 2. Shower activity associated with a tropical wave located about 1000 miles west-southwest of the Cabo Verde Islands has become a little better organized this morning. Environmental conditions are expected to be marginally conducive for development of this system during the next few days while it moves westward at 10 to 15 mph over the tropical Atlantic. By Friday and over the weekend, conditions are forecast to become less favorable for tropical cyclone formation. * Formation chance through 48 hours…low…20 percent. * Formation chance through 5 days…low…20 percent.
  • 3. Surface observations indicate that a weak low-pressure area has formed over the northwestern Gulf of Mexico. The associated shower and thunderstorm activity is currently disorganized, and little additional development is expected before the system moves inland over Texas tonight or Tuesday. * Formation chance through 48 hours…low…10 percent. * Formation chance through 5 days…low...10 percent.

NWS National Hurricane Center Miami FL 800 PM EDT Sun Jul 19, 2020

For the North Atlantic…Caribbean Sea and the Gulf of Mexico:

  • 1. Disorganized showers and thunderstorms over the central Bahamas and adjacent waters are associated with a tropical wave. Environmental conditions could become a little more conducive for development of this system over the Gulf of Mexico. This system is expected to move west-northwestward through the Straits of Florida Monday, over the southeastern Gulf of Mexico by Tuesday, across the central Gulf on Wednesday and reach the northwestern Gulf on Thursday. * Formation chance through 48 hours…low…near 0 percent. * Formation chance through 5 days…low…20 percent.

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