Invest 95E (development into a tropical cyclone likely in the near term)

A broad area of low pressure has formed approximately 300 miles southwest of Guatemala yesterday. Central convection has been on the increase, however, the low level circulation remained broad and elongated. Thus the system remains a disturbance at this time. Maximum winds are estimated at 25 knots.

Upper level analysis reveals a marginally favorable environment with good equatorial outflow and moderate (15 knots) northerly upper VWS. Mid-level humidity and SST (30C) are both conducive for further development. The system is tracking west-northwestward along a mid level ridge to the northeast in the Gulf of Mexico.

By 72h, the aforementioned ridge will weaken and this will allow a turn to the northwest with a decrease a forward speed, which is the main philosophy of the current track forecast. In addition, a slight interaction with the low to mid level low to the west is anticipated, which will also bring the system more poleward.

In the extended range, the system is expected to track toward a weakness in the steering ridge to its north where steering current is anticipated to be weaker.

There is a large spread in track between global models, with GFS taking the system abruptly northward near 72h with ECMWF much farther west. The current track is laid a bit west of the GFS in deference to the usually reliable ECMWF, with low confidence after 48h.

Given the current marginal environment and the loose structure of the cyclone, slow strengthening is indicated for the first 48h. Afterwards, poleward outflow should improve and northerly VWS is expected to decrease as the upper anticyclone near Mexico shifts westward.

Beyond 96h, poleward outflow is expected to diminish as the upper trough that is helping to ventilate the system shifts eastward and along-track SST will drop. These factors will result in gradual spin-down of the system.

The current intensity forecast is hedged a little below intensity consensus due to the fact that a firmer center has not yet formed. But closely follows HWFI at 72h and 96h. The forecast intensity at 120h is well above ICON as some of the guidance will have taken the system inland by that time, which is not the scenario predicted currently.

Overall, confidence is low with regard to intensity.

As there is low confidence in track, a more northerly track could result in issuance of watches and warnings.

Intensity forecast:

24/12z: 25 kt

25/12z: 30 kt (TD)

26/12z: 40 kt (TS)

27/12z: 60 kt

28/12z: 75 kt (Cat. 1)

29/12z: 60 kt

Update on TS Enrique (developed from Invest 95E)

A central dense overcast (CDO) has developed quickly and the cyclone appears to be rapidly strengthening. Therefore the short-term intensity forecast has been revised upward.

Models have also trended northeastward and the forecast track is shifted in that direction.

Northerly shear has abated and environment is expected to be very conducive in the next 48h. Beyond 72h, SST will decrease and outflow will diminish, leading to a weakening trend.

Intensity forecast:

26/00z: 55 kt (TS)

27/00z: 85 kt (Cat. 2)

28/00z: 90 kt

29/00z: 70 kt (Cat. 1)

30/00z: 55 kt

31/00z: 40 kt

Invest 97L (likely a TS within 24 hours and affect US mainland)

Deep convection and the associated low level circulation of a low pressure area (Invest 97L) have become better organized during the day. Subjective Dvorak classification from SAB was T1.5 at 12z, indicating the cloud pattern is sufficiently organized. However, ASCAT and visible imagery both reveal the system's circulation remains slightly elongated, resembling a sharp trough oriented SW/NE. Thus, the system is assessed as a tropical disburbance at this time.

The system is currently located in a favorable environment with sufficiently warm SST (27-28C), light to moderate westerly VWS (10-15 kt) and good upper level divergence. Precipitable water products also indicate the system is well separated from the dry Saharan layer north of the system. The system is being steered generally westward by the deep-layered steering ridge to the north.

The system is expected to continue on a rather rapid west-northwest trajectory under the steering influence of the aforementioned subtropical ridge during the next 48 hours. At the same time, the ridge is forecast by the models to extend westward some as a long-wave ridge propagates from the northeastern US into the Atlantic.

After 72h, a long-wave trough will develop across the eastern US in response to a weakening block behind. This should cause some erosion in the extension of the steering ridge and allow a slow recurve to the northwest into Cuba for the remainder period of the forecast. The current forecast is follows TVCN and GFS more closely and indicate a slightly sharper recurvature than the bulk of the models lying south of the forecast points. But is not as far north as the ECMWF deterministic run which tracks the system into Dominican Republic and exits into the Atlantic on a more northwesterly course.

The GFS and HWRF develops an outflow anticyclone at the back of the system will could shield it from northwesterly VWS. ECMWF does not develop such anticyclone and subjects the system to increased NW'ly shear. The current intensity forecast favor the former scenario and allow significant intensification to take place during the first 72h.

Between 48h and 72h, models indicate the presence of stronger low level easterlies which could impart some mid-level shear and lead to dry air entrainment. The current forecast follows this development and show slower intensification rates. Dry air, lower potential intensity and land interaction will be the primary limiting factor to strengthening and the current forecast peaks it at Catergory 1 hurricane and weakens it some at later times. It should be noted that the intensity forecast is highly uncertain as a track closer or farther away from land could greatly affect the outcome.

Intensity forecast:

30/12z: 30 kt (disturbance)

01/12z: 45 kt (tropical storm)

02/12z: 65 kt (Cat. 1)

03/12z: 70 kt

04/12z: 60 kt (tropical storm)

05/12z: 60 kt

Hurricane Elsa (05L)

24 hours ago, surface observation from Barbadoes confirmed that 05L has strengthened to a Category 1 hurricane. Aircraft reconnaissance shortly afterwards measured winds equivalent to 75 knots, although the mid level circulation at 700mb was not well developed.

Since then, dry air and mid level northwesterly shear have taken their toll and the convective structure of Elsa deteriorated, with the low level center racing ahead of the convective mass located further downstream. Near the time of writing, central convection is on the increase, partly obscuring the exposed center.

The recent aircraft data measured a maximum SFMR wind near 55 knots and flight level winds near 60 knots in the NE quadrant. The intensity is held at 65 knots at this time.

Elsa is located in a marginally favorable environment with moderate (20 knots) of northwesterly shear and with good divergence in all quadrants. Occasional dry intrusions are seen from the west. SST is favorable at 28C. The system is tracking rapidly west-northwestward along the deep-layered subtropical ridge to the northeast.

The system should begin to a gradual turn to the northwest shortly into the weakness of the steering ridge created by the deep trough currently over the eastern US. The forward speed should decrease.

The forecast track takes the system across Haiti and across Cuba's terrain. The system should decrease in intensity to a strong tropical storm due to land interaction and marginal environment.

After emergence into the eastern Gulf of Mexico, higher SST and improved poleward outflow could help the system to briefly re-organize, as suggested by the global models, though mid to upper level shear could still be significant. The current track is hedged just to the left of HWRI to account for the steering effects of lower level flow and in deference to GFS (AVNI).

The system is currently forecast to make landfall in Florida as a moderate tropical storm.

Intensity forecast:

03/12z: 65 kt (hurricane)

04/12z: 55 kt (tropical storm)

05/12z: 45 kt

06/12z: 50 kt

07/12z: 40 kt

08/12z: 35 kt (becoming extratropical)

QPF from WPC: (day 1 to 5), showing the west coast of Florida could receive rain totals of up to 7 inches.

Tropical Depression 07W

Tropical depression 07W is tracking west-northwestward along the southwest periphery of a deep-layered subtropical ridge at a speed of around 20 knots. Current 200-850mb vertical shear is analysed to be low (5-10 knots), however, very strong mid-level flow (30-35 knots) is preventing the system from acquiring a mid-level vortex to facilitate development. In addition, the main outflow mechanism is the presence of an upper inverted trough to the west, which is providing weak poleward outflow.

The system will continue to track west-northwestward at a rapid pace toward eastern Guangdong. Significant intensification is not expected due to the aforementioned marginal environment (significant mid-level shear and lack of upper level support)

Current intensity is being maintained at 30 knots based on 01z ASCAT and persistence.

Intensity forecast:

05/12z: 30 kt (tropical depression)

06/06z: 30 kt

06/12z: 25 kt

Invest 97W (likely to be a TD within the next 12 hours and move toward Hainan Island and intensify)

A broad area of low pressure is located in the central part of the South China Sea. It is producing widespread deep convection. The initial position is estimated with fair confidence based on low level turning (15.5N 112.5E). It is being steered northward to northwestward slowly at first by the deep-layered subtropical ridge to the northeast. The near equatorial ridge to the south is responsible for the current weaker steering environment.

Upper level environment is neutrally favorable (with low ~10 knots VWS and weak outflow mechanism). SST is conducive for development at >30C.

In the next 24 hours, the subtropical ridge will build westward, steering the cyclone to the northwest at a faster pace. At the same time upper level shear will remain at a low to moderate level (10-20 knots), allowing the cyclone to gradually intensify, although outflow should remain rather weak. A slower intensification rate is expected due to the large size of the system.

The system will make landfall over Hainan Island between 36h to 48h and this will lead to steady intensity trend.

Between 48h to 72h, the system is expected to emerge into the Gulf of Tonkin. Conditions will continue to be neutral with high SST (30-31C). However, easterly VWS could increase. Overall these conditions could lead to slight additional strengthening, with the system peaking at 40 knots prior to crossing into Vietnam.

Intensity forecast:

05/12z: 20 kt

06/12z: 30 kt (TD)

07/12z: 35 kt (TS)

08/12z: 35 kt

Tropical Depression 09W

Deep convection have persisted across the broad low level center of a tropical disturbance (Invest 98W). Subjective Dvorak estimates range from T1.0 to T1.5 at 12z and thus the system is classified as a 25-knot tropical depression.

Upper level environment is currently marginal for strengthening with moderate (15 knots) of westerly shear and good eastward outflow enhanced by an upper level low positioned northwest of the system. SST and mid-level humidity are both conducive for development.

Little change in upper level pattern is expected during the next couple of days as the upper low moves further northwestward which will continue to provide some ventilation to the system, while the system moves generally northward along the weak extension of the steering ridge to the east. Some westerly shear is expected during the period and together with the broad nature of the system, only slow intensification is indicated during the next 48 hours, as SST and mid-level humidity continues to support the system.

Between 48 and 96 hours, the GFS indicates that the upper low will weaken while a diabatic ridge in the vicinity of the system strengthens. These should cause a reduction in westerly shear and an increase in poleward outflow.

The scenario depicted by the GFS is favored at this time and the forecast indicates fast to rapid strengthening during this time frame.

The upper ridge should then build westward, cutting off the favorable outflow, as the system tracks westward toward slightly cooler waters near China and Taiwan coast. Therefore, the forecast shows steady intensity trend between 96h and 120h.

The forecast track is hedged slightly south of the 06z GFS deterministic run and is slower to account for the possiblity of binary interaction with a mid-level low to the east of the system. But the general philosophy remains consistent with recent global model runs: the system is expected to turn westward with an increase in forward speed as the mid level ridge across Japan extends westward. Beyond 48h, steering influence from a near equatorial ridge is expected to be minimal.

Overall there is low confidence in track and intensity forecast.

Intensity forecast:

16/15z: 25 kt (TD)

17/12z: 35 kt (TS)

18/12z: 45 kt

19/12z: 65 kt (Cat 1/Typhoon)

20/12z: 95 kt (Cat 2/Typhoon)

21/12z: 100 kt (Cat 3/Typhoon)

Tropical Depression 99W

Tropical disturbance 99W has acquired organized deep convection and a well-defined center as seen on IR and radar imagery. The initial intensity is assessed at 30 knots, slightly higher than Dvorak estimates between T1.0-1.5 (25 knots) based on surface observations. The system is tracking slowly westward under the weak steering influence of a low to mid-level ridge to the north.

Over the next couple of days, the subtropical ridge in the West Pacific is forecast to strengthen and extend southwestward toward the NE quadrant of the circulation, this will lead to a slow track northward toward the coast of Guangdong.

Upper level analysis reveals a favorable environment with weak VWS (5-10 knots) and this conditions will persist during the next couple of days. However, at present upper level outflow is relatively weak. During the next day, a weak upper ridge should begin to build north of the system enhancing poleward outflow.

As such, gradual strengthening is forecast until landfall between 48 to 72h. Afterwards, the track is expected to shift westward as the primary steering ridge in the NE re-orients due to the presence of TS In-fa (09W).

In the long term the system is expected to be caught within the broad mid-level circulation of TS In-fa and rotate anti-clockwise, emerging back into the South China Sea.

Due to the complex steering environment, track forecast confidence is low.

Intensity forecast

18/12z: 30 kt (TD)

19/12z: 35 kt (TS)

20/12z: 50 kt

21/12z: 30 kt

22/12z: 35 kt (TS)

23/12z: 40 kt

Typhoon In-fa (developed from TD 09W)

The tropical depression (09W) has developed steadily over the few days as upper level conditions began to improve. Current intensity is assessed at 95 knots, based on T5.0/90kt and ADT of 102 knots. The system is in a favorable environment with low (5-10 knots) VWS and moderate poleward outflow. SST is near 29C.

The upper low to the northwest, that was previously restricting divergence in the western quadrant of 09W, is forecast to continue weakening and allowing the diabatic ridge positioned northeast of the cyclone to build further, maintaining current upper level environment.

As the system is tracking toward an area of higher OHC, further intensification is expected until 36 to 48h, where along-track OHC/SST is forecast to drop, leading to steady weakening beyond 48h.

The typhoon should move in a westward direction during the next 24 hours, along the southern periphery of a deep-layered steering ridge to the north. Thereafter, the near equatorial ridge is forecast by models to amplify and the steering ridge to the north will begin to re-orient in response to an upstream developing trough. The system will then begin to turn to the northwest. Current track is much slower than ECMWF 06z models and is hedged closer to GFS since I expect the steering ridge to be weaker.

Beyond 96h, the system could be slow-moving due to weak steering current. Forecast track beyond 72h is highly uncertain.

Intensity forecast:

21/12z: 95 kt (Cat 2/Typhoon)

22/12z: 110 kt (Cat 3/Typhoon)

23/12z: 105 kt

24/12z: 85 kt (Cat 1/Typhoon)

25/12z: 65 kt

26/12z: 40 kt (TS)

TS Nepartak (11W)

A surface low is interacting with an upper level trough situated northwest of the elongated center. Strong eastward outflow from the upper trough is fueling deep convection offset to the east of the low level center. An ASCAT image at 10z shows areas of 30-35 knot winds underneath deep convection, and located not too far from the center. On this basis, the disturbance is upgraded to a tropical storm with maximum winds of 35 knots.

Overall environment is marginal for significant strengthening, with strong divergence and warm SST (28-29C) offset by moderate to strong westerly shear (20 knots) and dry mid-level air entrainment associated with the upper trough.

The system is tracking northward under the steering influence from a subtropical ridge to the northeast.

After 48h, 500mb geopotential height north and northeast of the cyclone will rise as an upper trough weakens and departs. This evolution should encourage a more northwesterly trajectory across the seas east of Japan.

Global models diverge beyond 48h, with ECMWF being the more southern member and GFS lying further northeast. The current forecast track lies between the two and favors a stronger ridge than the GFS depicts (which recurves the system northward toward Hokkaido) at later times.

Numerical models indicate continuous dry air entrainment as the system rotates around an mid to upper level low, in addition the present forecast track brings the system to a region of lower SST (26-27C) after 48h, where upper level divergence is expected to decrease, although the storm motion is somewhat in phase with upper level flow. These more hostile conditions argue against further intensification and thus the intensity forecast levels off during its track towards eastern Japan.

Landfall is expected to occur by 96h and the system will emerge into the Sea of Japan shortly afterwards, possibly as a weak tropical storm.

Intensity forecast:

23/12z: 35 kt (TS)

24/12z: 40 kt

25/12z: 45 kt

26/12z: 45 kt

27/12z: 35 kt

28/12z: 35 kt

Invest 90W (will develop into a tropical depression within the next 12-24 hours)

The latest shortwave IR and radar imagery indicate that a surface low pressure and its associated convection is becoming better organized. Upper level analysis from CIMSS reveals favorable environment with low (10-15 knots) easterly VWS and modest divergence toward the north and south. Along track SST is also favorable at 29-30C. The system is tracking eastward along 700hPa monsoonal flow.

Current forecast track anticipates little binary interaction with another low NE of Taiwan and thus the overall track are hedged further north than the GFS run and is closer to the ECMWF. The general philosophy is that Invest 90W will accelerate NE along the northwest periphery of the low to mid level subtropical ridge. The NE motion could be reinforced by the presence of a low pressure area to its north, as depicted by the ECMWF.

The system will track across warm waters with reasonably low shear (<20 kt). In addition, moderate outflow in all directions is expected to establish during the next 72 hours. Thus gradual strengthening is indicated during the next 72 hours. Thereafter, land interaction with Taiwan and later, increasing southwesterly shear could weaken it some.

Intensity forecast:

02/12z: 20 kt

03/12z: 30 kt (TD)

04/12z: 40 kt (TS)

05/12z: 50 kt

06/12z: 45 kt

07/12z: 40 kt (becoming extra-tropical)

Tropical Depression Mirinae (14W)

The system is expected to maintain a general NE track across the south of Japan, under the steering influence of a subtropical ridge centered west of the Dateline. Current forecast track is slower than the 00z ECMWF deterministic run due to the expectation of a weak system embedded in weaker southerwesterlies.

Slow strengthening is anticipated due to persistent shear and dry air entrainment offset by warm SST (28-29C). Beyond 72h, along track SST will decrease to 27C and VWS will increase to an excess of 25 knots, leading to weakening and extra-tropical transition.

Intensity forecast:

05/12z: 30 kt (TD)

06/12z: 35 kt (TS)

07/12z: 40 kt

08/12z: 40 kt

09/12z: 30 kt (becoming extratropical)

Invest 94L (expected to become a tropical cyclone within the next 24 hours)

A tropical disturbance, Invest 94L, is tracking west-northwestward toward the Caribbean Sea along the southern periphery of a subtropical ridge across the Central Atlantic. During the past few hours, deep convection has increased. Upper level analysis reveals a favorable environment with low (10-15 kt) VWS and modest westward outflow. The latest ASCAT pass reveals an elongated circulation with 20-25 kt winds in the western quadrant. Global models generally develop the system between 24 to 48 h as it tracks into the Caribbean Sea. The potential of formation of a tropical cyclone within the next 24 hours is now high.

Some dry air entrainment is expected in the long term along with at least moderate southwesterly VWS associated with an upper level low stretching across the Florida peninsula. In addition, the system could track across land, limiting intensification potential.

Toward the end of the forecast, an approaching mid-level trough should induce a more northwest motion closer toward Florida. At the same time, models indicate increased poleward outflow forced by the upper low and this could allow slight intensification if the vortex remains robust as it interacts with land.

Intensity forecast:

09/12z: 25 kt

10/12z: 35 kt (TS)

11/12z: 45 kt

12/12z: 40 kt

13/12z: 40 kt

14/12z: 45 kt

Potential Tropical Cyclone 07L (will impact the Antilles as a tropical storm, long term track and evolution is uncertain)

Convection has become more concentrated around the low level circulation of Invest 95L. Subjective Dvorak estimate at 12z ranges from T1.5 to T2.0 and the system is assessed as a tropical disturbance of 30 kt. Latest satellite imagery indicates the low level circulation is almost closed and the system is likely to become a tropical cyclone within the next 12-24 hours.

Although the indicated 200-850mb VWS is low (5-10 kt), however, deep convection associated with the mid-level circulation is offset to the west of the partially exposed LLC, due to strong mid-level flow, that is producing an effective easterly shear. Stronger outflow to the west is also contributing to the cloud pattern.

The GFS indicates that the mid-level shear could subside at around 48 h as the steering ridge weakens, however, the system is expected to interact with land shortly afterwards. This reduces the chance of further strengthening.

Between 72 to 96 h, a mid-level closed low that is responsible for the weakening ridge will cause the steering currents to back to a northeasterly direction, which favors a more southern track across the islands. Despite encountering rising humidity and a more favorable upper level outflow channel from an upper level trough (200mb) to the northeast, land interaction and upper westerly shear will most likely keep the intensity down to a low grade TS, if the circulation survives to that point.

The low level ridge will extend westward slightly as TS Fred moves poleward and the westerly component of the low level steering current could maintain a WNW direction at a faster pace.

Current forecast track lies near TVCN until 96 h and is south of TVCN at 120 h in anticipation of a strengthening low level ridge and the weak nature of the cyclone.

Intensity forecast:

14/12z: 30 kt

15/12z: 35 kt (TS)

16/12z: 40 kt

17/12z: 35 kt

18/12z: 35 kt

19/12z: 35 kt

TS Grace (developed from Invest 95L/PTC 07L)

Tropical Cyclone Grace continues to track generally westward with gradual intensification. One significant change is that the updated forecast anticipates a stronger cyclone and thus more poleward track in comparison with the first forecast.

As Grace is now expected to feel less terrain interaction, the forecast intensity is raised at all times.

At present, Grace is located in a favorable environment with low (10-15 kt) of westerly VWS (200-850mb).

In the long term, moderate westerly shear of 15-20 kt is anticipated up to 96 h as the system nears the base of an upper level trough, with improving mid-level moisture, after which the shear direction reverses to easterly and becomes more in phase with the forecast track.

That said, intensity forecast remains uncertain due to high sensitivity to track.

Intensity forecast:

14/12z: 40 kt (TS)

15/12z: 50 kt

16/12z: 50 kt

17/12z: 45 kt

18/12z: 50 kt

19/12z: 55 kt

TS Fred (developed from Invest 94L and now forecast to make landfall in NE Gulf coast as a TS)

TS Fred tracked across mountainous terrain and has weakened into a remnant low at one point. It is now over open water in the Gulf of Mexico where SST is around 30C. The area of upper divergence between an anticyclone and an approaching trough aloft created favorable environment for thunderstorm development and surface pressure has fallen in tandem with a better defined low level circulation.

Current intensity is assessed at 35 knots, based on surface observation in Key West. The system is located in a somewhat favorable environment with strong outflow mechanism aloft, high SST and moderate (15-20 kt) westerly VWS.

The pressure gradient aloft is forecast to increase with the approach of the upper level trough and VWS will increase to 20-25 kt as a result over the next couple of days. However, high SST and favorable divergence will support gradual development until landfall at around 36 h. The cyclone is tracking northwestward around the steering ridge to the northeast. A turn to the north is expected before landfall and the system will recurve NE as it becomes embedded in mid-latitude southwesterlies.

Intensity forecast:

15/12z: 35 kt (TS)

16/12z: 45 kt

17/00z: 50 kt (landfall in NE coast)

17/12z: 40 kt

18/12z: 30 kt (becoming post-tropical)

This might be a off-topic, but I gotta say, this is one of those few forum threads that are factually essential, and also have an educational tinge to it. Kudos to whomever drops us with updates regarding the latest storms brewing across the world's oceans.

TD Grace (07L)

Tropical Depression Grace has tracked westward steadily under the steering influence of a strong and deep-layered ridge to the north. This ridge will extend westward and be responsible for its future westward course across the Caribbean and the Gulf of Mexico.

Dry air entrainment from the west and land interaction has kept the system weak, despite radial upper level outflow.

By 36 h however, the system will track away from land into open water of 30C and models generally show varying degree of strengthening.

Westerly mid to upper level shear will diminish as the system gets closer to Yutacan and tracks into the Gulf of Mexico. Thus a faster intensification rate is indicated.

The system is expected to make landfall over Mexico by 120 h, possibly as a Category 1 or 2 hurricane. Weakening will soon follow.

Intensity forecast:

16/12z: 30 kt (TD)

17/12z: 30 kt

18/12z: 35 kt (TS)

19/12z: 50 kt

20/12z: 70 kt (Cat 1)

21/12z: 55 kt

TS Henri (08L) - Could directly impact New England Coast as an upper-end TS

Tropical Storm Henri (08L) has tracked northwestward over the past few hours, along the SW periphery of an upper level ridge centered.near Bermuda. Aircraft data indicates that the low level center (850mb) is located closer to the northern edge of deep convection - a result of moderate (15-20 kt) northerly VWS. The intensity at 12z is assessed at 55 kt. During the past few hours, deep convection has increased and the system appears to be on a slow strengthening trend over warm waters (29C).

Shear is forecast to decrease to 10 kt (based on GFS-SHIPS output) as upper level flow becomes southwesterly ahead of a mid-latitude trough. As such, gradual strengthening is forecast and the system is expected to become a hurricane within the next 24 hours.

A turn toward the north with an increase in forward speed is forecast while the system gets steered by a mid-level low to the west and a building ridge to the east, between 24 to 72 h. SST will be supportive until shortly before 48 h, at which it will fall sharply to 25C and shear will begin to increase.

The HWRF shows binary interaction with the cut-off mid to upper level low and is on the western side of the guidance at 48 and 72 h. My track is laid just to east of consensus to offset the less likely scenario depicted by HWRF as the system is expected to weaken significantly during that time, following the 500-700mb flow.

After 72 h the system will turn generally northeastward along mid-level westerlies and become a post-tropical cyclone at 96 h. Current track is on the slow and north side of the model spread to account for blocking of eastward motion by the ridge to the east.

Intensity forecast:

20/12z: 55 kt (TS)

21/12z: 65 kt (Cat 1)

22/12z: 70 kt

23/00z: 60 kt (TS)... Near the coast

23/12z: 50 (TS)... Inland

24/12z: 35 kt (post-tropical)

25/12z: 30 kt

Official information:

Ah. My search bar abilities apparently are dogshit. Thank you kindly weather dude.

The graphics here shows the possibility of taking a more westerly track toward NJ so the official track is not set in stone yet.

Broad area of low pressure to develop in Central America/SW Gulf of Mexico

Global models are in agreement that a broad area of low pressure will form in Central America or the southwestern Gulf of Mexico later this week.

Upper level environment is forecast to be generally favorable for tropical cyclone development (with anti-cyclonic outflow aloft), as the system moves west-northwestward into the southwestern Gulf of Mexico, under the steering influence of a strong low to mid-level ridge across the eastern US.

There is moderate confidence of a tropical cyclone formation later this week. The potential system could bring strong winds and rains to eastern Mexico and/or southeastern TX.

The tropical storm Isang was go outside of PAR(Philippine Area of Responsibility)

Invest 95L (East Pacific)

Tropical disturance 95E is located well south of Mexico City. It is tracking west-northwestward along the southern periphery of a low to mid level ridge over CONTUS. Visible imagery depicts a closed circulation in the eastern end of a deep convective band.

Multi-platform satellite surface wind analysis from CIMSS shows a strengthening low level circulation with winds near tropical storm strength at the north side of the circulation. Upper level flow is favorable for intensification with low (10 kt) easterly VWS and strong westward outflow aloft.

Global models show gradual development over the next 24 hours or so and the system is expected to become a tropical storm within the next 24 hours, while continuing west-northwestwards.

During the next 2 to 3 days, primary mid-level steering mechanism will transition to a building ridge SE of the system. At the same time upper level flow will have a more southerly component associated with the western flank of an upper levvel anticyclone. These factors will guide the system poleward closer toward the southwestern coast of Mexico.

Current forecast track is a little to the northeast of consensus to give more weight to GFS, which takes the system inland near 72 h.

Along track SST is conducive at 29C and this argues for steady strengthening over the next 72 h, possibly to a hurricane.

Track uncertainty is high as the spread between guidance members are large and there is a distinct chance of the system making landfall as shown in the GFS. The present track takes it near the coast of Mexico and continues a northwest trajectory toward Baja California Sur in the extended range, with additional intensification.

The 12z GFS-based SHIPS shows a 18% probability of a 65-kt RI in 72 h.

Due to the high uncertainty in track and the formative nature of the storm, significant adjustment may be necessarily in future updates.

Intensity forecast:

25/12z: 30 kt (disturbance)

26/12z: 40 kt (TS)

27/12z: 55 kt

28/12z: 70 kt (Cat 1)

29/12z: 75 kt

30/12z: 60 kt (TS)

Invest 99L (Low pressure area over the Caribbean. Significant strengthening likely and poses threat to Gulf coast)

Early visible images indicate that the low pressure area near the West Caribbean is gradually acquiring a surface circulation. In addition deep convection is becoming more organized with formative banding in the northeast quadrant.

The current intensity is assessed at 30 knots based on T2.0 from SAB and a surface observation of 25 knots from Jamaica. The system is tracking northwestward under the steering influence of a deep-layered ridge off the US East Coast.

The system is in a favorable environment with low (10-15 kt) VWS and radial outflow generated by an upper level anticyclone over the center. SST is favorable at 29C. The mid-levels in the vicinity of the system are gradually moistening with RH values in excess of 70%.

The deep-layered ridge is forecast by global models to remain in place during the next 2 to 3 days and the system is likely to maintain an overall NW track, toward the western tip of Cuba.

Global and regional models are still bullish with its future strengthening, with the most GFS and ECMWF runs deepening the system to near 960mb prior to landfall, while the HWRF deepens it to 940mb. Anomalously high SST in the Gulf of Mexico (30-31C, giving a maximum potential intensity of 160-170kt) is a likely major contribution factor.

Models maintain a trailing upper level anticyclone which should help sustain a robust poleward outflow channel. However, upper level outflow from a developing TS Nora (14E) in the East Pacific could restrict southwesterly outflow from the system. That said, models still predict a relatively low shear environment.

Therefore, significant strengthening is forecast as the system nears the Gulf coast. Current track is placed a little to the west of AVNI (interpolated GFS) in favor of a stronger mid-level ridge. The ridge is forecast by the models to weaken partly due to an approaching positively-tilted trough over interior US and upper level mass evacuation from the cyclone's outflow. As a result, the cyclone is expected to gradually re-curve to the north and northeast near landfall.

Hurricane conditions are possible in the northern Gulf coast later this week. Since the system has not yet developed a strong core, there is still uncertainty with regards to its strength and position at landfall, despite the relatively simple steering environment.

Intensity forecast:

26/12z: 30 kt (Low pressure area)

27/12z: 40 kt (TS)

28/12z: 60 kt

29/12z: 85 kt (Cat 2)

30/00z: 95 kt ... Near the coast

30/12z: 60 kt (TS)

31/12z: 35 kt

TS Ida (developed from Invest 99L)

Expected to rapidly intensify over warm Gulf waters and make landfall as a major hurricane, hurricane watches and storm surge warning currently in effect for part of the northern Gulf coast.

Invest 99L mentioned in the previous post has developed into a tropical storm yesterday. During the past few hours, satellite appearance has become much better organized with a developing central dense overcast obscuring the center. Flight data from recon aircraft measured a peak SFMR near 55 kt and maximum 850mb flight level winds near 70 kt in the NE quadrant. These data support an initial intensity of 55 knots at 15z. The minimum pressure at 13z is estimated at 996mb based on center dropsonde while flight extrapolated MSLP was 992mb at 15z, indicative of continued strengthening.

The system is tracking northwestward steadily over warm SST (29-30C) in the west Caribbean. Upper level analysis indicates the presence of moderate southwesterly shear associated with upper level low to its west, offset by strong divergece. This upper level low is forecast by models to weaken, allowing anticyclonic circulation aloft to expand westward above the system, as Ida emerges into the central Gulf of Mexico with SST above 30C. VWS is also expected to diminish.

Thus rapid strengthening is forecast once the system passes western Cuba.

Global model forecast wind fields show that a weak upper level ridge (at or above 300mb) is present across southern US, directly north of the cyclone. Given that Ida is expected to become a powerful and vertically deep cyclone, the upper ridge could induce a slight westward component to the direction of motion. Hence, the present track is laid closer to the western edge of guidance envelope until 72 h.

Thereafter, rapid weakening is forecast once the system is over land. At the same time, the primary steering ridge is forecast to weaken significantly and the system should re-curve NE along an advancing mid-latitude trough.

Intensity forecast

27/12z: 50 kt (TS)

28/12z: 75 kt (Cat 1)

29/12z: 110 kt (Cat 3)

30/00z: 115 kt (Cat 4) ... Near the coast

30/12z: 75 kt (Cat 1) ... Inland

31/12z: 35 kt (TS)

01/12z: 25 kt (TD)

For possible hazards, visit the NHC website or consult your local weather office.

Hurricane Nora (developed from Invest 94E)

Hurricane Nora (14E) is tracking north-northwestward along the western periphery of the steering ridge into an area of lower geopotential height over Mexico. This direction of motion is expected to continue over the next day or so, taking the system just offshore of southwestern Mexico. It should be noted that the 06z GFS deterministic run and HWRF takes the system inland.

A more northwesterly track is expected on Day 2 to 4 as the system approaches a secondary ridge over Western US. A major trough offshore of Western US is forecast to erode the secondary ridge, resulting a northerly direction of motion between 96 h and 120 h.

Although Nora is currently in a favorable environment with warm SST (29C) and good outflow in northern and southern quadrants with low VWS (10 kt), the system is approaching land. So only little, if any, strengthening is anticipated over the next 24 hours.

Afterwards, environment appears to be conducive at 48 and 72 h once the begins to move into the Gulf of California, where SST is at 30-31C. Models predict Nora to be located underneath an upper anticyclone which will provide low VWS and modest poleward outflow. At the same time, however, mid-level RH could decrease. Thus a steady trend is predicted during this time.

Beyond 72 h, continued dry air entrainment and a gradual increase in southerly VWS, as well as land interaction, could start a weakening trend. Current intensity forecast lies on the high side of guidance.

Intensity forecast:

28/12z: 70 kt (Cat 1)

29/12z: 75 kt

30/12z: 80 kt

31/12z: 80 kt

01/12z: 65 kt

02/12z: 45 kt (TS)

This looks like it's going to be bad. Hope everyone is safe.

Well, at least people have more time to prepare compared with the year 2005.

Back in those days it would be impossible to predict this level of strengthening and the rough landfall position days in advance.

Hurricane Ida making landfall in southeast Louisiana in a few hours as a Category 4 hurricane

Hurricane Ida maintained a symmetrical CDO with cloud tops of -70C and a defined infra-red eye as it nears landfall.

A dropsonde inside the eye measured a surface pressure of 931 mb with 12 kt surface winds, yielding an estimated minimum pressure of near 930 mb.

Maximum flight level winds (at 700 mb) observed was 148 kt (corresponding to surface winds of 133 kt)

Maximum SFMR winds observed was 130 kt. These data support an intensity of 130 kt (Category 4)

SST in the northern Gulf is around 30C, giving a maximum potential intensity between 150-165 kt.