KoritheMan's WunderBlog

Tropical weather analysis - July 31, 2012

By: KoritheMan, 1:23 AM GMT on August 01, 2012

Invest 99L

A vigorous tropical wave located about 1150 miles east-southeast of the Windward Islands is showing signs of organization. Last light visible satellite images and recent microwave data indicated a gradually improving circulation. Unfortunately, due to issues with the website, I have been unable to utilize ASCAT or OSCAT data, and WindSat missed the disturbance.



Figure 1. Latest infrared satellite image of Invest 99L. Image credit: NOAA

An upper low near 27N 44W has intensified over the past few hours, and has a rather large horizontal extent of cyclonic vorticity. Apparently, the southern end of this flow has reached the northern fringes of Invest 99L. As a result, upper-level outflow has improved in that direction.

All of the common factors appears to be present for intensification -- low shear, warm ocean temperatures, and a relatively moist environment. On the other hand, this low is rather close to the equator, which will limit the amount of spin the system can generate. In addition, the system is still embedded in the Intertropical Convergence Zone (ITCZ), a low-latitude belt of convection that is responsible for much of the precipitation across equatorial regions. Until 99L can break away from that, it will be slow to organize. There is currently very little indication of any northward component of motion, and 99L still remains below 10N. However, with the influence of the upper low spreading south, a slow increase in latitude should occur over the next few days. Although 99L has done well for itself up to this point, it is not uncommon for tropical waves or perturbations to look healthy while the ITCZ is aiding in precipitation. The test of time as it were, will come after the system breaks free from the grip of the ITCZ. At that point it will be forced to sustain itself on its own dignity. Since there is still dry air outside the comfort of the ITCZ, I find it a little hard to believe that 99L will rapidly organize.

Interestingly, the GFS dissipates the system as it moves through the central Caribbean. Although that portion of the Caribbean is generally unfavorable for tropical cyclogenesis, full-fledged tropical cyclones typically do a little better. Since the TUTT axis is north of the Greater Antilles, and I expect 99L to stay south of those islands, it is a little puzzling why this model weakens the system, especially considering it also shows low shear. Perhaps it is because the trade winds, as indicated by buoy reports, have picked up a little today. More likely, these are daily fluctuations within the strength of the Bermuda-Azores ridge, the sole driver of easterly winds in that region. Since these fluctuations are both natural and difficult to predict, I have not placed much weight on the GFS forecast of dissipation. In addition, there doesn't appear to be any significant low-level speed shear on water vapor imagery.

As for track, that's always the most important question, but it's also one of the hardest. Water vapor images show a large ridge over the central United States with an amplified trough downstream over the eastern United States and western Atlantic. While this would ordinarily be a motif toward recurvature, the global models are unanimous in slowly lifting out this feature over the next 72 hours. This evolution should allow 99L to avoid moving too far north through the next five days, especially considering its location. My current thinking is a generally west-northwest path through the eastern and central Caribbean. Where it goes after that is still speculative, and the model variability within the synoptic pattern favors an eventual landfall on the US east coast, the US Gulf Coast, or even Central America and/or Mexico.

I do expect gradual development of this disturbance, but I am not ready to give explicit mention of a tropical depression just yet.

Probability of development in 48 hours: 50%



Elsewhere

Elsewhere, a convectively active tropical wave is over the northeast Caribbean. There are no signs of organization, and upper-level winds are expected to remain unfavorable for development as the system moves west-northwest toward the Bahamas and south Florida. Locally heavy rains will continue impacting portions of the Greater Antilles through Wednesday.

Probability of development in 48 hours: 0%

2012 Atlantic hurricane season Invest 99L

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Tropical weather analysis - July 30, 2012

By: KoritheMan, 7:22 AM GMT on July 30, 2012

Invest 99L

After a month of nary a single invest, one has finally been declared this morning in the eastern Atlantic, in association with a tropical wave. This wave, centered about 750 miles southwest of the Cape Verde Islands, is showing signs of organization. The shower activity is displaced west of the wave axis due to easterly shear.



Figure 1. Latest infrared satellite image of Invest 99L. Image credit: NOAA

The SHIPS brings the system to just under hurricane strength early Saturday morning. The current shear is expected to abate; however, I note that the thermodynamics do not look all that favorable. The global models respond to this with differing solutions. The ECMWF does not develop it and eventually shoots it westward into Central America as it follows the lower-tropospheric flow. The CMC is the fastest in calling for a full-fledged tropical cyclone in about 72 hours. The GFS projects a more delicate balance and slowly develops the system through the weekend. I prefer the GFS solution given the unfavorable thermodynamics, and the system's relatively low latitude. Also, given the fairly large wind field with the system, entrainment of dry air into the circulation as the low attempts to consolidate is distinctly possible.

Water vapor imagery depicts a large upper low near 26N 41W dropping southward toward 99L. All of the models initialized this feature and do not show appreciable interaction between the two systems. However, this vortex appears to be fairly strong above 500 mb, so 99L develops quicker than anticipated, it would likely move more toward the west-northwest and potentially miss the Lesser Antilles. This is the solution favored by the CMC. Again, given the subsidence lying in the path of the system, this seems unlikely for now. The models also have differing thoughts on the synoptic pattern at longer ranges. The GFS and ECMWF generally show a stronger and westward-expanding ridge, while the CMC prefers to linger a trough along the eastern seaboard. I am not going to waste time hypothesizing how things will evolve. Right now all we have is a tropical wave worth monitoring, and we should leave it at that pending future developments in either direction.

But I will say that given the system's low latitude, and the fact that it should remain relatively weak for the next few days, prompts me to prefer a system that tracks through the Caribbean and eventually into the Gulf of Mexico. I'm not particularly comfortable with even saying that much though, but that is the sort of track I see in my crystal ball should the system consolidate in the area it's in now.

Probability of development in 48 hours: 20%

2012 Atlantic hurricane season Invest 99L

Updated: 7:26 AM GMT on July 30, 2012

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Tropical weather analysis - July 24, 2012

By: KoritheMan, 2:36 AM GMT on July 25, 2012

Invest 98L

A non-tropical area of low pressure producing winds to near gale force is centered about 700 miles east-northeast of Bermuda. Earlier microwave data suggested a well-defined surface circulation, with strong convective banding west of the center. Since that time, convection has weakened considerably -- or more accurately vanished, although low-cloud lines still suggest a decent circulation. More recent microwave data confirms this, but implies that the circulation is a little less organized than this afternoon.



Figure 1. Latest infrared satellite image of Invest 98L. Image credit: NOAA

An amplifying cold front over New England is poised to increase the net westerly shear over the disturbance. This, and the rapidly deteriorating structure suggests that 98L is not long for this world. The global models suggest its small circulation will become absorbed into the aforementioned low in about two to three days. It should be noted that before the merger occurs, the fast forward motion of the system combined with the steep pressure gradient to the east should maintain relatively strong winds across that portion of the surface low.

Probability of development within 48 hours: 10%



Invest 90E

A tropical disturbance centered about 1100 miles southwest of Manzanillo ("90E") has not made much progress today. In fact, the National Hurricane Center steadily decreased development probabilities since my previous forecast, now down to 40%.



Figure 2. Latest infrared satellite image of Invest 90E. Image credit: NOAA

Interestingly, anticyclonic flow is actually starting to develop above the vertical circulation, which suggests a lessening of the shear. While this would normally presage intensification, high cloud motions and the flat outflow pattern on the eastern side of the low suggests northeasterly shear. Environmental conditions still appear conducive for some eventual development of this system, although the disorganized nature of the circulation suggests that any such potential will be slow.

I still expect 90E to move west and cross into the central Pacific area of responsibility on Saturday. The global models are in good agreement with this scenario. Subsequent to crossing 140W, cooler waters should cause weakening. Additionally, if the system moves north of 15N, strong westerly shear associated with the mid-oceanic trough over Hawaii awaits it, guaranteeing a gruesome death. Analysis of the various global model forecast fields suggest that a rather large weakness will be present near the latitude of the Hawaiian Islands by the weekend. Ordinarily this would alarm me about a possible threat to the Hawaiian Islands. However, further analysis reveals that this weakness is not nearly as strong below that level. Since 90E is expected to lack vertical integrity by that time, a more westward to west-northwestward track to the south of the subtropical ridge seems like a more reasonable prognosis. However, it could pass about 100 miles south of the Big Island through early next week, which is likely to produce an interruption in the easterly flow, as well as enhance shower activity.

Probability of development in 48 hours: 40%

Eastern Atlantic development still possible

The possible tropical wave I mentioned yesterday has emerged from west Africa, accompanied by a decent lower-tropospheric signature. This wave still needs to be watched, as upper-level conditions could improve as it moves westward over the next few days. Another wave-like entity moving across Mali may also need to be watched given the convective vigor.

The African wave train is starting, and so is the season. I think.

2012 East Pacific hurricane season Invest 90E Invest 98L 2012 Atlantic hurricane season

Updated: 2:45 AM GMT on July 25, 2012

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Tropical weather analysis - July 24, 2012

By: KoritheMan, 6:11 AM GMT on July 24, 2012

Invest 90E

An area of low pressure centered about 950 miles south-southwest of Manzanillo has the potential to become a tropical depression over the next day or two. Considering its heroics and longevity, I remain unimpressed with this system, with the broad low-level center along the northern edge of the convective mass.



Figure 1. Latest infrared satellite image of Invest 90E. Image credit: NOAA

It is not immediately clear what is holding this system back. Waters are warm, shear is seemingly low, and an abundance of moisture surrounds the system. It could be due to local competition from the Intertropical Convergence Zone (ITCZ). Regardless, I have to assume that this system will organize further amidst the seemingly favorable environmental factors.

Based on the conglomeration of the various global model forecasts, 90E will be yet another system that crosses 140W longitude into the central Pacific basin. But before it actually gets there, there is a bit of disagreement concerning the evolution of a trough forecast to evolve off the west coast. The NOGAPS, GFS, and ECMWF have a less amplified, more zonal flow north of 90E, which would portend a westward track. The CMC and GFDL, on the other hand, have a more northerly solution underneath a more amplified steering regime. Based on current synoptic trends observed on water vapor imagery, I tend to favor the more western solution. By Friday, 90E is expected to turn north as it nears 135W, where cooler water and westerly shear are expected to bring out a swift demise.

I note that none of the global models have been particularly enthusiastic regarding development with this system, with the only real infatuation being with the GFS. Given the system's failed efforts to organize thus far, they may be onto something.

Probability of genesis in 48 hours: 70%

Atlantic waking up?

An area of convection over western Africa, possibly a tropical wave, was shown by the 0z GFS to develop into a hurricane and threaten Florida in the long-range. While this kind of pattern seems to thematic this year, it is far too early to speculate. But given that this model has been hinting that the eastern Atlantic should become more convectively active, this is something that cannot be ignored. Climatologically, we are only a couple weeks behind the typical arrival of the Cape Verde season, where some of the strongest hurricanes in the basin originate.

There is also a non-tropical low several hundred miles east-northeast of Bermuda. Although the system possesses a fairly robust circulation, environmental conditions are not conducive for significant development as it moves steadily northeastward.

Probability of genesis in 48 hours: 10%

Invest 90E 2012 East Pacific hurricane season

Updated: 6:16 AM GMT on July 24, 2012

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Tropical weather analysis - July 14, 2012

By: KoritheMan, 12:39 AM GMT on July 15, 2012

Emilia

Tropical Storm Emilia is hanging on. As of the most recent NHC advisory, the following was posted on the storm:

Wind: 50 mph, with higher gusts
Location: 15.5°N 132.9°W
Movement: W at 15 mph
Pressure: 997 mb
Category: Tropical storm

Although passage over briefly warmer waters helped to reinvigorate the convection over the last 12-24 hours, Emilia is finally showing signs of a consistent weakening trend. The SHIPS thinks the system is now over water temperatures of 24.5C, and that was as of 18z. Current convective trends would certainly lend some validation to that claim. SSMIS data from several hours ago indicated that the lower- and middle-tropospheric circulations were becoming decoupled. Dvorak numbers are correspondingly beginning to plummet.



Figure 1. Latest infrared satellite image of Tropical Storm Emilia. Image credit: NOAA

Time is running out for Emilia. It continues to move through a very dry airmass, and westerly shear is forecast to increase on Tuesday. This should decapitate whatever is left of the remnant low pressure area by that time.

Emilia continues to move westward south of the subtropical high. This general motion is expected to continue throughout the remainder of the forecast period. The models continue to suggest the possibility of a more south of west motion as the system moves into the central Pacific, but I am having a hard time seeing such a motion. My forecast track will thus not commit to such a sharp southward bend.

5-day intensity forecast

INITIAL 07/14 2100Z 45 KT 50 MPH
12 hour 07/15 0600Z 35 KT 40 MPH
24 hour 07/15 1800Z 30 KT 35 MPH...POST-TROP/REMNANT LOW
36 hour 07/16 0600Z 30 KT 35 MPH...POST-TROP/REMNANT LOW
48 hour 07/16 1800Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
72 hour 07/17 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW
96 hour 07/18 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW
120 hour 07/19 1800Z...DISSIPATED

5-day track forecast



Figure 2. My 5-day forecast track for Emilia.



Fabio

Hurricane Fabio has reached Category 2 strength. I mentioned yesterday that it had a chance to achieve such an accolade, but this was a little later in the game than I had anticipated. Regardless, the following was posted on the storm in the special advisory just released from the National Hurricane Center:

Wind: 105 mph, with higher gusts
Location: 16.4°N 115.4°W
Movement: WNW at 9 mph
Pressure: 972 mb
Category: 2 (Saffir-Simpson Hurricane Scale)

The hurricane has a remarkable satellite appearance, with earlier microwave data suggesting a large eye with a well-defined eyewall. Since that time, convection has increased in both coverage and intensity around the cloud-filled eye.



Figure 3. Latest infrared satellite image of Hurricane Fabio. Image credit: NOAA

There is still some northeasterly shear over the system, but it does not look as strong as in recent days. Fabio has probably peaked in intensity, given that it will soon traverse the 26C isotherm. However, it is interesting to note that the last few Eastern Pacific tropical cyclones have taken full advantage of warm waters, so who knows what Fabio has in store in the next few hours. In any case, Fabio should soon begin to weaken as underlying sea surface temperatures cool. By Monday, areal water temperatures decline sharply, and Fabio is expected to respond by rapidly deteriorating. The cyclone is forecast to become a remnant low in about four days, though it could occur a little sooner, especially if vertical shear increases over the hurricane at longer ranges. For now my intensity forecast mirrors that of the National Hurricane Center.

Water vapor imagery and real-time steering analyses suggest that the ridge to the north of the hurricane is weakening with the approach of a trough over the western United States. However, the imagery also suggests that this weakness is very slight, and the ridge is expected to only slowly deamplify. There is still some disagreement amongst the various model members as to how soon Fabio will turn, but in general they have come into better agreement today. I continue to favor the gradual -- rather than rapid -- northward turn I have indicated in previous forecasts. High-level moisture from Fabio's mid-level vorticity maximum is still expected to reach southern California on Thursday, leaving the low-level center far behind.

5-day intensity forecast

INITIAL 07/15 0000Z 90 KT 105 MPH
12 hour 07/15 0600Z 85 KT 100 MPH
24 hour 07/16 1800Z 75 KT 85 MPH
36 hour 07/17 0600Z 65 KT 75 MPH
48 hour 07/18 1800Z 55 KT 65 MPH
72 hour 07/19 1800Z 35 KT 40 MPH
96 hour 07/20 1800Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
120 hour 07/21 1800Z 25 KT 30 MPH...POST-TROP/REMNANT LOW

5-day track forecast



Figure 4. My 5-day forecast track for Fabio.

Tropical Storm Emilia Hurricane Fabio 2012 East Pacific hurricane season

Updated: 12:39 AM GMT on July 15, 2012

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Tropical weather analysis - July 13, 2012

By: KoritheMan, 2:24 AM GMT on July 14, 2012

Emilia

Emilia has weakened to a tropical storm. The latest NHC coordinates were as follows:

Wind: 50 mph, with higher gusts
Location: 15.5°N 127.2°W
Movement: W at 15 mph
Pressure: 996 mb
Category: Tropical storm

The cyclone continues to generate convection, and has actually gained a little bit of organization in recent satellite frames. However, arc clouds can be seen emanating from the eastern quadrant, meaning that Emilia is struggling with dry air. The deepest convection is limited to the southern semicircle. Not surprising considering that portion of the circulation is over slightly warmer water temperatures.



Figure 1. Latest infrared satellite image of Tropical Storm Emilia. Image credit: NOAA

Emilia is expected to continue weakening as it moves westward south of a strong subtropical high. Big brother Daniel seemed to fare better at this longitude than Emilia did. Perhaps it is because his little sister is passing over his cool wake. However, I have not analyzed the areal sea surface temperatures very much, so this is admittedly speculation on my part. In any event, the cyclone is forecast to dissipate by Sunday, quicker than in my previous evaluation. Emilia is expected to pass far enough south of the Big Island next week as to not deliver any appreciable rainfall. However, the vigorous cyclonic circulation associated with then post-tropical Emilia will undoubtedly disrupt the trade wind flow that normally dominates the region.

There isn't much new to say about the forecast track, either. The cyclone is expected to continue moving west until it crosses 140W longitude, at which point the models suggest a turn to the southwest could begin.

5-day intensity forecast

INITIAL 07/13 2100Z 45 KT 50 MPH
12 hour 07/14 0600Z 40 KT 45 MPH
24 hour 07/14 1800Z 35 KT 40 MPH
36 hour 07/15 0600Z 30 KT 35 MPH...POST-TROP/REMNANT LOW
48 hour 07/15 1800Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
72 hour 07/16 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW
96 hour 07/17 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW
120 hour 07/18 1800Z 20 KT 25 MPH...POST-TROP/REMNANT LOW

5-day track forecast



Figure 2. My 5-day forecast track for Emilia.



Fabio

Fabio strengthened to the fifth hurricane of the Eastern Pacific season earlier today, over a month ahead for the climatological date of August 26. The most recent NHC advisory had this to say:

Wind: 80 mph, with higher gusts
Location: 15.6°N 111.4°W
Movement: WNW at 10 mph
Pressure: 986 mb
Category: 1 (Saffir-Simpson Hurricane Scale)

The cloud pattern is gradually becoming better organized, and Fabio still has a chance to intensify a little more. However, the large-scale environment does not appear conducive to rapid intensification. A ragged eye feature is evident in satellite pictures, with vigorous convection encompassing it to the east.



Figure 3. Latest infrared satellite image of Hurricane Fabio. Image credit: NOAA

Fabio is still experiencing northeasterly shear, which appears to be defying me and sticking around longer than I had anticipated. But as alluded to yesterday, this shear does not appear strong enough to penetrate the core and cause weakening. I guess I owe the SHIPS credit after all, at least for predicting the shear to stick around.

Interestingly, there seems to be a flagrant dichotomy between the SHIPS SST output, and that provided by AOML. As of 0z, the former insists that Fabio is sitting underneath water temperatures of 27.6C, while the latter suggests that the hurricane is about to traverse the 26C isotherm. Lacking any real-time observations in the vicinity of the hurricane to confirm or deny either analysis, I have little choice but to judge by the current cloud pattern. With little apparent reason, convection is weakening in the western semicircle, which probably means that the SHIPS analysis of areal water temperatures is a little high. However, I sincerely doubt any portion of Fabio is over sub-26C water at the moment, and with little change in the environment since yesterday, I will continue to call for intensification for the next 12-24 hours. Thereafter, the hurricane should begin to weaken even though the shear is forecast to decrease. SSTs drop off sharply after about 48 hours, so rapid weakening is expected subsequent to that point. Fabio is forecast to dissipate by the end of the forecast period, although given the cold waters it could occur sooner. Although not explicitly shown, there is still a chance Fabio could briefly become a Category 2 hurricane prior to encountering the cooler waters.

As far as track, the models have generally come into better agreement, with Fabio expected to gradually turn north. A northeastward turn is possible at the end of the forecast period, although this is not explicitly indicated at this time. Fabio is likely to enhance moisture across portions of southern California and the desert southwest next week as its mid-level remnants move northward.

5-day intensity forecast

INITIAL 07/13 2100Z 70 KT 80 MPH
12 hour 07/14 0600Z 80 KT 90 MPH
24 hour 07/14 1800Z 80 KT 90 MPH
36 hour 07/15 0600Z 70 KT 80 MPH
48 hour 07/15 1800Z 60 KT 70 MPH
72 hour 07/16 1800Z 45 KT 50 MPH
96 hour 07/17 1800Z 30 KT 35 MPH
120 hour 07/18 1800Z 25 KT 30 MPH...POST-TROP/REMNANT LOW

5-day track forecast



Figure 4. My 5-day forecast track for Fabio.

Tropical Storm Emilia Hurricane Fabio 2012 East Pacific hurricane season

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Tropical weather analysis - July 13, 2012

By: KoritheMan, 6:30 AM GMT on July 13, 2012

Emilia

Emilia remains a hurricane, but is steadily weakening. The latest NHC advisory had this to say about the status of the hurricane:

Wind: 85 mph, with higher gusts
Location: 15.4°N 123.5°W
Movement: W at 12 mph
Pressure: 979 mb
Category: 1 (Saffir-Simpson Hurricane Scale)

The hurricane continues to wind down. An eye is no longer discernible on satellite pictures, and this feature is quickly vanishing in microwave imagery as well. Convection is thinning out in the eastern quadrant all the while, likely due to dry air infiltrating that portion of the circulation.



Figure 1. Latest infrared satellite image of Hurricane Emilia. Image credit: NOAA

There is little change to either the track or intensity forecast. Emilia is embedded in a large-scale easterly steering regime to the south of the subtropical ridge. The reliable global models suggest this pattern will continue, with little chance of poleward movement here on out. This is supported by water vapor imagery, which shows a swift easterly current expanding westward ahead of the hurricane. A weakness is evident west of 145W, but Emilia is expected to be too weak to respond to this feature by that time. My forecast track remains rather close to the National Hurricane Center.

Although upper-level winds remain light, a large area of dry air lies in the path of the cyclone. That, in combination with the sub-26C SSTs which will only get cooler, are expected to contribute to continued weakening. Emilia is forecast to dissipate Monday evening, in agreement with the state of the art GFS and ECMWF. Remnant shower activity may still overspread portions of the Big Island next week as the low passes to the south.

5-day intensity forecast

INITIAL 07/13 0300Z 75 KT 85 MPH
12 hour 07/14 1200Z 65 KT 75 MPH
24 hour 07/14 0000Z 55 KT 65 MPH
36 hour 07/15 1200Z 50 KT 60 MPH
48 hour 07/16 0000Z 40 KT 45 MPH
72 hour 07/17 0000Z 30 KT 35 MPH
96 hour 07/18 0000Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
120 hour 07/19 0000Z 25 KT 30 MPH...POST-TROP/REMNANT LOW

5-day forecast track



Figure 2. My 5-day forecast track for Emilia.

Fabio

Tropical Storm Fabio is intensifying. As of the latest NHC advisory, the following information was posted on the tropical cyclone:

Wind: 60 mph, with higher gusts
Location: 13.9°N 109.0°W
Movement: W at 10 mph
Pressure: 998 mb
Category: Tropical storm

The tropical storm is fairly well-organized, with numerous curved bands to the south of the center. The inner core appears to be slowly getting better organized, with earlier microwave images suggesting the formation of an eye. Such a feature is not yet evident on conventional satellite imagery.



Figure 3. Latest infrared satellite image of Tropical Storm Fabio. Image credit: NOAA

There is still some northeasterly shear over the system, but there is evidence that the anticyclone responsible for the shear has retreated eastward a little bit as a shortwave trough moves into the western United States. The SHIPS model doesn't want to fully decrease the shear until Fabio is well within sub-26C waters. However, despite its name, this isn't the most reliable model for hurricane intensity prediction, and in my experience its forecasts are based largely on continuity and persistence, neither of which are particularly useful as predictors for tropical cyclone intensity. The GFS doesn't think the shear will relax for another 12-18 hours. It probably has the right idea, but I also think it analyzes a bit too much shear over Fabio. I will forecast gradual strengthening for the next 12 hours, followed by a quicker pace of intensification thereafter. Fabio is expected to become a hurricane by around 0z Saturday, though if the shear relaxes sooner than indicated, or if an eye appears out from underneath the well-defined convective band near the center, this could occur sooner, especially since the lingering shear does not appear to be penetrating the core. By Sunday, Fabio is expected to begin moving into cooler waters, should promote weakening. Fabio is expected to weaken fairly rapidly over these waters, which will cool faster than they did with Daniel or Emilia.

The track forecast is a bit more complicated. Fabio is currently situated to the south of a deep-layer ridge. This ridge is forecast to slowly break down over the next few days as a series of shortwave impulses ride the belt of westerlies into the Pacific northwest. The net result will be a large baroclinic zone amplifying across that portion of the country. Although the models are good agreement on this, and for the first 48 hours of the track, there are notable discrepancies thereafter. The GFS and ECMWF suggest a more less amplified trough, and consequently show a slower recurve. The CMC shows a sharper turn to the north, as did the 18z HWRF. I prefer to side with the GFS and ECMWF pair, since they are difficult to beat when in agreement like this.

It is worth noting that a trough over the west coast and a ridge over the Rockies/Intermountain West is the exact pattern we have been cognizant of that would be capable of slamming a tropical cyclone into southern California. Although Fabio is not expected to be a tropical cyclone, its mid-level remnants may move into southern California on Thursday or Friday and deliver locally heavy rains. If Fabio was moving just a little faster, we could be talking about the potential for a tropical depression or tropical storm moving into southern California this time next week, which would be a rather significant historical event.

5-day intensity forecast

INITIAL 07/13 0300Z 50 KT 60 MPH
12 hour 07/13 1200Z 55 KT 65 MPH
24 hour 07/14 0000Z 65 KT 75 MPH
36 hour 07/14 1200Z 75 KT 85 MPH
48 hour 07/15 0000Z 85 KT 100 MPH
72 hour 07/16 0000Z 75 KT 85 MPH
96 hour 07/17 0000Z 45 KT 50 MPH
120 hour 07/18 0000Z 30 KT 35 MPH

5-day track forecast



Figure 4. My 5-day forecast track for Fabio.

Hurricane Emilia Tropical Storm Fabio 2012 East Pacific hurricane season

Updated: 6:31 AM GMT on July 13, 2012

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Tropical weather analysis - July 11, 2012

By: KoritheMan, 4:17 AM GMT on July 12, 2012

Emilia

Emilia made a bit of a comeback this evening, enough to make it a major hurricane again. As of the latest NHC advisory, the following was posted:

Wind: 115 mph, with higher gusts
Location: 15.0°N 119.1°W
Movement: WNW at 9 mph
Pressure: 962 mb
Category: 3 (Saffir-Simpson Hurricane Scale)

The hurricane hasn't really changed much. It continues to exhibit a large cloud-filled eye along with a well-defined outflow pattern, especially to the west. The storm continues to be hindered by easterly shear as evidenced by the disheveled appearance to the outflow in that direction. I suspect any such shear is confined below the outflow layer, giving some indication of mid-tropospheric shear.



Figure 1. Latest infrared satellite image of Hurricane Emilia. Image credit: NOAA

In any event, Emilia has probably made its last hurrah. The cyclone is currently sitting underneath 26C SSTs, but these already marginal water temperatures are forecast to steadily cool as the hurricane moves westward. This should counteract the expected weakening of the vertical wind shear currently afflicting the system. Emilia is likely to dissipate in about five days, although long-range global model prognostications suggest that a weak remnant low may approach the Hawaiian Islands this time next week, enhancing shower activity.

The hurricane is being propelled toward the west-northwest by a large amplitude ridge to the north which the global models insist will strengthen and build westward ahead of the tropical cyclone over the next few days. The net result should be a continued west-northwest motion in the interim, followed by a turn toward the west later in the period. This forecast track is rather close to the National Hurricane Center's, and to the multi-model consensus, except a smidgeon faster at day five to account for the possibility of the ridge being stronger than anticipated, as the spatial depiction of it in the model fields is rather impressive.

5-day intensity forecast

INITIAL 07/12 0300Z 100 KT 115 MPH
12 hour 07/12 1200Z 95 KT 110 MPH
24 hour 07/13 0000Z 85 KT 100 MPH
36 hour 07/13 1200Z 70 KT 80 MPH
48 hour 07/14 0000Z 55 KT 65 MPH
72 hour 07/15 0000Z 35 KT 40 MPH
96 hour 07/16 0000Z 30 KT 35 MPH
120 hour 07/17 0000Z 25 KT 30 MPH...POST-TROP/REMNANT LOW

5-day forecast track



Figure 2. My 5-day forecast track for Emilia.

Invest 98E

A well-defined area of low pressure is centered several hundred miles south of Acapulco. Although at first glance this low perhaps looks organized, satellite and microwave data suggest that the low-level center remains on the northeast edge of the convection due to moderate northerly to northeasterly shear. Earlier scatterometer data also indicated that the strongest winds are to the south of the center.



Figure 3. Latest infrared satellite image of Invest 98E. Image credit: NOAA

The current northeasterly shear is forecast to relax over the next 12-24 hours, which should allow the system to become a tropical depression or tropical storm on Thursday. Afterward, upper-level winds are expected to become quite favorable for development, and it is possible that 98E could eventually become a hurricane. The global models are in relatively good agreement with this prospect. By Sunday, the system is forecast to approach cooler waters and begin to weaken.

The track forecast is a little more difficult. Some of the models call for a straight northward shot into Baja California after Saturday, with remnant mid-level moisture eventually spreading into portions of southern California and the desert southwest. Others call for a more northwesterly motion that merely parallels the coastline. All will be made clear when the large baroclinic zone and its fancy upper level swirls move into and then amplify over the Pacific northwest. However, models differ with regards to the timing and depiction of this trough, with some calling for a flatter trough, and others calling for a more amplified trough. The more amplified regime would favor the more northward track. Considering the typically reliable ECMWF is showing a northward component ensuing over the weekend, this is something that cannot be rightfully ignored.

Probability of development within 48 hours: 90%

Invest 98E Hurricane Emilia

Updated: 4:18 AM GMT on July 12, 2012

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Tropical weather analysis - July 10, 2012

By: KoritheMan, 6:32 AM GMT on July 10, 2012

Daniel

Persistent Daniel remains a hurricane as of the latest NHC advisory:

Wind: 75 mph, with higher gusts
Location: 15.4°N 132.2°W
Movement: W at 17 mph
Pressure: 992 mb
Category: 1 (Saffir-Simpson Hurricane Scale)

The hurricane remains well-organized considering it is moving over sea surface temperatures of 24C. Daniel continues to generate deep convection, especially to north and the east. This is confirmed by a recent SSMI microwave overpass, which captured the inner core of the circulation quite well.



Figure 1. Latest infrared satellite image of Hurricane Daniel. Image credit: NOAA

Although Daniel remains in a low shear environment, a very dry airmass and cool water temperatures are expected to bring about weakening and eventual dissipation of the hurricane. In addition, the GFS and the GFS-based SHIPS algorithm foresee an abrupt increase in northwesterly shear in about 48 hours. Daniel is likely to drop back down to a tropical storm soon. Most of the models lose the circulation several hundred miles south of the Big Island on Friday the 13th. So do I.

There has been little change to the track philosophy with Daniel. It is being steered westward by a strong mid-level ridge. This ridge is already expanding westward ahead of the hurricane, and a continuation of this general pattern is expected throughout the remainder of the cyclone's existence.

My forecast track remains similar to the 12z ECMWF and that of the National Hurricane Center.

5-day intensity forecast

INITIAL 07/10 0300Z 65 KT 75 MPH
12 hour 07/10 1200Z 55 KT 65 MPH
24 hour 07/11 0000Z 45 KT 50 MPH
36 hour 07/11 1200Z 40 KT 45 MPH
48 hour 07/12 0000Z 30 KT 35 MPH
72 hour 07/13 0000Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
96 hour 07/14 0000Z 25 KT 30 MPH...POST-TROP/REMNANT LOW
120 hour 07/15 0000Z...DISSIPATED

5-day track forecast



Figure 2. My 5-day forecast track for Daniel.

Emilia

As expected, Emilia has reached major hurricane strength. The latest NHC advisory had this to say about the hurricane:

Wind: 120 mph, with higher gusts
Location: 13.3°N 112.2°W
Movement: WNW at 14 mph
Pressure: 959 mb
Category: 3 (Saffir-Simpson Hurricane Scale)

Emilia is a small but powerful hurricane. The eye has recently become cloud filled, but this is probably just a hiccup in the internal organization.



Figure 3. Latest infrared satellite image of Hurricane Emilia. Image credit: NOAA

Upper-tropospheric outflow remains well-defined, particularly to the north and west where a small upper low moving westward from Baja California is enhancing outflow. However, the hurricane appears to be undergoing some easterly shear, which was confirmed by recent microwave data showing an eyewall that was open to the northeast. A look at 850-200 mb wind shear analyses from UW-CIMSS shows that the anticyclone that was following Emilia has become displaced a few hundred miles to the east. Current trends on water vapor imagery provide some support for this idea. However, the shear does not appear strong enough to penetrate the inner core and cause weakening. Strengthening is still forecast, though it is uncertain how much longer Emilia can keep up the current pace of rapid intensification. Inner core fluctuations, a fancy way of saying eyewall replacement cycle, frequently occur with particularly intense hurricanes like Emilia. These cycles are extremely difficult to predict, however. Interestingly, the very same microwave pass alluded to earlier suggested that an outer band was forming outside the western eyewall, possibly the signal to an eyewall replacement cycle. Satellite images also reveal an increasingly distorted and gradually shrinking eye. However, the outer core does not yet appear to be strengthening, so I am going to assume Emilia is temporarily holding off on an eyewall replacement cycle. After 24 hours, changes to the inner core structure and then cooler waters are expected to bring about a weakening of the hurricane. However, Emilia is expected to remain a viable tropical cyclone throughout the forecast period.

Emilia is expected to continue moving generally toward the west-northwest, with a gradual westward bend near the end of the forecast period as the hurricane weakens and comes underneath the lower-tropospheric easterlies. A mid-level weakness will probably be present in the semipermanent Pacific subtropical high by then, so if Emilia is stronger than predicted at days four and five, it could come within range of the Hawaiian Islands after making the westward turn. For this reason, interests there should continue to remain vigilant of this hurricane. If Emilia did impact Hawaii, it would likely be no more than a tropical depression, and more likely a remnant low. However, tropical cyclones of any kind directly impacting Hawaii is rare in and of itself, which makes this possibility so significant. Aside from heavy rainfall, Emilia would likely not produce any weather out of the ordinary.

5-day intensity forecast

INITIAL 07/10 0300Z 105 KT 120 MPH
12 hour 07/10 1200Z 110 KT 130 MPH
24 hour 07/11 0000Z 115 KT 135 MPH
36 hour 07/11 1200Z 115 KT 135 MPH
48 hour 07/12 0000Z 100 KT 115 MPH
72 hour 07/13 0000Z 85 KT 100 MPH
96 hour 07/14 0000Z 65 KT 75 MPH
120 hour 07/15 0000Z 40 KT 45 MPH

5-day track forecast



Figure 4. My 5-day forecast track for Emilia.

Invest 98E

An area of disturbed weather has developed several hundred miles south of Acapulco. Satellite and scatterometer data suggests that this low remains disorganized. However, assuming Emilia doesn't interfere, conditions appear favorable for gradual development as the low moves slowly west-northwest parallel to the Mexican coast. Long-range model projections of the synoptic pattern suggest that there will be a trough over California capable of turning the system northward toward southern Baja. However, there is considerable uncertainty in such long-range forecasts. In the meantime, locally heavy rainfall may impact portions of the southern Mexico coast over the next day or so as the disturbance slowly consolidates.

Probability of development in 48 hours: 40%

Hurricane Daniel Hurricane Emilia 2012 East Pacific hurricane season Hurricane Invest 98E

Updated: 6:48 AM GMT on July 10, 2012

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Tropical weather analysis - July 9, 2012

By: KoritheMan, 6:29 AM GMT on July 09, 2012

Daniel

Hurricane Daniel is steadily weakening after unexpectedly peaking as a major hurricane around 6z Sunday. As of the latest NHC advisory, the following was posted:

Wind: 100 mph, with higher gusts
Location: 15.3°N 126.3°W
Movement: W at 15 mph
Pressure: 974 mb
Category: 2 (Saffir-Simpson Hurricane Scale)

Satellite images reveal warming cloud tops, especially in the eastern semicircle. The outflow pattern appears to have flattened as well, even though there is no indication of nearby vertical shear. Although there is no concrete evidence, this structure suggests that Daniel could be transitioning into an annular hurricane.



Figure 1. Latest infrared satellite image of Hurricane Daniel. Image credit: NOAA

Assuming there are no more surprises, I see a dismal future for Daniel. The hurricane is traversing 24C SSTs and is moving through a region characterized by very dry air. A further decrease to 23C is expected by Tuesday morning. The end result should be weakening, but if my mind is not playing tricks on me, and Daniel truly is acquiring annual characteristics, weakening may not be quite as rapid as we would typically expect over such cool waters. Dissipation is expected late on Thursday.

I am not sure what I can say about the track without repeating myself, and that's always annoying. Water vapor imagery shows a well-established ridge to the north, under which the hurricane should continue its westward trek. There is a rather large weakness in the Pacific subtropical high west of 140W, but Daniel is expected to be too weak to respond to this feature. The uniform westward motion is expected to take the cyclone well south of the Big Island late next week.

5-day intensity forecast

INITIAL 07/09 0300Z 85 KT 100 MPH
12 hour 07/09 1200Z 80 KT 85 MPH
24 hour 07/10 0000Z 65 KT 75 MPH
36 hour 07/10 1200Z 55 KT 65 MPH
48 hour 07/11 0000Z 45 KT 50 MPH
72 hour 07/12 0000Z 35 KT 40 MPH
96 hour 07/13 0000Z 30 KT 35 MPH...POST-TROP/REMNANT LOW
120 hour 07/14 0000Z 25 KT 30 MPH...POST-TROP/REMNANT LOW

5-day track forecast



Figure 2. My 5-day forecast track for Daniel.

Emilia

Emilia is almost a hurricane. As of the latest NHC advisory, the following coordinates were posted on this intensifying tropical cyclone:

Wind: 70 mph, with higher gusts
Location: 11.6°N 108.4°W
Movement: WNW at 14 mph
Pressure: 995 mb
Category: Tropical storm

All ingredients are now there for Emilia to undergo rapid intensification. The outflow pattern has improved significantly, even in the previously lacking western quadrant. Examination of high cloud vectors on satellite and water vapor imagery suggests that as Daniel becomes annular, the poleward outflow channel that was disrupting Emilia yesterday has diminished; the latter's cirrus is expanding, while the former's is exhibiting less cirrus and more high clouds.



Figure 3. Latest infrared satellite image of Tropical Storm Emilia. Image credit: NOAA

One interesting piece I've managed to put together regarding this complex puzzle is that a 3z SSMIS overpass showed an eye at both the 37 and 85 GhZ channels, as well as a formative eyewall; a warm spot actually tried to appear on conventional satellite images for a brief period several hours ago. Interestingly, said overpass also suggested that the low-level eye feature was displaced about 15-20 miles southwest of the mid-level one. I am not sure why this is case, since there appears to be no vertical shear affecting the cyclone. While Emilia may perhaps not be completely stacked, this particular overpass is probably being a little too hyperbolic in its analysis. Emilia is expected to become a major hurricane in about a day or so.

Emilia is forecast to move west-northwest for the next 36-48 hours. Thereafter, the guidance diverges. The ECMWF sees a strong subtropical high and keeps the system on a westward track. Conversely, the GFS suggests a more poleward track towards the large-scale troughing in the process of amplifying across the waters off the western United States coast. The mid-level flow across much of the Pacific north of 25N and west of 125W is predominantly out of the southwest. Given the synoptic trends observed in water vapor imagery, I am leaning more towards the more northerly GFS. However, ignoring the ECMWF would be a tragedy in itself, so I will keep the track south a little, but not much. I would expect the ECMWF, and the remainder of the global models that disagree, to join up with the GFS solution of a more northerly track over the next two days, particularly if Emilia strengthens as much as I think it will. A long-range threat to Hawaii is still possible.

5-day intensity forecast

INITIAL 07/09 0300Z 60 KT 70 MPH
12 hour 07/09 1200Z 70 KT 80 MPH
24 hour 07/10 0000Z 85 KT 100 MPH
36 hour 07/10 1200Z 100 KT 115 MPH
48 hour 07/11 0000Z 115 KT 135 MPH
72 hour 07/12 0000Z 110 KT 125 MPH
96 hour 07/13 0000Z 85 KT 100 MPH
120 hour 07/14 0000Z 65 KT 75 MPH

5-day track forecast



Figure 4. My 5-day forecast track for Emilia.

Hurricane Daniel Tropical Storm Emilia Hurricane

Updated: 6:33 AM GMT on July 09, 2012

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Tropical weather analysis - July 8, 2012

By: KoritheMan, 7:59 AM GMT on July 08, 2012

Daniel

Daniel continues to strengthen, making the most of its time prior to the onset of cool waters. The latest NHC advisory had him at Category 2 strength, though recent Dvorak estimates have been running anywhere from 5.0 to 6.0. A blend of these numbers support the bottom end of major hurricane strength. In any case, the official coordinates from the National Hurricane Center are as follows:

Wind: 105 mph, with higher gusts
Location: 14.9°N 121.2°W
Movement: W at 14 mph
Pressure: 969 mb
Category: 2 (Saffir-Simpson Hurricane Scale)

The hurricane hasn't changed much over the last few hours. An eye occasionally appears, only to become obscured by convection.



Figure 1. Latest infrared satellite image of Hurricane Daniel. Image credit: NOAA

SHIPS suggests that Daniel has exceeded its boundaries, and is now over waters cooler than 26C. Lacking any direct observations -- i.e ship and buoy reports -- I have no choice but to go along with this. If the hurricane isn't over such waters now, it soon will be, making void any and all speculation. I will audaciously say Daniel has peaked. Cool waters await the hurricane, as does subsidence. The end result should be weakening. Dissipation is expected by the end of the forecast period.

Not much has changed track wise. I am a bit to the south of the current NHC forecast track for the first 12 hours to account for the fact that Daniel may pass south of the 12z forecast point, as well as the strength of the ridge to the north. Otherwise it remains similar to previous packages. Daniel is not expected to pose a threat to Hawaii, and it should dissipate before making its closest approach to the Big Island.

5-day intensity forecast

INITIAL 0300Z 07/08 90 KT 105 MPH
12 hour 1200Z 07/08 85 KT 100 MPH
24 hour 0000Z 07/09 75 KT 85 MPH
36 hour 1200Z 07/09 65 KT 75 MPH
48 hour 0000Z 07/10 50 KT 60 MPH
72 hour 0000Z 07/11 40 KT 45 MPH
96 hour 0000Z 07/12 30 KT 35 MPH
120 hour 0000Z 07/13 25 KT 30 MPH...POST-TROP/REMNANT LOW

5-day track forecast



Figure 2. My 5-day forecast track for Daniel.

Emilia

Tropical Storm Emilia formed on Saturday. As of the latest NHC advisory, the following was posted:

Wind: 40 mph, with higher gusts
Location: 10.7°N 103.2°W
Movement: WNW at 16 mph
Pressure: 1003 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

Emilia is steadily organizing, although most of the current convection is to the west of the center in large bands. A well-defined outflow channel has developed to the north, with the associated cirrus signature emanating as far north as 16N. The well-defined outflow signature in this direction is directly attributable to a weak upper low moving across central Mexico.

Figure 3. Latest infrared satellite image of Tropical Storm Emilia. Image credit: NOAA

The large-scale pattern around Emilia is quite favorable for strengthening, with very warm SSTs of 29 to 30°C, low to nonexistent vertical shear, and of course high relative humidity values. It is no surprise that the SHIPS suggests rapid intensification. Indeed, the current structure, while still broad and somewhat disorganized, is suggestive of this possibility once the convection consolidates. Emilia is forecast to become a hurricane in about a day. Environmental and oceanic conditions are expected to remain conducive for intensification through much of Wednesday. After that time, the cyclone is forecast to reach cooler waters, and weakening is then expected to begin.

Emilia is under the influence of a large ridge to the north. The global models suggest the ridge will move in tandem with the tropical cyclone for the next 72 hours or so. After that, they diverge significantly with regards to the amplification of the synoptic pattern over the Pacific. Some are calling for a weaker ridge, while others call for a stronger ridge. There is little reason favor one over the other at this point, and reliable models are on both sides of the spectrum. To be conservative, I will blend the more southerly ECMWF and the more northerly GFS. This is a low-confidence forecast. In any case, I remain vigilant of a possible threat to Hawaii in the long-range, and interests across the islands, particularly across the Big Island, should closely monitor the progress of Emilia well into next week. At this point, it does not appear likely that Emilia will dissipate before reaching the general longitude of those islands.

5-day intensity forecast

INITIAL 0300Z 07/08 35 KT 40 MPH
12 hour 1200Z 07/08 45 KT 50 MPH
24 hour 0000Z 07/09 55 KT 65 MPH
36 hour 1200Z 07/09 70 KT 80 MPH
48 hour 0000Z 07/10 85 KT 100 MPH
72 hour 0000Z 07/11 105 KT 120 MPH
96 hour 0000Z 07/12 85 KT 100 MPH
120 hour 0000Z 07/13 75 KT 85 MPH

5-day track forecast



Figure 4. My 5-day forecast track for Emilia.

Hurricane Daniel Tropical Storm Emilia Hurricane

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Tropical weather analysis - July 6, 2012

By: KoritheMan, 4:25 AM GMT on July 07, 2012

Daniel

Daniel finally becomes a hurricane. Satellite images show a large and increasingly organized hurricane. As of the latest NHC advisory, the following was posted:

Wind: 75 mph, with higher gusts
Location: 14.5°N 117.1°W
Movement: W at 12 mph
Pressure: 988 mb
Category: 1 (Saffir-Simpson Hurricane Scale)

A faint eye tried to appear on geostationary satellite images a few hours ago, but has since been obscured by convection.



Figure 1. Latest infrared satellite image of Hurricane Daniel. Image credit: NOAA

Sea surface temperature analyses indicate that the hurricane does not have much time to strengthen, as Daniel is sitting underneath water temperatures right at 27C. Upper tropospheric shear remains light, and a continuation of this general trend is expected. The light shear conditions aren't expected to be enough to keep the cyclone from weakening, and the usual negatives -- cooling SSTs and their attendant dry airmass -- are expected to deliver the coup de grace to the hurricane. Daniel is expected to dissipate by the end of the forecast period. The hurricane still does not pose a threat to Hawaii, although it may pass about 150 miles south of the Big Island on Friday as a remnant area of low pressure. If so, it would likely only enhance local shower activity, and perhaps deliver some gusty winds. My intensity forecast mirrors that of the National Hurricane Center except at day five, when I am forecasting a 25 kt storm as opposed to a 30 kt one. This is out of respect for the ginormous shear wall I see depicted in the GFS.

Daniel is still forecast to gain latitude, but its westward motion as a whole is not expected to come to an abrupt halt. The global models remain in good agreement with this, and my forecast track continues to closely follow that of the National Hurricane Center for lack of a reason to adjust it. On a side note, I just love when a tropical cyclone is embedded within a large-scale pattern that is actually easy to predict. Saves me a headache or two.

5-day intensity forecast

INITIAL 0300Z 07/07 65 KT 75 MPH
12 hour 1200Z 07/07 70 KT 80 MPH
24 hour 0000Z 07/08 70 KT 80 MPH
36 hour 1200Z 07/08 65 KT 75 MPH
48 hour 0000Z 07/09 55 KT 65 MPH
72 hour 0000Z 07/10 40 KT 45 MPH
96 hour 0000Z 07/11 30 KT 35 MPH
120 hour 0000Z 07/12 25 KT 30 MPH...POST-TROP/REMNANT LOW

5-day track forecast



Figure 2. My 5-day forecast track for Daniel.

Invest 97E

The tropical disturbance south of the Gulf of Tehuantepec that has been under surveillance for the last several days was designated an invest today ("97E"). This low continues to organize, and could become a tropical depression over the next day or two. A small burst of convection has recently formed near the estimated low-level center, although there might be some weak easterly shear over the area.



Figure 3. Latest infrared satellite image of Invest 97E. Image credit: NOAA

Satellite and scatterometer data indicate a closed circulation. The depiction of this circulation on satellite images was not particularly impressive, certainly less so than the ASCAT data would suggest. That little trifle notwithstanding, environmental conditions appear conducive for additional development. I see little reason why 97E will not become our next hurricane.

As for track, global and dynamical model guidance suggests that the synoptic pattern will be fairly similar to what big brother Daniel is experiencing. However, the mid-level flow seems to be more southerly as the system approaches 140W this time next week, which could allow for a more northward motion than Daniel is expected to exhibit at that longitude. While long-range prognostications are riddled with uncertainty, as Debby so kindly showed us, I am concerned about a long-range threat to the Big Island.

Probability of development within 48 hours: 60%

Elsewhere

Most of the global models anticipate the development of a third tropical cyclone behind 97E/Emilia in about seven days. This system presumably comes in response to the tropical wave moving across the central Atlantic. It is decidedly too early to predict exactly where this system will go.

Hurricane Hurricane Daniel Invest 97E

Updated: 4:33 AM GMT on July 07, 2012

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Tropical weather analysis - July 6, 2012

By: KoritheMan, 7:30 AM GMT on July 06, 2012

Daniel

Tropical Storm Daniel is intensifying. As of the most recent NHC advisory, the following was posted:

Wind: 65 mph, with higher gusts
Location: 14.4°N 113.1°W
Movement: W at 13 mph
Pressure: 995 mb
Category: Tropical storm (Saffir-Simpson Hurricane Scale)

The cloud pattern hasn't changed significantly since the release of the advisory from the National Hurricane Center, although there appears to be more banding in the northern semicircle. Upper-tropospheric outflow is well-defined, except somewhat restricted to the south.



Figure 1. Latest infrared satellite image of Tropical Storm Daniel. Image credit: NOAA

Daniel has about another 24-36 hours under warm water temperatures before it begins to encounter the 26C isotherm. Although the cyclone is expected to remain embedded within a light shear environment throughout the next several days, water vapor imagery suggests that a large mass of dry air awaits Daniel west of 120W, likely associated with cooler waters. The result should be weakening, but not before Daniel becomes a hurricane. There is some suggestion by the GFS that northwesterly to westerly shear could increase across the system by Monday evening, as the tropical cyclone approaches the mid-oceanic trough in the vicinity of Hawaiian Islands. Although Daniel is expected to cross into the Central Pacific, it is unlikely to be a significant tropical cyclone when it reaches the longitude and/or latitude of Hawaii. However, interests there should still monitor it until its final progress can be determined.

Daniel is under the influence of a ridge to the north. This ridge has strengthened yesterday, just as the global models said it would. A continuation of a west to west-northwest motion is expected throughout the forecast period. The tropical storm is expected to cross 140°W longitude and enter the Central Pacific Hurricane Center (CPHC)'s area of responsibility late Tuesday or early Wednesday eastern time. Upon examining the global model fields, all of them are indicating a 500 mb weakness over and just north of the islands, in association with a weak cyclonic vorticity lobe, probably a portion of the mid-oceanic trough, a semipermanent feature of this basin. However, this weakness is not evident in the bottom half of the troposphere. Since Daniel is expected to be a weak system by that time, it will presumably respond to lower-tropospheric steering as opposed to mid-level steering. But things can change. Currently Daniel doesn't pose a direct threat to the Hawaiian Islands, but I will be monitoring synoptic trends in future forecasts.

5-day intensity forecast

INITIAL 07/06 0300Z 55 KT 65 MPH
12 hour 07/06 1200Z 65 KT 75 MPH
24 hour 07/07 0000Z 75 KT 85 MPH
36 hour 07/07 1200Z 80 KT 90 MPH
48 hour 07/08 0000Z 70 KT 80 MPH
72 hour 07/09 0000Z 55 KT 65 MPH
96 hour 07/10 0000Z 40 KT 45 MPH
120 hour 07/11 0000Z 30 KT 35 MPH

5-day track forecast



Figure 2. My 5-day forecast track for Daniel.

Gulf of Tehuantepec disturbance

A broad area of low pressure located several hundred miles south-southeast of the Gulf of Tehuantepec is producing disorganized showers and thunderstorms. Upper-level winds are favorable for slow development of this system over the next several days as it moves generally westward. Global models eventually develop this system into a hurricane following the same trajectory as Daniel.

Probability of development in 48 hours: 20%

Hurricane Tropical Storm Daniel

Updated: 7:32 AM GMT on July 06, 2012

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Tropical weather analysis - July 4, 2012

By: KoritheMan, 2:42 AM GMT on July 05, 2012

Tropical Depression Four-E

The area of low pressure we were previously tracking developed into the a tropical depression today. As of the latest NHC advisory, the following information was posted on the cyclone:

Wind: 35 mph, with higher gusts
Location: 13.6°N 108.9°W
Movement: WNW at 12 mph
Pressure: 1005 mb
Category: Tropical depression (Saffir-Simpson Hurricane Scale)

The storm is still not well-organized, but relative to earlier it is looking a little healthier. Given the current structure, it is likely that the diurnal convective maximum period this morning will be sufficient to bring the system up to a tropical storm.



Figure 1. Latest infrared satellite image of Tropical Depression Four-E. Image credit: NOAA

There still appears to be some northeasterly shear lingering in the area, but satellite images suggest that the depression is outrunning these negativities. The potential exists for strengthening through about 48 hours, and my forecast shows it becoming a hurricane. Thereafter, the cyclone is likely to cross a sharp sea surface temperature gradient, then encounter dry air and northwesterly shear. Most of the global models retain a circulation for the next five days, and I will consciously follow suit. Howver, the system is expected to be weakening over cool water at such times. It is improbable that this system will be able to hold together as a viable tropical cyclone long enough to impact the Hawaiian Islands. However, local rainfall enhancement can be expected along windward facing beaches in the middle of next week.

The cyclone is currently situated to the south of a well-established ridge. Little change to this pattern is expected in the global model forecast fields, and water vapor imagery corroborates this. Many Pacific tropical cyclones move west to west-northwest without ever threatening land. A continued generally west-northwest motion is expected for the next day or so, followed by a turn to the west as the storm finds itself sliding underneath the small weakness to the north, into a more uniform easterly flow.

My forecast track is in good agreement with the GFS and ECMWF consensus, albeit slower.

5-day intensity forecast

INITIAL 0300Z 07/05 30 KT 35 MPH
12 hour 1200Z 07/05 35 KT 40 MPH
24 hour 0000Z 07/06 45 KT 50 MPH
36 hour 1200Z 07/06 55 KT 65 MPH
48 hour 0000Z 07/07 65 KT 75 MPH
72 hour 0000Z 07/08 55 KT 65 MPH
96 hour 0000Z 07/09 45 KT 50 MPH
120 hour 0000Z 07/10 35 KT 40 MPH

5-day forecast track



Figure 2. My 5-day forecast track for Tropical Depression Four-E.

Another disturbance lies behind TD4-E

I am tracking another disturbance moving into the Gulf of Tehuantepec. Shower activity with this low is disorganized, and environmental conditions are only conducive for slow development over the next few days as it moves slowly westward.

Probability of development in 48 hours: 20%

Hurricane Tropical Depression Four-E

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Tropical weather analysis - July 3, 2012

By: KoritheMan, 2:25 AM GMT on July 04, 2012

Invest 96E

An area of low pressure centered about 500 miles south of Manzanillo is showing signs of organization, and satellite images indicate that a tropical depression may be forming. The cloud pattern is well-organized, and consists of a couple of banding features in the eastern semicircle trying to wrap cyclonically into the center.



Figure 1. Latest infrared satellite image of Invest 96E. Image credit: NOAA

I am uncertain if there is a closed circulation, as the data is conflicting. But if the system lacks one now, it shouldn't in the near future. Upper-level winds in the path of the low are expected to be very favorable for intensification, and it is possible that the system could become a hurricane before reaching cooler waters in about three days. Indeed, the outflow pattern is already excellent, and quite expansive.

Water vapor imagery shows that a large and powerful heat ridge is currently dominating much of the United States, bringing record heat in many locations. The southern extent of this ridge is forecast to remain firmly entrenched to the north of the system over the next several days, providing 96E with little opportunity to recurve. The global models are in excellent agreement on this scenario, and lacking any evidence to the contrary, so am I.

Long-range prognostications from the various global models suggest that this system may enter the Central Pacific Hurricane Center (CPHC) area of responsibility in a week or so. However, there would likely be little left of it at that time. Even so, given the current forecast track, it is unlikely that 96E will dissipate as fast as most Eastern Pacific tropical cyclones, since areal sea surface temperatures will remain warmer to the south.

Probability of development within 48 hours: Near 100%

Hurricane Invest 96E

Updated: 2:28 AM GMT on July 04, 2012

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Tropical weather analysis - July 2, 2012

By: KoritheMan, 10:56 PM GMT on July 02, 2012

Invest 96E

An area of low pressure is centered in the far eastern Pacific ("96E") several hundred miles south of Acapulco. The system is not well organized, but the overall circulation is slowly becoming better defined.



Figure 1. Latest infrared satellite image of Invest 96E. Image credit: NOAA

It is a bit puzzling why none of the intensity guidance forecasts strengthening, as the large-scale environment appears rather favorable. Analysis of water vapor imagery over the Gulf of Mexico suggests that an upper low -- or more accurately, a fragmented trough, is moving westward across the Bay of Campeche. I see little evidence of this feature closing off at this time. In addition, 96E appears to be a little too far south to be negatively impact by this low. The SHIPS didn't reflect this in its 5-day shear forecast, and in fact wants to take the system up to hurricane strength in about three days. On the other hand, the GFS, whose parameters are integrated into SHIPS, forecasts little intensification. Go figure.

In defiance of the models, which have time to catch up, and in deference to the seemingly favorable environment, I will forecast slow strengthening over the next couple of days.

This system is expected to move west-northwest through the next several days. The global models are rather fast with this system, and have it nearing 115W in four days. This doesn't seem entirely realistic given the amplitude of the ridge seen in water vapor images, especially factoring in the aforementioned Gulf low, which, although weak, could theoretically weaken the overhead ridge just a tad.

Probability of development in 48 hours: 40%

Elsewhere

The global models are insisting on developing a small tropical cyclone behind Invest 96E in a few days. It appears to come from the tropical wave currently moving through the central Caribbean. This is the very same wave that we were tracking east of the Lesser Antilles several days ago.

Hurricane Invest 96E

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About KoritheMan

I'm just a 23 year old with an ardent passion for weather. I first became aware of this interest after Tropical Storm Isidore struck my area in 2002.

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