Average 20 year old weather nerd. Plymouth State University Meteorology, Class of 2018. NOAA Hollings scholar. Summer 2016 intern at NWS Boston.
By: MAweatherboy1, 12:18 AM GMT on May 29, 2013
For the second time in about 2 weeks, a tropical cyclone has formed in the East Pacific basin, as it is off to a fast start so far this year. This cyclone, which has been upgraded from Tropical Depression 2E to Tropical Storm Barbara, was formed from the disturbance invest 92E that has been tracked off the coast of Central America for a few days. The storm is currently located about 145 miles SSW of Salina Cruz, Mexico, and is barely moving, perhaps drifting northward at 1-3mph. According to the latest advisory from the National Hurricane Center, Barbara's maximum 1 minute sustained winds are 40mph, and its minimum central pressure is 1004mb.
Figure 1: Tropical Storm Barbara. Deep convection has waned a bit in the past couple hours, which could be due to the diurnal convective minimum, but structure of the storm has been improving, which indicates it is likely strengthening.
Forecast for Barbara
Barbara is located in an environment that is conducive for the intensification of a tropical cyclone. Shear is low, waters are warm, and there is enough moist air. Despite this, there are two factors which will limit Barbara's intensity, which are proximity to land and time over water. The system's close proximity to Mexico has the potential to disrupt its circulation and allow for dry air off the land to get sucked into it. In addition, due to the (albeit slow) norhtward motion of the system, it only has about a day or so over water to strengthen. The official forecast from the NHC takes Barbara to 60mph in 24 hours before it makes landfall. Barbara is likely to continue a slow north to NNE motion before and after landfall. Once it makes landfall, steady weakening is likely as it moves over land. My forecast, not official of course, is shown below. I am generally in agreement with the NHC, but my peak intensity is a slightly higher, largely due to the recent organization. After landfall, there are several possibilities, as Barbara will generally be moving towards the Bay of Campeche. It's possible it could miss the Bay, or it could just enter it and fizzle out, or it is possible that the system could restrengthen once it reemerges, but for now, I am following the lead of the NHC and simply indicating dissipation over land.
Figure 2: My forecast for Barbara.
Figure 3: Official NHC forecast for Barbara.
Regardless of exact peak intensity, wind will not be the biggest issue with Barbara. Rather, heavy rainfall of 3-6 inches (locally more) will cause the potential for flash flooding and mudslides across the affected area. This is not to be taken lightly despite the fact that it is only a tropical storm.
Figure 4: 18z GFS estimated rainfall totals through 72 hours.
Atlantic Development Still Possible Next Week
The official start of North Atlantic Hurricane Season is now just a few days away, as it begins on Saturday, June 1. There are still indications on the models that tropical development may occur in either the western Caribbean or the Bay of Campeche towards the middle or more likely end of next week. An MJO pulse is still scheduled to arrive in that area around that time, and it is possible that leftover moisture from TS Barbara will aid in development on the Atlantic side. Personally, I have felt that development in the Bay of Campeche, which the operational GFS seems to somewhat be trending towards, seemed unlikely. However, it is possible that if TS Barbara emerges somewhat intact over the Bay, then it could regenerate here. The ECMWF model, while not really showing anything organized in terms of development, looks to be favoring the NW Caribbean as a potential location for moisture and low pressure that could develop into a tropical cyclone. This makes sense to me, and I feel like this is a situation that we will simply need to watch and wait for, as potential Atlantic development would still be several days away. I made this graphic a week or so ago and still stand by it, but we will also need to keep an eye on the Bay of Campeche.
That is all for today. Thank you as always for reading, and I hope you enjoy the rest of your week. Since I probably won't have another blog up before June 1- Happy Hurricane Season!
By: MAweatherboy1, 11:26 PM GMT on May 21, 2013
All is quiet right now in the global tropics, with no active tropical cyclones anywhere and no areas of interest being watched for development, and no development likely for the next few days at least. The next area to watch for tropical development will likely be the Eastern North Pacific basin, which has already seen one tropical storm this year, short lived Tropical Storm Alvin. Models, particularly the GFS and CMC, are hinting at the possibility of low pressure organizing at low latitude off the Central American coast in as little as 5-6 days. The CMC is even hinting at the possibility of two systems forming, though I find this unlikely. Here are some graphic representations of what I'm talking about.
Figure 1: 18z GFS, 132 hours.
Figure 2: 18z GFS 180 hours. The full resolution version of the model takes it to about 968mb, a solid hurricane.
Figure 3: 12z CMC, 120 hours. It starts developing the dominant low around 96 hours, but I believe that is too fast.
Figure 4: 12z CMC, 186 hours.
Figure 5: 12z GFS ensemble at 156 hours, showing strong agreement among the ensemble members, indicating the GFS is likely on to something.
The GFS, CMC, and to a lesser extent NAVGEM all show development in this general areas within the next week, while the ECMWF model does not. Once again, this model is likely struggling to pick up on tropical cylogenesis, one of its major weaknesses. Still, there are subtle hints from both it and its ensembles that it wants to show development in the area, and it may latch onto it before long. Here is my thinking on the matter. Obviously not anything groundbreaking here, this is similar to what the models show:
Figure 6: If a tropical storm does indeed develop in the East Pacific, it will be named "Barbara."
Could Atlantic Development Follow?
As the East Pacific shows signs of life, the Atlantic may be soon to follow. This basin's season officially begins on June 1, and there are indications that the first development of the season may come not long after this date as an MJO pulse arrives in the basin to spark possible development in the Caribbean Sea. Confidence is much lower on this possibility than on the East Pacific development, largely due to the fact that this is considerably further out in time. Based largely on what I have observed from the GFS, as well as what is climatologically favored this time of year when an MJO pulse arrives in the basin, I do think Atlantic development is a real possibility between June 1 and June 10, probably more towards the middle or end of that time period. I like speculating at these types of events, so here is my thinking as of right now:
Figure 7: My early thinking on the Atlantic development. This is not to be taken very seriously, and by no means does this indicate that I strongly feel development will occur in this time. I think it is a decent (40-60%) possibility, not a likelihood, and the possible tracks are of course dependent upon something forming in the first place. The tracks are mostly based off of some of the more common solutions that have been portrayed by the GFS.
Figure 8: 18z GFS, 348 hours, showing a fairly weak tropical system travelling close to the right-side path in my graphic; I have noticed this to be probably the most favored general option by the GFS. Development this run began at around 12 days in the area I have highlighted.
Whether this Atlantic development pans out or not, hurricane season is upon us, and it is once again time to make sure you have your emergency plan ready if you are in hurricane prone areas. Many indicators still point to this being a high impact year for the United States.
That is all for tonight; please feel free to weigh in with your thoughts in the comments section about either development possibility I discussed. Thank you as always for reading, and I hope you enjoy the rest of your week.
By: MAweatherboy1, 11:35 PM GMT on May 14, 2013
Happy East Pacific Hurricane Season! Indeed, in just hours, the first official tropical weather outlook for the Eastern North Pacific basin will be issued by the National Hurricane Center, officially beginning the season which runs from May 15-Nov 30. The East Pacific couldn't quite wait for the start of its season, however, as yesterday the first invest of the season, 90E, formed. This is certainly an exciting moment, as it is a strong sign that Atlantic Hurricane Season is also soon to be upon us. Invest 90E is currently located about 650 miles south of Acapulco, Mexico, and is drifting WNW, away from land, at 10-15mph. This general motion should continue for at least the next 3 days.
Figure 1: Invest 90E.
Satellite imagery reveals that 90E is a very typical, slowly organizing East Pacific invest. It has managed to establish itself as a separate entity from the intertropical convergence zone, which is always an early and important step in determining whether or not an invest will develop. The system has also managed to maintain convection for an extended period of time, and while the convection overall is not quite as strong as it was yesterday, it is definitely better organized, as 90E looks much more like a tropical system now than it did 24 hours ago. The latest (18z) update from the ATCF indicates that 90E is estimate to have maximum winds of close to 30mph and a minimum pressure of 1007mb. As of their 12:45 PM PDT Special Tropical Weather Outlook, the National Hurricane Center is giving 90E a 30% chance of developing within the next 48 hours. 90E is in an environment that is generally conducive to organization, with the SHIPS intensity model showing 90E traveling through less than 10kts of shear for the next three days, and a moist enough atmosphere for development. I am giving 90E a 40% chance of developing into a tropical cyclone within 48 hours, and a 70% chance within 96 hours. The GFS, CMC, and NAVGEM models all show some sort of development of 90E within 72 hours, while the ECMWF model, generally considered the world's best major global model, does not show development. This can likely be attributed to the glaring weakness of this model, which is forecasting tropical cyclogenesis. Because of the tendency of this model to not accurately capture development (such as for Cyclone Mahasen in the Bay of Bengal) I have mostly discounted its solution, as I believe 90E will develop into the East Pacific's first tropical depression, and possibly tropical storm, of the year. Should 90E strengthen to tropical storm status, it will be given the name "Alvin." My forecast for the system is below. This is meant to cover a period of about 5 days at a steady speed. The track forecast is based off a blend of the more northerly/easterly GFS, which never gets the system to 120W, and the more southerly/westerly CMC and NAVGEM, which do bring it to and past 120W. Intensity is less aggressive than models like the SHIPS (which brings 90E to 60kts in 72 hours) and GFS, but more aggressive than the NAVGEM and obviously the ECMWF which doesn't show development. I think this will become the basin's first named storm of the year.
Figure 2: My forecast track and intensity for 90E, not official. Map credit.
As always with invest forecasts, there is considerable uncertainty in both track and intensity, and future changes are a good bet. Still, there is no reasonable scenario that would have 90E impacting land in any way, as it should be a threat solely to marine interests, as most East Pacific storms are.
Figure 3: Recent visible image of 90E.
I hope to provide updates on 90E in the days ahead, and as I have mentioned in previous blogs I hope to provide fairly regular blog updates on Atlantic and East Pacific systems this year, though that will be tough for the next month or so as school finishes up for the year.
Thank you for reading, and I hope you enjoy the rest of your week.
By: MAweatherboy1, 9:32 PM GMT on May 06, 2013
As we begin this new week, there has been little change in the global tropics over the past few days. The focus for potential tropical development continues to be on the Indian Ocean, both the northern and southern part of the basin. The more imminent threat for development is in the southern Indian Ocean, where an area of low pressure at low latitude (less than 5 degrees) and far from land is organizing. This low is invest 94S, and is moving slowly to the SW. Maximum sustained winds are estimated to be in the range of about 25-30mph. The Joint Typhoon Warning Center is giving 94S a "medium" chance of development in the next 24 hours. I would give 94S about a 40% chance of developing in the next 24 hours, but a 90% chance of development within 72 hours.
Figure 1: Invest 94S.
94S is currently in a marginal environment at best for strengthening, with wind shear of up to 25-35mph being the biggest issue for the developing storm. In addition, the low latitude of 94S is inhibiting its ability to spin, which is of course how cyclones develop. While these problems should prevent immediate development, both are likely to become less obstructive in the next 24-48 hours as shear begins to relax and 94S slowly gains latitude. Global models clearly want to develop this system, and now even the reliable ECMWF, which was very hesitant to show development a few days ago, is fully on board for tropical development. The two questions then become where will 94S go, and how strong will it get? For now, the motion is mostly SW. The system will likely move pretty slowly for the next couple days, and could take a more southerly turn before eventually settling on a more WSW track. This will take it in the general direction of Madagascar and southeast Africa. At this point, however, it appears more likely that the system will dive south before it has an opportunity to threaten these areas. Regarding strength, the models are showing above average agreement on fairly significant intensification of the storm. My very preliminary thinking is shown in figure 2. As always when forecasting on a system that hasn't even developed yet, confidence is quite low, and major changes are possible.
Figure 2: My forecast track and intensity for 94S, by no means an official forecast.
My track does not include what happens to 94S beyond that, but as I mentioned the most likely scenario is that it goes south and becomes extratropical.
92B Also a Threat to Develop
Tropical development is also being watched for in the northern Indian Ocean over the next few days. The most likely source of development would be invest 92B, located over the southern Bay of Bengal. In my previous blog I noted invest 91B as the potential area of low pressure to watch for development in the northern Indian. This is indeed still an invest, but it has moved west and is unlikely to develop. Basically replacing it is 92B, which is a new low just in its formative stages. The forecast for 92B is more high stakes than the forecast for 94S because unlike 94S, 92B is likely to impact populated areas if it develops. Neither the official forecasting agency for this region, the India Meteorological Department (IMD) nor the unofficial agency for the region, the Joint Typhoon Warning Center, is currently acknowledging this system as an imminent threat for development. I would give 92B a 10% chance of development in the next 24 hours. Whether or not 92B will develop is less certain than whether or not 94S will develop. The majority of models do develop, and substantially intensify, 92B, but as has been the case for days, the ECMWF model does not develop the system. Because of its reliable track record, I am reluctant to disregard its solution, though I am still expecting development. I give 92B a 70% chance of developing within 96 hours. Because of the significant uncertainty regarding this system's future, I have not yet made a forecast for 92B, but as I mentioned on my previous blog yesterday I do think the system will develop, and at this point I am still favoring southeast India as a landfall location. The big question mark is strength, and that is just too uncertain to guess at right now. Today's 12z GFS at 180 hours seems reasonable to me.
Figure 3: 12z GFS at 180 hours, courtesy of Levi's model page.
Figure 4: Invest 92B, showing a large area of disorganized, shallow convection.
I do not anticipate doing a new blog until at least Wednesday, but if development of this system becomes more certain I will include my forecast in the comments section, along with potential forecast updates on 94S.
Thank you as always for reading, and I hope you have a great week!
By: MAweatherboy1, 12:36 PM GMT on May 04, 2013
We are now less than one month from the start of the 2013 Atlantic Hurricane Season, and less than two weeks away from the start of the Eastern North Pacific season. Both of these basins are currently quiet, however, with no development expected for at least the next 10 days. That is not the case in the Indian Ocean, however, as favorable atmospheric conditions, including a solid MJO pulse, are likely to lead to at least two cyclones forming in the next 5 days, with one in the Southern Indian Ocean and one in the Northern Indian Ocean. Currently, there are two areas of low pressure being watched that could develop into these systems. The Southern Indian low has been dubbed invest 94S, and has now been acknowledged by the Joint Typhoon Warning Center (JTWC) as having a "low" chance of developing within the next 24 hours. The system is currently very disorganized, as would be expected for a system in its formative stages. I would give 94S a 30% chance of developing within 48 hours, but an 80% chance that it will develop within 96 hours. The GFS, CMC, and NAVGEM models are all aggressive on development of this system, but it is important to note that the typically very reliable ECMWF model is showing much less in the way of development, just a weak cyclone. I see this as an outlying scenario, and therefore have mostly disregarded this model's solution. The models that do show development have not been particularly consistent on a potential track. The general theme from the GFS, which is the longest ranging major global model, has been to keep the system away from land. It has also suggested that the system may intensify quite a bit, though some runs, such as the most recent 6z GFS, indicate slower development and much less intensification. If the 12z run is weaker as well, we will need to consider the possibility that the GFS is trying to fall in line with the weaker ECMWF. I have not yet made a forecast for this system besides my development probabilities, but if it becomes more certain that it will develop than I will make a forecast.
Meanwhile, farther north, another disorganized low pressure system has formed over the southern Bay of Bengal, and has been dubbed invest 91B. In many ways, this system is quite similar to its Southern Indian counterpart 94S. It is unlikely to develop in the next 48 hours (I'd give it about a 20% chance), but more likely to develop within 96 hours (I'd say about a 70% chance). Once again, the GFS, CMC, and NAVGEM are all showing development, while the ECMWF is barely showing any development. Once again, I am inclined to go with the majority and I believe we will see development out of 91B. In terms of potential land impacts, this is definitely the system to watch. Places in the Bay of Bengal region, where this potential cyclone is likely to stay, are mostly not well developed and way overpopulated, making them extremely vulnerable to large loss of life totals in a major cyclone. The prime example of this, of course, is the low lying, extremely densely populated country of Bangladesh, which has a long history of major disasters caused by cyclones. I couldn't help but shudder at last night's CMC's depiction of the eventual landfall point of 91B, bringing it in as what certainly looked like a major hurricane equivalent, with Bangladesh in the right front quadrant. I do not see this as the most likely scenario, however, and I think that while the northern Bay of Bengal coast needs to keep an eye on this system, the places that should be most concerned are Sri Lanka and eastern (especially southeastern) India. Once again, I will hold off on any forecast until development and track become a little more certain.
Here are some of the more interesting point of last night's model runs, with images courtesy of Levi's model page.
0z GFS (high resolution) at 156 hours, with the Bay of Bengal storm at peak intensity (941mb!) and the Southern Indian storm at 973mb. Also, a weaker (995mb) cyclone is seen north of Madagascar. It is possible this develops as well, but it is too uncertain to get into at this point.
189 hours on the same run, with Sri Lanka taking a beating:
228 hours on the regular resolution GFS shows a weakening system nearing final landfall (the high res model doesn't do well with depicting landfalls of weakening storms- a noticeable trend in the models, especially the GFS, has been to weaken the storm before final landfall, which would be good).
End of the 0z GFS run, 384 hours, high res, showing the much weakened southern Indian storm off the Madagascar coast. This seems unlikely to me, I think it will stay much more out to sea.
Switching to 0z NAVGEM at 168 hours. The Southern Indian storm is clearly the stronger of the two, as the Bay of Bengal storm appeared to have its intensity held down by heavy interaction with Sri Lanka and southern India. It also appeared to show the storm trying to go into the Arabian Sea at 180 hours, the end of the run. I wouldn't rule this out, but it currently doesn't seem like the most likely scenario.
Only one frame is needed to sum up the 0z CMC, 216 hours, that is scary:
Finally, the 6z GFS. This is 171 hours (high res) with the Bay of Bengal storm at peak intensity (939mb!). Also, look how much weaker the Southern Indian storm is than on the 0z run, it's even weaker than the storm north of Madagascar:
And here's 228 hours (regular res) with the weakening Bay of Bengal storm making final landfall (north of the 0z run). Not much to speak of in the southern Indian:
This should be an interesting week or two out in this region. I will hopefully be able to provide more blogs if necessary.
Thank you as always for reading, and have a great weekend!
The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.