Invest 98L, the red circle, is likely to become a tropical depression/storm later today
The weather over portions of the Windward and Leeward Islands is not very pleasant today as the effects of 98L move in. Squally conditions, with winds to near tropical storm force, are occurring from Barbados to points north and west. These conditions will likely persist throughout the day, off and on, as the low pressure area slowly moves across the region.
The NHC indicates that the system is likely to become at least a tropical depression. Intensity guidance suggests that it will become a tropical storm and possibly even a hurricane before all is said and done. Water temps are very warm and upper level winds are becoming more favorable for continued development. It is going to be a stormy weekend for a good deal of the Lesser Antilles.
The track forecast from the computer models is fairly tight with not much spread over the next five days. It looks like what ever forms from this system will pass to the east of Puerto Rico while tracking right through the extreme northeast Caribbean. This would put most of the Leeward Islands within the worst of the weather conditions which will last for the next two or three days.
Once past the Caribbean, there is a chance that Bermuda could feel impacts from what would presumably be Rafael once this gets named. How strong it would be remains to be seen but we have observed time and again this season that tropical storms and hurricanes tend to reach their peak AFTER leaving the deep tropics. I would suggest that people in Bermuda pay close attention to the progress of this system.
Meanwhile, TS Patty has managed to hang on and survive the night in the face of increasing winds in the upper levels of the atmosphere. It won’t be too much longer until Patty is literally separated and sheared apart by the stronger winds aloft. In fact, the low level center is likely to track southwest while the rest of the energy with the storm is removed and whisked away to the northeast.
In the east Pacific, there is a disturbance that is likely to develop well off the coast of Mexico but it is moving away from land and won’t be an issue.
I’ll have another update here early this evening and will post the daily hurricane outlook video to our app early this afternoon.
98L getting better organized as it approaches the Lesser Antilles
The hurricane season has turned out to be quite active with plenty of named storms forming so far. Patty, which formed from 97L near the Bahamas this afternoon makes the 16th named storm and puts 2012 in the top-5 busiest seasons. Luckily, Patty will not only be short-lived, but it will also not affect land directly. Upper level winds will separate the low level center from the mid and upper level energy and Patty will dissipate rather quickly.
Meanwhile, 98L continues to become better defined and is on its way to becoming a tropical depression within the next couple of days. In fact, more of the intensity guidance suggests that environmental conditions could allow it to eventually become a hurricane. The timing of this is critical as we would hope that it would not strengthen much as it moves through the Lesser Antilles. Looking at the latest satellite images indicates that upper level winds are getting to be more and more favorable and we know that water temps are plenty warm in the region. Interests in the Windwards and Leewards need to be prepared for periods of squally weather as the developing storm system moves through tomorrow and through the weekend.
Most of the track guidance indicates a fairly sharp turn to the northwest beginning almost immediately. This would mean a track right through a majority of the islands of the eastern Caribbean. How close the system gets to Puerto Rico remains to be seen. I am more concerned with Bermuda in a few days as the steering pattern favors a turn north and then northeast. At this point, we could be looking at a minimal hurricane heading close to Bermuda. Stay tuned.
I’ll have more here tomorrow morning.
Satellite photo showing 97L (left, near the Bahamas) and 98L (right, near the Lesser Antilles)
There is quite a lot going on this morning with two very active systems in the Atlantic Basin. One is 97L near the Bahamas and the other, 98L nearing the Lesser Antilles.
First up- 97L. The small low pressure system has probably been a tropical depression for a few hours but it is not bothering any land areas so it does not really matter all that much. The NHC may upgrade it later this morning but the window of opportunity for it to intensify further is rapidly closing. However, the system has a vigorous and well defined low pressure area and is producing persistent convection and therefore has some time left to strengthen a little more. The big inhibitor will be very strong upper level winds that are approaching from the west. These winds will quickly disrupt the process of upward motion and shear out the low quite efficiently.
Next we have 98L which continues to get better organized as it approaches the Lesser Antilles. The main impact right now will be an increase in tropical downpours accompanied by periods of gusty winds. These conditions will spread across a good deal of the Lesser Antilles later today and through the upcoming weekend.
There is a good chance that 98L will become a tropical storm at some point over the next 72 hours or so and this could make for a rather stormy period for the islands. I do not see any solid indication that 98L will become a hurricane while passing through the region but its fairly slow movement means a prolonged period of heavy rains.
The steering pattern is such that we should see the system turn northwest and eventually north as it feels the effects of a strong trough in the western Atlantic. This is very common for this time of year and should easily turn what ever develops away from the Bahamas and Florida by early next week.
The remainder of the Atlantic and Caribbean are quiet with no additional areas of interest noted this morning.
In the east Pacific, there is a disturbance well to the south of Mexico that has potential for development as it moves westward and away from land.
I’ll have more on the two Atlantic features this afternoon with a complete video blog analysis posted to our iPhone app early this afternoon.
Vorticity chart showing the increasing spin or vorticity with both 97L and 98L
Check out the 850mb vorticity map from the University of Wisconsin site. It shows spin or vorticity at 5000 feet or 850 millibars in the atmosphere. You’ll see that 97L and 98L both have fairly decent signatures meaning there is decent spin associated with their circulations.
The NHC re-activated 97L earlier today and it’s obvious as to why. The small but well defined low pressure area just east of the southern Bahamas looks quite impressive. It’s sitting over very warm water with low shear at the present moment. If it does not get an upgrade tomorrow to at least a tropical depression, it would not shock me at all to see it added as one in the post-season analysis. Fortunately, it is not close enough to land areas to really matter right now but it goes to show how quickly these small systems can ramp up and not be “seen” by the larger scale global models.
Meanwhile, invest area 98L is also gaining strength as of late east of the Windward Islands. Most of the model guidance indicates a track towards and through portions of the Lesser Antilles with a gradual turn to the northwest with time. However, the longer it takes for the system to consolidate and deepen in to the atmosphere, the farther west it is likely to track. Interests in the Lesser Antilles and points north and west such as Puerto Rico and the Dominican Republic should be closely watching the progress of 98L. There are now a few intensity models which suggest that the system could become a hurricane later in the forecast period (after about 72 hours). I think this feature will begin to garner more and more attention over the next couple of days as it steadily increases its organization.
I’ll have more here on both of these systems in tomorrow morning’s blog post with a full video update posted to our iPhone app early tomorrow afternoon.
Invest area 98L to the east of the Lesser Antilles
It looks like invest area 98L is slowly getting better organized even in the face of fairly strong upper level winds. We normally do not look to the deep tropics this time of year but history has shown that we can have development out this far east in October.
Water temps in the path of the low pressure area are plenty warm and it appears that the upper level wind pattern will gradually improve over the next few days. The NHC has increased the potential for development to 30% though I suspect it will be another day or two before we see any marked increase in overall organization.
Most of the intensity guidance points to a moderately strong tropical storm forming within the next 72 hours or so. The statistical SHIPS model peaks at 55 knots but this assumes that we have a tropical cyclone already, which we do not. I think that the sooner the system can consolidate its energy and develop banding clouds instead of the rather amorphous look that it has now, the more it can intensify. Right now, the main issue will be heavy rain that is likely to spread across portions of the northern Lesser Antilles over the next few days. Fortunately, I do not see any indication that 98L is in any hurry to become a hurricane. This could change but right now, the factors against such an extreme event are outweighing those in favor.
As far as track is concerned, most of the reliable model guidance points to a path towards the Lesser Antilles with an eventual turn to the north. When this turn happens will obviously have a huge impact on which areas receive the squally weather that is certain to accompany the system regardless of development. I think it is safe to say that folks in the Lesser Antilles up through Puerto Rico and possibly even Hispaniola need to monitor the progress of 98L over the next several days. It is important to remember that heavy rain can pose serious flooding issues and that it does not take a named storm to cause big problems.
I’ll post another update here early this evening with any new info on 98L at that time. The remainder of the Atlantic is quiet. In the east Pacific, a broad disturbance to the south of Mexico and Central America bears watching as it tracks off to the west, away from land.