Patty becomes 16th named storm of the season; 98L likely to be 17th

98L getting better organized as it approaches the Lesser Antilles

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.

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Tropics quite active as we enter second 10 day period of the month

Satellite photo showing 97L (left, near the Bahamas) and 98L (right, near the Lesser Antilles)

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.

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97L is back and looking fairly well organized tonight as 98L heads towards Lesser Antilles

Vorticity chart showing the increasing spin or vorticity with both 97L and 98L

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.

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98L slowly developing, could have impacts on portions of Lesser Antilles this weekend

Invest area 98L to the east of the Lesser Antilles

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.

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Where is the El Niño?

August SST anomalies in the tropical Pacific

August SST anomalies in the tropical Pacific

Earlier in the year, it seemed almost a certainty that El Niño would develop in the tropical Pacific. As we moved through the spring and summer, the tropical Pacific began to warm and it looked like we were well on our way to seeing an El Niño develop. Then, it just stopped.

In recent weeks, the tropical Pacific has actually cooled significantly, especially in the

October SST anomalies in the tropical Pacific. Notice the cooling along the Equator

October SST anomalies in the tropical Pacific. Notice the cooling along the Equator

central Pacific. Just compare the two SST anomaly maps from August and now. You can clearly see a substantial decrease in SST anomalies across the tropical Pacific.

So what happened? It’s hard to say. The latest report from Australia’s Bureau of Meteorology site addresses the retreat in SST values across the region that was warming up until recent weeks. It seems that the pressure pattern across the Pacific changed and the abnormally weak trade winds picked up, cooling the sea surface rather quickly.

Sub-surface temperatures in the tropical Pacific. Notice the distinct cooling in recent weeks

Sub-surface temperatures in the tropical Pacific. Notice the distinct cooling in recent weeks

It is also very interesting to note that the sub-surface temperatures also have declined in dramatic fashion since the late summer. While there was a growing pool of warm water since the spring, it suddenly cooled and now we have a noticeable large area of cooler than normal sub-surface water across a large section of the Pacific. This means that the chances of seeing a true El Niño are getting quite slim.

Why is El Niño even an issue? Well, aside from the weather patterns that El Niño tends to have an influence on globally, if we look at the Atlantic hurricane season specifically, there tends to be a suppression of overall activity. This is mainly due to the increase in tropical convection over the Pacific which is due to the increase in sea surface temperatures because of the El Niño. Persistent tropical convection over the Pacific will usually mean stronger upper level winds and sinking air across the tropical Atlantic. These two negative factors limit the amount of development typically seen in the Atlantic main development region. It’s interesting that the end result seems to have been present this season. In other words, we have seen a limit to the numbers of hurricanes that have developed in the deep tropics. In fact, the ONLY major hurricane to form did so well outside of the typical breeding grounds and was very short-lived.

I do not understand why we had the effects of El Niño without the El Niño itself. Perhaps the atmosphere was responding as if there was an El Niño coming on even though the tropical Pacific was not quite there yet. Who knows? It’s all so complex and there are many interactions between the ocean and atmosphere that it’s difficult at best to know the real reasons behind some of this.

The bottom line is that El Niño has been put on hold, or so it would seem. It may be that it never fully takes root and this could have an effect on the upcoming winter season and most certainly the 2013 Atlantic hurricane season. None of the reliable climate models indicate an El Niño for the early part of 2013 and one could reasonably assume that there won’t be an El Niño during the peak of next year’s season in August-September-October. And yet, even with the near-El Niño observed this season, the Atlantic still has managed to produce eight hurricanes total. This is above the 100 year average. And, on the topic of abnormal sea surface temps, the tropical Atlantic was thought to have been cooler than normal this season. It wasn’t and still isn’t. In fact, a good deal of the tropical Atlantic is running nearly 1 degree C above normal right now. I guess there is a lot we still do not understand about our oceans and the atmosphere.

I’ll have another post here later this afternoon to address the current goings on in the tropics and what we might expect with 98L.

 

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