Hurricane season kicks in to busy mode with TD #5

August is considered the start to the main part of the hurricane season- and for good reason. This time of year the oceans are just about at their warmest and the atmosphere is calming down enough to allow for tropical cyclone formation. Actually, it is August 15 that many regard as the traditional start to the peak season period.

Today things are quite busy with the NHC beginning advisories on TD #5 – situated well east of the Windward Islands. It is forecast to become a hurricane once it reaches the central Caribbean Sea in about five days.

It is interesting to see this development take place because the region that TD5 is coming from was supposed to be fairly inhospitable this season with cooler than normal sea surface temps, etc. Instead, we see the opposite. Water temps across a good deal of the tropical Atlantic are running anywhere from .25C to 1.0C above normal. The below normal prediction definitely did not come to pass. So now we have an active tropical Atlantic and a depression to track.

First up for impact will be the Lesser Antilles as the depression slowly strengthens and moves on a WNW track. Luckily, it appears that conditions do not favor it becoming a hurricane before reaching the islands but this cannot be ruled out. A strengthening tropical storm can bring bursts of gusty winds to the surface, especially if it becomes convectively active. This can be monitored via satellite imagery. Watch to see how this plays out. If TD5 shows signs of developing deep thunderstorms, it is likely that it will cause some wind damage across the islands as it passes. I’ll examine this in the Hurricane Outlook Video that will be posted in our newly released HurricaneTrack App for iOS devices.

Water temps along the forecast track only get warmer and warmer. As long as upper level winds do not impede development, and the system does not track too close to South America, there is plenty of room for development. The official forecast shows it reaching hurricane strength near Jamaica in about five days. Obviously people in that region and beyond need to monitor the situation very closely.

As is usual with any tropical system, people want to know where it will ultimately end up. I wish I knew but I don’t. The steering pattern could lead it anywhere from Central America to some place along the U.S. Gulf Coast or across the Yucatan and in to Mexico. We’re simply going to have to wait for the guidance to help point the way as the days unfold. It certainly is a good time to be thinking about preparing for a hurricane no matter where you live. August is here and things will only get busier.

As I mentioned, the long awaited release of our mobile app took place today. It is available in the App Store as HurricaneTrack. That’s all one word, nothing else. Look for our logo with the HurricaneTrack.com in it, you’ll know it when you see it. The app will be a great way to keep up with news and info. It does not have maps or satellite pics, not yet. What it does have is information. In fact, when the time comes for us to head out in to the field for a hurricane mission, users of the app will have an incredible tool to keep up to date. Click on the “iPhone/Android App” link at the top banner for more info and to purchase today. The Android version is in the works and will be released just as soon as possible.

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Understand the seasonal forecast not for what it says, but for what it does not say

Tomorrow, Dr. Phil Klotzbach and the team from Colorado State University will issue their first quantitative forecast for the 2012 Atlantic hurricane season. As many who are tuned in to this info already know, the CSU team is likely going to forecast a season with less overall activity than we’ve seen in recent years.

I have already seen a few news reports that trickled out during the National Hurricane Conference last week that had headlines mentioning a “quiet” season ahead. I think that the video below sums up the reality of the seasonal hurricane forecast pretty well. Check it out and when the forecast comes out tomorrow and subsequent updates and additional forecasts are made throughout the rest of the season, keep the advice you hear in the video in mind.

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Is there an El Nino in the cards for 2012? Perhaps, but not looking as likely.

The mark of a busy hurricane season usually has one element missing from it: El Nino. That is to say, El Nino conditions in the Tropical Pacific tend to suppress Atlantic hurricane activity. This is due mainly to strong upper level winds that cut across the breeding grounds for hurricanes, thus limiting their numbers and intensities. However, one must remember infamous exceptions to this rule such as Andrew in 1992, an El Nino year. There are others as well which remind us of the adage “it only takes one”.

What about neutral years? What defines a neutral year anyway? Basically, when we see the sea surface temperature (SST) anomaly in the Tropical Pacific between .50 Celsius above or below normal, it is a neutral year (ENSO neutral). The scale is not tipped in one direction or another. Easy enough, right?

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How’s that La Niña going?

Subsurface Temps of the Tropical Pacific

Subsurface Temps of the Tropical Pacific

So far this winter, the La Niña that has been in place since last fall continues to hold strong. As the graphic from the Bureau of Meteorology in Australia indicates, subsurface temperatures across the tropical Pacific remain much colder than average over a large area. There is a growing region of subsurface warmth beginning to pool in the western Pacific but it lacks a real mechanism to drive it eastward- a so-called westerly wind burst. We typically don’t see those unless there is a significant pressure change across the Pacific and that shows up in the SOI or Southern Oscillation Index. When it is substantially negative, and persistently so, the trade winds often slow or even reverse, allowing the warm water gathering in the western Pacific to migrate eastward.

The latest update from the BOM also points out that long range climate models suggest a gradual warming of the tropical Pacific as the La Niña fades. This means it is likely that we’ll see a return to more average, or neutral ENSO conditions (ENSO stands for El Niño Southern Oscillation) by the time summer arrives in the Northern Hemisphere. There is also the possibility that the warming will continue and a weak El Niño could set in by next fall. I do not see any evidence yet to suggest that a strong El Niño is coming. However, this time of year, it is difficult to predict what will happen several months down the road but the large subsurface cold pool coupled with a fairly strong SOI signal over the past 30 to 90 days tells me that La Niña is going to be the rule for a few more months at least.

Why does any of this matter? Aside from the effects outside of the hurricane season, which are far too detailed to get in to in this post, we typically see a more active hurricane season when El Niño is not present. This is due to the stronger and more numerous instances of wind shear, the change of wind speed and/or direction with height, over the deep tropics. El Niño events promote this negative impact to tropical cyclones where as La Niña events usually do not.

For now, the La Niña pattern will continue but we’ll watch for signs that it is breaking down and then we’ll see how much warming takes place in the tropical Pacific. The end result could have an impact, one way or another, on the upcoming Atlantic hurricane season. I’ll post more about the ENSO state next month.

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