Tropical Storm Aletta Shifts Out to Sea; New Development Possible

Tropical Storm Aletta is currently moving westward in the middle of the Pacific Ocean, far west of Mexico, pretty much in the middle of nowhere. Winds are sustained at a fair 45 MPH, making for a moderately weak tropical storm. The system is expected to fade out as the westward movement continues, with an eventual turn to the north, before the system becomes post-tropical.

And of course, because the East Pacific needs more storms than the Atlantic (which should be achievable with the now-dead La Nina), we have an area of potential development over the next several days. While it is at 10% now, the National Hurricane Center has indicated that development appears possible over the next several days.

And lastly, we have an area of weak showers drifting around in the far northeast Atlantic. Yes, there is a circulation judging by visible clouds, but there is also a patch of tightly wrapped showers within the system. Needless to say, there is a 0% chance for development as it isn't even classified as an invest at this point.

Andrew

Severe Weather Targets Chicago, Milwaukee Today

There is a slight risk of severe thunderstorms today from northern Illinois into southern Wisconsin and southwest Michigan. Extreme northwest Indiana and eastern Iowa are also included in this risk.

Current surface analysis indicates a cold front will be sweeping south and east into the area highlighted, bringing what the Storm Prediction Center calls 'supercells and/or severe multicell line segments' to the region.

Considering the area highlighted is within warm temperatures but not so high humidities, these storms should not be incredibly rainy, so flash flooding is not anticipated in most areas. However, heavy rainfall in an area cannot be ruled out.
When the SPC is talking about these 'severe multicell line segments', they are discussing bowing segments of storms.

At around 6:00 PM CDT this afternoon, the SPC's WRF-NMM model is projecting that a line of strong storms will ignite in the region and likely produce some severe activity in the region.

The same WRF-NMM run off a different machine tells that the storms should be based farther west. Considering that the first image is from what I consider the 'operational' forecast, and it seems to be in line with the SPC, I will go with that solution.

Andrew

Short Term Tropical Outlook

Made May 14, 2012

This is a short term tropical outlook from The Weather Centre. This is meant as a guidance product and is not to be used in replacement of official forecasts from the National Hurricane Center (NHC).

Central America
For days, the FIM model has been projecting a tropical system to impact Cuba, Florida and possibly hitting the southern portions of the East Coast, although that has been in debate. What I have been seeing is what appears to be the monsoonal trough stationed in Central America at this time. Because convergence of moisture and winds are associated along the trough line, it is only a matter of time before something happens. Seeing as temperatures are above the necessary 80 degrees (F) in the red circle, and there will be converging winds and moisture in the area, showers and thunderstorms may very well propagate east into the Atlantic and fire up a tropical system, as is being projected now in the late May timeframe.

Gulf of Mexico
Temperatures in the area have surpassed 80 degrees (F) in the southern half of the region, an essential ingredient for tropical activity. Now, the monsoonal trough is not near the Gulf of Mexico, so there is not as much of a force to bring massive amounts of warm air into the atmosphere to make some thunderstorms. However, this could be the focal point for systems later on, and it will have to be watched.

Open Atlantic Waters
A ridge of high pressure appears to be extending into the region highlighted, and this would indeed discourage any storms from forming in the area, but also enhancing the potential for landfalling systems.

Tropical Cyclone May Make Landfall on Florida, South Carolina Shores

Warning: These forecasts are associated with very long range timeframes. This has a chance of not verifying at all, so use EXTREME CAUTION with this forecast.

The 12z FIM, which has been showing a tropical system developing in the Caribbean for the last 3+ days, is now showing the same system hitting Florida, and again in South Carolina in late May. Let's take a look.

Figure 1: MSLP from the 12z FIM on May 25th.

Figure 2: 10m winds (knots) from the 12z FIM, valid on May 25th.

As seen above, a tropical system appears poised to crash onto Florida shores, which may very well affect big cities like Orlando. Wind speeds indicate that this system would be of tropical storm status. I am very concerned about this situation. However, considering this is the first time the model is showing this scenario has me a little less convinced that it will happen (which is pretty low to begin with).

Figure 3: MSLP off the 12z FIM valid May 26.

Figure 4: 10m winds (knots) off the 12z FIM valid May 26.

As seen above, the system is then directed to make a second, weaker landfall in South Carolina. Wind speeds tell me that the system would be borderline-tropical storm status, unsurprising after the Florida landfall. Now, this model does appear to have the right idea with landfalling in South Carolina, with a steady windstream going to the west off of Africa. This west flow is then diverted against the tropical system, pushing it onshore.

Considering that the Atlantic is prepping for this hurricane season, this is not entirely out of the question, especially since this scenario has been trending on this model for at least 3 days.

Andrew

East Pacific Invest 90 - May 13, 2012

Invest 90 in the East Pacific has a 40% chance of development, as satellite imagery indicates a cluster of enhanced thunderstorms, with high clouds that appear to be making a swirling motion that may indicate rotation in the system. Should this happen, I would not be surprised to see this system really ramp up.

The track for Invest 90 looks to be split in 2 directions. The first one involves a potential landfall in Mexico, while the 2nd track, with more models, involves going out to sea with the system. Seeing as many storm systems in this position have gone out to sea in the past, this may be the solution for this system.

Intensity forecasts differ to soem degree, with only one model projecting tropical storm status winds. The short range models are pretty confident in a stagnant wind speed (maybe a slight uptick) over the next day and a half, with a drop off beyond that period.

Disregard AL92

The Tropical Cyclone Track Probability from Florida State University is projecting that Mexico has a 5% chance of a landfall from this system in 4 days. Mexico also has a 1% chance for landfall from the same system at hurricane status (Category 1 or 2). Hawaii has a measly 1% chance of landfall at any intensity.

Andrew