Tropical Storm Gert View

Anyone been watching the North Atlantic this weekend. Beautiful view of Tropical Storm Gert this midday Monday. It will remain well offshore the US East Coast and west of Bermuda as it re-curves to the north this week. I may also become a hurricane as it does so by mid-week thanks to interaction with the Gulf Stream and favorable pole-ward outflow as it interacts initially with the westerlies prior to extratropical transition late-week.

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On the docket this week for Weather & Climate News –

  1. The Great American Total Solar Eclipse is ONE WEEK AWAY! Will discuss national weather and other things eclipse-related.
  2. More on potential tropical activity.
  3. Will continue with Part 2 of WxClimoEd discussing impacts of Global Climate Change.

For the Eclipse, my fiance and I’ll be heading to Grand Island, NE for the eclipse where totality will last 2 minutes 33 seconds (compared to the south side of Lincoln where the eclipse will only last 1 min 45 sec). We’ll have our 1 yr old with us (his birthday is August 17!) and will hangout with a couple of my fiance’s relatives in town. Should be exciting!

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Category 1 Hurricane Franklin making landfall on the East Coast of Mexico

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Hurricane Franklin is making landfall on the East Coast of Mexico Wednesday night/early Thursday morning (~midnight CDT Thursday) with maximum sustained winds of 85 mph with gusts likely over 100 mph. Besides damaging wind gusts, very heavy rain – up to a foot or more – will be possible in the mountainous terrain once the system moves inland and weakens during the day Thursday. ┬áLife threatening flash flooding and mudslides will be the greatest threats to any populated mountain areas (storm surge will be the hazard for coastal areas in the hurricane warning area tonight).


NOAA Raises North Atlantic Tropical Activity Forecast

The National Oceanographic and Atmospheric Administration raised its confidence today that the North Atlantic Basin would have an “very active” season. They called for 14-19 named storms, 5-9 hurricanes, 2-5 major hurricanes. A normal season averages 11 named storms, 6 hurricanes, 2 major hurricanes.

The reasoning for this activity forecast include 1) No El-Nino in the Eastern Pacific which would otherwise produce unfavorable vertical wind shear and cooler sea surface temperatures in the North Atlantic 2) Above normal sea surface temperatures across the Caribbean, Gulf of Mexico and Main Development Region (open tropical Atlantic) 3) The continuation of the Atlantic Multidecadal Oscillation favoring above normal oceanic heat content.

So far, we are at 6 named storms, 1 hurricane, 0 major hurricanes (assuming no surprise intensification of Franklin prior to landfall).

Tropical Storm Franklin moving over the Yucatan Peninsula this afternoon

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Tropical Storm Franklin made landfall last night near Pulticub, Mexico at approximately 10:45 pm CDT with maximum sustained winds near 60 mph. ┬áSince last night, the system has continued to move over land, remaining fairly well-organized but has weakened some thanks to land interaction with maximum sustained winds now down to 45 mph as of 10 am CDT. However, the National Hurricane Center in Miami anticipates re-strengthening after it enters the Bay of Campeche tonight. The waters in the Bay are piping HOT – 30-32 degrees C (88-90 degrees). These waters are fuel for robust intensification. With that said, northerly wind shear over the Bay is expected to impact Franklin during the day Wednesday as it heads for mainland Mexico, limiting rapid intensification. However, it could be a 70-75 mph tropical storm/Category 1 hurricane when it makes its expected landfall late Wed night/early Thursday morning. If Franklin becomes the first hurricane of the season tomorrow, it would do so around the climatological average time for the North Atlantic Basin (1966-2009) of August 10th. A tropical storm warning and hurricane watch is in effect for the expected landfall region.

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After landfall, there is expected to be 8-12+ inches of rain over the mountainous terrain of Eastern Mexico. Flash flooding and life-threatening landslides are likely.

For those curious and who watch the tropics, you might have been tracking this system since it left West Africa last week.

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Models have continuously wanted to make something of it but of course as it goes, when it comes to tropical cyclones, until it actually develops, the evolution of the system is difficult for numerical models to pin down. This system is no different. However, the wave still has some cohesive structure and therefore potential in the next 5 days to develop into a tropical cyclone as it moves east-northeastward over the open Atlantic. As long as computer models continue to give the wave an opportunity to develop, it is worth watching.

The North Atlantic Tropics Looking to become Active Again This Weekend or Next Week

It’s August and with that it’s time for the North Atlantic to show its tropical cyclone “muscle”. Tropical waves become more numerous as mesoscale convective systems form over the tropics of West Africa and race off into the open Atlantic; their mid-level “vorticity” or spin the seed for possible further development. The National Hurricane Center in Miami has pegged one Thursday with an 80% chance of development between now and Tuesday (40% chance between now and Saturday).

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Shortwave infrared image (sometimes known as “nighttime visible”) taken at 8 pm EDT Thursday. This shows a cloud mass moving off West Africa associated with a new tropical wave south of the Cape Verde Islands. (NOAA)

Mid-range models suggest the system will develop possibly into a depression or tropical storm, moving generally westward toward the Lesser Antilles heading toward Tuesday. Much more on what will happen will depend on the system’s development. Mid-level dry air brought in from the Sahara Desert will be an issue for this system as it approaches the Lesser Antilles if it moves north of 15N. As far as upper-level winds, forecast shows a modestly favorable environment for development, but details will wait until down the road. Water temperatures in this part of the Atlantic – known as the Main Development Region (MDR) – are running up to 1.5 C (~3 F) above average with abundant warm sea surface temperatures above 26 C (79 F) west of 35 W.

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Current Sea Surface Temperatures over the tropical Atlantic Ocean. The orange-red and red shades indicate temps at and above 26 degrees C. (Wunderground.com)

Because of the strong semi-permanent “Bermuda High” expected to dominate the Central and Western Atlantic next week, this system will need to be watched by interests in the Western Atlantic Basin for potential impacts in case it does not curve northeastward out to sea because of the subtropical high pressure system to its north (assuming it develops).

Also of interest is a system in the Eastern Caribbean Sea. It is in a more hostile environment (shear and dry air main problems) and only has a 40% chance of development over the next 5 days.

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Shortwave IR image at 8:45 pm EDT showing generally disorganized thunderstorm activity associated with a tropical wave in the Eastern Caribbean. (NOAA)

The Atlantic has been running about a month ahead of schedule on named storms, but has been dead quiet on hurricanes. The 1966-2009 average for the first hurricane in the basin is coming up (August 10th), but given recent years of activity, the Accumulated Cyclone Energy (ACE) thru Aug. 2nd is running at its lowest level in the basin since 2009. But still 90% of the ACE on average occurs from here on out, so much can still happen, especially given the lack of one otherwise major hindering presence in El-Nino.

I’ll keep track of these disturbances in the coming days and have more for you if they develop into organized systems. Stay tuned!

Tropical Storm Emily impacting much of Florida Monday

Tropical Storm Emily formed last night over the eastern Gulf of Mexico.  An area of low pressure developed thunderstorm activity which managed to consolidate and organize as it approached the central gulf coast of Florida overnight. Meteorologists began to notice the increasing organization of the system on local radar and at 6 am EDT this morning, the National Hurricane Center in Miami declared the system “Emily”.

Regional radar showing huge rain extent associated with Emily near and south of the center.
Enhanced infrared image showing cloud temperatures of Emily. Coldest temps (reds) near center along central gulf coast.
 

As an upper atmospheric trough of low pressure digs southeastward from the upper-Midwest over the next 2-3 days, this is expected to steer Emily northeastward. It will move out of Florida by overnight tonight/early Tue and head off into the open waters of the Atlantic well-offshore the East Coast. Land interaction today will weaken it but it may regain some strength over the waters of the Gulf Stream mid-week.

Atlantic tropical cyclone statistics thus far this season: 5 named storms, 0 hurricanes, 0 major hurricanes. On July 31st, on average the Atlantic is expected (based on 1966-2009 data) to have observed only 1 named storm, 0 hurricanes, 0 major hurricanes (on Aug 1st, the average named storms increases to 2). As we go deeper into the month of August expect the hurricane numbers to go up thanks to favorable below average wind shear and above normal oceanic heat content currently in existence in the Main Development Region (MDR) of the Tropical Atlantic. 


This area is largely turned off in earlier months but ramps ups later in the season as tropical waves develop from the tropics of West Africa and moves south and west of the Cape Verde Islands. So the Atlantic still has a lot left in the tank as far as heat energy to release.

Hilary and Irwin making plans for a Fujiwhara waltz over the open ocean

Let’s learn something cool about the tropics!

The past couple of weeks, the Eastern Pacific Basin has been quite active with multiple active tropical cyclones churning, dying and new ones forming. All while the North Atlantic Basin has been largely silent. We’ll get into the pattern set up for tropical activity between the two basins in the coming few weeks in a moment. But first, let’s discuss two interest systems in process in the EPac – Hilary and Irwin.

(Intensities are as of 4 pm CDT Thurs)

Hurricane Hilary is currently a Category 1 with max winds of 75 mph moving to the west-northwest. Meanwhile, ~480 nautical miles southwest of Hilary is Tropical Storm Irwin. It has max winds of 60 mph and drifting westward. Neither system is a threat to populated land masses and both are quickly heading for cooler waters north of the subtropical Pacific, where much drier air also exists in the mid-levels of the atmosphere. Both will lead to rapid deterioration of the cyclones this weekend.

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Visible satellite image showing Tropical Storm Irwin and Hurricane Hilary in close proximity at 4 pm CDT July 27, 2017. Cooler waters are noted to the north producing stable air mass near the sea surface, including deep marine stratus clouds and “closed cell” cumulus cloud deck. Stable air mass is non-conducive for thunderstorms hurricanes need to sustain themselves.
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Same image at same time as above in the “water vapor” infrared channel, where mid-level water vapor is detected. The circled area is a fairly dry area where air is experiencing sinking motions, coinciding with the cooler surface waters and the lack of thunderstorm activity for deep atmospheric moisture. Deep dry air can disrupt thunderstorm activity in tropical cyclones and weaken them.

Later Sunday and into Monday, an amazing phenomenon is expected to occur. Because of the very close proximity of Hilary and Irwin – only several hundred miles apart – the two cyclones are expected to undergo a Fujiwhara Interaction. This describes when two vortices in close proximity begin to rotate around a common center or one around another if one is more dominant. It is named after the Japanese meteorologist Sakuhei Fujiwhara who first described the interaction scientifically in a 1921 paper.

It does not happen very often, but it is typically more common in the Western Pacific basin where a very large surface area of favorable tropical development and maintenance exists and many cyclones can develop simultaneously and sometimes in close proximity.

Numerical models have shown the possible interaction for days.

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The slideshow above displays the Hurricane Weather Research & Forecasting Model forecast initialized at 11 pm PDT Wednesday with the forecast valid 5 pm PDT Sunday – 11 am PDT Monday. This model is “nested” on Hilary to show its evolution (the colors are surface temperatures in degrees C and wind barbs are in knots). However, you can see Irwin orbiting around it on its south and east sides Sunday evening – Monday morning. Irwin will likely weaken and die (along with Hilary, not long after), or will become absorbed by Hilary.

Nature never ceases to amazes in what it can do with the laws of physics!