Wilkens Weather tracks 8 tropical cyclones in the Western Pacific this July

The West Pacific Ocean became quite active last weekend, with four concurrent storms. This tropical activity was triggered by an active Madden-Julian Oscillation (MJO) phase coupled with the seasonal positioning of the monsoon trough. There have been seven named storms since July 1, the most recent being Typhoon Nesat.

Earlier this month, Tropical Storm Nanmadol formed northeast of the Philippines and within 48 hours made landfall along the west coast of the Japanese island of Kyushu. Wilkens Weather meteorologists closely monitored this storm for customers operating in the East China Sea and commenced storm advisories 42 hours in advance of the Joint Typhoon Warning Center (JTWC).

Marine Meteorologist Bryce Link explained his decision to initiate advisories at 09UTC on June 30th, “Deep thunderstorms were centered around a developing surface low and the system was in a fantastic environment”. Bryce pulled the trigger on this storm when operational models such as the GFS and ECMWF generally showed no signs of tropical development. ECMWF ensembles showed a stronger signal for tropical development, but the operational signaled nothing at the time the first WWT advisory was issued.

20-26 July 2017 West Pacific Tropical Cyclone Development.png

Sea surface temperatures (SSTs) have been on the rise since Nanmadol tracked across the East China Sea in early July. Early in the month SSTs were in the mid-80s across a small portion of the East China Sea, where Nanmadol tracked, and generally anywhere south and east of Taiwan. The graphic above (from July 24th) shows that SSTs are now in the upper 80s to 90°F (31-32°C) across much of the same region. These above average SSTs and favorable ocean heat content have created a conducive environment for tropical development. In fact, the last two tropical cyclones to form, Roke and Nesat, developed in this very warm area near the Philippines.

Currently, Typhoon Nesat is flaring convection northeast of Luzon. Further intensification is expected prior to landfall over Central Taiwan. Nesat formed along the monsoon trough, which is active from the Gulf of Thailand through the central Philippines as depicted in the 850mb wind graphic below. Tropical cyclones will not form in the area of enhanced westerly flow due to the presence of moderate to high vertical wind shear. Nesat was the second typhoon to develop in 2017.

850mb TropicalTidbits Chart with monsoon trough manual overlay.png

Despite convective and tropical cyclone activity in this region, the first typhoon of 2017 (Noru) developed at a higher latitude (near 28°N). Noru became a tropical depression over 1,000nm east-southeast of Yokosuka, Japan on July 20th. Early on, Noru tracked westward in response to two competing ridges to the south and northeast. Then, the cyclone’s movement slowed and the steering flow pulled Tropical Storm Noru and Tropical Storm Kulap around a central point. Noru became a typhoon on July 24th and the two cyclones “danced” cyclonically around each other the following day, a phenomenon known as the Fujiwhara Effect.  The end result was Tropical Storm Kulap tracking across cooler waters and dissipating within 24 hours and Noru maintaining typhoon strength southeast of Japan. Wilkens Weather meteorologists forecast Typhoon Noru to persist over the Northwest Pacific Ocean into early August.

Author’s note: This blog was updated July 28th to reflect the latest tropical information.

 

From record heat to monsoon thunderstorms within a week

One of the most anticipated seasonal weather changes during the northern hemisphere summer is the North American Monsoon. This monsoonal circulation produces significant rainfall over western Mexico and the Southwestern United States in response to summer heating over the higher terrain. While the monsoon brings beneficial rain, it can produce hazardous conditions over the desert. Monsoon thunderstorms may produce frequent lightning, hail, powerful flash floods, and blowing dust.

500mb Height Forecast NAM_Pivotal Weather
500mb Winds, NAM 18hr forecast valid 18Z  July 16, 2017

The onset of the monsoon is strongly influenced by the positioning of a 500mb area of high pressure. When this high is positioned over the Four Corners region, winds at this level turn more easterly over Arizona. Easterly flow allows inverted troughs to move west across the area, providing greater instability for thunderstorm development. Of greater significance is the resulting deep moisture advection from the Gulf of California. In July, mid-level winds over the Gulf of California are south to southeasterly, rounding seasonal high pressure that extends westward across the Gulf of Mexico during summer. Surface winds over the same region are southerly, transporting significant low-level moisture from both the eastern Pacific and Gulf of California. Lower wind speeds and weaker high and low pressure circulations are expected during summer as a result of less temperature variations. This often creates slow-moving monsoon thunderstorms, bringing an elevated risk of flash flooding.

Surface Moisture and Winds GFS_Pivotal Weather.png
Surface Dew Point & 10m Wind, GFS 6hr forecast valid 06Z July 17, 2017

Sunday, July 16th was the first very active day of the 2017 American monsoon season with nearly ideal conditions for hazardous weather over Arizona. With monsoon moisture on the rise, a Flash Flood Watch was issued for south central Arizona, including Phoenix. The forecast called for numerous thunderstorms over the higher terrain, propagating west to southwest across the lower elevations through the evening hours. NWS Storm Prediction Center issued a mesoscale discussion that afternoon detailing the threat of severe winds. Prime ingredients downstream included 20-25 knot easterly mid-level flow and sufficient instability as most unstable CAPE approached 2000 J/kg. Several severe thunderstorm warnings were issued by the National Weather Service forecast office in Phoenix that evening. At 6:16pm, a blowing dust advisory was issued for Northwestern Pinal County into southern Maricopa County until 8pm.

Severe thunderstorm warnings continued through the evening and early overnight hours. Flash Flood Warnings were issued for 30 minute rainfall totals exceeding 0.5 inch north and west of Scottsdale, according to the Flood Control District of Maricopa County (FCDMC). It is common for lower elevation areas and valleys to experience their heaviest rains at night.NWS Phoenix Tweet 16 July 2017

According to NWS Phoenix, this activity brought temperatures down to 74°F, which was the first time the area had experienced 70° temperatures in nearly 30 days. It is typical of the monsoon to onset quickly, causing an abrupt change in weather conditions. Earlier this month, the Phoenix area was setting record high temperatures of 118-119°F.

Here are some strong wind reports from the storms this day:

16 July 2017 Wind Reports Table Arizona
More wind reports can be found here.

Frequency of Tropical Cyclones in Trinidad

Bret 19 June
Infrared Satellite of Bret nearing Trinidad valid 2100UTC 19 June 2017

The second tropical storm of the 2017 Atlantic hurricane season, Bret, tracked unusually far south impacting the island of Trinidad. Bret is only the 6th tropical system to have tracked across Trinidad in the past 100 years. Coincidentally, the last tropical storm to make landfall over Trinidad in 1993 was named Bret.

Since 1856, 43 storms have passed within 100nm of the island, but only two of these storms were major hurricanes. Typically, Trinidad is too close to the equator to experience strong tropical systems. According to WWT Meteorological Specialist, Marshall Wickman, “most systems at that latitude don’t get the Coriolis force needed for significant intensification”. Therefore, the bulk of the stronger storms and hurricanes tend to track to the north of Trinidad and Tobago.

Major Hurricane Ivan in 2004 and Flora in 1963 tracked too close for comfort. Both storms packed winds of 105 knots when within 60nm of the northern coast of the island.

For an area surrounded by water and unaccustomed to experiencing these storms, even a weak tropical storm can be frightening. 

“Trinidad experienced torrential rainfall and heavy winds for approximately three hours, especially in southern Trinidad. It was very scary and as I looked through the windows at my home, I prayed all through this period asking for protection”. 

When we checked-in with our Trinidad customers after Bret, it was heartwarming to hear that essential staff working on offshore and onshore facilities were safe. The main threats with this storm were heavy rainfall and flash flooding.

Flooding is major threat during any tropical cyclone and is not directly related to storm intensity. To learn how to stay safe during flood events, visit the National Weather Service’s flood resource page

A dangerous heat wave, cold front, and tropical storm kick off summer 2017

Summer is officially underway in the northern hemisphere beginning today, June 20th. Quite the range of weather conditions are forecast across the United States today. In the East, a cold front moves offshore New England and stalls across the Carolinas. Showers and storms remain a threat near the stalled boundary from the Carolinas to the Gulf coast, while comfortable 50 degree dewpoints filter in behind the front in the Northeast. Cloudiness and rain chances will keep high temperatures near to below average across this region for the start of summer.

Residents along the Gulf Coast are watching a tropical storm brewing over the north central Gulf of Mexico. Louisiana residents are beginning to feel the effects from the outer rainbands of the storm. Flash Flood Watches are in effect from Southeast Louisiana to the eastern Florida Panhandle. Tropical Storm Warnings are in effect for portions of the Louisiana and Texas coastlines.

Across the Great Plains, temperatures are near average with mostly sunny skies to start the season. While this afternoon will be warm, in the upper 80s to low 90s, outdoor temperatures will feel more comfortable than they did over Father’s Day weekend. If you live in Central Oklahoma, like me, you may recall dewpoint temperatures climbing to 75 degrees Saturday morning, and persisting near 73 degrees through mid-afternoon. Dewpoint temperatures are a measure of moisture in the atmosphere, so higher dewpoints correlate to higher moisture content and humidity. Although the actual high temperature was only 92 degrees, when you factor in the moisture and humidity, the maximum heat index was 104 degrees.

What does this mean? Heat Index calculations use air temperature and dew point temperature to determine an “apparent” temperature, which is how your body feels when you are experiencing summer heat. The National Weather Service (NWS) Heat Index calculations are for shady areas, so it’s important to know that direct exposure to sunlight can increase the “apparent temperatures” by 10 to 15 degrees. High heat index values, generally over 100 degrees, are given an heightened awareness of hazardous outdoor conditions. Local NWS offices issue special heat advisories and excessive heat warnings for moderate to extreme heat indexes, when the risk of heat-related illnesses is highest. A day with a high heat index feels uncomfortable and sometimes oppressive. Sweat is slow to evaporate and the body struggles to cool down. Direct exposure to the sun only exaggerates this. 

But, it’s not just the feel-like temperatures that are uncomfortable and dangerous. In the desert southwest, temperatures are normally in the 100s in June with very low dewpoints. The start of the 2017 summer will be no different with above average, and potentially record-breaking heat, forecast across much of the Southwest.

Heat advisories and excessive heat warnings are in effect for Arizona and portions of California and Nevada through Friday. Hot summer days in the desert can feel like you are walking into an oven! Outdoor structures, such as playgrounds, are often unusable. A recent test in Tuscon, Arizona found that a children’s slide in the sun can reach 150 degrees, which is more than hot enough to cause a second-degree burn.

Heat Safety NWS Vegas.png

Take precautions and stay safe during the 2017 summer season!

 

Why we treat some Invest areas like tropical storms…

It’s critical that offshore operators are aware of tropical hazards well in advance of tropical storm development. 

Tropical Storm Bill, June 16 2015
Infrared Satellite of Tropical Storm Bill approaching the Texas coast.

Two years ago we were monitoring an area of disturbed weather near the Yucatan Peninsula. At the time, forecast models indicated that a trough of low pressure would move offshore the Yucatan within the next 24 hours and form a closed circulation as it tracked northwest toward the Texas coastal bend. Hurricane Carlos, off the southern coast of Mexico, was feeding in abundant tropical moisture from the Pacific, aiding thunderstorm development. Over the next few days, upper-level winds over the Gulf weakened, enhancing convection and improving the low-level circulation. Within 36 hours a tropical storm was designated over the northern Gulf of Mexico. About 15 hours later, Tropical Storm Bill made landfall over Matagorda Island, Texas with maximum sustained winds near 60 mph.Read More »

Hurricane Preparedness: Offshore Operations

Tropical cyclones have significant impacts on marine operations worldwide. Prior to experiencing tropical cyclone threats, offshore facilities must secure equipment, shut-in wells, and evacuate personnel. Operations can remain shut down for extended periods in the event that an offshore platform or rig is damaged or destroyed. Damaged pipelines along the seafloor are a common cause of interruptions to oil and gas supply.

To prevent structural damage and spills, control costs, and ensure the safety of personnel, accurate weather forecasts and advanced notification of tropical hazards are paramount. Even a weak tropical cyclone can produce hazardous weather conditions and put coastal and offshore operators at risk. Be sure to determine your exposure to the risks associated with tropical cyclones before the start of this Atlantic hurricane season.

Wilkens Weather provides a suite of online and mobile tracking tools to warn our customers of these risks. To be confident that you’re prepared this hurricane season, trust in the tropical expertise and tools provided by WWT: Read More »

A Review of Houston Heavy Rain Events in 2015-2016

April 16, 2016 Houston Flood Olivia Kintigh
Houston Tax Day Flood 2016

Houston, Texas rainfall was above average (49 inches) in 2015 and 2016. This was in sharp contrast to the 24 inch deficit in rainfall a few years prior. 2015 was the 5th wettest year on record for Houston, with 70.03 inches at KIAH and 77.13 inches at KHOU. Records at KIAH and KHOU, date back to 1889. Here’s a look back at the heavy rainfall events that resulted in these excessive totals:Read More »

Where are the Christmas Winds?

The climate of Trinidad is strongly influenced by the North Atlantic High, also referred to as the Bermuda High or Azores High, based on its seasonal positioning. During the fall season, the Atlantic High moves southward in response to the southward push of low pressure systems and their associated cold fronts over North America and the North Atlantic. The high’s southward position and lower sea surface temperatures, north of 10°N, result in strong easterly trade winds across the eastern Caribbean during winter. This increase in winds typically occurs around mid to late December, giving them the seasonal name: the Christmas Winds.    Read More »

South China Sea Monsoon Low

WWT Satellite Monsoon LowOver the past several days, an area of low pressure (Invest 91W) developed within the monsoon trough/ITCZ, generating bands of showers and thunderstorms across the southern South China Sea. As a result, fresh winds extended to the Borneo coast and Malay Peninsula over the weekend. Strong to near-gale force northerly winds also occurred along the northwest side of the low when it intensified this morning. Global models often underdo monsoon winds within these lows and these systems should always be monitored closely for tropical development. Read More »

Weather Forecasting in the Adriatic

WWT Adriatic Sea WaterspoutHigh terrain extending across Italy and central Europe yield a challenging environment for weather forecasting in the northern Adriatic Sea, especially during the winter months. The Alps, 120 miles wide with several peaks over 15,000 ft, block colder air to the north and often deflect it to the east over the Balkan States. The cooler air accumulates over the Balkan Peninsula, eventually reaching the height of the mountain passes. This induces a Bora, a local downslope wind effect that is common and at times violent during the cold season, usually from October through March. The Bora is one of two local winds that impact marine customers in this region. The other being Sirocco winds, a strong southeast wind, which often build over the course of a couple of days ahead of a Bora or impending low pressure system and is usually forecast with less uncertainty.Read More »

Wilkens Weather tracks 8 storms in the West Pacific this August

WWT West Pacific Tropical Summary

The West Pacific Ocean was quite active last week, with 2-3 concurrent storms. This recent tropical activity, while not unprecedented, has been above average.  Over the past several weeks, an upward Madden-Julian Oscillation phase extending across the West Pacific coupled with the existing monsoon trough.  This pattern has yielded eight named storms since August 3, the most recent being Typhoon Lionrock. Read More »