Late July Heavy Rains and Flooding in the Midwest

Flood imageSignificant flash flooding during the early morning of Tuesday, July 26th, 2022, occurred along the I-70 corridor in Missouri and I-64 corridor in Illinois. Multiple thunderstorms with rainfall rates exceeding 2in/hr. affected this area, including the St. Louis metropolitan area with up to 12 inches of rain falling from northern Montgomery County in Missouri to St. Clair County in Illinois. The storm caused multiple swift water rescues and scores of flooded interstates and homes across the St. Louis metropolitan area.  One fatality was reported in St. Louis City, where a man drowned in his car.

These thunderstorms caused a narrow, but intense swath of heavy rainfall: most of the area saw at least a few inches of rainfall with a narrow band of 6 to 12 inches stretching from east central Missouri to southwest Illinois.

rainfall map

Multi-Radar Multi-Sensor (MRMS) 24hr Radar-Estimated Rainfall as of 12pm on July 26th.

 

In addition, deadly and destructive flooding is also occurring in Kentucky and other parts of Appalachia July 28th-30th as several inches of rain have fallen over the area in a short period of time and is a life-threatening situation similar to the disaster in St. Louis earlier this week.   Floodwaters have claimed at least 25 lives in Kentucky and have washed away homes, roads, and bridges. Kentucky’s governor expanded a state of emergency declaration and said the death toll was likely to increase.Flood Map

What is the cause?

The heavy rain fell north of a stationary front (a boundary between warm humid air and cooler air to the north) across southern Missouri and Illinois, and eastward into Kentucky. Strong low-level winds (around 5,000 feet) brought in high amounts of low-level moisture which interacted with the front and with an upper-level jet stream to the north and produced a mesoscale convective system (complex of thunderstorms moving across the same area for more than 6 hours). This type of weather pattern is not unusual as there have been many similar warm-season heavy rainfall events in the central US in the past that were produced by mesoscale convective systems (MCSs) that developed above and north of a surface front in the past.

A conceptual model for the meteorological setup of the flash flooding event that occurred on July 26th, 2022 in the St. Louis metropolitan area. Image Credit NOAA NWS St. Louis

 

 

A paper written by Moore et al. (2003) found that the heavy-rain region of elevated MCSs is located, on average, about 160 km (100 miles) north of a semi stationary frontal zone, in a region of low-level moisture convergence that is elongated westward on the cool side of the frontal boundary.

In an earlier paper published by NOAA in 1994, stated that “flash flooding often results from intense, long-duration rainfall associated with MCSs. During the summer of 1993, the continuous development and movement of  MCSs over portions of the Missouri and upper Mississippi River  basins  for  several  months  contributed  to  numerous individual flash-flood events and prolonged large-scale river  flooding,  resulting  in  48  fatalities  and  economic losses  estimated  at  $20  billion”.

A conceptual model for the meteorological setup of the flash flooding event that occurred on July 26th, 2022 in the St. Louis metropolitan area. Image Credit NOAA NWS St. Louis

 

References

July 26th, 2022 Historic Flash Flooding in the St. Louis Metro Area, NOAA NWS Office, St. Louis Mo.

Moore et al. (2003) in the AMS Weather and Forecasting journal, The Environment of Warm-Season Elevated Thunderstorms Associated with Heavy Rainfall over the Central United States

NOAA,  1994:  The  Great  Flood  of  1993.  Natural  Disaster  Survey, NOAA, Rockville, MD

Junker,  N.  W.,  R.  S.  Schneider,  and  R.  A.  Scofield,  1995:  The  meteorological conditions associated with the great Midwest flood of  1993.  14th  Conf.  on  Weather  Analysis and  Forecasting, Dallas, TX, Amer. Meteor. Soc.,

 

 

 

 

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Heat Wave in Western Europe tied to Sea Temperatures?

temp anomaly

2m Temperature Anomaly Forecast

Another heat wave is currently developing over Western Europe and the media are pointing the finger at climate change but more likely is a result of a growing area of negative sea surface temperature (SST) anomaly that has developed over the eastern North Atlantic that is enhancing undulations in the jet stream.

 

Currently below normal SST anomalies have developed over the eastern North Atlantic with the greatest negative anomaly between the Azores and the coast of Portugal while positive anomalies remain over the western Mediterranean, Bay of Biscay, English Channel and Baltic Sea. 

Sea Surface Temperature Anomaly (C)

 

 

These conditions tend to favor upper-level troughs to develop over the eastern North Atlantic with ridging building over western Europe, and in fact is the current situation.  As the upper-level ridge builds over western Europe, the air temperatures at the surface increase accordingly.  Over several days the ridge will drift eastward spreading the heat into central Europe. 

250 mb Wind Forecast

 

Whether or not the SST anomalies are associated with climate change is open to debate.  

Ref:   Impact of North Atlantic SST and Jet Stream anomalies on European Heat Waves,  Julian Krüger et al.  

 

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Tropical Storm Bonnie forms over Southwestern Caribbean

Satellite image TS Bonnie over the southwestern Caribbean Sea

The disturbance that has been tracking across the southern Caribbean Sea has intensified into Tropical Storm Bonnie based on an Air Force Reserve Hurricane Hunter finding a well-defined circulation center located about 100 n mi east of the Nicaragua coast. The max winds are still only about 35 knots. Bonnie is moving just south of due west at 260/17 knots and is forecast to emerge over the tropical North Pacific on Saturday.

Bonnie remains in a low-shear and warm SST environment and is forecast to intensify during the next 12 hours prior to landfall. Heavy rainfall is likely across portions of Nicaragua and Costa Rica today into Saturday. Areas of life-threatening flash flooding and mudslides are expected.  Tropical storm conditions are expected on San Andres today, along the Caribbean coasts of Costa Rica and Nicaragua within the Tropical Storm Warning areas by this evening, and along the Pacific coasts of Costa Rica and Nicaragua overnight and early Saturday.

NHC Forecast Track TS Bonnie

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Potential Tropical Cyclone Two nearing Caribbean

sat photo

Satellite Image with surface wind field

Potential Tropical Cyclone Two continues to produce vigorous deep convection and also exhibits some banding features, however, reports from an Air Force Hurricane Hunter aircraft indicate that there is no well-defined center of circulation.  Interaction with land and fast forward motion will likely limit intensification until the system reaches the southwestern Caribbean Sea later this week when significant strengthening is possible.

wind risk

NHC Risk for Gale Force (Tropical Storm) winds

Heavy rainfall is expected across the Windward Islands and northeastern Venezuela tonight through Wednesday. Winds to tropical-storm-force are expected over portions of the southern Windward Islands tonight, over Islas Margarita Wednesday morning, and over the ABC Islands by Wednesday evening.  Tropical storm conditions are possible along the northeastern coast of Venezuela tonight and Wednesday evening.

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How’s the Weather Cruising the North Atlantic during July?

July Pilot Chart

PILOT CHART NORTH ATLANTIC JULY

Overview

During the month of July, the Azores to Bermuda High dominates the North Atlantic weather extending from the North Sea to the Gulf of Mexico with a mean center near 35N/35W.    Storm tracks have shifted north of 50 North latitude, except for one primary track from off the Carolina Coast northeastward towards the Denmark Strait. 

Fog occurrence during July is 10% or higher north of a line from Long Island to Ireland. July is also the foggiest month of the year over the Grand Banks with a 40% to over 50% risk for visibility of 2 miles or less. Icebergs can still be found southeast and east of Newfoundland during July 

Wind and Waves

South of the Azores-Bermuda high to about 10 N latitude, winds tend to be from the northeast to east averaging Beaufort force 4 (11-16 knots) with waves mostly about 1-1.5 meters (3-5 feet),  except winds tend to be more northerly off the coasts of Iberia and northwestern Africa. Northeast to east winds average Beaufort Force 5 (17-21 knots) with waves around 2 meters (6-7 feet) prevailing over the central Caribbean Sea. South of 10 N, winds are more likely to be from the south at Beaufort Force 3 (7-10 knots) with waves 0.5 meters (2 feet) or less. 

North of the Azores-Bermuda high winds tend to be mostly from the southwest to west averaging Beaufort Force 4 (11-16 knots) with waves mostly about 1-1.5 meters (3-5 feet).

Gale Risk

July Surface Pressure, Storm Tracks and Gale Risk

July Surface Pressure, Storm Tracks and Gale Risk

The risk of encountering gale force (Beaufort Force 8/34 knots) or higher winds is near zero south of about 35 N latitude this month.  Between 35 N and 50 N latitudes, the risk for gales is low at 1% or less and north of 50 N latitude the risk is only 1-4 %. 

 

Temperatures

The air temperatures range from 4 C (39 F) in the Davis Strait to about 28 C (82 F) over the Southwest North Atlantic, Gulf of Mexico and Caribbean Sea.  Sea surface temperatures range from under 5 C (41 F) in the Davis Strait to about 28-29 C (82-84 F) in Gulf Mexico, Caribbean and the southwestern North Atlantic.

Tropical Cyclones

There is an increasing risk for tropical cyclone development during July with the highest risk (14%) occurring in the north-central Gulf of Mexico. 

Pilot Chart TC Frequency North Atlantic July

Pilot Chart TC Frequency North Atlantic July

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How’s the Weather cruising the Caribbean and Gulf of Mexico during July?

July Piot Chart

NOAA Atlas of Pilot Charts for Gulf of Mexico and Caribbean in July

Wind

Caribbean Sea
Easterly winds mostly Beaufort force 4 (11-16 knots) prevail this month, except forces 4-5 (11-21 knots) prevail over the central Caribbean north of Columbia. Over the southwestern Caribbean the wind will back east to northeast and diminish to forces 3-4 (7-16 knots) and over the northwestern Caribbean, winds tend to be from the east forces 3-4 (7-16 knots).  There is a low (about 1%) risk for encountering gale wind forces 8-9 (34-47 knots) over the central Caribbean north of the Columbian coast during July. 

Gulf of Mexico
East to southeast winds, mostly forces 3-4 (7-16 knots) prevail, except becoming more variable in direction forces 2-3 (4-12 knots) over the Northeast Gulf and southeast to south forces 3-4 (7-16 knots) over the Northwest Gulf.

Waves

Generally waves average 2-5 feet (0.5-1.5 meters), however, over the Central Caribbean 6-8 foot (2-2.5 meter) waves will prevail. The risk for rough seas of 8 feet (2.4 meters) or higher is less than 10% across the Gulf of Mexico, the northwestern and the easternmost Caribbean, however, the risk increases to 30-45% over the central Caribbean Sea, especially north of Columbia. 

Temperature 

Over the Gulf of Mexico air temperatures average around 82-84 F (28-29 C) over the Gulf of Mexico and 81-83 F (27-28.5 C) across the Caribbean. 

Land Temperature
Overall, most Caribbean destinations see morning lows of 74-80 F (23-27 C) during July with daytime highs mostly 86-92 F (30-33 C). The hottest locations are Aruba, Cancun, Cozumel and the Caymans with afternoon high temperatures averaging at or above 90 F (32 C). 

Tropical Cyclones

There is an increasing risk for tropical cyclone development during July with the highest risk (14%) occurring in the north-central Gulf of Mexico. 

NOAA Pilot Chart Tropical Cyclone Frequency North Atlantic July

 

 

 

 

 

 

 

 

Rainfall

Rainfall during July varies quite a bit from 1.2 inches in Aruba to about 9.6 inches in Belize. The wettest locations include Belize, Bahamas, Trinidad, Dominica, St. Lucia and Martinique.  Drier locations include Aruba and Curacao, Cancun, Montego. St. Maarten, and St. Thomas.  

 

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2022 North Atlantic Hurricane Outlook

Hurricane Dorian

NOAA image of Hurricane Dorian, Cat. 5 off the Florida coast taken at 13:20Z September 1, 2019

The 2022 North Atlantic Hurricane Season officially begins on June 1st and ends on November 30th. During the most recent 30-year period (1991-2020) there has been, on average, about 14-15 named tropical cyclones.  Of these, about 7-8 become hurricanes and 3-4 become major hurricanes. NOAA has recently published their Seasonal Hurricane Outlook calling for increased activity again this hurricane season. The prediction for another active season is attributed to several climate factors, including the ongoing La Niña that is likely to persist throughout the hurricane season, warmer-than-average sea surface temperatures in the Atlantic Ocean and Caribbean Sea, weaker tropical Atlantic trade winds and an enhanced west African monsoon. 

2022 outlook

NOAA 2022 Atlantic Hurricane Season Outlook

For the 2022 hurricane season, NOAA is forecasting a likely range of 14 to 21 named storms, of which 6 to 10 could become hurricanes, including 3 to 6 major hurricanes (category 3, 4 or 5). The range of total named storms (14-21) is provided with a 70% confidence.  The predicted range runs from near normal to well above normal which suggests that there is still a good bit of uncertainty for this upcoming season.

Listing of 2022 Atlantic Hurricane Season Outlooks

Sea Surface Temperature Trends

Among several important factors cited in the NOAA outlook are “warmer-than-average sea surface temperatures in the Atlantic Ocean and Caribbean Sea”. The one outlier among the various projections is the outlook from the University of Arizona which  expects this season not to be as active as last season, however, they expect to review their outlook in early June based on more reliable sea surface temperatures.  

Sea Surface Temperature Anomaly North Atlantic

Tropical North Atlantic and Caribbean Sea Surface Temperatures (SST) have cooled recently as we approach the start of the North Atlantic Hurricane Season on June 1st.  In the Atlantic Main Development Region (MDR) SSTs cooled from mid-February to mid-April, followed by a warming trend into the second week of May which recently has reversed.   Only the Gulf of Mexico and southwestern portion of the North Atlantic has remained abnormally warm.

The cooling trend, “IF IT CONTINUES”, will have the effect of reducing the amount of tropical cyclone activity this season, compared to last season.   We shall see!

Sea Surface Temperature Anomaly Trend for the Main Development Region

 

Sources

Colorado State University
Tropical Storm Risk
University of Arizona
NOAA
Accuweather
Accuweather
UK Met Office
NC State University
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What to expect transiting the Indian Ocean during June

June Pilot Chart

NOAA Pilot Chart Average Surface Pressure and Tropical Cyclone tracks over Indian Ocean in June

 

South Indian Ocean

A ridge of high pressure normally extends from South Africa eastward to the west coast of Australia, mainly between 25-30 south latitudes. Southward of about 35 south latitude, westerly winds prevail averaging forces 5-6 (17-27 knots) with significant wave heights generally 2-3 meters.  Northward of the prevailing ridge, winds tend to be from the southeast averaging force 4-5 (11-21 knots) with waves mostly 1.5-2 meters, becoming southeast to south forces 3-4 (7-16 knots), waves 0.5-1 meter nearing the equator. 

The risk for encountering gale force (BF8/34kt) or higher winds is 10% or less from the equator to about 35 S latitude then increases from 10% to 26% southward of 35 S.  The risk of encountering waves of 12 feet (3.7 meters) or higher is 30-40% from about 40S southward, diminishing to  20-30% near 30 S and generally 15% or less north of 20 S latitude. 

North Indian Ocean 

Arabian Sea

The Southwest Monsoon establishes itself in June and the frequency of gales increases rapidly over the western half of the Arabian Sea reaching over 10% with the highest risk near 14 N 57 E.

June Monsoon

Monsoon over Arabian Sea during June

The risk of encountering waves of 12 feet (3.7 meters) or more increases over this area from less than 10% in May to as high as 40% or more in June. In the same area there is also a 5% risk of encountering waves of at least 20 feet (about 6 meters). 

Bay of Bengal

Generally a southwest monsoon prevails in June, averaging forces 4-5 (11-21 knots) with waves mostly 1.5-2 meters.

Tropical Cyclones

Cooler temperatures in the southern hemisphere in June reduce the risk for tropical cyclone development to less than 1 every decade. Over the North Indian Ocean there is a 70% risk for tropical cyclone development and mostly confined to the eastern Arabian Sea and Bay of Bengal.  

June IO Pilot Chart

NOAA Atlas of Pilot Charts for Indian Ocean in June

 

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What’s the weather like cruising the Caribbean and Gulf of Mexico during June?

JUNE

ATLAS OF PILOT CHARTS JUNE

Wind

Caribbean Sea
Easterly winds mostly Beaufort force 4 (11-16 knots) prevail this month except force 5 (17-21 knots) over the central Caribbean north of Columbia. Over the southwestern Caribbean the wind will back more into the northeast and diminish to mostly forces 3-4 (7-16 knots). Over the northwestern Caribbean, winds tend to be more from the east to east-southeast force 4 (11-16 knots).

Gulf of Mexico
East to southeast winds, mostly forces 3-4  (7-16 knots) prevail.

Waves

Generally waves will average 2-5 feet (0.5-1.5 meters) however, over the Central Caribbean, waves average 6-8 foot (2-2.5 meters).  The risk for encountering rough seas of 8 feet (2.4 meters) or higher is less than 10% across the Gulf of Mexico, the northwestern and easternmost Caribbean, however, the risk increases to 20-30% over the central Caribbean Sea, especially north of Columbia. 

Temperature 

Over the Gulf of Mexico air temperatures average near 81-84 F (27-29 C) over the Gulf of Mexico and the western and central Caribbean Sea but 80-82 F (27-28 C) over the eastern Caribbean.

Overall, most Caribbean destinations see morning lows of 74-80 F (23-27 C) with daytime highs 86-92 F (30-33 C). The hottest locations are Aruba, Cancun, Cozumel and the Caymans with afternoon high temperatures averaging at or above 90 F (32 C). 

Sea Temperature 

Sea surface temperatures average 81-83 F (27.5-28.5 C) for most of the Gulf of Mexico and Caribbean Sea this month, except 80-82 F (27-28 C) in the eastern Caribbean.

Rainfall

Rainfall continues to increase in the Caribbean during June, however, Aruba remains dry with Antigua and St. Maarten also being relatively dry this month. Higher rainfalls are likely in Central America, especially Belize and Costa Rica.  In addition, the Bahamas also see heavier rainfalls during June.

 Tropical Cyclones

The risk for tropical cyclones increases in June with the highest risk (10-17%) occurring over the Gulf of Mexico and an 8-11% in the Northwest Caribbean Sea. The risk diminishes to 3-5 % for the Southwest Caribbean and 2% or less for the eastern Caribbean. 

TC Risk June

Frequency Occurrence of Tropical Cyclones in June  (SST shown in Green)

 

 

 

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North Atlantic Weather Routes limited by Icebergs

500 mb chart

NOAA OPC 72 hour 500mb Forecast Chart

Upper-level blocking over the northeastern North Atlantic into northwestern Europe and a large cut-off low over the central North Atlantic, south of 40N latitude, will persist for the next few days. This pattern will allow for relatively light easterly winds and seas to persist across the North Atlantic north of  45N while strong to gale conditions persist south of 45N all the way down to 25N over the west-central North Atlantic. 

NOAA OPC 72 hour Surface Forecast

This pattern should allow shorter great circle routes between North Europe and the US East Coast, however, at this time the North Atlantic icebergs are drifting southward off of Newfoundland to near 45 N latitude limiting the shorter route options to keep clear of the icebergs.

North Atlantic Iceberg chart via North American Ice Service

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